Opinion

Allen v. United States

588 F. Supp. 247
1984 U.S. Dist. LEXIS 16822

Court: District Court, D. Utah
Filed: May 10, 1984
Status: Published
Author: Jenkins
On the bench: Jenkins
Cited by: 42 cases
Authority: More cited than 95.2%

Reversed on other grounds by Irene H. Allen v. United States, 816 F.2d 1417 (1987)

determining whether plaintiffs’ injuries were causally connected to radiation exposure based upon overwhelming weight of scientific evidence that such a relationship existed as to certain diseases

How later courts described this case

determining whether plaintiffs’ injuries were causally connected to radiation exposure based upon overwhelming weight of scientific evidence that such a relationship existed as to certain diseases
noting that although increased incidence might be deemed “insignificant” by a scientist or statistician, it may well be that it “is still far more likely than not” that “the observed increase is related to its hypothetical cause rather than mere chance”
noting significant variation in experts’ interpretations of statistical evidence relating to the likelihood that plaintiff’s cancer was caused by exposure to radiation
“Once ingested or inhaled, the degree of exposure actually experienced depends upon the highly variable physical and chemical qualities of each individual radionuclide.”

Written by the judges who cited it.

The opinion

MEMORANDUM OPINION

JENKINS, District Judge.

In a sense this case began in the mind of a thoughtful resident of Greece named Democritus some twenty-five hundred years ago. In response to a question put two centuries earlier by a compatriot, Thales, concerning the fundamental nature of matter, Democritus suggested the idea of atoms. This case is concerned with atoms, with government, with people, with legal relationships, and with social values.

This case is concerned with what reasonable men in positions of decision-making in the United States government between 1951 and 1963 knew or should have known about the fundamental nature of matter.

It is concerned with the duty, if any, that the United States government had to tell its people, particularly those in proximity to the experiment site, what it knew or should have known about the dangers to them from the government’s experiments with nuclear fission conducted above ground in the brushlands of Nevada during those critical years.

This case is concerned with the perception and the apprehension of its political leaders of international dangers threatening the United States from 1951 to 1963. It is concerned with high level determinations as to what to do about them and whether such determinations legally excuse the United States from being answerable to a comparatively few members of its population for injuries allegedly resulting from open air nuclear experiments conducted in response to such perceived dangers.

It is concerned with the method and quantum of proof of the cause in fact of claimed biological injuries. It is concerned with the passage of time, the attendant diminishment of memory, the availability of contemporary information about open air atomic testing and the application of a statute of repose.

It is concerned with what plaintiffs — laymen, not experts — knew or should have known about the biological consequences that could result from open air nuclear tests and when each plaintiff knew or should have known of such consequences.

It is ultimately concerned with who in fairness should bear the cost in dollars of injury to those persons whose injury is demonstrated to have been caused more likely than not by nation-state conducted open air nuclear events.

The complaint in this action alleges that each plaintiff, or his predecessor, has suffered injury or death as a proximate result of exposure to radioactive fallout that drifted away from the Nevada Test Site and settled upon communities and isolated populations in southern Utah, northern Arizo

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na and southeastern Nevada. Each of the plaintiffs or their decedents resided in that area. Each claims serious loss due to radiation-caused cancer or leukemia. Each asserts that the injury suffered resulted from the negligence of the United States in conducting open-air nuclear testing, in monitoring testing results, in failing to inform persons at hazard of attendant dangers from such testing and in failing to inform such persons how to avoid or minimize or mitigate such dangers.

A. JURISDICTION

This Court has jurisdiction of this action pursuant to 28 U.S.C. § 1346 (b) (1976) and the Federal Tort Claims Act, 28 U.S.C. §§ 2671-2680 (1976). Venue of this action is proper pursuant to 28 U.S.C. § 1402 (b) (1976).

The Federal Tort Claims Act (FTCA) is the exclusive legal remedy for claims against the United States “for money damages ... for ... personal injury or death caused by the negligent or wrongful act or omission of any employee of the Government while acting within the scope of his office or employment, ... ”' This action was tried to the Court, without a jury, pursuant to the requirement of 28 U.S.C. § 2402 (1976) that “[a]ny ■ action against the United States under section 1346 shall be tried by the court without a jury, ...”

See O’Connor v. United States,

269 F.2d 579 (2d Cir.1959).

B. NATURE OF THE ACTION

This action is a consolidation of the individual claims of the 1,192 named plaintiffs in this lawsuit. This is not a class action.

Cf.

Annot., 48 A.L.R.Fed. 860 (1980). Trial was held in this action beginning September 14, 1982 and concluding with final arguments on December 17, 1982. The trial encompassed 24 of the claims in their entirety. Pursuant to the suggestion of the court these cases were selected by plaintiffs’ and defendant’s counsel as “bellwether” cases. The effort was to provide a selection of “typical” cases which when decided and reviewed may provide a legal and factual pattern against which the remaining issues in the pending cases may be subsequently matched.

The trial was conducted as well so as to make a full and complete record concerning legal, historic, and scientific matters common to all of the 1,192 plaintiffs with the idea in mind of avoiding future duplication of effort.

See Park Lane Hosiery Company, Inc. v. Shore,

439 U.S. 322 , 99 S.Ct. 645 , 58 L.Ed.2d 552 (1979). Other than as noted in this opinion, this court has not decided the remaining issues in the claims of the more than 1,100 plaintiffs that are still pending in the consolidated case.

This opinion decides claims of individuals, each with his own history and relationship to the open air nuclear tests. It fully decides 24 separate cases, tied together by common legal, historic and scientific threads of unique importance.

C. THE TRIAL

This action has been pending since August 30, 1979. It has been the subject of extensive pre-trial motions, dealt with on a preliminary basis by this Court’s earlier opinion. See

Allen v. United States,

527 F.Supp. 476 (D.Utah 1981). That opinion in a general way defined the framework for the trial that followed.

During the course of trial, this court received into evidence the testimony of 98 witnesses as well as more than 1,692 documentary exhibits.

The evidence provides

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testimony of witnesses ranging from those who participated in the testing program and related operations to highly trained and gifted “experts” offering conflicting opinions, to claimants who seek solace for their test-blamed sorrow.

The record contains historic documents, internal agency memoranda newly declassified, agency directives and correspondence, epidemiological studies, scientific texts and articles, as well as extracts from news media of the day and public information pamphlets.

D. THE PROBLEM OF UNCERTAINTY

We all seek to simplify and to order. The mind eschews the uncertain. We strain for certainty and perfect knowledge in an infinitely complex and dynamic universe. In doing so, we often fail to distinguish between those things which we directly experience, see, feel, hear, taste, smell — facts we experience — from those facts we infer. Each is a form of knowledge. Each we say we know. But we must be constantly aware of the nature of that which we say we “know”.

For example, we “know” of the existence of the atom. We “know” of the existence of gamma rays. We have never seen an atom or a gamma ray. We infer that atoms exist. The atom is a mind-created abstract model which provides a convenient, coherent and consistent explanation of an immense collection of perceived effects.

It is a model fashioned by many minds after a meticulous sifting of the observed and the reported.

But, we remain uncertain still of our scientific certainties.

This court has attempted to formulate an ordered theory of decision. While the effort lacks the mathematical purity of physical theory, it is the

judicial

resolution of the questions raised by this case with which the court is concerned. The theory of decision melds the method of science with principles of law and public policy.

In doing so, the court endeavors to follow the suggestions offered in a recent address by Chief Judge Howard T. Markey of the U.S. Court of Appeals for the Federal Circuit:

The differences between the judicial and the scientific-technological processes are profound and pervasive. Failure to recognize that difference has led to judicial expressions of frustration and an unfortunate tendency to rest judicial decisions on current, and often transient, “truths” and “facts” of science and technology. The purpose and function of science is to learn physical facts____

The purpose and function of law is to resolve disputes and to facilitate a structure for the organization of a just society — in a word, to provide justice.

Science normally evolves a new, general physical principle from hypotheses proven by numerous specific experiments. The normal judicial process is precisely the reverse, for, when properly conducted, it applies an existing, generally accepted moral or social value — an eth

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ical principle — a rule of law — to a specific problem____

Judges and lawyers must approach with great care, the idea that court decisions can be justified solely on the findings of science, lest the quest for justice be lost along the way.

For the particular “scientific truth” relied upon may prove transient indeed.

s}c :js :J: s¡‘ j}: ;}:

Markey, “Needed: A Judicial Welcome for Technology,” 79 F.R.D. 209 , 210-211 (1979). Judge Markey highlights a premise of this court’s theory of decision:

The first need, then, is to view technological evidence as merely one evidentiary element in the judicial matrix of decision and not necessarily as the

sole justification

for the judge’s legal decision.

Id.

at 211 (emphasis in original).

At the core of this case is a fundamental principle — a time-honored rule of

law,

an ethical rule, a moral tenet:

[T]he law imposes [a duty] on everyone to avoid acts in their nature dangerous to the lives of others.

Devlin v. Smith,

89 N.Y. 470, 477 , 42 Am.Rep. 311 (1882);

see also Thomas v. Winchester,

6 N.Y. 397 , 57 Am.Dec. 455 (1852). The more particularized rules of negligence and proximate cause as a basis for liability which are applied in the body of this opinion are rooted in this principle of duty. In this case, as in any other case in tort law, the answer to the ultimate question: “Who should bear the burden of the risks created by the defendant’s conduct?” is ultimately a question of policy and of public values.

In the law, as in science, one always faces uncertainty.

This court, faced with the duty of judgment in this case, does not have the luxury of the zealous absolutists who “know beyond doubt” that each and every cancer in the Great Basin is the result of open air atomic testing, or of their absolutist counterparts who “know beyond doubt” that none resulted. The court is disciplined by the record and the application of rules of law.

The court’s findings of fact have a certainty that is relative to the evidence presented to the court by others. They are not fixed in absolute terms. Judicial determination of facts in this case is indistinguishable from fact-finding in other cases no matter how “complex” the facts here might be.

Thus, this opinion speaks in terms of “natural and probable” consequences, “substantial” factors and things “more likely than not.”

In the pragmatic world of “fact” the court passes judgment on the probable. Dispute resolution demands rational decision, not perfect knowledge.

II. BACKGROUND: BASIC PRINCIPLES OF RADIATION AND NUCLEAR PHYSICS

Evaluation of the risks and consequences of exposure to atomic radiation in this case demands some familiarity with the concepts of radiation physics and its basic language. Such familiarity is a prelude to the knowledgeable application of rules of law.

It does not come easily. It did not come easily for the court.

The effort of the court has been to set forth as best it can the peculiar language and pertinent concepts of radiation physics as the court understands them from the record, to enable those concerned to under

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stand the legal relationships of the parties as found by the court and the legal consequences of party action.

The synopsis found in the next section of this opinion is part of the judicial effort to understand this case. It does supply some of the reasons why this court has found as it has found and has decided as it has decided. It does supply some of the reasons why the rules of law discussed and applied in subsequent sections have been applied as they have.

A. Scientific Notation and Mathematical Prefixes

Nuclear physics explores the universe using numbers and quantities which range from the extremely large to the infinitesimally small. To simplify the task of using numbers larger than 10 or less than 1, a shorthand system of expression has been devised that relies upon exponential powers of ten.

Scientific notation,

as this system is called, works in this fashion: Consider, for example, the number 100. One hundred is one way of expressing the quantity 1 x 100, or 1 x (10 x 10). Using exponents, this expression is shortened to 1 X 102, which still means 100. Similarly, 1,000 (1 X 10 X 10 X 10) may be expressed as 1 X 103 (or simply 103) one million (1,000,000) as 1 x 106 (or 106) and so forth. More complex numbers may be expressed in this fashion:

6,205,000,000 = 6.205 X 109

1,899,205 = 1.899205 X 106

89,450,000,000,000 = 8.945 x 1013

Decimal fractions may be expressed in scientific notation as well. For example, 0.01 equals Vioo or, as we have seen Vio2. The common form of stating this fraction in scientific notation is 1 X 10~2, or 10~2. Thus a negative exponent indicates a fractional quantity while a positive exponent indicates a value greater than 1.

Consider the following examples:

(1) 0.0032 = 32/10,000 = 32/104 = 32 x 10~4 or, more commonly, 3.2 x 10“3

(2) 0.65 = 65/100 = 65/102 = 65 X 10~2 or 6.5 X 10"1

(3) 0.000042 = 42/1,000,000 = 42/10"6 or 4.2 X 10~5

Scientific notation proves extremely useful in performing mathematical operations involving very large or very small numbers. Multiplication is accomplished through simple multiplication of the initial terms and through

addition

of the exponential terms. For example,

(1) 6,500,000 X 42,120,000,000 = ?

Switching to scientific notation gives us

(6.5 X 106) x (4.212 X 1010) = ?

which is computed in this fashion:

(6.5 x 4.212) x 10<6 +10> = 27.378 X 1016

or, expressed in simplest form, 2.7378 x 1017. This expression seems far simpler to write than 273,780,000,000,000,-000, which is the more conventional form. Fractions are multiplied in the same fashion:

(1) 1.2 X 10-4 X 6.88 X 10"12 = ?

(1.2 x 6.88) X 10(H) 1 H2)) = 8.256 X 10"16,

a number expressed conventionally as .0000000000000008256.

Division of numbers expressed in scientific notation is accomplished in a parallel way:

(1) 6.2 x 106 4- 3.8 x 102 = ? (6.2 4- 3.8) X 10<6-2> = 1.6315789 X 104

(2) 3.2 X 1018 4- 4.5 X 1011 = ? (3.2 -4- 4.5) X 10<18-n> = .71111 X 107 or 7.1111 X 106 — a short way of saying 7,111,100.

(3) 1.62 X 10-2 4- 6.04 x 106 = ? (1.62 4- 6.04) x 10«-2)-6> = .2682 X 10"8 or 2.682 x 10“9 — a short way of writing 0.000000002682.

Numbers such as these are commonplace in nuclear physics. For example, Planck’s Constant, a fixed number defining the proportional relationship between the frequency of a light wave and its energy, is ex

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pressed as 6.6261965 X IO-34, a term far more easily handled in computations than is 0.0000000000000000000000000000000006-6261965, its conventional equivalent.

Scientific notation makes it possible for a small electronic calculator with an eight-digit or ten-digit display to calculate numbers ranging from 1099 to 10~99. Mathematical operations beyond either limit of that range have no practical value; nothing in our experience is either that large or that small.

The mathematics used in nuclear physics is simplified for practical purposes through use of scientific notation. Another system of simplification involves units of measurements routinely used by humans in describing matter, energy and their interactions. At this point in history, science maintains a preference for units in the metric system. Mass is measured in grams, length in units called meters, volume in litres, energy in units such as ergs or joules. Often, calculations are made in terms of very large or very small quantities — thousands of units or infinitesimal fractions of units. One may be working with a thousand grams or a million grams or with a billionth of a gram. A system of word prefixes has been devised under the International System of Units to adjust units to more closely relate to the actual quantities being utilized. Table 1 lists these prefixes and their definitions.

TABLE 1. Prefixes for the Units in the International System

[[Image here]]

Thus, when one is working with 6 x 103, or 6,000 grams, one is also working with 6

kilo

grams. Likewise, if the quantity is 0.000000082 grams, or 8.2 x IO"8 g, a more workable expression may be 8.2 x 10~2 or .0820

micro

grams (yg). As will be seen, it is not uncommon to speak of micrograms, or

pico

curies (a tiny unit of radioactivity) of fallout material deposited in human bodies, or of kilograms of material, or

mega

curies of fallout radioactivity generated by detonation of a nuclear weapon.

The difference between a picocurie of radioactivity and a megacurie of radioactivity is a factor of 1018 or 1,000,000,000,000,000,-

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OOO.

Yet both units are meaningful to the evidence in the record before this court.

See

Part IV(A),

infra.

Simply by referring to Table 1, one can determine what multiple or fraction of a standard unit is being discussed in the text. Quick reference to Table 1 prefixes will aid the reader in identifying the units used and in making a meaningful comparison of quantities.

B. The Atom: Protons, Neutrons and Electrons

After centuries of careful observation, our best answer to Thales’ 2,500-year-old question “What is the world made of?” seems to be that all matter is composed of

atoms. See

G. Amaldi,

The Nature of Matter

(1966). Atoms are very tiny packages of mass which have specific physical qualities.

In the natural world around us, science has identified 92 species of atoms commonly referred to as

elements.

Each element has unique physical and chemical properties. Each element’s atoms differ slightly in structure and composition from the atoms of any other element. Some elements are familiar: copper, iron, oxygen, gold, carbon, calcium and two dozen others are well known as part of our own chemical makeup, or as part of the everyday world around us. Others, such as praseodymium, rubidium, and polonium, are far more obscure. Each, however, represents a different type of atom.

In addition to the 92 “natural” elements, scientists have produced a dozen more “synthetic” elements, such as plutonium, which are heavier, and often more unstable and short-lived than their “natural” brethren.

A complete list of the known chemical elements is found in Table 2.

[[Image here]]

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[[Image here]]

The differences between atoms of different elements are accounted for by variations in their composition and structure. All atoms are thought to be composed of three types of smaller particles: protons, neutrons and electrons. A

proton

is a tiny particle with a mass of approximately 1.672 X 10~24 gm, or 1.007 atomic mass units.

Each proton carries a positive electric charge.

electron

is a particle with a negative electric charge equivalent to that of a proton but with 1/1837 the mass of a proton, or 5.5 x 10-4 amu. An electron has a diameter of approximately 1 x 10~12 cm.

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neutron

is a subatomic particle having no electric charge (hence the name) yet having a mass of l.0087 amu — slightly heavier than a proton. An atom of a particular element represents a specific combination of protons j neutrons and electrons.

Far from being randomly distributed within an atom, these particles are ordered according to specific principles of structure:

(1) Each atom contains a nucleus at its center;

(2) Protons and neutrons are located within the nucleus;

(3) The nucleus is tiny in relation to the atom itself, comprising about 1/100,000th of the volume of the atom, yet containing almost all of its mass;

(4) Electrons orbit the nucleus in constant motion, and in patterns better described using the physics of standing waves;

(5) An electrostatically neutral atom is one with an equal number of electrons and protons; an atom with an imbalance of protons and electrons will itself act as a charged particle, called an

ion.

Ions — electrically charged atoms — are often far more reactive with other atoms than are neutral, unionized atoms;

(6) Electrons are distributed in the space around the nucleus in stable orbitals, which correspond to a discrete amount of energy, often called an energy state;

(7) Only certain energy states, or orbitals, are allowed in atoms of a given element;

(8) An electron may move from one energy level to a higher energy level, by absorbing energy from an outside source in an amount equal to the difference between the two energy levels; an electron may fall to a lower energy level by emitting energy in the amount of the difference between the two levels. The energy is emitted in the form of a photon.

An electron may absorb energy, (i.e., become “excited”) to a degree sufficient to allow it to leave the atom altogether. This phenomenon is called

ionization,

and is the key to innumerable chemical reactions.

The simplest element is hydrogen, whose atoms consist of a single proton in the nucleus and a single electron in the surrounding orbitals. The number of protons in the nucleus determines the number of electrons in the atom’s orbital shells, which has significant effect on the atom’s chemical characteristics. The number of protons is often referred to as the

atomic number

and is identified in the literature by the symbol Z. An element’s atomic number determines its place in an important scheme of classification known as the Periodic Table. See Table 3.

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[[Image here]]

From:

Handbook of Chemistry and Physics

(50th ed. Weast 1969).

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The elements in each column grouping, or period, share similar electron structures, physical and chemical properties.

See

I. Asimov,

Understanding Physics: The Electron, Proton, and Neutron

13-18 (1966); C. Hammond, “The Elements,” in

Handbook of Chemistry and Physics,

pp. B-2 to B-40 (64th ed. Weast 1983).

In addition to the atomic number, atoms are described according to

atomic weight,

symbolized by the letter A, which quantifies the total mass of an atom as expressed in atomic mass units (amu). The atomic weight of hydrogen is approximately 1.00797 amu, the single proton being the source of almost all of its mass. Heavier elements have nuclei containing neutrons as well as more protons. Helium, for example, has two protons and (usually) two neutrons in its nucleus, giving it an atomic number (Z) of 2 and atomic weight (A) of approximately 4.0026. While varying the number of protons will change the atom from one element to another, varying the number of neutrons changes the atomic weight of the atom without radically affecting its physical or chemical properties. Atoms of the same element which have different numbers of neutrons in the nucleus are referred to as

isotopes

of the element. Hydrogen, for example, has three isotopes: the most common form, protium, has no neutrons; deuterium, or heavy hydrogen, has one proton and one neutron; tritium, the heaviest, has two neutrons for each proton. Isotopes are often referred to by an abbreviation of their atomic weights called a

mass number.

Radium (Z = 88, A = 226.054) becomes simply radium 226 or 226Ra. Radium 224 (A = 224.0202) is another isotope of the same element having two less neutrons. In lighter elements the number of neutrons and protons in the nucleus tends to be equal, or nearly so. In the heavier elements toward the bottom of the Periodic Table, neutrons outnumber protons. Lead, for example, has 82 protons (Z = 82) and an average of 115 neutrons (A = 207.19) in its nuclei, compared to Calcium (Z = 20, A = 40.08) or Neon (Z = 10, A = 20.183).

C. Radiation and Radioactivity

Perhaps the simplest definition of radiation is the one most easily understood:

radiation is a transfer of energy through space

(or some other accommodating medium). Usually energy is radiated in the form of light or heat, though as we shall see, energy can be radiated through emission of particles having momentum.

Despite its outward appearance, light— or, more broadly,

electromagnetic radiation

— is not transmitted as a continuous flow of energy. When light is radiated, its energy is packaged in discrete units,

tiny bundles of energy called

photons.

Careful observation has disclosed that photons have some properties which are best explained if they are considered as waves; other properties are best explained if photons of light are thought of as particles. The energy of a particular photon, or light wave-particle, is related to its frequency as follows: E = Av Where E is energy (in ergs), v is the frequency (in Hertz) and

is a number known as Planck’s Constant. See note 9,

supra.

The relationship may also be described in terms of wavelength.

E = «4-)

E is energy

is Planck’s constant

c is the speed of light

is the wavelength

In short, the higher the frequency (or the shorter the wavelength) of light, the greater its energy. Visible light falls roughly midway on the spectrum of light energy with wavelengths [

] ranging from

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7 x 10~5 cm for red light through 4 x 10~5 cm for violet. Wavelengths longer than those for visible light fall toward the infrared end of the spectrum: radar waves, radio waves, and microwaves have photons of less energy than visible light. Light wave-particles of greater energy range from ultraviolet light having sufficient energy to cause sunburn cm) to x-rays, gamma rays (X" 10 ~8 to 10~10cm) and high energy cosmic rays (A> 10~12 cm) which are of particular interest to this lawsuit.

Differences in photon energy are crucial. We are constantly awash in an invisible ocean of radio waves which pass by — and through — our bodies with no perceivable harmful effect. However, exposure to gamma rays, which easily may be one-hundred

trillion

(1014) times more powerful than broadcast radio waves, raises serious human health concerns. See Part IV,

infra.

At the end of the last century, scientists in Europe led by Wilhelm Roentgen discovered basic techniques for producing high energy photons — “x-rays”, Roentgen called them — in the laboratory. By bombarding a metal plate within a sealed glass vacuum tube with high-voltage electrons, invisible radiation was produced which would cause certain chemicals to fluoresce brilliantly, and which could fog or darken photographic plates wrapped in paper, or even concealed within a box.

See

S. Glasstone,

Sourcebook on Atomic Energy

48-51 (2d ed. 1958); I. Asimov,

Understanding Physics: The Electron, Proton and Neutron

33-35 (1966). In 1896, the French physicist Henri Becquerel discovered that the same kind of penetrating radiation emanated from uranium salts.

In 1898, Marie Curie gave this phenomenon of constant emission of penetrating, ionizing radiation the name

radioactivity.

S. Glasstone,

Sourcebook on Atomic Energy,

at 53; see Mme. Sklodowska-Curie, 126

Comptes Rendus

1101 (1898). One of the first properties observed in both x-rays and radioactive substances was the induction of an electrical charge in the air surrounding an x-ray tube or immediately in contact with a sample of radioactive material. This

ionizing

effect enabled early researchers to detect such radiation using very simple devices. “[T]o detect nuclear particles we detect

ionization.”

E. Pollard & W. Davidson,

Applied Nuclear Physics

43 (1942) (emphasis in original). Radiation detection and measurement techniques are still very heavily dependent upon this particular quality.

See e.g.,

N. Tsoulfanidis,

Measurement and Detection of Radiation

(1983).

As we shall see, the adverse health effects of exposure to radiation are also a product of ionization. See Part IV

infra.

D. Ionizing Radiation: Alpha, Beta, and Gamma Rays.

Early research work by Ernest Rutherford and others using heavy radioactive elements such as radium, polonium, thorium and uranium, disclosed that ionizing radiation emanating from radioactive materials could be resolved into three different types:

alpha

rays (a),

beta

rays (/?) and

gamma

rays (y). Application of a strong magnetic field to a stream of ionizing radia

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tion emitted by a sample of radium salts readily deflected beta rays in a fashion indicating that beta radiation carries a negative charge. See Fig. 1.

RADIO-ACTIVE SUBSTANCES. 33

[[Image here]]

Fig.

1. Mine. Marie Sklodowska Curie,

Radioaclire Subslancen,

thesis presented to the Faculty of Sciences, Paris, !!)():) (pap. reprint ed. 1961), at 3!I-;54.

Less easily deflected in the opposite direction were alpha rays, which were deduced to have a positive electrostatic charge and greater momentum than beta

*270

rays. Gamma rays passed undeflected by the strongest magnetic fields; their highly penetrating qualities led researchers to conclude that gamma rays and x-rays were very similar (which they are).

See e.g.,

J. Cork,

Radioactivity and Nuclear Physics

11 (1947). Soon it was determined that beta rays exhibited all the properties of high-energy electrons, while alpha rays were identified as consisting of the nuclei of helium atoms stripped of both outer electrons. Both gamma rays and x-rays were found to consist of very short wavelength high energy photons.

Of crucial importance was the discovery that radioactivity is the product of internal processes within the nucleus of the atom rather than the result of excitation by some undetected outside source of energy. Radioactivity properties are unaffected by external forces, such as heat, light or pressure, or by any chemical reaction.

Instead, they operate according to specific principles of nuclear physics.

The basic principle finds simple expression in the work of Pollard and Davidson: “This process, the passage from one nearly stable nucleus to one which is stable, is the underlying process of radioactivity.”

Applied Nuclear Physics

102 (1942). Recalling that the nuclei of atoms are made up of various combinations of protons and neutrons, and that within atoms of a given element, the ratio of neutrons to protons may vary from isotope to isotope, careful observation of radioactive properties reveals that some proton/neutron ratios tend to be far more stable than others. Radioactivity represents the mechanism of internal adjustment by which less stable nuclei transform their composition into a proton/neutron ratio having greater stability. Emission of an alpha particle, for example, lightens the nucleus in evenhanded fashion; the numbers of neutrons and protons are each reduced by 2. Radioactive transformation by a-particle emission is observed most often in the decay of heavy elements (Z > 84),

such as uranium (Z = 92, A = 238), which ultimately “decay” to the very stable nuclear structure found in lead 206 (Z = 82, A = 206):

284Po-*

282Pb + 2He ( «-particle)

A nucleus which has a greater ratio of neutrons to protons than is found in more stable forms may emit a beta particle (/?-) — a high energy negative electron — as one of the neutrons is transformed into a proton. Strontium-90, with 38 protons and 52 neutrons, is radioactive. It decays by ,6-emission into Yttrium-90, with 39 protons and 51 neutrons. Yttrium-90 in turn decays into Zirconium-90 by /6-emission. Zirconium-90 with 40 protons to 50 neutrons, is the stable, naturally predominate isotope of that element. Radioactivity ceases.

90c /6 90,. /6 90„ , , , . , 38Sr--► 39Y -u — > 40Zr (stable)

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Atoms with an overabundance of protons may decay by emitting a positively charged electron, or positron (/3+), or by capturing an electron from a nearby orbital. Either process reduces the number of protons and increases the number of neutrons by 1.

For example,

U80

-> (stable) + /? + (positron)

When the radioactivity properties of the nuclides

are plotted on a graph of numbers of neutrons (N) and protons (Z), a pattern emerges. See Fig. 2.

[[Image here]]

Fig. 2.

L). Halliday,

Introductory Xu clear Physics

9 (1950).

*272

Radioactive decay enhances nuclear stability not only by adjusting the total number of particles, but also by carrying away discrete bundles, or quanta, of energy from the nucleus. Alpha particles don’t quietly drift away from the nucleus of Plutonium-239; they are propelled away at high speed with an energy of more than 5

MeV

— five million

electron volts.

While 5 MeV is a trifling amount of energy in the sphere of human endeavors, at the atomic level it is enormous. In 1919, Rutherford bombarded nitrogen atoms with

particles of lesser energy. The

particles slammed into the nitrogen nuclei, yielding oxygen nuclei — a different element — and a free proton:

gHe (

particle ) + —-> XgO + Jh (proton)

E. Pollard & W. Davidson,

Applied Nuclear Physics

5-6 (1942).

A nucleus may also expel energy through emission of a gamma ray (y) of a particular wavelength. Likelihood of gamma emission depends on the specific nuclides. Strontium-90 does not emit gamma rays during decay. Iodine-131 does. Cobalt-60 emits

two

gamma rays in the MeV range, and has been used as an important source of radiation in the treatment of cancer. The detailed properties and mechanics of radioactivity and nuclear transformations are as awe-inspiring as they are complex. Why it is, for example, that unstable heavy nuclei emit

particles poses a challenging theoretical question, the answer to which is beyond the scope of this inquiry.

Yet a specific understanding of the statistical behavior of radionuclides

(e.g.,

concepts such as radionuclide “half-life”) and of the ways in which ionizing radiation interacts with other matter is crucial to adequate analysis of the causation and negligence issues raised in this action.

E. Statistical Nature of Radioactivity

Current theory holds that events at the atomic or sub-atomic level occur according to statistical probabilities rather than any strict determinism.

Radioactive decay in any given quantity of a radioactive element occurs at a constant rate, yet no one can tell at what time any particular atom will decay. We know only the probability that it will decay within a chosen time period, or viewed another way, that over a chosen period of time, x number of nuclei in our sample will decay into “daughter” nuclides. The most important expression of this statistical approach is found in the concept of

half-life.

The half-life of a radionuclide is the specific length of time during which half of the nuclei in any amount of the radionuclide will have decayed- For example, if you start with a one gram sample of radium-226 (226Ra), after 1,600 years only half of the sample (0.5 gm) remains 226Ra. The other half has undergone radioactive decay:

ppR ppp 4 88 Ra---> 86 Rn + 2 He + Q (energy)

After another 1,600 years, only half of that remainder is still 226Ra (0.25 gm). Passage of 1,600 more years witnesses decay of one-half of that fraction, leaving Vs gram (0.125 gm) of 226Ra. The process of decay continues at this rate until no more 226Ra remains. To say, therefore, that a radionuclide such as strontium-90 has a half-life of 28.1 years means that half of the quantity existing at the beginning of the 28.1 years remains Sr at the end of that time.

*273

Half-life varies dramatically from radionuclide to radionuclide. Some isotopes last for half-lives of only a few seconds; others last far longer. Uranium (¶3 U), although radioactive, has a half-life of 4.51 X 109 years — nearly the age of the earth itself. See R. Heath, “Table of the Isotopes,” in

Handbook of Chemistry and Physics

B-232 to B-316 (64th ed. Weast 1983).

Half-life is indicative not only of the persistence of a radionuclide in the laboratory or the environment, but also of the intensity of its radioactive decay. Radiation yielded by one gram of iodine-136, an isotope found in the fireball of a nuclear explosion, is intense: emitting

¡3

particles and y rays in the MeV range, 136I decays rapidly, reflecting a half-life of 83 seconds.

53 I----> 54 Xe (stable) +

p -

+ y + Q (energy)

Consequently its radioactivity fades rapidly. After 15 minutes, less than V2000 of the original amount is identifiable as 136I. After an hour more, the fraction remaining is nearly 2.28 x 10~15 of the original amount. In contrast, Plutonium-239, a radionuclide present in every nuclear fallout cloud to date,

persists with a half-life of 24,400 years. Consequently, all but a fraction of the estimated 3 tons of 239Pu deposited on the earth by fallout can still be found somewhere. See “Sources and Effects of Ionizing Radiation”, Report of the United Nations Scientific Committee on the Effects of Atomic Radiation (1977), PX-706/DX-605 [hereinafter cited as the

UNSCEAR Report

(1977) ], at 148.

Half-life is

not

an average lifetime for a radionuclide;

it is an expression of rate, of the statistical probability of decay over a specific time period.

The half-life of a radionuclide gives some immediate insight into its behavior and the nature of the hazard that might be associated with it. A small quantity of radionuclide with a half-life in the order of minutes will not persist long enough to present a significant hazard a few days later and it is not likely to become dispersed very far by natural forces. In contrast, a radionuclide with a half-life on the order of several years may represent a long-term hazard and become widely dispersed if not held in containment....

*274

1 F. Whicker & V. Schultz,

Radioecology: Nuclear Energy and the Environment

44 (1982). The quantity of radioactive material that persists in relation to the number of half-lives is illustrated in Fig. 3.

[[Image here]]

. Fig. 3. Relationship of time, expressed as number of half-lives, to the ■quantity of a ¡radioactive substance.

Quantity of radioactive material may be expressed in either of two ways: (1) the mass of the material; or (2) its radioactivity. To say, however, that a sample of Strontium-90 has a mass of x grams does not by itself offer any perspective on the amount of ionizing radiation being emitted by the sample at any given moment. The activity of a known mass of radioactive material may be computed as follows:

A* = 0.693 m N A Ty2 A Fj.

Where A* is the activity of the sample; m is the mass of the sample;

A is the atomic weight of the radionuclide;

T'/2 is the half-life in years (or whatever);

Ft is the conversion factor from years (or whatever) to a desired time period,

e.g.

minutes; seconds, etc.

NA is a constant, known as Avogadro’s number, expressing the number of atoms

*275

in a mole (a mass in grams equal to the nuclide’s atomic weight) of material. See 1 F. Whicker & V. Schultz,

Radioecology: Nuclear Energy and the Environment, supra

at 45. For example, a 1.2 gram sample of sodium-24, an important radioactive by-product of nuclear weapons testing having a half-life of 15.0 hours, would have an initial activity of

= (0.693) (1.2 grams) (6.022 x 10^3 atoms/mole) (15.0 hours) (24 grams/mole) (3600 seconds/hr.) = 3.864 x 10” disintegrations per second.

This activity represents a rate of emission paralleling that of a sample of pure radium-226 having a mass of 1.0557 x 107 grams, or

10.5 metric tons.

Of course, 24Na activity would fade quickly in comparison to the 226Ra; the mean life of 24Na atoms would be 21.64 hours, while atoms in our 10.5 metric tons would persist for a mean life of 2,308.8

years,

making it a far more serious hazard overall.

Expression of radioactivity in terms of rate of decay

(e.g.,

disintegrations per second) is a common measurement. The most frequently used unit of activity is the

curie

(Ci), which represents a mass undergoing 3.7 x 1010 disintegrations per second. Practical quantities of radioactive materials are more easily expressed in fractional units, such as

millicuries

(mCi),

microcuries

(¡uCi), or yucocuries (pCi), representing 10~3, 10-6 and 10~12 curies, respectively.

A tiny new unit, the

Becquerel

(Bq), represents an activity of one disintegration per second, or the equivalent of 27 pCi. Yet the radioactive fallout yield of even a “nominal” nuclear device is more easily expressed in

mega

curies — millions of curies of activity.

*276

Measurement in curies does not, however, define the type or energy of the radiation being emitted. That information is specific to each radionuclide and is important to the evaluation of the risk created by exposure to curie, millicurie, or microcurie amounts of material.

F. Interactions of Radiation with Matter

Each type of radiation emitted by radioactive materials interacts with other matter in important yet distinct ways. Alpha particles carry an electrostatic charge of +2 units. When an

particle passes near another atom, the electrons in its orbital shells are attracted to the

particle by virtue of their own negative (-) charge. Some electrons are merely excited by the event, i.e., they move from a lower to a higher energy state while remaining in orbit around the nucleus. For many others, however, the coulombic attractions of the

particles are too strong; these electrons are stripped away from their original atoms and travel freely for a time, leaving the mother atom in an ionized state. Balance of electric charges is soon restored, but in reaching neutrality, some atoms form new combinations with other atoms— new molecules are born. In many ways, an

particle can be visualized as a tiny, speedy electromagnet, sweeping free electrons into its path.

The electrostatic attraction is a mutual one; the electrons in nearby atoms are attracted by — and attract — the speeding

particles. The coulombic forces energize the electrons, pulling them away from atoms by giving them sufficient energy to escape. At the same time the electrons act as a drag on the

particle. Its energy is reduced by the amount that the electrons’ energy is increased. According to fundamental physical law,

the energy is conserved, neither created or destroyed. The ionization that occurs in the path of an

particle represents a

transfer

of energy. The amount of energy transferred per unit of distance traveled by the

particle is known as a

linear energy transfer

(LET).

See e.g.,

Committee on the Biological Effects of Ionizing Radiations,

The Effects on Populations of Exposure to Low Levels of Ionizing Radiation: 1980,

at 13 (1980), DX-1025 (hereinafter cited as the “BEIRIII Report”). Alpha radiation is “high-LET” radiation; so many electrons are excited or ionized by

particles that a great deal of energy is transferred in a short distance. The range of an

particle traveling through matter thus tends to be fairly short. As soon as the

particle has transferred the bulk of its energy, it slows down sufficiently to capture two electrons of its own, becoming a neutral, inert helium atom.

*277

The range of an

particle depends largely upon the energy of the particles and the density of the medium through which it passes. Radioactive «-emitters shower their surroundings with particles having an energy between 0.1 MeV and 10 MeV. Such energies give the alpha radiation a range in air of less than 10 cm. The range in more dense material, for example paper, aluminum foil, or human cell tissue is far less, on the order of a few pm. The range of « particles, or conversely, the stopping power of material bombarded by them, is computed with good accuracy through a system of mathematical formulae not directly relevant here.

For the purposes of this case, the general range of « particle radiation, i.e., a few centimeters in air, a few microns (pm) in living tissue

is important information to use in assessing the risks presented by potential and actual exposure to a-emitting radionuclides.

Beta particles

(0-)

interact with matter somewhat differently than

radiation. As a consequence of

particles having far less mass than an « particle (M^g = 1/7360 M'«) and a negative rather than

*278

positive electric charge,

relatively low linear energy transfer (LET) takes place per unit of distance traveled. Beta particles are far more easily deflected by collisions with other electrons or nuclei, and cause ionization of atoms by colliding with other electrons or by passing near enough to repel electrons (having the same negative charge). Having a low LET factor, however, means that

¡3-

particles in the 100 Kv-2 MeV energy spectrum have significantly greater range and penetrating power than do a particles carrying even twice as much energy. They may traverse several meters in air at speeds approaching that of light. J. Cork,

Radioactivity and Nuclear Physics

118 (1947). In cell tissue,

j3-

particles may leave a trail of ionization several millimeters in length.

Beta particles, like other ionized electrons, also radiate energy in the form of gamma rays as they are deflected by nuclei and slow down, eventually returning to orbitals of other atoms. This “braking” radiation, called

Bremsstrahlung,

may in turn strike other electrons, exciting them into further ionizations.

Gamma radiation interacts with matter in several different ways: (1) photoelectric absorption; (2) Compton scattering; (3) pair production; (4) Rayleigh scattering; or, it may not interact at all, passing through the exposed material completely unimpeded. Since gamma rays have no electric charge, ionization by gamma radiation occurs only when a gamma ray strikes an orbital electron. If a gamma ray striking an electron is totally absorbed, the electron is stripped away from the atom, and possessed of the full energy of the gamma ray, careens through surrounding matter in a fashion very much akin to a

¡3

particle. Thousands of ionizations result. This “photoelectric” effect is the dominant form of interaction for gamma rays whose energy is less than 1.0 MeV.

For gamma rays of greater energy (0.3-3 MeV), the phenomenon known as Compton scattering is predominant: a gamma ray striking an electron may only impart a portion of its energy to the particle. The ionized electron is driven in one direction, the gamma ray photon, now of lesser energy, is deflected on a new path. In Compton scattering, a gamma ray may thus ionize several electrons before its energy is wholly transferred.

For gamma rays of an energy of 1.02 MeV or greater another interaction may occur if the photon strikes a nucleus: the gamma ray can disappear, leaving a positron

(y8

+) and an electron (/?-) in its place. This phenomenon, known as pair production, ultimately generates further gamma radiation: when the positron comes in contact with another electron both particles are annihilated, yielding two gamma photons of an energy approximating 0.51 MeV each. These go on to ionize other electrons, or pass out of the irradiated material entirely. At energies above 10 MeV, pair production is the predominant interaction. See I F. Whicker & V. Shultz,

Radioecology: Nuclear Energy and the Environ-

*279

merit

51 (1982). Finally, gamma rays of low energy (<100 Kev) may experience Rayleigh scattering, the elastic deflection of the gamma photon by an electron with no energy being transferred to the electron.

Gamma radiation by itself does no damage to exposed matter — if it passes through without collision.

When the gamma rays collide with electrons, as they may at any point along their path, ionizations occur just as if the matter had been bombarded with high energy beta particles. As we shall see, ionization of matter in living tissue may cause serious harm to the affected cells, and ultimately, the whole organism.

A fourth type of radiation emitted by nuclear explosion, free neutrons, also causes ionization in a somewhat indirect fashion. A neutron may be absorbed by a nucleus with which it collides, yielding a free proton, an

particle, another neutron, or a gamma ray. These charged particles and gamma rays interact with matter as previously described. Neutrons may also collide with nuclei and scatter them without being absorbed. Neutrons remaining in the free state decay into free protons and

fi-

particles at a rate giving them a half-life of roughly 10.8 minutes:

on —>

\v + g

+ v

(v is an antineutrino) H. Semat & J. Albright,

Introduction to Atomic and Nuclear Physics

447, 498-500 (5th ed. 1972).

While neutron interactions are a significant health concern in cases of direct exposure to a nuclear explosion or to a nuclear reactor, they are important to this case in only one respect: free neutrons from a nuclear explosion will interact with the surrounding air or with soil drawn up into the mushroom cloud, forming radioactive isotopes through absorption reactions. This additional activity adds to the radioactive burden of the fallout cloud, increasing the total risk of radiation exposure from the event. See Part III,

infra.

G. The Mass-Energy Relationship

Mention has already been made of the Laws of Conservation of Mass and Energy — the concepts that in any chemical reaction the total mass of the system remains constant, and that in any physical interaction the total energy of the system remains constant. In an absolute sense, neither matter nor energy is created or destroyed in any reaction. Yet an atomic bomb, a device containing only a few kilograms of metallic material yields energy — heat, light, and explosive force — in incredible amounts.

The key is found in a simple, fundamental relationship between matter and energy, a relationship which Albert Einstein originally defined and which most people have at some time seen expressed as

E = me2

*280

E represents energy, expressed in ergs; m represents mass, expressed in grams; c is the speed of light, expressed in cm/second (c = 2.9979250 X 1010 cm sec-1). Put together in the simplest terms,

matter and energy are equivalent.

Matter may be converted to energy by a factor of approximately 9 X 1020 ergs per gram.

9 x 1020 ergs, if released all at once, generate the explosive power of approximately 21.5 kilotons of TNT — more than either of the bombs dropped on Japan.

Cf.

S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons

13 & Table 1.45 (3d ed. 1977) DX-1242. A “nominal” yield nuclear device (approx. 20 kt TNT) derives its energy from the annihilation of a little less than one

gram

of matter.

If E = me2, then m = E/c2. Using this equation and a conversion factor (1 kt TNT equals 4.18 X 1019 ergs) then the quantity of matter consumed can be calculated:

m = (4.18 X 10 19 ergs) (20) (9 x 10 cm “Vsee

m = 9.288 X 10“1 grams, or 0.9288 gm.

Similarly, the energy released in radioactive decay can be precisely accounted for by finding the difference in mass between the mass of the original nuclide and the mass of the daughter nuclide and emitted particles. The decay products will be a tiny bit lighter.

H. The Nuclear Fission Process

The discovery of radioactivity at the turn of the last century led quickly to further discoveries. The nature and properties of alpha, beta and gamma radiation were closely scrutinized. In 1920, physicists predicted the existence of a new particle — the neutron — having roughly the same mass as a proton, but no electric charge. In 1932, experimental bombardment of beryllium metal with

particles yielded a new highly penetrating form of radiation that British physicist James Chadwick correctly identified as neutrons. By 1937, reports were published indicating that elements heavier than uranium could be synthesized through bombardment of uranium with neutrons.

By early 1939, Otto Hahn and Fritz Strassman published evidence that bombarding uranium with neutrons produces an unprecedented reaction: fission of the uranium nuclei into two lighter fragments.

It was soon determined that fis

*281

sion of uranium yielded two fragments of unequal mass, at least two additional free neutrons, and a shower of gamma rays and neutrinos. The atomic numbers (Z) of the two fragments add up to 92, the atomic number of uranium. The weights of the fission products and the three neutrons released by fission

add up to an amount slightly less than the mass of the uranium atom plus one neutron: a difference of approximately 0.18 amu.

235 92 U + 236. 92 XT) 141. 56' B a

92 36 Kr + 3 on +Q

where Q represents the energy released in this reaction. H. Semat & J. Albright,

Introduction to Atomic and Nuclear Physics

510 (5th ed. 1972). Conversion of that mass difference to

energy

according to E = me2 gives an energy (Q) of nearly 175 MeV. The two fission products are both highly radioactive nuclides which soon decay to stable elements (141Pr and 92Zr), releasing 22 MeV of additional energy in the process. The sum of these energies is nearly 200 MeV per fission of 235U — close to the energy value determined by theoretical calculation. See S. Glasstone,

Sourcebook on Atomic Energy

390-393 (2d ed. 1958); H. Semat & J. Albright,

Introduction to Atomic and Nuclear Physics

509-510 (5th ed. 1935); 3 E. Hyde, et al.,

The Nuclear Properties of the Heavy Elements: Fission Phenomena

5 (1971).

If gauged according to everyday human activity, 200 MeV is a small amount of energy, hardly noticeable. Yet at the atomic level, 200 MeV is enormous; even the radioactive decay of powerful «-emitters such as 226Ra or 239Pu barely releases V40 of the energy yielded per event by fission. Normal chemical processes, such as those involved in the combustion of fossil fuels, involve energies per atom on the order of a few eV, not MeV.

See

H. Semat & J. Albright,

supra

at 570.

The phenomenon of uranium fission generated great excitement from the moment of its discovery. Not only was fission a fascinating theoretical novelty once thought to be totally impossible, and not only did each fission of an uranium nucleus release dramatic quantities of energy, but the process offered a key to something much greater: couldn’t the free neutrons released by one fission event be used to trigger two or three others? Scientists imagined a fission

chain reaction

in which each fission event leads to one or two more, ultimately yielding energy in practical,

*282

even explosive quantities. Assume, for example, that a chain reaction could be produced in which each fission of 285U would lead to two more (2:1). See Fig. 4.

[[Image here]]

Figure 4. An expanding chain reaction, in which the number of neutrons doubles with every fission, from 1, 2,4, 8, 16, 32 to trillions. The fission of some nuclei releases 3 neutrons, giving a tripling at each stage, from 1, 3, 9, 27, 81, 243,... to trillions of neutrons. Nuclear processes are so fast that the trillions of neutrons can be generated from one in less than a millionth of a second, giving a nuclear explosion.

From: J. Calvin Giddings,

Chemistry, Man, and Environmental Change

425 (1973) [illustration by Alexis Kelner].

*283

While a single fission instantly yields nearly 180 MeV, or 3.2 X 10~n joules of energy, a chain reaction growing at the 2:1 rate would produce after 40 generations nearly 1.1 X 1012 fission events,

yielding nearly 2 X 1014MeV, or 32 joules — enough power to set a small light bulb aglow for a second or two. After 37 more generations, the total yield approaches 4.3 x 1012J, or roughly the equivalent of 1 kiloton of TNT. Five additional generations would produce a total energy equivalent to 33 kt of TNT.

Cf.

S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons

13 (3d ed. 1977) DX-1242. Assuming a perfect 2:1 chain reaction, an explosive yield of 33 kilotons would require fission of 4.8 x 1024 atoms, or approximately 1,887 grams of 235U — less than five pounds.

This amount is close to the actual mass of fissionable 235U that would be consumed in a device of 33-kt yield. Under normal conditions, however, a 1.8 kg lump of 235U will not be “critical”, i.e., undergo a chain reaction that will result in an explosion. The actual “critical mass” of fissionable metals, whether 236U, 239Pu, 233U or whatever, which will spontaneously produce such a reaction has been estimated to be in the range of 3-30 kg

, depending on a number of factors. In smaller amounts, too many neutrons escape through the surface of the' metal to sustain the reaction. A nuclear fission bomb, therefore, will contain a larger subcritical mass of fissionable material than is actually consumed in the subsequent fission reaction. •

In a weapon, a “critical” or “supercritical” mass of 235U may be achieved in one of two ways: (1) through violently forcing two subcritical quantities of metal together; or (2) by compressing a subcritical mass upon itself to the point that it becomes supercritical.

This second method, the

implosion

technique, is the far more efficient — and far more technically difficult — design.

See also

J. McPhee,

The Curve of Binding Energy

75-95, 108-10 (1974).

The reaction would take place very quickly. Each generation would complete its fission in 0.01

micro

seconds (millionths of a second). An 82-generation chain reaction would take approximately 0.82 microseconds to complete. In fact, fission chain reactions in 235U can proceed more rapidly; on the average, 236U fission releases 2.5 neutrons per event, permitting a chain reaction of greater than the 2X rate. Glasstone reports that one kiloton of TNT equivalence can be reached by the 51st generation.

58 generations would yield roughly 100 kiloton TNT equivalence.

*284

It is seen, therefore, that 99.9 percent of the energy of a 100-kiloton fission explosion is released during the last 7 generations, that is, in a period of roughly 0.07 , microseconds. Clearly most of the fission energy is released in an extremely short time period. The same conclusion is reached for any value of the fission explosion energy.

S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons

¶ 1.57 at 17 (3d ed. 1977), DX-1242. Thus, for a 100-kiloton 235U bomb, the chain reaction starts and ends in 0.58 microseconds, the last 0.08 microseconds of that process determining the gross energy yield of the fission device.

The time-scale of a nuclear chain-reaction explosion is not merely curious atomic trivia. The energy yield in the last 0.1 microsecond of fission is a critical factor determining weapons design, as are considerations such as rate of neutron escape per “generation.” As a fission reaction proceeds, the tremendous release of nuclear energy creates immense heat and pressure; the temperature at the core of the mass of uranium or plutonium reaches millions of degrees Celsius by the 51st fission “generation.”

Intense heat causes intense pressure, forcing the mass apart violently. To achieve maximum explosive yield, the device — by now a superheated mass — must somehow hold together long enough for the next seven or eight generations of fission to take place. Consequently, nuclear weapons designers have worked on ways of encasing the fissionable portion of a device in a “tamper”, a shell of heavy material which by mere inertia

will hold the mass

*285

together for the crucial 0.07-0.08 microseconds. Using tamper material that will also reflect neutrons serves two purposes: (1) containment of the fissionable material long enough to achieve high yield; and (2) increasing the number of free neutrons available for fission by reducing the rate of neutron escape from the reacting mass. Uranium-238, for example, proves useful for this purpose.

The testing of various materials as tampers for neutron reflectors was among the many purposes of the series of open-air detonations at the Nevada Test Site. The value, for example, of beryllium as a neutron reflector might be one of many technical questions answered by a specific test.

.This type of testing has varying impact on the radioactive fallout burden in surround- , ing areas; use of a heavy tamper of 238U leaves far higher quantities of plutonium in the fallout cloud than does the fission process itself. The 238U in the shell, bombarded with neutrons from the chain reaction and vaporized by its heat, is converted in significant part to 239Pu by this reaction:

238 92 U +■ ¿n 239 -TT*. 92 u

239„ 93NP 239 94 Pu

Some unreacted 238U would remain as well. If the neutrons emitted by the bomb’s initial processes are of sufficient energy, 238U will itself undergo fission, adding to the energy of the explosion and to the quantity of highly radioactive fission products in its fallout.

The greater time-scale permitted by use of efficient tamper/reflector material as well as improved design technique is indispensable to another process: the nuclear fusion reaction of a hydrogen bomb.

I. The Hydrogen Bomb

The reality of the fission bomb in turn opened the door to the possibility of a device utilizing the nuclear processes of the sun and stars,

nuclear fusion,

to achieve energy yields in the megaton range.

Rather than splitting heavy atoms, to produce energy, fusion binds the lightest elements together into new atoms. At the core of the sun, temperatures range into the millions of degrees, Celsius. In that heat, the nuclei of hydrogen atoms develop energies greater than 100 kev, permitting a number of reactions to occur:

(1) Jh + Jh---> yH +

+ 1.4 MeV

(2) yH + yH---> yH + J H + 4.03 MeV

(3) yH + *H---> gHe + o11 + 8-27 MeV

(4) yH + yH---> gHe + y + 5 MeV

(5) yH + yH--->

2He

n + 17.6 MeV

(6) yH + 32Ee---> gHe +

H + 18.4 MeV

(7) ®He + ®He---> gHe + 2 Jh + 13 MeV

(8) yH + *H---> gHe + 2 *n + 11.3 MeV

*286

The end result is the conversion of hydrogen to helium with the release of significant energy:

4 Jh-► gHe + 2/3+ +

+ 26.7 MeV

S. Glasstone,

Sourcebook on Atomic Energy

442-443 (2d ed. 1958).

The reactions proceed at widely varying rates; fusion of two ¶ nuclei at the core of the sun, for example, takes between 109 and 1011 years.

Fusion reactions of the heavy isotopes of hydrogen, in contrast, take between 1 and 30 microseconds at a temperature of 20 million degrees Celsius. These reactions were of interest to those who sought to develop the hydrogen bomb. The temperatures in the core of a fission explosion approach those found in the sun and other stars, even if only for a time period of about 1 microsecond. Development of a hydrogen bomb, therefore, required development of a nuclear fission “trigger” that could create temperatures in the 20 million to 200 million degree range and maintain them long enough to initiate nuclear fusion reactions using tritium (,!iH) and deuterium (2H). This in turn would ignite additional deuterium-deuterium reactions, or might utilize the lithium-6 reaction

®Li + Jn--»gHe + Jh + 4.8 MeV

to generate more tritium-deuterium fusion.

At 200 million degrees Celsius a deuterium-tritium mixture will “ignite” in as little as 0.28 microseconds (compared to a reaction time of roughly 4.8 microseconds to ignite deuterium fusion by itself),

see e.g.,

W. Lawrence,

The Hell Bomb

41, 46 (1950), with an energy yield per reaction of 17.6 MeV, compared to 3.2 or 4.0 MeV. See S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons

¶ 1.69 at 21 (3d ed. 1977) DX-1242. Pound for pound, heavy hydrogen will yield 1.5 to 4 times as much energy through fusion than does uranium or plutonium in a fission device. Using a large amount of deuterium fuel, a thermonuclear explosion can produce energy in the range approaching 100 megatons of TNT.

A number of the tests in the 1950’s at the Nevada Test Site were directly related to development of a suitable fission bomb

*287

“trigger” device for producing a hydrogen fusion explosion. Actual tests of fusion-based, or thermonuclear, bombs took place in the United States’ Pacific Test Range in the Marshall Islands, but preliminary work was done on an expedited basis at NTS in reaction to fears concerning rapid weapons development by the U.S.S.R.

See e.g.,

“AEC Test Program,” AEC 388/1 (Dec. 24, 1950, DX-82; “AEC Pre-Greenhouse Test Program,” AEC 388/3 [Ranger Series] (Jan. 5, 1951) DX-83.

Development of the “super”, as the hydrogen bomb was then called, was one goal behind establishment of the NTS; improvement of fission weapons in an atmosphere of national emergency caused by events in Korea was another. See 2 R. Hewlett & F. Duncan,

Atomic Shield: A History of the United States Atomic Energy Commission

535 (1969), DX-1002; Nevada Test Org., “Background information on Nevada Nuclear Tests” (May 1, 1957), PX-245.

III. NUCLEAR FALLOUT

A. Nature of Fallout Radioactivity

The processes of nuclear fission and nuclear fusion release tremendous amounts of energy as predicted by Einstein’s postulate E = me2. Both processes directly produce reaction products, gamma radiation and free neutrons of significant energy. Many of the gamma rays are absorbed by air surrounding the bomb which along with the reactants themselves, generate tremendous amounts of heat. A luminous “fireball” forms around the exploding device within the first second following detonation, glowing at many times the apparent brightness of the sun.

The fireball quickly expands outward as a toroidal (i.e., doughnut-shaped) cloud of superheated material, drawing great amounts of cooler air up into the familiar “mushroom” cloud associated with atomic explosions. See Fig. 5.

*288

[[Image here]]

For those who are exposed directly to the explosion of a fission or thermonuclear device, the heat, the blast, the gamma and neutron radiation pose serious and often lethal risks of injury.

See

Comm, for the Compilation of Materials on Damage Caused by the Atomic Bombs ...,

Hiroshima and Nagasaki: The Physical, Medical, and Social Effects of the Atomic Bombings

105-334 (pap. ed. 1981) [hereinafter cited as

“Hiroshima and Nagasaki"].

The plaintiffs in-this action, however, do not allege direct exposure to atomic blast effects. Instead they are concerned with exposure to the residual radiation present in the smoky ashes of the fireball.

The residual radioactivity of an atomic explosion — the material which becomes “fallout” — is derived from three sources: (1)

fission products,

i.e., the nuclear fragments resulting from the splitting of uranium or plutonium nuclei; (2)

unused nuclear fuel

(esp. plutonium), and (3)

induced activity,

i.e., radionuclides generated by bombarding stable elements in the bomb materials, air, tower metal, soil, seawater, etc. with neutrons. Any detonation of a nuclear device produces residual radioactivity in these three ways. The amount of material contributed by each process, however, varies with the specific qualities of each explosion.

*289

(1)

Fission Products

The direct products of the nuclear fission process are the most important source of fallout radioactivity.

Neither uranium nor plutonium split into standardized fragments; fission results in the formation of more than 200 different isotopes of 36 elements, ranging from zinc (Z = 30) to dysprosium (Z = 66). The most common fission products have mass numbers of 95 and 139; those with mass numbers approximating 117, representing fission into nearly equal halves, comprise 1% or less of the total. Yield of other products grouped in relation to mass number is generally illustrated in Fig. 6.

[[Image here]]

Figure 6. Graph showing yields of fission product chains of ”5U as a function of mass number. [After "Plutonium Project Report on Nuclei Formed in Fission,"

Revs. Modern Phys.,

18, 539,(1946).]

*290

Both uranium and plutonium have a significantly greater number of neutrons than protons, See Table 4.

[[Image here]]

This imbalance is carried on into the fission products, which usually have more neutrons than do the naturally occurring isotopes of the same elements.

Consequently, all but a few of the fission product radionuclides are extremely unstable — and highly radioactive. They seek stability through emission of beta particles, which shifts the nuclear ratio in favor of protons. Many also release excess energy in the form of gamma radiation. Most products must undergo a series of/5-decay transitions before reaching a stable, or nearly stable ratio of particles. The characteristics of each product’s series, called a

decay chain,

is important to a determination of the total yield of fission products.

Consider, for example, the fission product krypton-95: it experiences six /5-decay transitions before reaching a stable nuclide (half-lives are given in parentheses):

[[Image here]]

The n/p ratio of 95Kr is 1.63; the n/p ratio for 95Mo is 1.26, far closer to parity, lending it greater stability. Some decay chains are as long

(e.g.,

90Br or 144Xe); others are notably shorter. A select few fission products are “born” stable, contributing no radioactivity to the fallout clouds

(e.g.,

96Zr, 162Sm, or 86Kr). A fairly complete listing of fission product decay chains is provided in Appendix A of this opinion.

While the existence (or nonexistence) of 95Kr in the fireball of a nuclear explosion or the core of a nuclear reactor is a curious theoretical novelty, it is not by itself very significant. Overall review of the properties of all known fission products, however, disclose important general characteristics of fission product activity:

1. fission products, if radioactive, emit B- particles an average of 3 times before reaching stability;

2. many fission products also emit gamma rays;

3. the half-lives of most fission products and “daughter” nuclides in the decay chains are very short when compared to naturally occuring nuclides such as 238U or even 226Ra; and

4. the chemical and physical properties of fallout will change as radioactive decay proceeds down the chains.

From these generalizations, we may infer that the explosion of a fission device produces an intensely radioactive cloud of fallout which. releases tremendous beta and gamma radiation in the first few hours and which declines at a rapid rate until only the longer-lived radionuclides and stable isotopes remain. These inferences are borne out by the experimental evidence derived from atomic testing.

*291

A “nominal” 20-kiloton fission bomb releases a massive quantity of radioactivity into the environment. Less than two kilograms of fission products yield activity more easily measured in

megacuries

— millions of curies, even if only gamma radiation is considered. See Table 5.

[[Image here]]

Table 5. T represents the elapsed time since detonation of the 20-kt fission device, [source: U.S. Atomic Energy Comm.,

Assuring Public Safety in Continental Weapons Tests

91 n. 6 (1953), PX-740.]

Glasstone and others report that for gamma rays, the fission product radioactivity at

seconds following detonation of a “nominal” 20-kt bomb may be estimated according to the formula:

Ay(in Mci) = 4.1 x l()24(t-i.2) d sec-1 3.7 x 1016 d sec-1

Further, “[t]he rate of emission of beta particles from the fission products is roughly twice that of gamma-ray photons; hence at a time t see. after detonation:”

Ayg(in Mci) = 8.2 x lQ24(t-i-2) d sec-1 3.7 x 1016 d sec-1

S. Glasstone, ed.,

The Effects of Atomic Weapons

¶ 8.11-8.12 at 251 (1950), PX-690/DX-470;

See also

Hamilton, “The Metabolism of the Fission Products and the Heaviest Elements,” 49

Radiobiology

325-43 (1947), PX-640; Dunning, “Criteria for Establishing Short-Term Permissible Ingestion of Fallout Material,” 19(?)

Am.Ind.Hyg.Assoc.J.

111-20 (Apr. 1958), DX-701; Finkel, “Relative Biological Effectiveness of Internal Emitters,” 67

Radiology

665 (Nov. 1956), PX-669; AEC Symposium, “The Shorter-Term Biological Hazards of a Fallout Field,” 147-232 (Dec. 1956) PX-699/DX-641; K.Z. Morgan, “Tolerance Concentrations of Radioactive Substances,” 51(4)

J.Phys. & Colloid Chem.

984-1003 (July 1947), PX-823.

One of the other factors affecting the distribution of radionuclides in various tissues is one wholly independent of either nuclide or organism: in food chains that contain an abundance of stable nutrient elements

{e.g.,

calcium, iodine-127, potassium), absorption of the chemically analogous radionuclides

{e.g.,

strontium-90, the iodine isotopes, cesium-137) is significantly reduced in comparison to ecological systems that are nutrient-poor. See 1 F.W. Whicker & V. Schultz,

Radioecology: Nuclear Energy and the Environment

142 (1982). A person whose diet provides an abundant supply of potassium, for example, will absorb and retain less cesium-137 from contaminated food than will someone whose diet lacks that nutrient. Similar effects are observed in livestock, poultry and fish. Fresh water fish, for example, will retain cesium-137 and strontium-90 in their tissues at a rate 200 times greater than will salt water fish. See

id.

at 143, tbl. 1.

Radioactive isotopes of nutrient elements, or of elements that are chemically similar to nutrients, are far more likely to be absorbed and retained than many of the relatively insoluble metal oxides found in fallout debris. A frequently used method of comparing relative rates of retention is computation of the

biological half-life.

The biological half-life is simply the time period in which one half of a given quantity of absorbed material leaves the body. The rate at which a particular radionuclide leaves tissue varies from organ to organ:

The biological excretion rate of an element from the human body is not necessarily the same for the whole body and for a particular organ. In fact, in most cases, the biological elimination rates are different for different organs and for the body as a whole. For example, the biological half-life of iodine is 138 days for rejection from the thyroid, 7 days for the kidneys, 14 days for the bones, and 138 days for the whole body.

N. Tsoulfanidis,

Measurement and Detection of Radiation

497 (1983).

Before the internal exposure attributed to a particular contaminant may be evaluated, the biological half-life of the nuclide must be adjusted to account for radioactive decay. While iodine-131 has a biological half-life (in the thyroid) of 138 days, its 8-day radioactive half-life determines that an absorbed quantity of iodine-131 will have decayed almost entirely before a meaningful fraction of it is eliminated by the body. The energy released by radioactive decay will largely be diffused along thousands of ionization tracks in the absorbing tissue.

*300

Adjustment of the two half-lives, radioactive and biological, yields an

effective half-life

of 7.6 days.

The radioactive, biological and effective half-lives for several common radionuclides are listed in Table 8.

[[Image here]]

*301

N. Tsoulfanidis,

Measurement and Detection of Radiation

498 (1983).

If the radioactive and biological half-lives are known, the effective half-life may be calculated according to the formula:

Te = (Tr)(Tb) Tb '+ Tr

where Te is the effective half-life, Tr the radioactive half-life and Tb the biological half-life. J. Gofman,

Radiation and Human Health

422-24 (1981), PX-1046.

Computation of the total radiation exposure or dose rate from the effective half-life of a specific radionuclide requires more than simple mathematics:

As a result of the combined radioactive and biological elimination of a radioisotope from the whole body or from an organ, the dose rate to the body or the organ is not constant over time. Consider an amount of a certain radioisotope that delivers a dose rate equal to DE(O) at the time of ingestion. If the effective half-life of the isotope is Te, the total dose delivered to the body, or the organ, over a period of time T is

DEr =

DEO^T^*

= (1 -

e~^T)

= (-£)]

If the time period T [is much greater than] Te, then

DEtot + DE(O)Te —rñz

N. Tsoulfanidis,

Measurement and Detection of Radiation

497-499 (1983). Crucial to the whole calculation is the use of accurate information concerning the quantity of radionuclide ingested; the formula is useless if DE(O) is unknown. How much fallout debris one ingests and absorbs is a product of all of the variables previously discussed. Plainly, accurate estimation of internal radiation exposure is not a simple process.

Exposure to fallout debris involves all of these variables,

and the sum of these calculations for not one, but

dozens

of biologically significant radionuclides.

See e.g.,

Y. Ng et al., “Prediction of the Maximum Dosage to Man from the Fallout of Nuclear Devices — IV. Handbook for Estimating the Maximum Internal Dose from Radionuclides Released to the Biosphere,” LLRL (May 1968), PX-720.

The complexity of the problem yields a great temptation for everyone to generalize. Abstract computations derived from hypothetical models are far easier than painstaking calculations based upon exacting observation and analysis. It is far easier to project a hypothetical dose of radiation received worldwide from an evenly distributed and known quantity of one radionuclide than it is to calculate in 1984 the total dose, that Sally Jones or Timmy Smith received by 1962 from eating unknown quantities of food or milk from unknown sources contaminated with unknown yet

real

quantities of fallout radioactivity of largely unknown composition. Consequently, hypothetical (especially worldwide) projections are common in the literature; analyses of specific persons or particular small communities are rare.

The record in this case is replete with examples of analysis based upon worldwide or nationwide projections. More localized studies are far fewer in number. Of the group concerning the Nevada/Utah/Arizona area, several were undertaken only after the commencement of this lawsuit. A

*302

common characteristic of each study, however, is the presence of at least one hypothetically derived generalization about phenomena which are incurably variable — -and unpredictable at least to some extent.

How much fallout radioactivity follows the complex network of environmental and biological pathways to reach man is determined in the first instance not by the dynamics of the pathways but by the initial amount of the fallout debris that is deposited at a particular place in time. This initial distribution pattern is itself a product of important and often unpredictable variables. In the standard handbook on the subject — published in 1950, a year

before

Nevada testing began — the authors observed:

With regard to the internal radiation hazard, it is not possible to make any sound estimate of the amount of material which is likely to be ingested in various circumstances. A person working under normal indoor conditions, for example, would absorb much less than one engaged in an occupation in which there was much dust. Children, because of their habits and closeness to the ground, would be expected to ingest more than adults. These factors would greatly complicate a rehabilitation program, and make it almost impossible to attempt to assess universal permissible contamination levels.

J. Hirschfelder, S. Glasstone, et al.,

The Effects of Atomic Weapons

¶ 12.74 at 396 (1950), PX-690/DX-470.

C. Factors Affecting Fallout Distribution

The fallout yield of a nuclear explosion is predictable with some degree of accuracy, so long as certain information about the device is known. How airborne fallout is ultimately dispersed in the environment, however, is far less amenable to abstract calculation. ' Fallout distribution is influenced by a series of variables which seemingly multiply without end. Yet fallout dispersal has been the subject of repeated generalization at the theoretical level. Monitoring techniques have assumed and relied upon the soundness of various dispersal models. The validity of many radiation exposure and dosage estimates in turn has depended in large part on the accuracy of those monitoring techniques.

From the moment of detonation, radioactive material is dispersed unevenly; while the head of the mushroom cloud contains 90% of the fallout activity, distribution within the cloud is anything but uniform. As the cloud expands, large fallout particles begin falling to the surface, while winds propel smaller particles of radioactive dust away from the site of the explosion. Hot gases diffuse quickly into the surrounding air, blending with the environment in the eddies of numberless air currents.

Weather has a dominant influence on how and where a fallout cloud is dispersed. Important variables include the altitude to which the cloud rises and the wind speed and direction at the higher altitudes through which the cloud may rise. The degree of wind shear, i.e., a change in wind direction at different altitudes, can materially affect the dispersal of the cloud, yielding a wider, shorter spread of particles than would be observed if no wind shear was present. Precipitation may dramatically alter the rate at which fallout particles fall to the surface; if the fallout cloud enters a storm cloud system, a “rainout” could bring 90+% of the fallout debris to the surface in one hour. See S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons ¶

¶ 9.57-9.74 (3d ed. 1977), DX-1242.

During much of the era of atmospheric nuclear testing, considerable attention was paid to the analysis of fallout distribution patterns, using data gathered by teams of fallout monitors on the ground, by aircraft which pursued fallout clouds in flight and

*303

by automatic sampling and recording instruments placed at selected locations across the country. The empirical data gathered through monitoring

describes

(at least to some extent) the fallout process. Scientists quickly developed several varieties of mathematical models of fallout in an effort to

explain

and to

predict

the patterns in which nuclear residues would be deposited.

As carefully constructed as the models have been, however, they admittedly offer only general guidance as to what the actual fallout distribution from a given detonation will be. That guidance is to be handled with caution:

Idealized fallout contour patterns have been developed which represent the average fallout field for a given yield and wind condition.

No attempt is made to indicate irregularities which will undoubtedly occur in a real fallout pattern

because the conditions determining such irregularities are highly variable and uncertain____

S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons

¶ 9.83 at 423 (3d ed. 1977), DX-1242 (emphasis added). The uncertainty factor can be considerable. Consider, for example, the Rand Corporation’s “Project Sunshine” report in 1953: by collecting samples of dust on sticky gummed paper at 92 monitoring stations in the United States and 15 more outside the country, the project sought to estimate the distribution of fallout radioactivity — particularly strontium-90 — produced by the “TUMBLER/SNAPPER” test series in Nevada (April to June 1952). The Report notes that

It would appear that unless the efficiency of collection of the gummed paper was as low as 10 to 15 per cent, 80 per cent or more of the Tumbler/Snapper activity remained suspended in the atmosphere for periods after June 18, 1952,

or that large quantities of activity fell in areas not sampled.

Report on “Project Sunshine",

at 30 (Aug. 6, 1953), PX-1027/DX-743 (emphasis added). In other words, nearly two weeks after the last TUMBLER/SNAPPER explosion (June 5, 1952) the monitoring system could not account for 80 + % of the beta-emitting fallout debris from that series. Perhaps as the report suggests, it was still airborne. Perhaps not. One thing is certain: the TUMBLER/SNAPPER fallout went

somewhere.

Fallout studies conducted during the BUSTER/JANGLE series conducted earlier that year (1952) described considerable difference in fallout distribution:

Variations in the measured concentrations [on] the ground were large and frequent, and in many cases could not be adequately explained. Consequently, the exact meaning of the results of the surface monitoring program is not known. Research should be undertaken to determine what specific meteorological and other factors cause these variations.

“Transport of Radioactive Debris from Operations Buster and Jangle,” WT-308 (EX), PX-739/DX-133, at 112.

*304

Even the fraction of the fallout collected at the sampling stations used for TUMBLER/SNAPPER, or the forty-four U.S. and forty-nine world wide stations used to monitor fallout from Operation Ivy, a Pacific test program, showed tremendous variation:

However, as we have seen from the Tumbler/Snapper and Ivy fallout measurements, the fallout from individual explosions

varies by a factor of200, either way,

from the average for stations outside the test sites. Consequently we can expect that even if all the Sr90 from the A-bomb explosions has fallen out, the concentration of Sr90 will vary over the earth’s surface within this factor.

Because of this possible extreme variation of

Nr90

deposition

— localized

but long-range

— St60

contamination may well be the most important aspect of the Sunshine project.

Id.

at 34, PX-1027/DX-743 (emphasis in original). The report further observes that the observed range of strontium-90 concentrations in the environment was burdened “with a large measure of uncertainty.”

Id.

Some error in gummed paper monitoring may have resulted from the assay procedures used by the AEC. At the agency’s New York laboratory, the beta “activity of each sample is counted for 20 minutes or 640 counts whichever comes first.” Atomic Energy Comm’n,

Assuring Public Safety in Continental Weapons Tests

106-107 (1953) PX-740; no sample, it seems, was permitted to be “hotter” than 640 counts. Additionally, before counting, the samples of gummed paper or filter paper were “dry ashed in an electric furnace”,

id.,

at temperatures high enough to drive away isotopes of iodine, an important fission product, and possibly other “volatile” products as well.

Finally, it is interesting to note that beta-emitting fallout levels in Utah — immediately downwind from the NTS — were monitored by

one

sampling station in Salt Lake City, while Colorado had six such stations, Montana seven, New York nine, and California ten. See Fig. 8.

*305

[[Image here]]

The model of fallout distribution that justifies placement of eight monitoring stations in western New York while leaving much of Utah, Nevada and northern Arizona vacant is not described. Perhaps the NTS monitoring network was deemed adequate for communities surrounding the NTS. The 1953 Sunshine Project Report does indicate, however, that the highest peak and average beta measurements following TUMBLER/SNAPPER were recorded in Nevada, Utah and Idaho (two monitoring stations). Project Sunshine, PX-1027/DX-743, at 28.

As a rule, NTS monitors counted only

gamma

radiation at off site locations in Nevada and Utah, ignoring the beta count altogether.

See

Part VIII,

infra.

Those who undertook the actual monitoring of real nuclear fallout in the early 1950s soon rediscovered something not predicted — or predictable — in the idealized mathematical models: the existence of “hot spots,” or small areas of noticeably higher fallout deposition in the same general geographic areas. A “hot spot” might display two or three — or even 2 or 3 thousand— times the radioactivity found in neighboring terrain.

Hot-spots have appeared in curious places. Perhaps the most noticed example was the hot-spot discovered near Troy, New York, following a rainstorm in 1953. Following the storm, Geiger counter readings ranged from 5 milliRoentgens per hour downtown to localized hot-spots reading as high as 120 milliRoentgens per hour. See

e.g.

Clark, “The Occurrence of an Unusually High-level Radioactive Rainout in the Area of Troy, N.Y.,” 119

Science

619 (1954). The Troy hot-spot developed 36 hours after a detonation in Nevada more than 2,000 miles away.

On a number of occasions, monitors working on and off the Nevada Test Site

*306

detected many localized points of higher fallout deposition which differed by a factor of 2 or 3 — or much more — in fallout activity compared to readings taken a few feet away.

Other factors complicate the fallout distribution picture even further. Once on the ground, fallout particles may be resuspended and redistributed by wind and weather, or by human activities, such as farming or ranching. Rain may wash settled particles into streams and ponds. The contour and vegetation of the landscape plays a significant role in shaping the ultimate patterns of fallout deposition. Even the size of the fallout particles themselves can have a significant effect on when and where fallout is deposited:

Because particles of different sizes descend at different rates and carry different amounts of radioactive contamination, the fallout pattern will depend markedly on the size distribution of the particles in the cloud after condensation has occurred. In general, larger particles fall more rapidly and carry more activity, so that a high proportion of such particles will lead to greater contamination near ground zero, and less at greater distances, than would be the case if small particles predominated.

S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons, supra,

¶ 9.62 at 415. Very tiny particles may remain suspended in air for a long period, irradiating persons and objects as they pass by, but without leaving substantial fallout deposited on the ground. Each time that a nuclear device is detonated in the atmosphere, or its residues are permitted to enter the atmosphere

{e.g.,

venting from an underground test), every one of these variables interact in varying degrees to determine where the fission products, unspent uranium or plutonium and induced activity products will finally come to rest.

D. Factors Affecting Total Exposure to Fallout Radiation

The most significant single factor determining the extent of radiation exposure from nuclear fallout is

time.

As noted above, the fission and induced activity products of a nuclear explosion are often very unstable and decay very rapidly. Theoretical estimates by Glasstone and others predicted an overall decay rate expressed as t-1-2, where t represents the time elapsed since detonation. S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons, supra,

¶¶ 9.146-9.153 at 450-52. Actual measurements following some of the Nevada tests indicated that the decay rate in the short period immediately following the explosion was even higher

{e.g.,

t~L3 or tr1-4). A large portion of the radiation emitted by fallout materials will thus be spent in the first hours and days following the detonation. While some fallout components such as plutonium, cesium-137, strontium-90, and iodine-129 will persist in the environment for many years following a test, most of the 200 or more radionuclides decay and disappear far more quickly.

While the high rate of decay of fallout materials materially reduces the risk of exposure over a long period, it also indicates that contact with fallout in the first minutes or hours following detonation can easily result in serious radiation exposures.

Besides the mere passage of time, other factors operate to reduce, or attenuate the degree of radiation exposure experienced from fallout. From an external exposure standpoint, distance from radioactive materials reduces the effective dose, particularly from alpha and beta radiation. The highly ionizing quality of alpha radiation allows it only a short range in air before, the particle energies are spent, perhaps a distance of a few centimeters, or an inch or two. Beta particles, as low-LET radiation, can travel greater distances by virtue of their weaker ionizing qualities; “[m]any of the beta particles emitted by the fission products traverse a total distance of 10 feet (or more) in the air before they are absorbed. However, because the particles are continually deflected by electrons and nuclei of the medium, they follow a tortuous path, and so their effective (or net)

*307

range is somewhat less.” S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons, supra,

¶ 9.115 at 440. More dense materials,

e.g.,

water, wood, glass, paper, and brick, experience far greater ionization along the particle tracks, which consequently are much shorter, perhaps one-thousandth of the range observed in air. See

id.,

¶ 9.116.

Where, however, the material exposed is living tissue, either through deposit of particles on the skin or inhalation or ingestion of fallout materials into the body, alpha and beta radiations can pose a serious risk of acute and long-term injury. Clearly, radiation exposure from fallout can be materially reduced simply through physical processes, i.e., removal of fallout particles from skin, clothing, hair and immediate surroundings by thorough washing, use of face masks around contaminated dust to avoid inhalation, and careful handling of food and water to avoid or minimize contamination by radioactive materials.

Gamma radiation ionizes far fewer air molecules as it passes through, permitting it a far greater range in air than the charged-particle radiations. As described previously, gamma radiation is a form of electromagnetic radiation similar in its physical qualities to visible light, radio waves, and ultraviolet rays. The far greater energy of gamma radiation permits it to penetrate and pass through dense materials with a range considerably greater than either alpha or beta particles. Clothing stops alpha particles and most beta particles, but is poor shielding against gamma rays, many of which will pass through both fabric and wearer relatively unimpeded. More substantial materials, such as building materials or soil, can significantly reduce or attenuate gamma radiation exposures when placed between the source and the person at risk. Table 9 lists the relative fraction of gamma exposure experienced by a person within a protective structure contrasted with one standing unprotected in a fallout field.

[[Image here]]

S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons, supra,

table 9.120 at 441. In terms of alpha, beta and gamma radiation, the potential exposure that may be experienced during a radioactive fallout event can be materially reduced simply by

*308

staying indoors (assuming the contamination is kept outdoors) until the exposure hazard has abated. Washing of fallout materials into the soil, either by rainfall or deliberate effort, will further attenuate the rate of gamma exposure, as does turning under the soil itself when the surface is contaminated with fallout. The shielding effect of buildings and dwellings is augmented simply by washing down the roof and large wall surfaces, reducing the effect of being geometrically surrounded by radiation sources. See

id.,

¶¶ 9.14-9.20 at 439-441.

Fallout material which has been washed into soil, or has been deposited at a distance, or behind surface features or structures — embankments, walls, or other solid obstructions — presents far less exposure hazard than radioactive residue in close proximity or direct contact with the persons involved.

Weathering, shielding, time, and distance all have some impact which lessens the dose of radiation actually absorbed by people in a potentially hazardous fallout situation, or other instance of radioactive contamination. These factors may in some cases reduce actual exposure to one-half or less of the potential dose rates that may arise in a given situation. However, whether one gains the full benefit of the gamma-shielding effects of housing materials, for example, depends heavily upon human factors. It depends in part upon knowing or being effectively warned to seek shelter indoors when fallout materials may be precipitating outdoors.

Internal exposure arising from ingestion, absorption or inhalation of radioactive fallout materials presents some different problems governed by additional variables. The complex pathways by which radioactive materials make their way into biological and environmental systems have already been mentioned in this Part. See also, F.W. Whicker & V. Schultz,

Radioecology: Nuclear Energy and the Environment

(1982) (2 vols.). Where nuclear contamination is present, great care must be taken to avoid inhaling or consuming fallout materials in food and water. Once ingested or inhaled, the degree of exposure actually experienced depends upon the highly variable physical and chemical qualities of each individual radionuclide. Many fallout contaminants inhaled or ingested as dust are in the form of relatively insoluble metal oxides. These may pass quickly through the body, radiating tissues as they pass by, but not persisting in any of them for extended lengths of time. Others, whose solubility is greater and which may have chemical properties similar or identical to important nutrients, can quickly find their way into sensitive human tissue. As noted above, the radioactive isotopes of iodine quickly migrate to thyroid gland tissues; strontium and barium isotopes find their way to important bone tissue. Once absorbed, the fallout radionuclides diminish in accordance with a combination of radioactive and biological half-lives. See Part III (B),

supra.

Some contaminants, such as plutonium with its effective half-life in the bones of 400 years, become practically permanent sources of ionizing radiation within the body itself. See

e.g.,

Tr. at 2791 (testimony of Dr. Karl Z. Morgan).

The different ecological characteristics of several important radionuclides are listed in Table 10.

*309

Table 10,

[[Image here]]

*310

[[Image here]]

*311

1 F.W. Whicker

V. Schultz,

Radioecology: Nuclear Energy & the Environment

163-166 (1982) (table). The list is not exhaustive; the complex processes of the nuclear fission furnace produce 200 other nuclides, each having distinct chemical, physical or radioactivity properties. See Appendix A,

infra.

Combined with unspent fuel and neutron-activated radionuclides,

The fission products can produce injury either as an external source of radiation or, if they gain entry into the body, by acting as an internal radioactive poison, quite analogous to radium poisoning. This latter consideration is a major concern, since the amounts required within the body to produce injurious effects are minute compared to the quantities necessary to induce damage by external beta and gamma irradiation.

Hamilton, “The Metabolism of the Fission Products and the Heaviest Elements,” 49 Radiobiology 325 (1947), PX-640. Prediction of internal exposure from such varied toxins becomes an exceedingly complex task, for it is apparent that “no radionuclide that is produced should be ignored until a critical analysis demonstrates that it is insignificant.” Y. Ng, et al.,

Prediction of the Maximum Dosage to Man From the Fallout Nuclear Devices: —IV. Handbook for Estimating the Maximum Internal Dose from Radionuclides Released to the Biosphere,

Lawrence Radiation Laboratory, UCRL-50163 Part IV (1968), PX-720, at v. [hereinafter cited as “LLRL Handbook for Estimating Maximum Internal Dose”]. While many fission products decay and nearly vanish before making their way into the food chain, others persist with tremendously variable effect upon the degree of internal radiation exposure received.

Even where metabolic or ecological variables can be ignored, as in estimation of externa] alpha, beta, and gamma dose from exposure to fallout debris, the calculations are not simple. See

e.g.,

Broido & Teresi, “Analysis of the Hazards Associated With Radioactive Fallout Material (I) — Estimation of ƴ- and ß- Doses,” 5

Health Physics

63-69 (1961), PX-563.

Clearly, where exposure to radioactive fallout is concerned, the complexity and the variability of the multitude of factors makes careful and comprehensive monitoring and measurement a genuine necessity, if external and internal doses are to be accurately evaluated. Assessment of the risks posed by the infiltration of nuclear debris into the daily life of off-site residents in communities in Utah, Nevada and Arizona is a demanding task at best. Where the available data generated from actual measurements of fallout activity and contamination is grossly inadequate and incomplete, the difficulty of the task is compounded a thousand-fold. See Parts VIII, IX,

infra.

IV. BACKGROUND: BASIC PRINCIPLES OF HEALTH PHYSICS

A. Units Used in Radiation Dosimetry

The testimony and exhibits in the record as well as the scientific literature concerning radiation and health make use of a variety of units to express or describe the amounts of radiation people are exposed to or have absorbed into their tissues. In evaluating information and analysis of radiation hazards, it is useful to identify the specific units being used and the concept and quantity that each unit expresses.

Radiation-induced damage to biological tissue results from the absorption of energy in or around the tissue. The amount of energy absorbed in a given volume of tissue is related to the type, energy, and number of radiations traversing the tissue volume, and the interactions which occur between the radiations and the atoms and molecules of the tissue.

1 F.W. Whicker & V. Schultz,

Radioecology: Nuclear Energy and the Environment

63 (1982).

(1.)

Rad

The most commonly used unit to describe radiation

dose,

that is, the actual amount of ionizing radiation absorbed by living tissue, is the

rad.

Measurement of radiation dose

*312

in rads is accomplished by dividing the total radiation energy delivered by the mass (in grams) of the tissue which absorbs it. A rad expresses an energy/mass ratio:

Historically, the

erg

has been used to describe energy delivered by ionizing radiation. If 100 ergs of energy are deposited in 1 gram of tissue, the tissue is said to have received 1

rad

of radiation____

The definition of the rad says nothing about the

time

it takes to deliver 100 ergs per gram of tissue. In some cases good reason exists to be concerned about the

rate

of delivery of radiation, and in these cases we would express radiation doses in terms of rads per minute, rads per hour, or rads per year. For many purposes we shall be concerned with total rads delivered, and not with their rate of delivery.

J. Gofman,

Radiation and Human Health

46 (1981), PX-1046 (emphasis in original).

Like other units discussed so far, the rad may be more conveniently expressed in fractional form:

milli

rad (mr) = 0.001 rads (or 10-3 rads)

micro

rad (fir) = 0.000001 rads (or 10~6 rads)

Larger multiple units, such as

kilo

rad (1,000 rads) have little application to measurement of doses to specific individuals; absorbed in a short time, such a dose would likely be fatal. See S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons

577 (3d ed. 1977), DX-1242. Recently, however, more use has been made of a unit from the international system of units, the

Gray.

A Gray (Gy) represents the absorption of 1 joule (107 ergs) of energy in 1 kilogram (1,000 grams) of tissue. Simple calculation disclosed that 1 Gray represents 104 ergs per gram of tissue, or a dose equalling 100

rads.

J. Gofman,

Radiation & Human Health, supra,

at 46. A dose of one rad would equal 0.01 Gray. 50 millirads would equate to 0.0005 Gray.

Except for a few recent scientific publications, the testimony and exhibits in this case speak in terms of rads rather than Grays, as will the text of this opinion.

Radiation dose expressed in rads can be related to radioactivity expressed in curies through simple mathematical calculation. Assuming that all of the energy released by the beta decay of 1

picocurie

(pCi) of radioactive material evenly dispersed in 1 kilogram of tissue is actually absorbed in that tissue, the dose

rate

to that tissue, expressed in rads per hour, would equal:

Dose rate (rads/hr) = (2.134 x 10~9) x (average decay energy [MeV])

See id.

PX-1046, at 418-19. The total dose received to the kilogram of tissue (e.g., the lungs of an adult person), may be calculated using an equation previously discussed:

Total Dose (rads) = (dose rate/0.693) x (Te) X (k)

where Te is the effective half-life of a specific radionuclide,

see e.g.

Table 8,

supra,

and k is a mathematical term which converts Te into hours. See N. Tsoulfanidis,

Measurement and Detection of Radiation

499 (1983).

For example, 1 pCi of iodine-131, with an average decay energy approximating 0.6 MeV, would deliver ionizing radiation in the form of beta particles at the rate of 1.28 X 10~9 rads per hour, for a total dose of nearly 3.37 x 10-7 rads, or 0.33

micro

rads, based upon an effective half-life of 7.6 days. This is a very small dose of beta radiation. The picocuries can add up, however, as illustrated by an example:

By drinking milk contaminated with radioactive fallout debris, a child absorbs 20,000 PCi of iodine-131 into the tissue of her thyroid gland. The thyroid gland of a child is far smaller than a kilogram, weighing in the neighborhood of 2-4

grams.

Rather than being distributed

*313

throughout a full 1,000 grams of living tissue, the energy is concentrated in far fewer radiosensitive cells. Correcting our calculation for the differences in contamination and tissue mass, we find:

(2.134 x IO-9) (0.6) (20,000) (1000/4) x (7.6 days) (24 hr/day) 0.693 = 1.68 rads to the child’s thyroid gland from

From a quart or so of contaminated milk, our example child could receive a radiation dose to a sensitive organ significantly higher than “background” levels due to the presence of a single fission product.

Besides iodine-131, nuclear fission produces various quantities of 11 other radioactive iodine isotopes, with half-lives ranging from a few seconds (e.g., 5.9 sec. 138I) to 16 million years (129I). National Council on Radiation Protection and Measurements,

Protection of the Thyroid Gland in the Event of Releases of Radioiodine,

NCRP Rep. No. 55 (1977), DX-1179, at 13-14, 15 (table); see Appendix A.

The example calculation is far from totally abstract. One study of milk sampled from Utah dairies shortly after the 100-ki-loton SEDAN test at the Nevada Test Site in 1962 estimated the concentration of 131I to vary between 0 and 800,000 pCi per litre (1.05 quarts). Pendleton, et al., “Differential Accumulation of 131I From Local Fallout in People and Milk,” 9

Health Physics

1253, 1255 (1963), PX-32. Further, it was estimated as a result of an accident involving the Windscale nuclear reactor in the United Kingdom in October 1957, 20,000 curies of 131I was released into the atmosphere:

Sufficient pasture contamination occurred to require the confiscation of milk for several days in a 200-square-mile area downwind of the reactor____ The milk produced in a much smaller area remained contaminated above the confiscation level chosen by the British for more than a month. As a result of this confiscation and other precautionary procedures, the mean absorbed dose to the thyroid glands of children downwind of the Windscale reactor was estimated to be 16 rad, and the mean adult absorbed dose was estimated to be 4.0 rad.

NCRP Report No. 55 (1977),

supra,

DX-1179, at 14 (citations omitted). While radioactive fallout debris from Nevada was dispersed over a much wider area than was contamination at Windscale, a “nominal” 20-kiloton fission device yields 250,000 curies of 131I, representing between 2.9 and 3.1 percent of the total fission products.

Id.

DX-1179, at 14 (table); 1 F.W. Whicker & V. Schultz,

Radioecology: Nuclear Energy and the Environment

92, 107 (tables) (1982).

The calculation performed above demonstrates that

rads

of radiation dose to internal organs may arise from p/cocuries of contamination. 250,000 curies (Ci) of 131I is equivalent to 2.5 X 1017, or 250,000,000,-000,000,000 picocuries (pCi) of 131I — still barely 3% of the total fission product yield.

At the very least, one can say that where fallout is concerned, a lot can go a very long way.

Estimation of radiation dose from external sources, particularly multiple sources of gamma radiation, requires far more complex calculations.

See e.g.,

H. Cember,

Introduction to Health Physics

ch. 6 (1969); AEC Symposium, “The Shorter-Term Biological Hazards of a Fallout Field,” at 23-84 (1956), PX-699/DX-641; Broido & Teresi, “Analysis of the Hazards Associated with Radioactive Fallout Material (I) — Estimation of ƴ- and

ß-

Doses,” 5

Health Physics

63-69 (1961), PX-563.

Radiations of external origin that may be absorbed in living tissues include nat

*314

ural or man-generated rays from the atmosphere, earth, water, and other tissues or organisms. The type of external exposure that is probably the simplest to evaluate is that resulting from a “point source” of photons. Photon emitters have a gamma ray exposure constant, termed I , which has the units of roentgen per hour per curie at an air distance of 1 m. The value of I , may be calculated for any gamma-emitting radionuclide and it is dependent upon the number of photons emitted per disintegration and the energies of the photons. Values of I are, for example, 0.33 and 1.32 R/hr/Ci for .187Cs and 60 Co, respectively..:. The exposure rate (E) in roentgen per hour at any distance (d) in meters can be calculated for a point source containing A* curies by

E = IY A*

Nonpoint sources and causes in which several gamma emitters are more, difficult to evaluate. The case in which the radionuclide is distributed within a mass of substance is even more difficult to evaluate because of absorption and scattering of photons prior to their exit from the substance.

If such complexities are great enough, direct measurement of exposure rate may be necessary.

1 F.W. Whicker & V. Schultz,

Radioecology ..., supra,

66-7 (emphasis added and footnotes omitted).

See also

Radiological Health Handbook, PHS Publ. 2016 (1970); K. Morgan & J. Turner, eds.,

Principles of Radiation Protection

(1967). The tremendous variability of potential gamma and beta radiation exposures from nuclear fallout renders accurate and thorough

measurement

of radiation intensity an unavoidable necessity.

See

H. Knapp, “Gamma Ray Exposure Dose to Non-Urban Populations from the Surface Deposition of Nuclear Test Fallout,” T10-16457 (July 1962), PX-717.

(2.)

Roentgen

The complexity of dose calculation involving gamma exposure often makes actual measurement of radiation in rad units impractical.

Frequently, it is not convenient to measure dose in rads. In the particular case of irradiation of organisms or tissues from an external X- or gamma ray source, it is more convenient to measure the radiation exposure at the surface of the tissue of interest using an appropriate instrument or device.. The dose to the tissues can be estimated from the measured exposure from theoretical considerations. The fundamental unit of radiation exposure which is applicable only to X- or gamma radiation, is the

roentgen

(R), which is defined as

1 R = 2.58 x 10"4 coul/kg air

This definition of the roentgen is equivalent to the production by X- or gamma rays of 1 electrostatic unit of charge of either sign per cubic centimeter of dry air at 0° C and 760 mm mercury. The roentgen quantity is defined on the basis of production of ionization in air because it is normally measured with an air-filled ionization chamber.

1 F.W. Whicker & V. Schultz,

Radioecology ..., supra,

at 63 (emphasis added and footnote omitted). Simply expressed, the roentgen unit describes a certain degree of ionization caused in air by gamma rays. In the process of ionization, of course, some gamma energy is absorbed by the air, approximately 88 ergs per gram, or 0.88 rad. N. Tsoulfanidis,

Measurement and Detection of Radiation

485 (1983). The greater density of living tissue results in greater absorption of the same amount of gamma radiation; a roentgen of gamma radiation in air equates with approximately 94 ergs absorbed per gram of tissue, i.e., 0.94 rads at the surface. Gamma rays with energies ranging from 0.3 MeV to 3.0 MeV permit a rough equivalence between 1 roentgen (R) of exposure and 1 rad (r) of absorbed dose in soft tissues. See S. Glasstone & P. Dolan,

The Effects of Nuclear Weapons

¶ 8.18 at 329-30 & n. 4, 638 (3d ed. 1977), DX-1242.

*315

(3.)

rem

In strict terms, a

rem

of ionizing radiation, or

roentgen equivalent man,

describes “[t]hat amount of ionizing radiation of any type which produces the same damage to man as 1 roentgen of about 200-kv X radiation____”

Handbook of Chemistry & Physics,

at F-103 (64th ed. Weast 1983). The rem describes a quality of ionizing radiation not encompassed by either of the first two units: neither rad nor roentgen say anything about the penetrating qualities of particular radiation or differentiate between high-LET and low-LET radiation.

We know that the linear energy transfer (LET) is much higher for some radiations than for others. For those biological effects where LET matters, the rad unit must be modified to a unit that shows the greater effectiveness of one kind of radiation over another. A term has been introduced, the

relative biological effectiveness,

RBE,

to express this difference is effectiveness.

J. Gofman,

Radiation and Human Health, supra,

PX-1046, at 47. Defined in terms of a dose of gamma radiation producing a certain biological effect,

e.g.,

chromosome lesions, cell-killing, etc., a rem represents the proportionate amount of other ionizing radiation that will produce the same biological effect, i.e., the same number of chromosome lesions, dead cells, etc. The specific proportion of one to the other, the RBE, varies according to type and energy of radiation, the type of cell exposed, the biological effect being studied, the total radiation dose, the dose rate, and other factors. N. Tsoulfanidis,

supra,

at 486. The same kind of radiation may have many RBE ratios.

As a general rule, biological damage increases as the amount of energy deposited per unit of distance traveled, the linear energy transfer (LET), increases. High-LET radiation, such as alpha particles, neutrons and fission fragments are often significantly more damaging than low-LET radiation, such as gamma ray photons, beta particles, and positrons, which have far less mass, and travel far greater distances, leaving less ionization in their wake.

Id.

J. Gofman,

supra,

at 26-29. In modern health physics, the concept of

quality factor,

or Q, is used to describe distinctions between radiations based upon linear energy transfer values. N. Tsoulfanidis,

supra,

at 486-87. While low-LET radiations may have a “Q” of 1, 5-MeV alpha particles may have a “Q” of 10 or even 20.

Id.

Whether expressed in terms of Q or RBE, the relative effects of different radiations is critical to accurate calculation of biological risk associated with radiation exposure. Once more, an example is instructive:

A cattle rancher inhales a particle of fallout debris containing 1 pCi of radioactivity due to plutonium-239, an alpha emitter with a decay energy approximating 5 MeV. The particle becomes trapped in lung tissue.

The alpha particles having a range in tissue of approx. 40¡um, the amount of energy delivered to the surrounding lung cells per hour may be calculated as follows:

(3.7 x IQ'2 /s/p Ci) (5 MeV) (1.602xlQ-13J/MeV) (3.6xl05) (4/3) (4.0 x 10-5) 3 (103kg/m8)

an amount equal to 39.7 rads/hour of radiation to the surrounding tissue, probably less than a microgram of epithelial cells in the bronchial tubes.

See

N. Tsoulfanidis,

supra,

at 490-91; J. Gofman,

supra,

at 484.

For many biological injuries, however, alpha particles of MeV range energy are

*316

assigned an RBE, or Q, of 10. Multiplying the absorbed dose by this factor yields a dose rate in

rems

per hour: (39.7 rads/hour) X RBE (10) = 397 rems/hour

Thus the 3,970 ergs/gram of alpha energy bombarding the few cells nearest to the fallout particle has the biological effectiveness of 39,700 ergs/gram of low-LET beta or gamma radiation delivered to the same tissue. Ionizing radiation delivered at that rate to those cells likely would kill or seriously damage almost all of them. Fortunately, they represent an extremely tiny fraction of total lung tissue. Inhalation and retention of many more particles, however, could do far more damage to the bronchial linings.

Once the task of evaluating a particular exposure to radiation in terms of its relative biological effectiveness has been accomplished, the expression of dose in rem units is easily transferred or compared with other dose estimates expressed in rems. The risk arising from exposure to various radiations — alpha, beta, gamma or neutrons, among others, may be standardized and directly compared. A dose expressed in rems identifies a certain quantum of biological effect, regardless of source.

In much of the literature, testimony and documentary evidence now before this court, however, doses of low-LET radiation expressed in rads are treated as equivalent to doses expressed in rems. Only as to alpha radiation is a distinction usually made. See Table 11.

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1 F.W. Whicker & V. Shultz,

supra

at 66.

To be fully effective, analysis of data and measurements concerning exposure of human beings to ionizing radiation must be made with particular reference to the units in which the information is expressed. Whatever unit is used, be it rad, roentgen, rem, or some fractional or multiple variant of these units, it describes the exposure to ionizing radiation or absorption of its tremendous energies by living tissue.

See also Radiation Quantities and Units,

ICRU Rep. No. 19 (July 1971), DX-1105.

B. Radiation Energy: Quantity vs. Quality

So far this discussion has dealt with the units of radiation measurement in terms of each other, and other measurements of radioactivity, such as the curie, or the concept of half-life. It is important, however, to make at least a general comparison between the kinds and quantities of energy infused into biological systems by ionizing radiation and those imparted by more common, more familiar physical processes. It is one thing to define a unit called “rad” in

*317

terms of 100 other units of energy called “ergs”, or an international unit known as the Joule.

How much energy does an erg represent, or a rad?

Perhaps the best comparison of amounts — and qualities — of energy can be drawn between ionizing radiation and heat. To do so, though, requires definition of one more unit describing energy:

The

calorie

is the familiar unit in chemistry that describes energy transfers involving heat. One calorie is that amount of energy which will raise the temperature of one gram of water by one degree centigrade [or Celsius]. (This definition does change some at different temperatures of water, but for our purposes here we can neglect those small changes.).

The best estimates are that approximately 400 rads of whole-body radiation, if delivered rapidly, are sufficient to cause 50% of the exposed humans to die within a period of days to weeks. This is the so-called acute radiation sickness. Is this a great deal of energy in heat terms? Some simple calculations show that it is not.

Since 1 rad represents the absorption of 100 ergs per gram of tissue, it follows that 400 rads represents the absorption of 40,000 ergs per gram. The conversion factor from ergs to calories is 2.39 x 10-8. Therefore,

40,000 ergs x 2.39 xlO"8 gram calories = 9.56xlO'4 calories erg gram

We can round this off to approximately 10~3 calories/gram (or 0.001 calories/ gram).

Biological tissue is quite comparable with water in the amount of heat required to raise its temperature by one degree centigrade [or Celsius]. So we shall say that the required amount is one calorie per gram for biological tissue too. Therefore, our HP3 calories/gram from the absorption of 400 rads of ionizing radiation energy would be enough to raise the temperature of biological tissue by 0.001 centigrade. Not much of a fever! We tolerate fevers of several degrees centigrade (not thousandths of a degree) in a variety of infectious diseases. Yet the amount of ionizing radiation that can kill half of the humans exposed to it, would — if converted first into heat — raise temperatures only by 0.001° centigrade.

This points up the biologically deadly difference between energy in the form of heat versus the same amount of energy in the form of ionizing radiation____

The difference resides in the fact that thé energy of ionizing radiation is not distributed the way the thermal energy of a fever is, the latter being distributed among all the molecules of a gram of tissue. Instead, the energy of ionizing radiation is transferred from photons to single electrons [or from charged alpha or beta particles], which in turn transfer all their energy to

relatively

few electrons in

relatively

few molecules. The transfer occurs in extremely concentrated fashion compared with the even diffusion of heat energy. Therefore, the energy delivered by ionizing radiation is energetic enough to break

any

chemical bond, even the strongest ones in living tissue____

J. Gofman,

Radiation and Human Health

52-53 (1981), PX-1046 (emphasis in original). It is not the

quantity

of energy penetrating the cells of the human body, but rather the

quality

of the energy, the nature of its interaction with cellular chemistry, which makes exposure to ionizing radiation an extraordinary hazard. As described in Part II,

supra,

alpha, beta and

*318

gamma radiations streak through matter at high energy and high speed, stripping electrons away from any chemical compound or individual molecule with which they come in close proximity or direct contact. The ionized molecules may reunite as before, with no detectable damage. They may also react with each other or with other molecules nearby, forming new and not necessarily useful compounds, reflecting a temporary, or perhaps a permanent injury to the chemical structures originally present.

From the standpoint of biological injury, energy absorbed in the ionization of air, or a multitude of inanimate objects, is essentially meaningless. A glass of water which has been irradiated by alpha, beta or gamma rays poses no risk to health greater than any other water — unless, of course, it has become contaminated with radioactive material that would bombard internal organs with additional radiation if ingested. Far more important is the interaction of ionizing radiation with the tightly ordered, extremely complex and relatively fragile molecules of life.

Of particular concern is the effect of ionization on the lengthy and critically important strands of genetic material found in each living cell.

C. Ionizing Radiation and Chromosomes

At the interior of each living cell is found a

nucleus

of specialized proteins, enzymes, and other chemicals. The nucleus appears for most purposes to be the control center of the cell. It contains the long, spiralling molecules of DNA (deoxyribonucleic acid), which carry encoded within their delicate patterns the entire genetic “blueprint” controlling the structure, composition and numberless chemical activities of the individual cell, the tissue in which it is found, and — somewhere within its strands — the remainder of the instructions followed by all of the other specialized cells that make up an incredibly detailed living organism. The DNA molecules are joined together in discrete units called

genes,

which in turn are grouped together in a series of genetic superstructures, called '

chromosomes.

Each of the billions of cells in the human body, with the exception of red blood cells, contains an invariable normal count of 46 chromosomes within its nucleus. Within those chromosomes are carried more than 5

billion

individual bits of genetic information, carefully stored in the chemical patterning of the DNA molecules. C. Sagan,

Cosmos

276 (1980);

See also

Part IX(C),

infra.

F. Radiation Exposure: Internal, External, Whole-Body, Partial-Body

Prior sections of this opinion discuss and emphasize the fact that the potential for radiation injury from nuclear fallout debris is not limited to the dose received from gamma-emitting (or beta-emitting) radionuclides outside the body. There also exists

*327

the potential for serious exposure from radioactive debris inhaled, ingested or absorbed into the human body from contaminated food, water, milk, or dust. At the cellular level, however, the distinction between external and internal dose disappears. The amount of chemical disruption that a cell experiences from whatever source of radiation in any direction or at any distance is the important consideration. The phenomenon of internal exposure simply allows shorter-range alpha and beta particles greater access to more sensitive cells and tissues.

An important distinction must be drawn however, between radiation dose to the whole body and estimated radiation doses to specific organs. The biological impact of 300 rads absorbed by the skin is distinctly different in nature and severity from the impact of a 300-rad whole-body dose. Where whole-body exposure is concerned the absorbed energy is being visited upon nearly every gram of living matter in the body. A partial-bo'dy dose absorbed by a particular organ, such as the thyroid, the bone marrow, or the lung may be of considerable importance to the organ involved, but signifies far less relative damage to other organs and tissues.

In reviewing articles, studies, documents and testimony, considerable error in risk estimation may be avoided simply by paying heed to whether exposure and dose are being expressed in terms of the whole body or a particularized organ or system.

G. Other Sources of Radiation Exposure

Fallout from atmospheric nuclear testing in Nevada is only one of a collection of sources of exposure to ionizing radiation, both man-made and naturally occurring. First, every person living on the earth receives some amount of radiation from the natural sources generally blanketed under the term “background” radiation. Natural background radiation derives from a number of sources: naturally occurring heavy elements, such as uranium, thorium, radium, radon, and polonium, and a few lighter radionuclides which are readily incorporated into living tissue in trace amounts,

e.g.,

potassium-40 and carbon-14. Natural radioactivity is all around us, in soil, in building materials, and in trace amounts in meat, vegetables, fruits, grains and drinking water.

Additional background exposure is traced to cosmic rays, high-energy gamma rays and atomic particles which rain down from the sun through the atmosphere. People living at higher altitudes receive slightly more radiation than those who live at sea level, as do people

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