Draft Guidance on the Benchmark Dose Modeling for the Radiological Criteria for License Termination of Uranium Recovery Facilities

NUCLEAR REGULATORY COMMISSION

Draft Guidance on the Benchmark Dose Modeling for the

Radiological Criteria for License Termination of Uranium Recovery

Facilities

AGENCY: Nuclear Regulatory Commission.

ACTION: Notice of availability; opportunity for comment.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is soliciting

comments on draft guidance for the radium benchmark dose approach,

associated with the final rule, ``Radiological Criteria for License

[[Page 17691]]

Termination of Uranium Recovery Facilities,'' that is in this

publication. The guidance will be incorporated into the NRC final

Standard Review Plan (SRP) for the Review of Reclamation Plans for Mill

Tailings Sites and the SRP for In-Situ Leach Uranium Extraction License

Applications. Public comments should be submitted within sixty (60)

days of publication of this Notice.

SUPPLEMENTARY INFORMATION:

Background

In 10 CFR 40.4, uranium milling is defined as any activity

resulting in byproduct material. 1 Therefore, Part 40,

Appendix A, applies to in situ leach (ISL), heap leach, and ion-

exchange facilities (i.e., uranium recovery (UR) facilities) that

produce byproduct material, as well as to conventional uranium and

thorium mills. The draft guidance only addresses UR facilities because

there are no currently licensed or planned thorium mills.

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\1\ Byproduct material means the tailings or waste produced by

the extraction or concentration of uranium or thorium from any ore

processed primarily for its source material content, including

discrete surface wastes resulting from uranium solution extraction

processes.

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Decommissioning of ISLs and mills are similar in that the type of

soil and building contamination is the same, consisting mainly of

residual radium (Ra-226) and uranium (U-nat). The applicable cleanup

standards for soil radium in Criterion 6(6) address the main

contaminant at uranium mills in the large areas (hundreds of acres)

where windblown contamination from the tailings pile has occurred, and

at ISLs in holding/settling ponds and process solution spills. In other

mill and ISL site areas proximate to locations where radium

contamination exists (e.g., under the mill or process building or in a

yellowcake storage area), uranium would be the radionuclide of concern.

Thorium (Th-230, the parent of Ra-226) would be the radionuclide of

concern at some mill raffinate evaporation ponds.

Because Part 40, Appendix A, provides only decommissioning soil

radium 2 and ground-water protection criteria, Criterion 6

(6) was amended to address criteria for residual radionuclides, other

than radium in soil, for decommissioning of lands and structures at UR

facilities. The final rule, ``Radiological Criteria for License

Termination of Uranium Recovery Facilities,'' added a paragraph after

the radium in soil criteria in Criterion 6(6), to read:

\2\ The concentration of radium, as a result of byproduct

material, averaged over areas of 100 square meters, should not

exceed the background level by more than 5 pCi/g (0.19 Bq/g) in the

first 15 cm (6 inches) of soil, and 15 pCi/g (0.56 Bq/g) for every

subsequent 15 cm (6 inch) layer.

Byproduct material containing concentrations of radionuclides

other than radium in soil, and surface activity on remaining

structures, must not result in a total effective dose equivalent

(TEDE) exceeding the dose from cleanup of radium contaminated soil

to the above standard (benchmark dose), and must be at levels which

are as low as is reasonably achievable.

If more than one residual radionuclide is present in the same

100-square-meter area, the sum of the ratios for each radionuclide,

of concentration present to the concentration limit, will not exceed

``1'' (unity). A calculation of the peak potential annual TEDE

within 1000 years to the average member of the critical group that

would result from applying the radium standard (not including radon)

on the site, must be submitted for approval. If the benchmark dose,

before application of ALARA, exceeds 100 mrem/yr, the staff will

consult the Commission before approving the decommissioning plan.

This requirement for dose criteria does not apply to sites that have

decommissioning plans for soil and structures approved before the

effective date of this rule.

The final rule, ``Radiological Criteria for License Termination of

Uranium Recovery Facilities,'' requires the use of the soil radium

standard to develop a site-specific dose benchmark for the cleanup of

residual radionuclides, other than radium, at UR sites. The radium

benchmark approach ensures that the dose limit across the UR site will

be equal for all radionuclides (other than radon).

The NRC-licensed sites subject to the new rule currently include

four uranium mills (one operating, others in stand-by status), seven in

situ leach (ISL) facilities, and any new UR facility licensed by NRC

after promulgation of the rule (two ISL license applications are under

review at NRC, also in the Agreement States, several ISLs in Texas

could be affected by the rule). These sites are located in semi-arid

(7-15 inches (18-39 cm) of precipitation), high evapo-transpiration,

sparsely populated (1-5 people per sq. mile (0.4-3 per sq. km)) areas

of New Mexico, Utah, Wyoming, and Nebraska. The land use around these

facilities is predominately mining and ranching, and the potable water

aquifer is usually 100-200 feet deep. Also, many of the sites have

natural (in situ) uranium and/or radium deposits or mine pits that

create a wide range of radium, thorium and uranium background values.

Because of these unique properties and the specific regulations in 10

CFR Part 40, Appendix A, the UR facilities are exempt from the

decommissioning criteria in Part 20 Subpart E, as specified in Section

20.1401(a).

The benchmark dose applies to surface cleanup (buildings or the top

15 cm (6 inches) of soil) of radionuclides other than radium and it is

the estimated dose resulting from cleanup of areas to 5 pCi/g (0.19 Bq/

g) Ra-226 at that site. For the small areas requiring the use of the

radium subsurface soil standard, the estimated dose resulting from 15

pCi/g (0.56 Bq/g) Ra-226 at that site and for those areas, would be

used. The same concept of regulation (using a Ra-228 benchmark dose)

would be applicable to thorium mills, if any are licensed in the

future.

The draft guidance on dose modeling and implementation of the

radium benchmark approach was developed in conjunction with the final

rule and the SRPs under development for uranium mill site reclamation

and ISL licensing. The draft SRPs have already been published for

comment as NUREG-1569 (NRC, 1997) and NUREG-1620 (NRC, 1999). After

review of the comments received on the draft guidance, the final

benchmark dose guidance will be incorporated into the final SRPs for UR

facilities.

Draft Guidance: Standard Review Plan--Chapter 6

6.0 Decommissioning Plan for Soil and Buildings--The Radium

Benchmark Dose Approach

A mill reclamation plan, required for licensing or license renewal,

generally focuses on the tailings disposal cell and contains only brief

mention of anticipated decommissioning activities. The licensee submits

a detailed mill or ISL decommissioning plan and a soil cleanup/

verification plan for NRC approval at least six months before

decommissioning is to begin. The general requirements for a

decommissioning plan, and the remediation and verification of soil Ra-

226 contamination cleanup are addressed in Chapter 5 of the Standard

Review Plan (SRP). This chapter discusses the evaluation of the radium

benchmark dose approach for the cleanup of thorium and uranium,

specifically dose modeling and its application to site cleanup

activities that should be addressed in the decommissioning plan.

This chapter applies to those uranium recovery (UR) facilities

licensed by the NRC and subject to the new requirements for cleanup of

contaminated soil and buildings under 10 CFR Part 40, Appendix A,

Criterion 6(6) (as amended in 1999). The facilities that did not have

an approved

[[Page 17692]]

decommissioning plan at the time the rule became final are required to

reduce residual radioactivity, i.e., byproduct material, as defined by

Part 40, to levels based on the potential dose, excluding radon,

resulting from the application of the radium (Ra-226) standard at the

site. This is referred to as the radium benchmark dose approach.

This chapter would also apply to any future thorium processing

facilities and uranium heap leach operations, because Part 40 defines

uranium milling as any activity resulting in byproduct material. This

chapter also applies to any revised decommissioning plan submitted for

NRC review and approval, after the final rule is effective. However, if

a subject licensee can demonstrate that no contaminated buildings will

remain, and that soil thorium or total uranium levels are not

discernable from background, radium benchmark dose modeling is not

required. Other aspects of decommissioning are addressed in Chapter 5

of this SRP.

In order for NRC staff to evaluate the radium benchmark dose

modeling and the implementation of the modeling results, as proposed in

the building and soil decommissioning plan, an understanding of the

site conditions and site operations is essential. The required site

information should be provided by the licensee, or relevant portions of

previously submitted documents (e.g., environmental assessments,

license renewal, reclamation plan, and characterization report) should

be summarized and referenced. The information should include: (1)

processes used at the facility; (2) type and location of possible

contamination; (3) geologic and climatic data; and (4) surrounding land

use information (also see Section 3 of Inspection Procedure 87654).

6.1 Radium Benchmark Dose Modeling

6.1.1 Areas of Review

In implementing the radium benchmark approach, the licensee

calculates the peak potential dose for the site resulting from the 5

pCi/g (0.19 Bq/g) concentration of radium in the surface (top 15 cm (6

inches)) soil. The dose from the 15 pCi/g (0.56 Bq/g) subsurface radium

limit would be calculated for any area that may require subsurface

cleanup. The dose modeling review involves examination of the computer

code or other calculations employed for the dose estimates, the code or

calculation input values and assumptions, and the modeling results

(data presentation).

6.1.2 Review Procedures

The radium benchmark dose modeling review consists of ascertaining

that an acceptable dose modeling computer code or other type of

calculation has been used; that input parameter values appropriate

(reasonable considering long-term conditions and representative of the

application) for the site have been used in the modeling; that a

realistic (overly conservative is not acceptable as it would result in

higher allowable levels of uranium or thorium which would not be ALARA)

dose estimate is provided; and that the data presentation is clear and

complete.

6.1.3 Acceptance Criteria

The radium benchmark dose modeling results will be acceptable if

the dose assessment (modeling) meets the following criteria:

(1) Dose Modeling Codes and Calculations

The assumptions are considered reasonable for the site analysis and

the calculations employed are adequate. Reference to documentation

concerning the code or calculations is provided (for example, the

RESRAD Handbook and Manual (Argonne, 1993a and b)).

The RESRAD code developed by the U.S. Department of Energy (version

5.82, 1998) (see website www.ead.anl.gov/resrad/html), may be

acceptable for dose calculations because, while the RESRAD ground-water

calculations have limitations, this does not impact the UR sites that

have deep aquifers (ground-water exposure pathway is insignificant).

The DandD code developed by the NRC (version 1.0, August 1998, see

website ftp://nwerftp.nwer.sandia.gov/nrc/DandD/; also see the website

at http://techconf.llnl.gov/radcri/dose-top.html) provides conservative

default values, but does not allow for modeling subsurface soil

contamination, and does not allow calculation of source removal due to

soil erosion. Neither the RESRAD nor the DandD code would be adequate

to model the dose from off-site contamination, but codes such as GenII

would be considered.

If the code or calculation's assumptions are not acceptable for

site conditions, adjustments have been made in the input to adequately

modify these assumptions.

The RESRAD code assumes a circular contaminated zone. The shape

factor (external gamma, screen R017) must be adjusted for a non-

circular-shaped area.

The code or calculation provides an annual dose (total effective

dose equivalent (TEDE)) estimate (mrem/yr).

The DandD code provides the annual dose, but RESRAD calculates the

highest instantaneous dose. However, RESRAD results are acceptable for

long-lived radionuclides that do not move rapidly out of surface soils.

(2) Input Parameter Values

The code/calculation input data are appropriate for the site and

represent current or long-term conditions, whichever is more applicable

to the time of maximum dose. When code default values are used, they

are justified as appropriate (representative) for the site. Excessive

conservatism (i.e., upper bound value) is not used as this would result

in a higher dose and thus higher levels of uranium and thorium would be

allowed to remain on site.

Previously approved MILDOS code input parameter values may not be

appropriate, because derived operational doses in the restricted area

may be an order of magnitude higher than acceptable doses for areas to

be released for unrestricted use.

Site-specific input values are demonstrated to be average values of

an adequate sample size. Confidence limits are provided for important

parameters so that the level of uncertainty can be estimated for that

input value. Alteration of input values considers that some values are

inter-related (see draft NUREG-1549, Appendix C) (NRC, 1998a) and

relevant parameters are modified accordingly. The preponderance of

important parameter values are based on site measurements and not

conservative estimates. One or more models consider the annual average

range of parameter values likely to occur within the next 200-year time

period, for important parameters that can reasonably be estimated. Some

other considerations for the input parameter values are as follows:

a. Exposure Pathways and Scenarios for the Critical Group

The scenario(s) chosen to model the potential dose to the average

member of the critical group\3\ from residual radionuclides at the site

reflects reasonable probable future land use. The licensee has

considered ranching, mining, home-based business, light industry, and

residential farmer scenarios, and has justified the scenarios modeled.

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\3\ As defined in 10 CFR Part 20, ``the group of individuals

reasonably expected to receive the greatest exposure to residual

radioactivity for any applicable set of circumstances.''

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Based on one or more of these projected (within 200 years is

reasonably foreseeable) land uses to define the critical group(s), the

licensee

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has determined and justified what exposure pathways are probable for

potential exposure of the critical group to residual radionuclides at

the site.

Dairies are not likely to be established in the area of former UR

facilities, and even if some milk cows were to graze in contaminated

areas, the milk would probably be sent for processing (thus diluted),

and not be consumed at the site. Therefore, milk consumption is not a

likely ingestion exposure pathway. Also, a pond in the contaminated

area providing a significant quantity of fish in the resident's diet is

not likely, so the aquatic exposure pathway may not have to be modeled.

However, the external gamma, plant ingestion, and inhalation pathways

are likely to be important.

The radon pathway is excluded from the benchmark dose calculation

as defined in Criterion 6(6) of Appendix A, to 10 CFR Part 40. This

also reflects the approach in the main decommissioning rule

(radiological criteria for license termination, Part 20 subpart E).

b. Source Term

If the RESRAD code is used, the input includes Pb-210 at the same

input value as for Ra-226. The other radium progeny are automatically

included in the code calculations. The chemical form of the

contamination in the environment is considered in determining input

values related to transport, or inhalation class (solubility in the

lung) for dose conversion factors.

c. Time Periods

The time periods for calculation of the dose from soil Ra-226

include the 1000-year time frame. The calculated maximum annual dose

and the year of occurrence is provided in the results.

d. Cover and Contaminated Zone

A cover depth of zero is used in the surface contamination model

and a depth of at least 15 cm (6 inches) for the subsurface model. The

values for area and depth of contamination are derived from site

characterization data. The erosion rate value for the contaminated zone

is less than the RESRAD default value because in regions drier than

normal, the erosion rate is less, as discussed in the RESRAD Data

Collection Handbook (Argonne, 1993a), and the value is justified. The

soil properties are based on site data (sandy loam or sandy silty loam

are typical for UR sites) and other input parameters are based on this

demonstration of site soil type (see RESRAD Handbook pages, 23, 29, 77,

and 105).

The evapo-transpiration coefficient for the semi-arid UR sites is

between 0.6 and 0.99. The precipitation value is based on annual values

averaged over at least 20 years, obtained from the site or a nearby

meteorological station.

The irrigation rate value may be zero, or less than a code's

default value, if supported by data on county or regional irrigation

practices (e.g., irrigation water is obtained from a river not a well).

The runoff coefficient value is based on the site's soil type, expected

land use, and morphology of the region.

e. Saturated Zone

The dry bulk density, porosity, ``b'' parameter, and hydraulic

conductivity values are based on local soil properties. The hydraulic

gradient for an unconfined aquifer is approximately the slope of the

water table. For a confined aquifer, it represents the difference in

potentiometric surfaces over a unit distance.

If the RESRAD code is used, the nondispersion model parameter is

chosen for areas greater than 1000 sq. meters (screen R014), and the

well pump rate is based on irrigation, stock, or drinking water well

pump rates in the area.

f. Uncontaminated and Unsaturated Strata

The thickness value represents the typical distance from the soil

contamination to the saturated zone. Since the upper aquifer at UR

sites is often of poor quality and quantity, the depth of the most

shallow well used for irrigation or stock water in the region is chosen

for the unsaturated zone thickness. A value of 18 meters (60 feet) is

typical for most sites and 15 meters (50 feet) for the Nebraska site,

but regional data are provided for justification. The density,

porosity, and ``b'' parameter values are similar to those for the

saturated zone or any changes are justified.

g. Distribution Coefficients and Leach Rates

The distribution coefficient (Kd) is based on the site's soil

physical and chemical characteristics. The leach rate value of zero in

the RESRAD code is acceptable as it allows calculation of the value. If

a value greater than zero is provided, justification for the value is

also provided.

h. Inhalation

An average inhalation rate value of approximately 8,395

m3/yr is used for the activity assumed for the rancher or

farmer scenario (based on Draft Letter Report, Sandia, 1998a). The mass

loading for inhalation (air dust loading factor) value is justified

based on the average level of airborne dust in the local region for

similar activities as assumed in the model.

i. External Gamma

The shielding factor for gamma is in the range of 0.33 to 0.55 (PG-

8-08, NRC 1994; DandD code screening default value), based mainly on

the type (foundation, materials) of the house likely to be built on the

site.

The time fractions for indoor and outdoor occupancy are similar to

default values in RESRAD and draft guidance developed for the main

decommissioning rule (NUREG/CR-5512, Volume 3, NRC, 1996b). For

example, the staff would consider fraction values approximating 0.7

indoors and 0.15 outdoors for a resident working at home, and 0.5

outdoors and 0.25 indoors for the farmer scenario.

The site specific wind speed value is based on adequate site data

(the average annual wind speed for the UR sites varies from 7 to 13 mph

(3.1 to 5.5 meters/sec)). The maximum and annual average wind speed are

also considered when justifying/evaluating proposed erosion rates.

j. Ingestion

Average consumption values (g/yr) for the various types of foods

are based on average values as discussed in NUREG 5512, Volume 3, or

the Sandia Draft Letter Reports (1998a and b), or are otherwise

justified. Livestock ingestion parameters are default values, or are

otherwise justified.

For sites with over 25 acres of contamination, the fraction of diet

from the contaminated area is assumed to be 0.25 for the farmer

scenario (Sandia 1998a), or is otherwise justified based on current or

anticipated regional consumption practices for home-grown food. Because

of the low level of precipitation in the UR facilities regions,

extensive gardens or dense animal grazing are not likely, so the

percentage of the diet from contaminated areas is likely to be lower

than the code default value.

Note that the default plant mass loading factor in the DandD code

can reasonably be reduced to 1 percent (Sandia, Draft Report, 1998c).

The depth of roots is an important parameter for UR licensees using the

RESRAD code. The value is justified based on the type of crops likely

to be grown on the site in the future. For vegetable gardens, a value

of 0.3 is more appropriate than the RESRAD default value of 0.9 meters

that is reasonable for alfalfa or a similar deep-rooted plant.

[[Page 17694]]

(3) Presentation of Modeling Results

The radium benchmark dose modeling section of the decommissioning

plan includes the code or calculation results as the maximum annual

dose (TEDE) in mrem/yr, the year that this dose would occur, and the

major exposure pathways by percentage of total dose. The modeling

section also includes discussion of the likelihood of the various land

use scenarios (reflecting the probable critical groups) modeled, and

provides the variations in dose (dose distribution) created by changing

key parameter values to reflect the range of dose values that are

likely to occur on the site. The section also contains the results of a

sensitivity analysis (RESRAD code can provide a sensitivity analysis

via the graphics function) to identify the important parameters for

each scenario.

Note: As indicated in Criterion 6(6), if a licensee submits a

radium benchmark dose result that is 100 mrem/yr or higher, the

staff will consult with the Commission before approving the

decommissioning plan based on this value.

6.1.4 Evaluation Findings

If the staff review, as described in this section, results in the

acceptance of the radium benchmark dose modeling, the following

conclusions may be presented in the technical evaluation report (TER).

The staff has completed its review of the site benchmark dose

modeling for the ________________ uranium recovery facility. This

review included an evaluation using the review procedures in the Title

II SRP (NRC, 1999), Section 6.1.2, and the acceptance criteria outlined

in SRP Section 6.1.3.

The applicant has provided an acceptable radium benchmark dose

model and staff evaluation determines that: (1) the computer code or

set of calculations used to model the benchmark dose is appropriate for

the site; (2) input parameter values used in each model are site-

specific or reasonably estimates; (3) the dose modeling information

includes adequate estimates of dose uncertainty.

6.2 Implementation of the Benchmark Dose

6.2.1 Areas of Review

The results of the radium benchmark dose calculations are used to

establish a surface and subsurface soil dose limit for residual

radionuclides other than radium, as well as a limit for surface

activity on structures that will remain after decommissioning. The

staff reviews the licensee's conversion of the benchmark dose limit to

soil concentration (pCi/g) or surface activity levels (dpm/100 cm \2\)

as a first step to provide cleanup levels. Alternatively, the licensee

can derive the estimated dose from the uranium or thorium contamination

(as discussed in Section 6.1.3) and compare this to the radium

benchmark dose.

The cleanup levels adequately consider the ALARA principle and the

unity rule to demonstrate that the Part 40.42 (k) requirements (the

premises are suitable for release and reasonable effort has been made

to eliminate residual radioactive contamination) can be met.

6.2.2 Review Procedures

The decommissioning plan section on cleanup criteria will be

evaluated for appropriate conversion of the radium standard benchmark

dose to cleanup limits for soil uranium and thorium and/or surface

activity concentration. The plan will also be examined to ensure

reasonable application of the ALARA principle to the cleanup guideline

values.

6.2.3 Acceptance Criteria

(1) The soil concentration limit is derived from the site radium

dose estimate. The modeling performed to estimate mrem/year per pCi/g

of Th-230 and/or U-nat follows the criteria listed in Section 6.1.3. In

addition, the U-nat source term is represented as percent activity by

49.14% U-238, 49.14% U-234, and 0.71% U-235, or is based on analyses of

the ore processed. For a soil uranium criterion, the chemical toxicity

is considered in deriving a soil concentration limit if soluble forms

of uranium are present.

Detailed justification for the inhalation pathway parameters is

provided, such as the determination of the chemical form in the

environment, to support the inhalation class.

The derived Th-230 soil limit will not cause any 100 square meter

(m \2\) area to exceed the Ra-226 limit at 1000 years (i.e., current

concentrations of 14 pCi/g Th-230 surface and 43 pCi/g subsurface, if

Ra-226 is at approximately background levels).

(2) In conjunction with the activity limit, the ALARA principle is

considered in setting cleanup levels (derived concentration guideline

levels). The ALARA guidance in draft Regulatory Guide 4006 is

considered.

In recent practice at mill sites, ALARA is implemented by removing

at least two more inches (5 cm) of soil than is estimated to achieve

the radium standard. (reduce any possible excess or borderline

contamination). At mills, it is generally cheaper to remove more soil

than to do sampling and testing that may indicate failure and require

additional soil removal plus additional testing.

(3) The unity rule is applied to the cleanup if more than one

residual radionuclide is present in a soil verification grid (100 m

\2\). This means that the sum of the ratios for each radionuclide of

the concentration present/concentration limit may not exceed ``1''

(i.e., unity).

(4) The subsurface soil standard, if it is to be used, is applied

to small areas of deep excavation where at least 15 cm (6 inches) of

compacted clean fill is to be placed on the surface.

(5) The surface activity limit for remaining structures is

appropriately derived using an approved code or calculation.

If the DandD code is used, data is provided to support that 10% or

less of the activity is removable; otherwise the resuspension factor is

scaled to reflect the site-specific removable fraction. Note that this

code assumes that the contamination is only on the floor, which can be

overly conservative. If the RESRAD-Build code is used, the modeled

distribution of contamination on walls vs. floor is justified.

6.2.4 Evaluation Findings

If the staff review, as described in this section, results in the

acceptance of the application of the radium benchmark dose modeling to

the site cleanup criteria, the following conclusions may be presented

in the technical evaluation report.

The staff has completed its review of the proposed implementation

of the benchmark dose modeling results for the ________________ uranium

recovery facility. This review included an evaluation using the review

procedures in the Title II SRP, Section 6.2.2, and the acceptance

criteria outlined in SRP Section 6.2.3.

The licensee has provided an acceptable implementation of the

benchmark dose modeling results to the proposed site cleanup activities

and staff evaluation determines that: (1) The cleanup criteria will

allow the licensee to meet Part 40.42(k) and Part 40, Appendix A,

criterion 6(6) requirements; (2) the soil and structures of the

decommissioned site will permit termination of the license because

public health and the environment will not be adversely affected by any

residual radionuclides.

6.3 References

Argonne National Laboratory (for the U.S. Department of Energy),

``Data Collection Handbook to Support Modeling the Impacts of

Radioactive Material in Soil,'' ANL/EAIS-8, April 1993a.

[[Page 17695]]

Argonne National Laboratory (for the U.S. Department of Energy),

``Manual for Implementing Residual Radioactive Material Guidelines

Using RESRAD, Version 5.0,'' ANL/EAD/LD-2, September 1993b.

Sandia National Laboratories, ``Review of Parameter Data for the

NUREG-5512 Residential Farmer Scenario and Probability Distributions

for the DandD Parameter Analysis,'' Draft Letter Report, January 30,

1998a.

Sandia National Laboratories, ``Review of Parameter Data for the

NUREG-5512 Building Occupancy Scenario and Probability Distributions

for the DandD Parameter Analysis,'' Draft Letter Report, January 30,

1998b.

Sandia National Laboratories, ``Comparison of the Models and

Assumptions Used in the DandD 1.0, RESRAD 5.61, and RESRAD-Build

Computer Codes with Respect to the Residential Farmer and Industrial

Occupant Scenarios Provided in NUREG/CR5512.'' Draft Report, October

15, 1998c.

U. S. Nuclear Regulatory Commission, ``Residual Radioactive

Contamination from Decommissioning,'' NUREG/CR-5512, PNL-7994, Vol.

1, 1992.

U.S. Nuclear Regulatory Commission, Office of Nuclear Material

Safety and Safeguards, Division of Waste Management, Policy and

Guidance Directive PG-8-08, ``Scenarios for Assessing Potential

Doses Associated with Residual Radioactivity,'' May 1994.

U. S. Nuclear Regulatory Commission, ``Residual Radioactive

Contamination from Decommissioning--User's Manual,'' NUREG/CR-5512,

Vol. 2, October 1996a.

U. S. Nuclear Regulatory Commission, ``Residual Radioactive

Contamination from Decommissioning--Parameter Analysis,'' (DRAFT FOR

REVIEW), NUREG/CR-5512, Vol. 3, April 1996b.

U.S. Nuclear Regulatory Commission, Office of Nuclear Material

Safety and Safeguards, ``Draft Standard Review Plan for In Situ

Leach Uranium Extraction License Applications,'' NUREG-1569, October

1997.

U.S. Nuclear Regulatory Commission, ``Decision Methods for Dose

Assessment to Comply With Radiological Criteria for License

Termination,'' Draft NUREG-1549, July 1998a.

U.S. Nuclear Regulatory Commission, Draft Regulatory Guide-4006,

``Demonstrating Compliance With the Radiological Criteria for

License Termination,'' August 1998b.

U.S. Nuclear Regulatory Commission, Office of Nuclear Material

Safety and Safeguards, ``Draft Standard Review Plan for the Review

of a Reclamation Plan for Mill Tailings Sites Under Title II of the

Uranium Mill Tailings Radiation Control Act,'' NUREG-1620, January

1999.

Notice of Opportunity To Provide Comments

The Commission hereby provides notice of opportunity for public

comment on the draft guidance addressing the radium benchmark approach

for decommissioning UR facilities. Written comments should be sent,

within sixty (60) days from the date of publication of this Federal

Register Notice (FRN), to the Chief, Rule and Directives Branch, U.S.

Nuclear Regulatory Commission, Washington, DC 20555-0001. Comments may

also be provided electronically on the NRC Uranium Recovery Branch

website and the final rule FRN may also be viewed (http://www.nrc.gov/

NRC/NMSS/URANIUM/guidance.htm).

FOR FURTHER INFORMATION CONTACT: Ms. Elaine S. Brummett, Uranium

Recovery and Low-Level Waste Branch, Mail Stop T7-J9, Division of Waste

Management, Office of Nuclear Material Safety and Safeguards, U.S.

Nuclear Regulatory Commission, Washington, D.C. 20555-0001. Telephone

301/415-6606.

Dated at Rockville, Maryland, this 1st day of April 1999.

For the Nuclear Regulatory Commission.

N. King Stablein,

Acting Chief, Uranium Recovery and Low-Level Waste Branch, Division of

Waste Management, Office of Nuclear Material Safety and Safeguards.

[FR Doc. 99-9036 Filed 4-9-99; 8:45 am]

BILLING CODE 7590-01-P