# Disposal of High-Level Radioactive Wastes in a Proposed Geologic Repository at Yucca Mountain, NV

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URL: https://www.frixlaw.com/law-library/documents/fr%3A01-27157

## Record

- **Collection:** Federal Register
- **Document type:** Rule
- **Published:** November 2, 2001
- **Citation:** 66 FR 55732

## Text

NUCLEAR REGULATORY COMMISSION
10 CFR Parts 2, 19, 20, 21, 30, 40, 51, 60, 61, 63, 70, 72, 73, and 75
RIN 3150-AG04
Disposal of High-Level Radioactive Wastes in a Proposed Geologic Repository at Yucca Mountain, NV

AGENCY:

Nuclear Regulatory Commission.

ACTION:

Final rule.

SUMMARY:

The Nuclear Regulatory Commission (NRC) is publishing licensing criteria for disposal of spent nuclear fuel and high-level radioactive wastes in the proposed geologic repository at Yucca Mountain, Nevada. As mandated by law, this final rule changes the Commission's technical requirements and criteria, as necessary, to be consistent with final environmental standards for Yucca Mountain issued by the U.S. Environmental Protection Agency (EPA). The criteria address how a repository system at Yucca Mountain must perform and specify that the system must comprise both natural and engineered barriers. The final rule includes licensing criteria; participation in license reviews by the State, affected units of local government, and Indian Tribes; records and reporting; monitoring and testing programs; performance confirmation; quality assurance; personnel training and certification; and emergency planning. Criteria set out in this final rule apply specifically and exclusively to the proposed repository at Yucca Mountain. Consistent with this intent, the Commission is also changing its generic criteria for disposal of spent nuclear fuel and high-level radioactive wastes in geologic repositories. These changes make clear that the generic criteria, specified elsewhere in the regulations, do not apply, nor may they be the subject of litigation, in any NRC licensing proceeding for a repository at Yucca Mountain.

EFFECTIVE DATE:

December 3, 2001.

FOR FURTHER INFORMATION CONTACT:

Timothy McCartin, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, telephone (301) 415-7285, e-mail tjm3@nrc.gov; Janet Kotra, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, telephone (301) 415-6674, e-mail jpk@nrc.gov; or Clark Prichard, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, telephone (301) 415-6203, e-mail cwp@nrc.gov.

SUPPLEMENTARY INFORMATION:

I. Background.

II. Implementation of the Environmental Protection Agency Final Standards.

III. Public Comments and Responses.

1. Regulatory Process and Licensing Process.

1.1. Promulgation in Advance of EPA Standards.

1.2. Differences Between Part 63 and EPA Standards for WIPP.

1.3. Multi-Staged Licensing.

1.4. Reasonable Assurance.

2. Requirements for the Preclosure Period.

2.1. Preclosure Safety Analysis.

2.2. Retrievability.

2.3. Performance Confirmation.

2.4. Preclosure Operations Activities.

2.5. Emergency Planning Criteria.

3. Requirements for the Postclosure Period.

3.1. Postclosure Safety Assessment.

3.2. Individual Dose Limit.

3.3 Calculation of Expected Dose.

3.4. Infant and Children Dose Standard.

3.5. Location of the Critical Group or RMEI.

3.6. Critical Group Characteristics and Reference Biosphere.

3.7. Absence of Separate Ground-Water Protection Criteria.

3.8. Multiple Barriers and Defense in Depth.

3.9. Compliance Period.

3.10. Human Intrusion Standard.

3.11. Postclosure Aspects of Repository Design.

4. General Requirements.

4.1. Quality Assurance.

4.2. Changes, Tests, and Experiments.

4.3. Land Ownership and Control.

5. Selected Topics.

5.1. Public Out-Reach.

5.2. Other Comments.

6. Beyond the Scope of This Rulemaking.

6.1. Hearing Process.

6.2. Transportation.

6.3. Other Comments.

IV. Changes From the Proposed Rule.

V. Section-by-Section Analysis of Part 63.

VI. Section-by-Section Analysis of Corresponding Changes to Other Parts.

VII. Voluntary Consensus Standards.

VIII. Finding of No Significant Environmental Impact: Availability.

IX. Paperwork Reduction Act Statement.

X. Regulatory Analysis.

XI. Regulatory Flexibility Certification.

XII. Backfit Analysis.

XIII. Small Business Regulatory Enforcement Fairness Act.

I. Background

On February 22, 1999 (64 FR 8640), the Commission published a proposed rule for public comment that would establish licensing criteria for disposal of spent nuclear fuel and high-level radioactive waste in the proposed geologic repository at Yucca Mountain, Nevada. The Energy Policy Act of 1992, Pub. L. 102-486 (EnPA) directed the Commission to make its requirements for geologic disposal consistent with new standards for Yucca Mountain the Environmental Protection Agency (EPA) would develop. The legislation also specifies the type of standards the NRC is to implement [that is, standards which limit individual dose and which are based on and consistent with the National Academy of Sciences' (NAS) 10 recommendations]. The Commission proposed a new, separate part of its regulations, 10 CFR part 63, that would apply only to the proposed repository at Yucca Mountain. The Commission also proposed to leave its existing, generic regulations at Part 60 in place, changed only to state that they do not apply, nor may they be the subject of litigation, in any NRC licensing proceeding for a repository at Yucca Mountain.

In setting forth these criteria, the Commission sought to establish a coherent body of risk-informed, performance-based criteria for a Yucca Mountain facility that is compatible with the Commission's overall philosophy of risk-informed, performance-based regulation. Stated succinctly, risk-informed, performance-based regulation is an approach in which risk insights, engineering analysis and judgment, and performance history are used to (1) focus attention on the most important activities, (2) establish objective criteria based upon risk insights for evaluating performance, (3) develop measurable or calculable parameters for monitoring system and licensee performance, and (4) focus on the results as the primary basis for regulatory decision making. The Commission believes that creating a new part of its regulations accomplishes these objectives better than modifying the generic requirements. The Commission prefers a wholly new part 63 that reflects the fundamentally different approach laid out for Yucca Mountain by EnPA and the final EPA standards, an approach unlike that contemplated when the generic criteria were issued. Specifically, EnPA defined an approach that requires the performance of a Yucca Mountain repository to comply with health-based standards, developed by EPA and based on the recommendations of the NAS. EPA has established standards for Yucca Mountain that consider risk to a hypothetical individual and are to be the only such standards for the postclosure performance of the repository. This approach differs from that taken in the existing generic criteria which relies on quantitative, subsystem performance standards.

The public comment period, originally ending on May 10, 1999, was

extended to June 30, 1999, in response to many requests for extension (64 FR 24092; May 5, 1999). During the public comment period, the NRC staff held a series of public meetings in Nevada to discuss the proposed rule and solicit public comment. Meetings were held at Las Vegas and Beatty, Nevada, on March 23 and 25, respectively. Later, NRC held more meetings at Amargosa Valley, Las Vegas, and Caliente, Nevada, on June 15, 16, and 17, respectively. In developing this final rule, NRC considered comments received at these meetings along with written comments sent to NRC. The NRC also held a facilitated round table discussion on defense in depth as applied to a possible repository at Yucca Mountain on November 2, 1999, in Las Vegas.

The EPA published final radiation protection standards for the potential Yucca Mountain repository (40 CFR part 197) on June 13, 2001 (66 FR 32073). The EPA standards differ from the performance objectives proposed by the Commission at 10 CFR part 63. EPA established an annual individual protection dose limit of 0.15 mSv (15 mrem), and EPA included separate ground-water protection criteria in its final standards for the purpose of protecting ground water. In formal comments on EPA's proposed standards, dated November 3, 1999, the NRC staff supported a somewhat different approach. The NRC approach, which the Commission believes is adequately protective of public health and safety and ground water, used a comprehensive, all-pathway limit. However, the ultimate decision was EPA's to make and, as called for under the EnPA, the Commission will change its technical requirements and criteria to be consistent with EPA's final standards.

II. Implementation of the Environmental Protection Agency Final Standards

The U.S. Environmental Protection Agency (EPA) published Public Health and Environmental Radiation Protection Standards for Yucca Mountain, Nevada, at 40 CFR part 197 on June 13, 2001 (66 FR 32073). The Energy Policy Act of 1992, Pub. L. 102-486 (EnPA) directs the Commission to modify its technical requirements and criteria to be consistent with these standards. The Commission has imported the EPA standards into its final 10 CFR part 63 regulations in as transparent a manner as possible. Three categories of changes were necessary to accomplish this. First, the two subparts of the EPA standards—subpart A for storage and subpart B for disposal—have been added to part 63 as subparts K and L, respectively. Second, in most cases, the Commission adopted wording precisely as it appears at 40 CFR part 197. The Commission also made nonsubstantive changes that conformed to the regulatory style of the proposed part 63, and other U.S. Nuclear Regulatory Commission (NRC) regulations; removed unnecessary references to NRC; and adapted or removed redundant definitions. Lastly, as the implementing authority for the EPA standards, we have provided additional specifications and requirements based on the proposed part 63 rule and public comments we received in the areas where it is appropriate to do so. Indeed, EPA has acknowledged NRC's authority to add implementing requirements. As part of its rulemaking process, the Commission proposed and received comments on many aspects of radiation exposure scenarios, including several matters relevant to implementation of the EPA standards. Although EPA publication of the standards postdated the formal comment period for proposed part 63, the Commission has provided further specifications in subpart L, where needed, for clarification. We believe these additions are consistent with EPA's intent and are responsive to public comments we received. A brief summary of key aspects of the Commission's implementation of EPA's Standards in the final part 63 regulations appears below.

Radiation Standards for Storage

NRC has adopted the 0.15 mSv/year (15 mrem/year) dose limit for members of the public, during the storage period, and the associated requirements for determining compliance with the standards. The EPA standards identify the standards for storage as applicable at Yucca Mountain during the time period before closure of the proposed repository. In proposed part 63, NRC characterized this phase as “preclosure.” Therefore, we are implementing EPA's standards for storage to apply to the preclosure time period.

Radiation Standards for Disposal

The NRC has adopted the 0.15 mSv/year (15 mrem/year) dose limit for the reasonably maximally exposed individual, during the disposal period, and the associated requirements for determining compliance with the standards.

Ground-Water Protection Standards

NRC has adopted the ground-water protection standards and the associated requirements for determining compliance with the standards.

Radiation Standards for Human Intrusion

NRC has adopted the 0.15 mSv/year (15 mrem/year) dose limit for the reasonably maximally exposed individual as a result of a human intrusion and the associated requirements for determining compliance with the standards. One aspect of EPA's final standards is the specification of the characteristics of a postulated scenario for evaluating the consequences of human intrusion. NRC fully supports and has adopted the characteristics of the human intrusion scenario as specified in 40 CFR part 197 and has specified one additional requirement to further characterize the scenario. Specifically, part 63 provides that no particulate waste material falls into the borehole, and that DOE should assume the exposure scenario includes only those radionuclides transported to the saturated zone by water (e.g., water enters the waste package, releases radionuclides, and transports radionuclides by way of the borehole to the saturated zone). This change responds to a public comment seeking clarification of this aspect of the human intrusion scenario in proposed part 63. The Commission considers the additional requirement to be appropriate for addressing the comment and to be a matter of implementation of the EPA final standards. Further, the requirement is consistent with the human intrusion scenario as specified in 40 CFR part 197.

Reference Biosphere

The EPA standards for Yucca Mountain specify criteria that pertain to the characteristics of a reference biosphere, for use in the performance assessments that are required to show compliance with the postclosure standards for disposal. NRC fully supports and has adopted, in part 63, the characteristics of the reference biosphere as specified in 40 CFR part 197 and has included an additional requirement on characteristics of the biosphere that are consistent with EPA's final standards and that were discussed in proposed part 63 (64 FR 8640; February 22, 1999). Specifically, part 63 provides a further requirement for biosphere pathways by stating these pathways * * * “must be consistent with arid and semi-arid conditions.” This addition, from proposed part 63 (64 FR 8677), clarifies the bounds on what DOE needs to consider and is consistent with present knowledge of

how the climate could change over the next 10,000 years.

Reasonably Maximally Exposed Individual

The EPA standards specify characteristics of the reasonably maximally exposed individual (RMEI) for use in the performance assessments used to demonstrate compliance with standards for disposal. The NRC fully supports and has adopted the characteristics of the reasonably maximally exposed individual from 40 CFR part 197, and has included requirements specifying additional characteristics that are consistent with the EPA standards and were discussed in proposed part 63 (64 FR 8640). First, part 63 provides that the reasonably maximally exposed individual * * * “is an adult with metabolic and physiological considerations consistent with present knowledge of adults.” This addition, suggested for the average member of the critical group in proposed part 63 (64 FR 8677), clarifies assumptions DOE must make in estimating the radiation exposure to the reasonably maximally exposed individual. This addition is considered to be consistent with EPA's standards because: (1) The standards specify a consumption rate for water (i.e., 2 liters per day) that corresponds with that of an adult; and (2) a dose limit of 0.15 mSv (15 mrem) for an adult is protective of children as well as other age groups. The requirement that metabolic and physiological considerations are consistent with present knowledge of adults is consistent with EPA's final standards, which state that DOE should not project changes in human biology (66 FR 32133).

Second, although the EPA standards specify a representative volume approach for demonstrating compliance with the separate ground-water protection standards, they leave to NRC the approach for demonstrating compliance with the individual protection standard for disposal. EPA's approach for ground-water protection specifies a representative volume of 3,000 acre-feet for estimating the concentrations of radionuclides. The 3,000 acre-feet representative volume of ground water is consistent with assumptions for the critical group described in proposed part 63 (64 FR 8646). Specifically, in the proposed part 63, we suggested consideration of a farming community of up to 100 individuals, living on 15 to 25 farms. Fifteen to 25 farms are consistent with current conditions in the town of Amargosa Valley, Nevada, and would be the number needed to produce the range of locally produced food that is currently consumed in this area. The purpose of identifying 15 to 25 farms and specifying 100 individuals was to provide DOE with flexibility in determining an appropriate water demand consistent with a farming community of that size. A community of 15 to 25 farms would pump a sufficiently large volume of water and involve a broad range of exposure pathways. Of primary importance is the ingestion pathway, through consumption of water, crops, and animal products. The Commission considers that the water demand of between 15 and 25 farms can be represented by a volume of at least 3,000 acre-feet and, thus, is consistent with the farming community proposed for comment in part 63. Additionally, the preamble to EPA's final standards stated the NRC could use an approach to assess water usage in the hypothetical community, in which the RMEI resides, that was similar to the representative volume approach used for ground-water protection (i.e., consider a representative volume of 3,000 acre-feet). Therefore, the Commission removed the flexibility provided DOE to determine an appropriate water demand. This revised approach limits speculation on water demand and provides DOE with a specific value for the water demand that the NRC staff finds acceptable to estimate the RMEI dose. Part 63 specifies that the reasonably maximally exposed individual uses well water with an average concentration of radionuclides based on a representative volume of water of 3,000 acre-feet.

Unlikely Features, Events, and Processes

The EPA standards exclude unlikely features, events, and processes (including sequences of events and processes) from analyses for estimating compliance with the standards for human intrusion and ground-water protection. However, the EPA standards do not specify a frequency for unlikely features, events, and processes, and acknowledge that a value is to be specified by NRC (66 FR 32135). NRC fully supports excluding unlikely features, events, and processes from analyses for estimating compliance with the standards for human intrusion and ground-water protection. Although we have provided no specific quantitative value for determining when exclusion of unlikely features, events, and processes is appropriate, the final regulations require DOE to exclude unlikely features, events, and processes from the specified analyses upon prior approval of the Commission for the probability limit used for unlikely features, events, and processes. The Commission recognizes that specification of a probability limit for unlikely features, events, and processes, as is done for “very” unlikely features, events, and processes, would be a more direct approach. Although the Commission considers a frequency for unlikely features, events, and processes would fall somewhere between 10
−8
to 10
−4
per year, the Commission has decided not to specify a value in the regulations at this time. The Commission plans to conduct an expedited rulemaking to quantitatively define the term “unlikely.” Consideration will be given to whether a range of values or a single specific value should be used as well as the appropriate numerical value(s). The expedited rulemaking will provide an opportunity for public comment to assist the Commission in determining an appropriate approach.

Total Effective Dose Equivalent

The EPA and the NRC use different quantities to assess the total dose to exposed members of the public (including the RMEI). EPA uses the annual committed effective dose equivalent (annual CEDE), defined as the sum of the committed effective dose equivalent from internal doses resulting from one year's exposure to radioactive materials, and the effective dose equivalent from external radiation exposure during the year. The NRC uses the total effective dose equivalent (TEDE) for the same purpose. There are differences between TEDE and annual CEDE in some contexts. Specifically, in determining the external dose component of TEDE, NRC specifies use of the deep-dose equivalent at 10 CFR 20.1003. The deep-dose equivalent is a point measurement that does not sum the doses to the organs or tissue through use of weighting factors. This approach may reflect the fact that compliance with part 20 is customarily assessed using a Thermo-Luminiscent Device (TLD) or a film badge, and the results of such measurements reflect deep-dose equivalent. By contrast, in determining annual CEDE, the external dose component is determined using the effective dose equivalent, which involves summing the products of organ doses and weighting factors. In those situations in which the two measures of external dose differ, the effective dose equivalent approach probably provides a better estimate for measuring radiation risk.

Nonetheless, NRC's part 20 does allow for consideration of weighting factors for individual organs in the case of external exposures on a case-by-case

basis.
See
10 CFR 20.1003, Footnote 2 to Table on Organ Dose Weighting Factors. In practice, computer codes used by NRC in decommissioning and HLW disposal currently calculate external doses using effective dose equivalent and not deep-dose equivalent.
See
NUREG/CR 6676, “Probabilistic Dose Analysis Using Parameter Distributions Developed for RESRAD and RESRAD-Build Codes,” 3-1 (July 2000); NUREG-1464, “NRC Iterative Performance Assessment,” 7-5 (October 1995); and NUREG/CR-5512, “Residual Contamination from Decommissioning, User's Manual DandD Version 2.1,” Vol. 2, E-1 (April 2001). Consequently, use of organ doses and organ weighting factors, from Federal Guidance Report 12 and ICRP in its Publication 26, for external doses in assessing compliance with dose limits for members of the public in the general environment and the individual protection standard in connection with a geologic repository will yield exactly the same result as applying annual CEDE. As a result, in assessing compliance with the individual protection standard, the staff intends to use effective dose equivalent for assessing external exposure.

For purposes of assessing actual doses to workers at the Yucca Mountain repository, however, the Commission has directed that deep-dose equivalent be used in determining TEDE. This ensures consistency with NRC's regulations for limiting doses to occupationally exposed workers.

Requirements for Environmental Impact Statement

EPA's standards require DOE to estimate peak dose under the evaluations for individual protection and human intrusion. The results of these evaluations are to be included in DOE's environmental impact statement (EIS). The Commission has modified part 63 to include the provision that DOE must include peak dose estimates in its EIS, but notes that there is no standard that must be met with respect to these peak dose calculations, and that there is no finding that the NRC must make with respect to these peak dose calculations nor may they be the subject of litigation in any NRC licensing proceedings for a repository at Yucca Mountain. However, DOE still must carry out its responsibilities under the National Environmental Policy Act in accordance with the final EPA standards.

Definitions

Barriers

Proposed part 63 and EPA's final standards define “barriers” slightly differently. The Commission believes there is no substantive difference between the two definitions and has adopted the EPA definition at § 63.2. The EPA definition, among other things, provides that the Commission would determine a time period over which a material, structure or feature would perform its intended function. The regulation at § 63.115 requires DOE to describe the capability of each barrier to isolate waste. The description would include information on the time period over which DOE asserts that each barrier will perform its intended function including any changes during the compliance period. This information on expected performance will enable NRC to determine the period of time that any particular material, structure or feature prevents or substantially reduces the rate of movement of water or radionuclides from the Yucca Mountain repository to the accessible environment, or prevents the release or substantially reduces the release rate of radionuclides from the waste.

Ground Water

Proposed part 63 and EPA's final standards define “ground water” differently. To implement the EPA standard, part 63 has adopted the EPA definition for ground water and revised the use of the term “ground water” in the proposed rule accordingly. The single definition for ground water is provided at § 63.302.

High-Level Waste

Proposed part 63 and EPA's final standards define “high-level waste” slightly differently. The Commission believes there is no substantive difference between the two definitions and has modified its definition to more closely reflect the definition provided in the Nuclear Waste Policy Act of 1982 and the final standards.

Important to Waste Isolation

Proposed part 63 defined “important to waste isolation” in the context of meeting the individual dose limit for the postclosure period of the repository (i.e., disposal). This use of the term is important in defining the scope of the requirements for: DOE's quality assurance program (specified at subpart G); multiple barriers (specified at 10 CFR 63.113); performance confirmation (specified at subpart F); and changes, tests, and experiments (specified at 10 CFR 63.44). The Commission has expanded the definition of the term, “important to waste isolation” to include both the dose limit and the separate ground-water protection limits contained in the EPA standards.

Performance Assessment

Proposed part 63 and EPA's final standards define “performance assessment” slightly differently. The Commission believes there is nosubstantive difference between the two definitions and has adopted the EPA definition at § 63.2.

III. Public Comments and Responses

In preparing the final rule, the NRC staff carefully reviewed and considered more than 700 discrete comments enclosed in about 160 individual letters received during the public comment period. The NRC staff also identified and evaluated an additional 193 comments made at public meetings. To simplify the analysis, the NRC staff grouped all written and oral comments on the rule into the following six major topic areas:

(1) Regulatory Process and Licensing Process;

(2) Requirements for the Preclosure Period;

(3) Requirements for the Postclosure Period;

(4) General Requirements;

(5) Selected Topics; and

(6) Beyond the Scope of This Rulemaking.

1 Regulatory Process and Licensing Process

1.1 Promulgation in Advance of EPA Standards

Issue 1:
Is NRC's action in promulgating part 63 in advance of EPA standards beyond the scope of its authority?

Comment.
Many of those who commented on the NRC's proposed part 63 expressed concern that NRC was “usurping” EPA's authority by declaring its own standards and technical requirements in advance of EPA's issuance of final standards. For example, the State of Nevada pointed out the EnPA does not mandate a new Commission rule specific to Yucca Mountain to replace its general rule for licensing geologic repositories. It only requires modification of NRC's technical requirements and criteria, as necessary, to be consistent with new EPA standards once they are published. Further, the State pointed out that EnPA does not authorize the Commission to expand its licensing jurisdiction to include proposing standards for human safety and environmental protection

that are within the statutory mandate and jurisdiction of EPA.

Response.
The Commission acknowledges the statutory role given to EPA for setting standards for Yucca Mountain. It is with full recognition of that role that the Commission is publishing final criteria that are consistent with EPA's published standards. In the supplementary information published with the proposed rule, the Commission stated clearly that “* * * the authority and responsibility for setting public health and safety standards for radioactive waste disposal rest with EPA” (64 FR 8643; February 22, 1999). The Commission went on to say that “* * * [w]hen EPA issues final standards for Yucca Mountain or if new HLW legislation is enacted into law, the Commission will amend its criteria at 10 CFR part 63, if necessary, to be consistent with the final standards” (ibid. 8644).

It is true the EnPA did not direct the NRC to develop a new rule specific to Yucca Mountain to replace its general rule for licensing geologic repositories. It is also true the EnPA does not diminish NRC's authority under the Atomic Energy Act to conduct rulemaking nor to select the manner in which it will revise regulatory requirements. In the proposed rule, the Commission explained that since the initial technical criteria at 10 CFR part 60 were promulgated more than 15 years ago, there has been notable evolution in the capability of technical methods for assessing the performance of a geologic repository at Yucca Mountain. The Commission stated that “(t)hese new methods were not envisioned when the part 60 criteria were established and their implementation for Yucca Mountain will avoid the imposition of unnecessary, ambiguous, or potentially conflicting criteria that could result from the application of some of the Commission's generic requirements at 10 CFR part 60” (64 FR 8641). The Commission recognized that its generic part 60 requirements will need updating if applied to sites other than Yucca Mountain. However, the Commission elected not to conduct an update of part 60 now but, instead, decided to place all the regulations needed for the licensing of a repository at Yucca Mountain in a separate CFR part.
See
Response to Issue 3. The Commission explained that it “believes this to be the most direct and time-efficient approach to the specification of concise, site-specific criteria for Yucca Mountain that are consistent with current assumptions, with site-specific information and performance assessment experience, and with forthcoming EPA standards that must also apply solely to Yucca Mountain” (64 FR 8643). Consistent with the views expressed by most commenters, the Commission has awaited EPA's publication of final standards for Yucca Mountain and has changed its technical requirements and criteria to conform to EPA's standards, as required by law.

Issue 2:
Should NRC wait for EPA to release final standards before completing part 63?

Comment.
Commenters differed on the issue whether NRC should proceed with proposed part 63 or wait until after EPA publishes final standards. Commenters in favor of NRC moving forward with the proposed part 63 supported the proposed approach as protective of public health and safety and the environment. They cited timely specification of NRC regulations for the potential repository as a benefit for the national program. Others, however, believed that it was premature for NRC to publish final regulations. They felt that doing so would be contrary to the sequence set by Congress in the EnPA which directs EPA to issue radiation standards first and then for NRC to conform its technical requirements to those standards. These commenters saw no reason for NRC to act outside this time sequence and favored withdrawal of the proposed rule and resubmittal with any necessary adjustments after promulgation of EPA standards.

Response.
The EnPA specified that EPA was to publish radiation standards for Yucca Mountain not later than 1 year after receipt of the findings and recommendations of the National Academy of Sciences (NAS). It also directed NRC to modify its technical requirements and criteria not later than 1 year after EPA publishes final standards. The Commission believes that this schedule reflects Congress' intent to have a final regulatory structure before DOE would start preparation of a license application if Yucca Mountain were recommended as a site for a geologic repository. The NAS published its recommendations in August 1995. The NRC explained when it published its proposed rule, on February 22, 1999, that it had decided to proceed, even in the absence of EPA standards, because of the short time period allotted NRC to conduct its own rulemaking. In one year, NRC would have to modify its standards and requirements and to implement certain assumptions in the EnPA related to the effectiveness of postclosure oversight of the repository. The Commission also believed it was in the best interest of the national program to proceed, given that DOE could be in a position to submit a license application to NRC in 2002 (64 FR 8641). It is important to recognize that most of the requirements proposed at part 63 involve matters that are unaffected by the final EPA standards (e.g., licensing procedures, records and reporting, monitoring and testing programs, performance confirmation, quality assurance, personnel training and certification, and emergency planning). Now that EPA has published final standards, NRC is prepared to complete its implementing regulations at part 63 with due regard to the requirement in EnPA to be consistent with EPA's standards.

Issue 3:
Why is there a need to develop a site-specific disposal regulation for the Yucca Mountain site?

Comment.
Several commenters questioned NRC's need to develop a whole new body of site-specific regulations as opposed to revising its generic regulations at part 60, as necessary, to conform to the new, site-specific standards to be developed by EPA. These same commenters noted that certain portions of proposed part 63 depart significantly from part 60 (e.g., there are no quantitative subsystem requirements) and, in the view of several commenters, weaken the safety requirements for any proposed repository at Yucca Mountain.

Response.
The Commission is establishing a new, separate part of its regulations (at part 63) that would apply only to the proposed repository at Yucca Mountain. The Commission will leave existing, generic regulations at part 60 in place, modified only to state that they do not apply, nor may they be the subject of litigation, in any NRC licensing proceeding for a repository at Yucca Mountain. The Commission believes this to be the most direct and efficient approach for specifying concise, site-specific criteria for Yucca Mountain that are consistent with current assumptions, with site-specific information and performance assessment experience, and with EPA standards that apply solely to Yucca Mountain.

In developing these criteria, the Commission sought to establish a coherent body of risk-informed, performance-based criteria for Yucca Mountain that is compatible with the Commission's overall philosophy of risk-informed, performance-based regulation [“Use of Probabilistic Risk Assessment Methods in Nuclear Regulatory Activities—Final Policy Statement” (60 FR 42622; August 16, 1995)]. Stated succinctly, risk-informed, performance-based regulation is an

approach in which risk insights, engineering analysis and judgment (e.g., defense in depth), and performance history are used to: (1) Focus attention on the most important activities, (2) establish objective criteria for evaluating performance, (3) develop measurable or calculable parameters for monitoring system and licensee performance, (4) provide flexibility to determine how to meet the established performance criteria in a way that will encourage and reward improved outcomes, and (5) focus on the results as the primary basis for regulatory decision making. The Commission believes that creating a new part of its regulations to accomplish these objectives is preferable to modifying its generic requirements, given that EnPA and NAS laid out a fundamentally different approach for Yucca Mountain than was contemplated when the generic criteria were promulgated. Specifically, EnPA and NAS outlined an approach that would require the performance of a Yucca Mountain repository to comply with health-based standards established in consideration of risk to individuals in a hypothetical group. The law also stated that the new health-based standards were to be the only quantitative standards for the postclosure performance of the repository. This approach departs from the approach taken in the existing generic criteria which rely on compliance with cumulative release limits and separate, quantitative, subsystem performance objectives. Further, the Commission's current approach is consistent with EPA standards for Yucca Mountain. Therefore, after carefully considering the public comments, the Commission remains of the view that it is best to develop site-specific regulations—regulations that reflect an improved scientific understanding of the site; are based on state-of-the-art analyses; are consistent with the Commission's philosophy to implement risk informed regulation; and implement the separate, site-specific standards that EPA has issued for Yucca Mountain.

Commenters correctly pointed out that there are significant differences between part 60 and part 63. In the Commission's view, the part 63 regulations do not in any way lessen DOE's responsibility to site, design, and operate the proposed repository safely. Much has been learned regarding the expected performance of geologic repositories in general (Nuclear Energy Agency, Lessons Learnt from Ten Performance Assessment Studies, Paris, France, NEA/OECD Working Group on Integrated Performance Assessments for Geologic Repositories, 1997), and a potential Yucca Mountain repository in particular over the nearly two decades since part 60 was written. Part 63 reflects and incorporates much of this new information. The risk-informed, performance-based approach used to develop the rule (see SECY-97-300, “Proposed Strategy for Development of Regulations Governing Disposal of High-Level Radioactive Wastes in a Proposed Repository at Yucca Mountain,” U.S. NRC, December 24, 1997) eliminates arbitrary or prescriptive siting and design criteria, as well as detailed requirements such as quantitative subsystem performance objectives. That being said, however, part 63 still requires DOE to demonstrate reliance on multiple barriers and defense in depth, preservation of the retrieval option, implementation of a performance confirmation program, transparency in decision making, and application of rigorous quality assurance (QA). Moreover, as a result of public comments, other provisions have been added to part 63 to ensure the adequacy and sufficiency of DOE's compliance demonstrations. (See Multiple Barriers and Defense in Depth for additional discussion on quantitative subsystem requirements.)

1.2 Differences Between Part 63 and EPA Standards for WIPP

Issue:
Why is there a difference between the performance objectives in NRC's proposed 10 CFR part 63 for Yucca Mountain and EPA's 40 CFR part 191 standards used to certify the Waste Isolation Pilot Project (WIPP)?

Comment.
Many commenters expressed concern that NRC's proposed regulations for Yucca Mountain provided less protection than EPA's standards for WIPP. They regarded NRC's proposed regulations as less stringent than the standards for WIPP. Many cited the absence of separate criteria for protection of ground water in NRC's proposed regulation as evidence that the WIPP standards, which include separate requirements for protection of ground water, are more restrictive. Commenters also cited the differences in the individual protection limits [0.15 mSv/year (15 mrem/year) for WIPP compared to 0.25 mSv/year (25 mrem/year) limit for Yucca Mountain], and the compliance location (5 km for WIPP compared to approximately 20 km for Yucca Mountain). Generally, commenters asked NRC to set standards similar to, or more stringent than, those for WIPP. Some argued that a greater level of protection for people near Yucca Mountain was needed to offset potential exposures from other sources in the region (i.e., the Beatty low-level waste site and the Nevada Test Site, NTS).

Response.
Final EPA standards adopted numerical limits that are comparable to those applied at WIPP. Consistent with the views expressed by a majority of commenters, the Commission has awaited EPA's publication of final standards for Yucca Mountain and is adopting final part 63 criteria that are consistent with those limits, as required by law.

1.3 Multi-Staged Licensing

Issue 1:
Should DOE be allowed to begin to place waste in the repository or to store waste in surface facilities once NRC has determined that there is enough space for initial operations, or should DOE have to wait until site construction is complete?

Comment.
Many commenters indicated that NRC should not allow DOE to place waste in the repository until construction is complete. These commenters had general concerns that only after construction is completed would emergency equipment and safety precautions be available in case of an accident; and that any waste, if emplaced before completing construction, may pose an unnecessary risk to the construction workers. Alternatively, other commenters suggested that storage of waste at the repository should be allowed during construction as long as it does not pose any additional health or safety risk. The Nuclear Energy Institute (NEI) suggested that part 63 should be changed so that NRC could authorize DOE to construct all or part of the geologic repository operations area (GROA), and could authorize early use of the surface facilities to store waste.

Response.
The proposed rule retained the licensing phases as described at part 60. Once construction of the GROA is substantially complete (as specified at § 63.41), DOE may update its application and the Commission may issue a license to receive and possess source, special nuclear, or byproduct material at the GROA. Prior to issuing such a license, the Commission must make certain findings, such as: (1) Activities to be conducted at the GROA comply with the rules and regulations of the Commission, which will include radiation protection for workers; (2) adequate protective measures can and will be taken in the event of a radiological emergency; (3) there is no unreasonable risk to the health and safety of the public; and (4) construction of the GROA has been substantially completed. Construction is deemed

substantially complete, for this purpose, if among other things, DOE has completed construction of sufficient underground storage space for
initial
operations. Thus, part 63 provides DOE flexibility to plan for efficient repository operations for receipt and emplacement of waste because of the significant length of time required to complete excavation of the entire underground facility.

The DOE has not indicated to the Commission any intention to seek an authorization for early use of the surface facilities for storage of spent nuclear fuel. Such an authorization likely would necessitate a change to (or an exemption from) the regulations. Before NRC would make changes of this type to its regulations, NRC would need to publish the proposed changes and seek public comment.

Issue 2:
Should DOE have to prepare a second EIS to support a decision to issue a license amendment for permanent closure, as this may constitute a major Federal action?

Comment.
Commenters stated that the license amendment for permanent closure is a major Federal action and should require a new EIS (i.e., not rely upon the EIS prepared for the license application). They expressed the view that a decision to issue an amendment for permanent closure would include a decision that retrieval of the waste is not necessary and that the expected impacts of the waste affecting the environment far into the future and far beyond the site are acceptable. They also pointed out that the decision to issue the license amendment will be based, in part, on performance confirmation data collected after the original EIS is submitted. One commenter was concerned that the proposed requirement at § 51.67 did not explicitly state the need to include measures to mitigate impacts including transportation.

Response.
The regulations require DOE to supplement its EIS, if necessary, when the application for the license amendment for permanent closure is submitted [§ 63.51(b)]. The decision involved in granting the amendment would be a subset of decisions made in the original EIS and any supplements. A supplement to the EIS would need to address such things as substantial changes to the proposed action or significant new circumstances or information relevant to environmental concerns. The Commission believes the commenters' request for requiring DOE to consider these matters at the time of permanent closure is adequately covered by the regulations.

The Commission did not adopt the suggested change to § 51.67 to include a specific requirement to consider mitigation measures that the Council on Environmental Quality (CEQ) regulations dictate for the contents of the EIS, which include requirements for consideration of measures to mitigate impacts including transportation. DOE would need to comply with applicable CEQ requirements, and the Commission does not believe any regulatory changes are necessary to ensure compliance by DOE.

Issue 3:
Is there any limit on the types and amounts of radioactive materials (e.g., tons of HLW) that DOE would be allowed to receive and possess at Yucca Mountain if these materials were for site characterization activities or testing during construction?

Comment.
EPA suggested that, under the proposed rule (§§ 63.7(a) and 63.74(a)(1)), DOE could take any types and amounts of radioactive materials onto the site if it claimed that the materials were for site characterization activities.

Response.
EPA correctly notes that proposed part 63 does not place any specific quantitative limit on the amount of radioactive materials DOE might use for site characterization or testing. However, a specific numerical limit is unnecessary. Section 113(c)(2)(A) of the NWPA prohibits the DOE from using radioactive material in conducting site characterization activities unless the Commission concurs that such use is necessary. Under § 63.16(a), if DOE's planned site characterization activities include onsite testing with radioactive material, the Commission must determine whether the proposed use of radioactive material is necessary. The Commission would not concur in any DOE proposal to bring radioactive materials on site unless it was convinced that both the types and amounts were needed for site characterization. The proposed part 63 would not have allowed DOE to receive and possess “any types or amounts” of radioactive materials as suggested by EPA. Thus, changes to the proposed regulations are not needed.

Issue 4:
In a multi-staged licensing approach, does the NRC require that all information be available at the first stage (i.e., construction authorization) or will DOE be allowed to provide certain information in a “staged” manner consistent with that particular stage of the licensing process?

Comment.
DOE commented that it intends to provide a sufficient level of information to allow the NRC to make a finding of reasonable assurance at the time of the construction authorization in accordance with § 63.31. However, DOE stated that it would be helpful if the Commission would clarify its intent regarding the level of information required in the license application. In particular, DOE recommended three changes to proposed subpart B: (1) The language of § 63.21(b)(3) calling for “a detailed plan” to provide physical protection for HLW should be changed to a “description of the plan” to provide physical protection for HLW because this would be more consistent with the language used in other provisions of § 63.21(b) and would reflect what DOE believes to be an adequate level of detail on this subject; (2) the proposed § 63.24(a) requirement that the application be as complete as possible at the time of docketing based on reasonably available information should be moved to § 63.21(a) because this section provides requirements for the content of the license application; and (3) the proposed finding that the Commission would make to authorize construction at § 63.31(a)(6) that “DOE's proposed operating procedures to protect health and to minimize danger to life or property are adequate” should be changed to “DOE's proposed plan to develop operating procedures” because, at the time of construction authorization, details of the repository design will not, in some cases, be sufficient to support development of operating procedures and DOE does not believe that the procedures need to be in place at this stage of the licensing process. Another commenter suggested that the regulations for each licensing stage should be modified to state explicitly that the corresponding Commission finding must take into account “the scope of the authorization requested and the information available.”

Response.
part 63 provides for a multi-staged licensing process that affords the Commission the flexibility to make decisions in a logical time sequence that accounts for DOE collecting and analyzing additional information over the construction and operational phases of the repository. The multi-staged approach comprises four major decisions by the Commission: (1) Construction authorization; (2) license to receive and emplace waste; (3) license amendment for permanent closure; and (4) termination of license. The time required to complete the stages of this process (e.g., 50 years for operations and 50 years for monitoring) is extensive and will allow for generation of additional information. Clearly, the knowledge available at the time of construction authorization will be less than at the subsequent stages. However,

at each stage, DOE must provide sufficient information to support that stage. DOE has stated its intent to submit, and NRC expects to receive, a reasonably complete application at the time of construction authorization to allow the Commission to make a construction authorization decision. This is reflected in the requirement at § 63.24(a) that the application be as complete as possible in light of information that is reasonably available at the time of docketing. The Commission believes the regulations, as proposed, provide the necessary flexibility for making licensing decisions consistent with the amount and level of detail of information appropriate to each licensing stage. However, we agree with DOE that the proposed requirement at § 63.24(a) speaks to the content of the initial application, as well as to all subsequent updates, and, therefore, it has been included at the end of § 63.21(a).

Regarding DOE's recommendation that the requirement for a “detailed plan” to provide physical protection be changed to require a “description of the plan,” the Commission agrees that the suggested revision provides greater consistency with other provisions of § 63.21(b) and with § 72.24(o) and has revised § 63.21(b)(3) to require “(a) description of the detailed security measures for physical protection of high-level radioactive waste in accordance with § 73.51 of this chapter.” Notwithstanding this change, DOE must provide sufficient information at each stage of the licensing process to support that stage, and DOE must provide sufficient detail necessary to allow NRC to review DOE's design.

Regarding DOE's recommendation that the requirement that “DOE's proposed operating procedures” are adequate be changed to require the adequacy of “DOE's proposed plan to develop operating procedures,” the Commission believes a proposed plan to develop operating procedures is not sufficient to meet the requirement at § 63.31(a)(6). However, to support the construction authorization, the DOE must provide a sufficient level of information to allow NRC to review DOE's design, which would include any operating procedures that affect design.

Issue 5:
Is there any control over the site after license termination?

Comment.
Commenters expressed general concern regarding oversight of the site after license termination. One commenter supported the approach in proposed part 63 that leaves a single agency (DOE) responsible for control over the site after license termination.

Response.
License termination represents the end of NRC involvement with the repository. However, the Commission would not terminate the license unless and until all requirements have been met by DOE. License termination removes NRC oversight of the Yucca Mountain site, leaving DOE as the single Federal authority responsible for the site. Under the proposed part 63, the license amendment for permanent closure must include a DOE program for continued oversight to prevent any activity at the site that poses an unreasonable risk of breaching the geologic repository's engineered barriers or increasing radiation exposure of individual members of the public beyond allowable limits. The final part 63 continues to retain these same requirements. This is consistent with statutory direction in section 801(b)(2) of EnPA that the Commission's requirements assume that, following repository closure, the inclusion of engineered barriers and DOE's postclosure oversight will be sufficient to prevent any activity at the site that poses an unreasonable risk of breaching the repository's engineered or geologic barriers, and prevent any increase in the exposure of individual members of the public to radiation beyond allowable limits. The NRC will review the adequacy of DOE's program for continued oversight at the time DOE submits an application to amend the license for permanent closure.

Issue 6:
Are the standards for issuance of a license sufficiently clear?

Comment.
EPA asked why the term “unreasonable risk” was used at § 63.41(c) and suggested that reference to the dose limit may be more appropriate. EPA also asked what the basis was for judging what is necessary for “common defense and security” at § 63.42.

Response.
The standards for issuance of a license specified at § 63.41 and conditions of the license at § 63.42 provide a general description of standards and conditions that the Commission will apply to a license application for an HLW repository at Yucca Mountain. They would include, among other things, compliance with dose limits established by EPA in its final standards for Yucca Mountain. Although the terms identified by EPA (i.e., “unreasonable risk” and “common defense and security”) are general terms, clarification for what is required is provided earlier in the regulation. In particular, requirements for the content of the license application (specified at § 63.21) describe and clarify the types of analyses and information that would be necessary for DOE's demonstration of compliance with these standards and conditions including, among other things, reference to dose limits and physical protection of the repository (i.e., common defense and security). Revision of § 63.21 in the proposed rule to provide additional clarification of these terms is considered unnecessary.

1.4 Reasonable Assurance

Issue 1:
Should a concept other than “reasonable assurance” be incorporated into the implementing regulations for Yucca Mountain?

Comment.
EPA commented that generic disposal standards at 40 CFR Part 191 require compliance to be demonstrated with “reasonable expectation,” and that proposed NRC implementing regulations for Yucca Mountain at Part 63 require demonstration with “reasonable assurance.” EPA believes that a connotation has developed around “reasonable assurance” that could lead to an extreme approach of selecting worst case values for important parameters. EPA believes that “reasonable assurance” is appropriate for operating facilities or in the context of the nuclear power plant licensing program where facilities operate under active institutional controls during their lifetime. It is not appropriate, in EPA's view, for the licensing of a repository where projections of performance have inherently large ranges of uncertainty. EPA prefers “reasonable expectation” because it believes “reasonable assurance” has come to be associated with a level of confidence that is not appropriate for the very long term analytical projections that will be necessary for evaluating Yucca Mountain.

Another commenter expressed the view that the majority of people in the HLW field view “reasonable assurance” as being more stringent than “reasonable expectation.” This commenter expressed the concern that it is likely that by requiring “reasonable assurance” the NRC will be seen as implementing EPA's standards in a manner more stringent than intended by the EPA. The commenter also indicated that if it is NRC's position that the two terms are synonymous in the context of HLW disposal, then this should be made more explicit.

Response.
Confidence that DOE has, or has not, demonstrated compliance with EPA's standards is the essence of NRC's licensing process. It is the Commission's responsibility to determine whether DOE has or has not demonstrated compliance. The Commission does not believe that NRC's use of “reasonable assurance” as a basis

for judging compliance compels focus on extreme values (i.e., tails of distributions) for representing the performance of a Yucca Mountain repository. Further, if DOE is authorized to file a license application, and if the Commission is called on to make a decision, irrespective of the term used, the Commission will consider the full record before it. That record will include many factors in addition to whether the site and design comply with the performance objectives (both preclosure and postclosure performance standards) contained in Subparts E, K and L. The Commission could consider the QA program, personnel training program, emergency plan and operating procedures, among others, in order to determine whether it has confidence that there is no unreasonable risk to the health and safety of the public.

To avoid any misunderstanding and to achieve consistency with final EPA standards, the Commission has decided to adopt EPA's preferred criterion of “reasonable expectation” for purposes of judging compliance with the postclosure performance objectives. The Commission is satisfied that a standard of “reasonable expectation” allows it the necessary flexibility to account for the inherently greater uncertainties in making long-term projections of a repository's performance. The Commission agrees with EPA and others that it is important to not exclude important parameters from assessments and analyses simply because they are difficult to precisely quantify to a high degree of confidence. By adopting what EPA has characterized as a more flexible standard of “reasonable expectation” for determining compliance with postclosure performance objectives, the Commission hopes to make clear its expectations. The Commission expects that the required analyses of postclosure performance will focus on the full range of defensible and reasonable parameter distributions, and that they should not be constrained only to extreme physical situations and parameter values. For other determinations regarding compliance of the repository with preclosure objectives, the Commission will retain a standard of “reasonable assurance,” consistent with its practice for other licensed operating facilities subject to active licensee oversight and control.

Issue 2:
Does the term “reasonable assurance” denote a specific statistical parameter related to either the probability distribution of calculated individual doses or important variables used in that calculation?

Comment.
EPA commented that a connotation has developed around “reasonable assurance” that could lead to an extreme approach to selecting worst case values for important parameters used to calculate individual dose (for example, precipitation rates, seepage rates, and flow in the unsaturated zone). According to the EPA, that approach, coupled with an equally extreme approach in selecting engineered barrier performance factors, would lead to assessments that represent situations with little or no probability of occurring but which become the basis for licensing decisions. The EPA concludes that the application of the “reasonable assurance” standard: (1) Is inconsistent with the NAS recommendation to use “cautious, but reasonable” assumptions when projecting the performance of the geologic repository; and (2) would result in applying margins of safety beyond the standard for individual protection set by EPA, which, in effect, alters that standard.

Another commenter noted that the proposed part 63 makes it clear that compliance is to be based on calculations of “expected annual dose” and that this requirement is completely consistent with the recommendation in the NAS report on “Technical Basis for Yucca Mountain Standards,” which recommends that the mean values of calculations be the basis for comparison with the NAS recommended standards. However, the commenter was concerned that “reasonable assurance” may be interpreted to be more stringent than the mean values of calculations of individual dose and recommended that it be made clear that, in the context of Yucca Mountain, “reasonable assurance” refers to the mean or expected value of the relevant probability distribution.

Response.
As stated previously, in order to avoid further misunderstanding of its intent, the Commission will adopt EPA's preferred standard of “reasonable expectation” for purposes of judging compliance with the numerical postclosure performance objectives. However, the Commission wants to make clear that its proposed use of “reasonable assurance” as a basis for judging compliance was not intended to imply a requirement for more stringent analyses (e.g., use of extreme values for important parameters) or for comparison with a potentially more stringent statistical criteria (e.g., use of the 95th percentile of the distribution of the estimate of dose).

2 Requirements for the Preclosure Period

2.1 Preclosure Safety Analysis

Issue 1:
Is the use of an Integrated Safety Assessment (ISA) appropriate for evaluation of the preclosure safety of a repository at Yucca Mountain?

Comment.
One commenter questioned the use of an ISA, as derived from chemical process safety analyses, to evaluate preclosure safety because there is not yet much experience in regulating with the ISA and suggested that requirements for monitored retrievable storage (as contained in part 72) should be applicable to the GROA and should be used in place of the proposed requirements of part 63.

Response.
The Commission considers necessary the analysis referred to in the proposed rule as an “integrated safety analysis”. However, for clarity, in the final rule, the Commission has changed the name of the analysis to “preclosure safety analysis” (PSA).

The proposed rule identifies the need for, and general scope of, the analysis to be done to demonstrate compliance with the performance requirements for the operational phase of the repository (§§ 63.111(a) and (b) and 63.112(e)). The Commission did not intend to imply, however, that a particular approach, such as that used for chemical process safety analyses, was required. The Commission's intention was to identify ISA as a broad category of analyses to be used by DOE in its evaluation of repository operations and design in the context of meeting the preclosure performance objectives. ISA was proposed as a general term for these preclosure analyses, much as the general term “performance assessment” is used to denote the analyses used to evaluate postclosure performance. To avoid confusion with any particular type of analysis associated with other industrial facilities, the term “ISA” will be replaced by the more general term “preclosure safety analysis (PSA).” The Commission intends that DOE have broad flexibility in structuring its PSA for purposes of demonstrating compliance with the requirements at § 63.112.

The Commission recognizes that there are similarities between a facility regulated by Part 72 and the GROA facilities proposed for Yucca Mountain. However, there are important differences (e.g., Part 72 does not consider a mined facility) that make it impractical to merely adopt the requirements of the current part 72. The Commission has used and adopted relevant portions of existing regulations (e.g., part 50), including part 72, to the

extent practical, during the development of proposed part 63.

Issue 2:
Is the probability of a design basis event (DBE) based on the event sequence or just an initiating event? Are the criteria for Category 2 DBEs too stringent?

Comment.
DOE suggested that the rule should be clarified as to whether event sequences or single initiating events are to be used in determining the probabilities of DBEs. DOE also noted that the proposed rule would define Category 2 DBEs as those that have one chance in 10,000 of occurring before permanent closure of the repository or an annual probability of about 10
−6
. DOE stated that:

Designing to this probability is a reasonable goal in general, but that there are specific concerns with applying the definition to natural events, which have existing precedent for the magnitude and frequency of events to be included *ensp;* *ensp; A 1010
−6
earthquake is far beyond normal design considerations.

DOE suggested the following definitions of DBEs:

Definition for Category 1 DBEs should be revised to read: “natural events and human-induced event sequences.”

Definition for Category 2 DBEs should be revised to read: “other human-induced event sequences that have at least one chance in 10,000 of occurring before permanent closure of the geologic repository, and (b) appropriate consideration of natural events (phenomena) that have been historically reported for the site and the geologic setting (referred to as Category 2 events).”

Response.
The Commission agrees that the basis for determining the probability for design basis events and what initiating events should be considered in the safety analysis should be clarified. The Commission considers that the changes to the rule suggested by DOE are not sufficiently clear and has not adopted these changes in the final rule. However, the Commission has revised the rule for clarity as follows: (1) A new term “initiating event” is defined; (2) the present term “design basis event” is replaced with a new term “event sequence;” and (3) § 63.102(f) is revised to clarify the scope of the PSA and the requirements for the inclusion or exclusion of specific, naturally-occurring, and human-induced hazards in the safety analysis.

The proposed rule described the ISA (referred to as PSA in final part 63) as a systematic examination of the hazards and their potential consequences [see § 63.102(f)]. In the Supplementary Information for the proposed rule, Category 2 design basis events were discussed as follows:

The analysis of a specific Category 2 design basis event would include an initiating event (e.g., an earthquake) and the associated combinations of repository system or component failures that can potentially lead to exposure of individuals to radiation. An example design basis event is a postulated earthquake (the initiating event) which results in (1) the failure of a crane lifting a spent fuel waste package inside a waste handling building, (2) damage to the building ventilation (filtration) system, (3) the drop and breach of the waste package, (4) damage to the spent fuel, (5) partitioning of a fraction of the radionuclide inventory to the building atmosphere, (6) release of some radioactive material through the damaged ventilation (filtration) system, and (7) exposure of an individual (either a worker or a member of the public) to the released radioactive material.

The Commission intended that the probability of the entire event sequence, including initiating event(s) and the associated combinations of repository system or component failures, be considered in dose calculations. The proposed rule has been revised by replacing the previous term “design basis event” with new terms “initiating event” and “event sequence” and associated definitions. These changes clarify that the appropriate probability is based on the entire event sequence, which includes the initiating event(s) and associated combinations of repository system or component failures relating to the potential release of radioactive material.

The two critical aspects of the PSA in the context of this issue are (1) the identification of the event sequences that have probabilities greater than or equal to one chance in 10,000 of occurring before permanent closure and (2) the associated dose consequences. Following the intent of risk-informed performance-based regulation, designation of specific design basis criteria in the regulation is not appropriate. The goal of the DOE design activity should be to demonstrate that the dose limits expressed in § 63.111 will be met, taking into consideration site-specific information regarding the geologic setting and human activities in the surrounding environs. For example, if a hazard (or the low probability events of the hazard spectrum) is deemed unreasonable for the Yucca Mountain site, DOE can exclude it from consideration in the PSA provided proper technical justification is presented in accordance with § 63.112(d). Thus, while the regulation specifies a lower limit on the probability of event sequences, the risk-informed NRC regulation anticipates that DOE will develop a clear technical basis for the event sequences included/excluded from the PSA. The Commission did not intend to specify cut-off probabilities for initiating events but recognizes that certain initiating events may not be appropriate for inclusion in the PSA. Therefore, the rule, at § 63.102(f), has been revised to include the following description of considerations that can be used by the DOE to limit the inclusion of initiating events in the PSA:

Initiating events are to be considered for inclusion in the preclosure safety analysis for determining event sequences only if they are reasonable (i.e., based on the characteristics of the geologic setting and the human environment, and are consistent with precedents adopted for nuclear facilities with comparable or higher risks to workers and the public).

Issue 3:
How should doses be estimated in evaluating repository operations during the time before permanent closure? Can different approaches be used for evaluating Category 1 and Category 2 DBEs (event sequences)?

Comment.
Further clarification is needed on the scope of the dose calculations associated with DBEs (event sequences).

For Category 1 DBEs [event sequences], DOE recommended a realistic or best-estimate analysis for direct exposures from a single event. For airborne pathways, DOE proposed including submersion, inhalation, and ingestion. DOE also recommended that the doses from all Category 1 DBEs (event sequences) be aggregated.

For Category 2 DBEs (event sequences), DOE recommended dose calculations be based on suitably conservative values for direct exposure and airborne pathways including submersion, and inhalation, but not ingestion. DOE recommended that ingestion not be considered because the focus is on an acute dose, not a dose that occurs slowly over time as is the case for ingestion. Also, the emergency planning would mitigate, if necessary, contamination relevant to ingestion. DOE also recommended that Category 2 DBEs [event sequences] be analyzed on an event sequence by event sequence basis.

Response.
The Commission has revised the proposed rule, at § 63.111(b)(1) and (2), to clarify that (1) the doses from consequence analyses for Category 1 event sequences are to be aggregated to a single estimate and (2) the dose from the consequence analysis for each Category 2 event sequence is to be estimated for that specific event sequence only. Thus, each Category 2 event sequence dose is to be evaluated

separately. The doses from Category 2 event sequences that might occur at different times during the preclosure period are not to be aggregated.

DOE raised a number of concerns with the scope of the dose calculations associated with event sequences. Generally, DOE called for details that are typically found in regulatory guidance rather than regulation. Although such guidance is expected to be included in the Yucca Mountain Review Plan (YMRP) rather than in the regulation, the NRC staff response to DOE's concerns regarding dose calculations associated with event sequences is summarized below.

Within the context of the ISA (PSA), DOE is expected to identify the relevant initiating events and event sequences and estimate potential radiologic exposures. Part 63 provides flexibility to DOE in selecting an appropriate approach for estimating doses, including selection of pertinent exposure pathways and the degree of conservatism or realism to include in the analysis. DOE will need to defend and support whatever approach it selects for identifying initiating events and analyzing event sequences. In the selection of a particular approach, DOE will need to consider the uncertainties and limitations associated with a particular method of analysis and data.

DOE suggested that a “realistic or best-estimate” analysis is appropriate for Category 1 event sequences, and a “suitably conservative” analysis is appropriate for Category 2 event sequences. Once again, the approach in the rule is to provide DOE flexibility to select the type of analysis it believes most appropriate for the license application. Whatever approach DOE uses will need to be supported, taking into account uncertainties. Therefore, analyses relying on point values (e.g., best estimate values) will need to discuss how uncertainties are taken into account.

DOE suggested that dose estimates for Category 1 DBEs (event sequences) should be aggregated into a single annual dose estimate. This approach is consistent with historical practices and is acceptable to NRC. DOE also suggested that the potential dose arising from the occurrence of each Category 2 DBE (event sequence) should be estimated separately (i.e., not be aggregated). The Commission agrees that each Category 2 event sequence is to be evaluated individually, as this approach is consistent with historical practices. Also, analyzing each event sequence separately provides a high degree of transparency in the analysis, thus allowing NRC to evaluate the postulated events, the associated event sequences, and the engineered components that affect the likelihood and magnitude of potential releases of radioactive material. The Commission has revised the rule at § 63.111(b)(1) and (2) to clarify that dose estimates for Category 1 event sequences are to be aggregated, but those of Category 2 event sequences are to be analyzed and documented individually.

DOE also suggested that, for Category 2 DBEs (event sequences), dose calculations for ingestion are not necessary. The Commission sees no compelling logic for the specific pathways for dose calculations being different for Category 1 and Category 2 event sequences. Dose should be calculated considering all pathways relevant to an event sequence. Consistent with the Commission requirements elsewhere, the DOE must consider all pathways in demonstrating compliance with § 63.111. The risk-informed regulation anticipates that DOE will present in its license application the magnitude of, and the technical basis for, the dose contribution of various pathways, including the technical bases for eliminating any pathway.

Issue 4:
What precedents, if any, do NRC regulatory guides developed for other applications, such as nuclear power plants, have for use in developing DBEs (event sequences) for a potential repository at Yucca Mountain?

Comment.
DOE asked for clarification about the role of precedents in other regulatory guides (e.g., consideration of earthquakes, aircraft crashes, tornadoes, and flooding) in determining what should be considered in the development of DBEs (event sequences) (especially for Category 2). DOE also commented that development of credible natural events, for Category 2 DBEs (event sequences), would require only following applicable regulatory precedents and considering severe natural phenomena that have been historically reported for the site and geologic setting.

Response.
The applicability of regulatory guidance developed for facilities other than a high-level waste repository will need to be considered on a case-by-case basis for applicability to high-level waste disposal at Yucca Mountain. For the guidance to be appropriate, it should be generally applicable to nuclear facilities with comparable or higher risks to workers and the public than the potential repository at the Yucca Mountain site (see discussion under Issue 2).

Issue 5:
What is the status of NRC's provisional acceptance of DOE's Topical Report on Seismic Design for Yucca Mountain with respect to event sequences in part 63?

Comment.
DOE inquired about the status of NRC's provisional acceptance of DOE's Topical Report on Seismic Design for Yucca Mountain with respect to event sequences in Part 63.

Response.
DOE's Topical Reports 1 and 2 on Seismic Design for Yucca Mountain were provisionally accepted prior to NRC's issuance of proposed requirements at part 63. The applicability of DOE's seismic design methodology will be reviewed after final part 63 requirements are in place and DOE has completed Topical Report 3.

Issue 6:
Should there be an explicit requirement for an analysis of the effects of any plans for use of the air space above the GROA?

Comment.
One commenter recommended an analysis of the effects of any plans for use of the air space above the GROA.

Response.
Any plans for use of the air space above the GROA that would affect compliance with the performance objectives should be included in the PSA. The Commission finds no reason for a separate requirement for such an analysis.

Issue 7:
Will NRC have its own experts to evaluate what can happen during repository operations or will NRC rely on the DOE analysis?

Comment.
One commenter inquired whether NRC had independent experts to develop probabilities for DBEs, or would NRC simply rely on DOE analyses.

Response.
The Commission will perform an audit review of the DOE license application including a review of the technical basis for initiating events and event sequences. In performing the audit review, the NRC will use a variety of its technical staff with appropriate technical experience and skills, and experience with comparable activities for other facilities (handling of nuclear fuel at nuclear reactors and fuel fabrication facilities) regulated by NRC. Additionally, the NRC's HLW contractor (The Center for Nuclear Waste Regulatory Analyses, CNWRA) has a wide range of technical expertise to assist NRC staff in any review conducted.

Issue 8:
Is the terminology in the rule consistent and adequate to convey what is required?

Comment.
DOE identified instances where particular words or phrases in Part 63 lacked clarity and suggested the following changes:

Section 63.112(b) should be revised to read: “An identification and systematic analysis of naturally-occurring and

human-induced hazards at the geologic repository operations area, including a comprehensive identification of potential design basis events” (The definition of DBEs makes no link to consequence, whereas § 63.112(b) inappropriately implies such a link).

The word “accidents” in § 63.112(e) should be replaced with “design basis events” (the word “accidents” is not defined (also in § 63.161)—use of DBE is consistent with language elsewhere in part 63).

Response.
The Commission agrees that the use of the word “accident” in § 63.112(e) is vague and will replace “accident” by “event sequence.” Additionally, the Commission has revised the language at § 63.112(b) to remove the inappropriate reference to consequences.

Issue 9:
Should the proposed rule prescribe requirements for the ISA (PSA)?

Comment.
DOE noted that prescribing requirements for the ISA (PSA) at § 63.112 was inconsistent with the overall performance-based approach in the rule.

Response
. The rule identifies topics that need to be included in the PSA but does not prescribe either the methodology to use or the depth to which these topics need to be addressed. part 63 appropriately identifies the topics that need to be included in the PSA to ensure DOE's analysis is complete and yet gives DOE flexibility to determine the level of detail needed to address each topic properly. This performance-based approach provides DOE latitude to adjust the technical rigor of its evaluation of any particular topic in a manner that is consistent with the topic's importance to safety.

2.2 Retrievability

Issue 1:
Will NRC require DOE to demonstrate that the waste package is retrievable?

Comment.
Some commenters were concerned that NRC's proposed regulations required DOE to submit plans for retrievability, but did not require an actual demonstration that the plans were feasible. Some commenters suggested that the NRC should require DOE to demonstrate the feasibility of its retrieval plans.

Response.
If necessary to protect public health and safety, waste package retrieval in a deep geologic repository would be a first-of-a-kind endeavor with unique engineering and geotechnical challenges. The Commission recognizes that the retrieval operation would be an unusual event, and may be an involved and expensive operation (U.S. Nuclear Regulatory Commission, “Staff Analysis of Public Comments on Proposed Rule 10 CFR part 60, ‘Disposal of High-Level Radioactive Wastes in Geologic Repositories',” Office of Nuclear Regulatory Research, NUREG-0804, December 1983; p. 11). As such, DOE can expect that its plans and procedures in this area will receive extensive, detailed review by the NRC staff as part of any construction authorization review. The feasibility and reasonableness of DOE's retrieval plans will be reviewed by the NRC staff at the time of the license application submittal.

However, the Commission does not envision that DOE will need to build full-scale prototypes of its retrieval systems to demonstrate that its retrieval plans are practicable at the time of construction authorization. Rather, DOE needs to design (and build) the repository in such a way that the retrieval option is not rendered impractical or impossible.

Issue 2:
Why did NRC set an upper limit for retrieval at 50 years after waste emplacement operations are initiated?

Comment.
Some commenters expressed a belief that the period of waste package retrieval could be accomplished beyond 50 years, and there should be flexibility for extending the period of retrievability to longer time periods. One commenter suggested that the repository should be monitored to determine if there will be problems (e.g., too high a temperature, too much water inflow) that would require the waste to be retrieved. The same commenter suggested that stewardship of the waste be maintained (indefinitely) so that waste could be made available for future energy needs.

Response.
The 50-year limit on waste retrieval operations was adopted from the generic requirements found at part 60. At the time part 60 was first promulgated, the Commission solicited comment on what was then a proposed 110-year retrieval period (46 FR 35282; July 8, 1981). However, after an analysis of public comments, it was determined that the Commission's earlier proposal was excessive, and the shorter 50-year period was decided upon (U.S. Nuclear Regulatory Commission, “Staff Analysis of Public Comments on Proposed Rule 10 CFR part 60, ‘Disposal of High-Level Radioactive Wastes in Geologic Repositories',” Office of Nuclear Regulatory Research, NUREG-0804, December 1983). In specifying this time period, the Commission noted that the 50-year period was “provisional” and subject to possible modification (i.e., longer periods) in light of both the planned waste emplacement schedule and completion of the performance confirmation program and a review of those results. After 50 years of waste emplacement operations and performance confirmation, the Commission previously reasoned, it is likely that significant technical uncertainties will be resolved, thereby providing greater assurance that the performance objectives will be met. It should be noted that DOE is free to design the repository for retrieval periods greater than 50 years. In fact, the Commission understands that DOE is contemplating working designs that may provide for a retrieval period of up to 300 years (see “Supplement to the Draft Environmental Impact Statement for a Geologic Repository for the Disposal of Spent Nuclear Fuel and High-Level Radioactive Waste at Yucca Mountain, Nye County, Nevada,” Office of Civilian Radioactive Waste Management, DOE/EIS-0250DS, May 2001). Thus, as recommended in this comment, allowance for longer waste retrieval periods greater than 50 years is permitted under the regulation.

As for longer retrieval periods that would permit the recovery of the HLW as a potential resource, the Commission has previously noted that its retrieval provision is not intended to facilitate recovery. Waste retrieval is intended to be an unusual event only to be undertaken to protect public health and safety.

Issue 3:
If retrieval is necessary, what happens to the retrieved waste?

Comment
. One commenter inquired as to the disposition of the waste if it is determined that retrieval is necessary.

Response
. Proposed Part 63 does not specifically address any required actions for the handling of retrieved waste from an operating geologic repository, but § 63.21(c)(19) [moved to § 63.21(c)(7) in the final rule] does require that DOE's Safety Analysis Report include a description of its plans for the alternate storage of the radioactive wastes, should retrieval be necessary. Retrieved waste would need to be controlled in compliance with applicable regulations at the time of retrieval.

2.3 Performance Confirmation

Issue 1:
What is the objective of the performance confirmation program?

Comment.
DOE commented that the general requirements for performance confirmation at § 63.131(a) and requirements for confirmation of geotechnical and design parameters at § 63.132(a) do not reflect the Commission's risk-informed, performance-based approach to regulation because the requirements do

not explicitly focus the performance confirmation program on data linked to the performance assessment. DOE stated that the performance confirmation program, when tied to a performance-based approach, should focus on the verification of the performance assessment. DOE stated that this approach would allow DOE and NRC to focus attention and resources on those parameters and processes that are significant contributors to repository performance and to uncertainties in that performance.

Response.
The objective of the performance confirmation program is to confirm the assumptions, data, and analyses that led to the findings that permitted construction of the repository and subsequent emplacement of the wastes. Consistent with NRC's performance-based approach, the NRC will make findings with respect to each of the performance objectives in Part 63, Subpart E, and not just the postclosure performance objective specified at § 63.113(b). The general requirements for the performance confirmation program at § 63.131(a)(1) and (a)(2) state that the program must provide data that indicate whether: (1) Subsurface conditions encountered and changes in those conditions during construction and waste emplacement are within limits assumed in the licensing review and (2) natural and engineered systems and components required for repository operation, and that are designed or assumed to operate as barriers after permanent closure, are functioning as intended and anticipated. These requirements are intended to encompass subsurface conditions and design assumptions related to both operational (preclosure) and postclosure repository performance. Should the Commission authorize construction of a geologic repository at Yucca Mountain, the NRC staff will conduct an ongoing, performance-based inspection program to evaluate DOE's compliance with the performance objectives and any conditions established in that construction authorization per § 63.75.

The general requirements at § 63.131(a) explicitly link the performance confirmation program to DOE's performance assessment, albeit in terms of the barriers designed or assumed to function after permanent closure. Although the primary focus of the performance confirmation program is on postclosure performance of the repository, and the NRC recognizes DOE's desire to focus on verifying the performance assessment (e.g., postclosure performance), it is important that the general requirements also include consideration of operational aspects of repository performance, for example, the ability to retrieve waste as required at § 63.111(e). An organized program of collecting subsurface information during repository construction and operation that confirms the design assumptions regarding the ability to retrieve waste is therefore an important performance confirmation activity. The NRC believes that the general requirements at § 63.131(a) allow DOE the flexibility to develop and implement an effective performance confirmation program focused on confirming assumed subsurface conditions and assumed functionality of geologic and engineered systems and components important to postclosure performance (i.e., performance of barriers important to isolation) and/or preclosure repository operations (e.g., retrievability). In the proposed rule, the definition of performance confirmation in § 63.2 and the discussion of performance confirmation in § 63.102(m) do not clearly reflect the intent of § 63.131(a) and have been revised accordingly in the final rule. To adopt the changes to §§ 63.131(a) and 63.132(a) requested by DOE would remove consideration of operational aspects of repository performance from the performance confirmation program. For these reasons, the Commission does not agree that these changes are appropriate and has not adopted them.

Issue 2:
Are the requirements for the performance confirmation program too prescriptive?

Comment.
Some commenters were concerned with the level of detail provided in the requirements for the performance confirmation program. NEI commented that the regulation should provide for ongoing programs of monitoring and testing to improve information but also stated that the specified requirements should be made less prescriptive. NEI stated that §§ 63.132-134 (respectively, Confirmation of geotechnical and design parameters, Design testing, and Monitoring and testing waste packages) were inconsistent with the overall performance-based nature of the regulation. NEI recommended that these requirements be deleted because they are unnecessary and counterproductive to § 63.131 in that they provide more detail and remove flexibility already in the rule. NEI also recommended minor word changes to the definition of performance confirmation in § 63.2 and the discussion of performance confirmation in § 63.102(m) to lessen the potential for overly prescriptive interpretations of what is expected of the performance confirmation program. DOE commented that the minimum list of geotechnical parameters in § 63.132(c) is overly prescriptive and is not needed or appropriate. DOE recommended revising the requirement to state that DOE will determine the parameters, measurements, and observations appropriate for inclusion in the program. DOE also recommended revising § 63.133, which restricted design testing to in situ testing, to allow performance of some of the design testing at other locations, such as laboratories, other test facilities, or boreholes outside of the repository block. In addition, DOE also suggested revising the wording of § 63.133(c) to make it clear that testing of backfill is required only if backfilling the emplacement drifts is planned. Another commenter noted that while § 63.134 requires a program to monitor and test waste packages, the commenter found no statement of objectives or criteria for the monitoring and test program. The commenter was concerned that the regulation could be used to drive a very large and costly full scale test program and recommended that the objectives and criteria be stated.

Response.
The Commission agrees with the commenters that §§ 63.132-134 were too prescriptive and has modified these sections accordingly. However, the Commission does not agree with the comment that §§ 63.132-134 are inconsistent with the overall performance-based nature of the rule and therefore should be deleted. The Commission believes the requirements for performance confirmation set forth in §§ 63.132-134 are consistent with the overall performance-based approach to part 63. Consistent with this approach, the rule does not prescribe specific subsystem requirements. The absence of subsystem requirements is a concern to a number of commenters. Some commenters believe that the rule places too much reliance on the total system performance assessment (refer to discussion of issues under Postclosure Safety Assessment and Multiple Barriers and Defense in Depth). The Commission believes these concerns are partly addressed through an effective performance confirmation program focused on confirming assumed subsurface conditions and assumed functionality of geologic and engineered systems and components important to postclosure performance and the related performance assessment. Specific concerns that these requirements are either too prescriptive or too limiting are discussed in the following paragraphs.

Section 63.132 (Confirmation of geotechnical and design parameters)

provides additional requirements related to the underground facility including comparing the original design bases and assumptions to information obtained during construction and operation, determining their significance to performance, and reporting this information, including recommended design changes, to the Commission. Section 63.132(c) does prescribe specific measurements and observations to be made by DOE. Because the design of the repository is evolving, it is not clear that, in the future, this list will be an acceptable minimum list of measurements and observations to be made. For the same reason, it is not clear that, in the future, all items in the list will be technically justifiable within the context of operational and postclosure performance of the repository. The Commission believes that it is DOE's responsibility to specify the important geotechnical and design parameters to be evaluated through observation and measurement during construction and operation, subject to NRC approval through review and evaluation of the license application. DOE will provide this information in their performance confirmation plan included in the license application. If necessary, the NRC staff will provide guidance to DOE in this area through pre-licensing interactions and/or the YMRP. Section 63.132(c) has been revised to reflect these considerations.

Section 63.133 (Design testing) provides requirements for in situ testing of seals and backfill and the thermal interaction effects of waste packages, backfill, rock, and ground water. DOE's recommendation that § 63.133 be revised so as to not limit testing to in situ testing only is reasonable. Section 63.133(a) has been revised accordingly. The NRC has also revised § 63.133(a) to generally reference “engineered systems and components,” with examples, so as to not limit tests to specific features that may or may not be included in the final design of the repository. Finally, the Commission has revised § 63.133(c) to require specific testing of the effectiveness of backfill placement and compaction only if backfill is included in the repository design.

Section 63.134 (Monitoring and testing waste packages) provides specific requirements for monitoring and testing waste packages consistent with the objectives of the performance confirmation program established at § 63.131(a). Waste packages are important engineered components designed to operate as barriers after permanent closure. Because the assumed long-term performance of waste package materials is based on short-term experimental data, monitoring waste package performance and related laboratory experiments are appropriate performance confirmation activities. Although the NRC recognizes the need for reasonable cost constraints, it is important to note that it is DOE's responsibility to develop the details of a performance confirmation plan that focuses on those natural and engineered systems and components important to repository performance and operation. The requirements allow DOE the flexibility to develop a focused and effective performance confirmation program. An alternative approach would be to prescribe in detail the specifics and limits of that program. The Commission does not want to limit DOE's options regarding testing methodologies and has chosen not to follow that approach. Note, however, that NRC will evaluate the adequacy of the performance confirmation program in the course of its review of the license application.

Issue 3:
Is the performance confirmation data required to be used in the updating of the performance assessment?

Comment
. EPA recommended that performance confirmation data should be explicitly identified as information to be included in the update of the performance assessment required at the time of the amendment for permanent closure [§ 63.51(a)(1)].

Response.
The Commission agrees with the commenter and has modified the rule accordingly.

2.4 Preclosure Operations Activities

Issue:
Should the proposed rule specify environmental monitoring requirements for regulating releases from the preclosure operational activities?

Comment.
The EPA commented that requirements for environmental monitoring during the operational phase of the repository were not in the proposed rule and there were no methods stated in the rule for enforcement of the preclosure requirements.

Response.
The Commission considers that proposed part 63 has sufficient requirements for environmental monitoring during the operational phase of the repository and is not revising the rule on this issue. The Commission has included environmental monitoring requirements for radioactive releases in part 63. Sections 63.111 and 63.112 require DOE to account for, design against, and monitor any potential event sequences that could lead to radioactive releases. As part of the PSA (§ 63.112), for example, DOE is to describe its design and operating procedures for monitoring and controlling radioactive releases. Consistent with its National Environmental Policy Act (NEPA) responsibilities, DOE has already described its plans and procedures for the monitoring (and mitigation) of environmental impacts due to the operation of the geologic repository, including radioactive releases, in its DEIS for Yucca Mountain.

Regarding the comment on the lack of enforcement methods in the rule, subpart J of part 63 addresses enforcement at a level of detail that the Commission has typically used in all its regulations. Specific policy and procedure issues for enforcement activities are described in NRC's “General Statement of Policy and Procedure for NRC Enforcement Actions,” the NRC enforcement manual, and supplemental guidance. The Commission believes this is an appropriate approach for its regulations and will retain the current language as in the proposed rule under subpart J. The Commission plans to develop specific changes to the enforcement policy and procedures as part of development of inspection and oversight plans for implementation of part 63.

2.5 Emergency Planning Criteria

Issue 1:
If local emergency first-responder capabilities and emergency medical services are not sufficient for reacting to nuclear accidents at the geologic repository, will the NRC require DOE to enhance existing local capabilities in the Yucca Mountain region?

Comment.
Commenters expressed concern that current local emergency and medical services are not adequate to respond to potential nuclear accidents at a geologic repository at Yucca Mountain. Accordingly, it was suggested that NRC include, as a license condition to operate the repository, a requirement that DOE enhance local capabilities for responding to potential nuclear accidents.

Response.
Part 63 (Subpart I) requires DOE to submit an emergency plan for coping with radiological accidents. NRC's review of DOE's emergency plan will evaluate the adequacy of the plan including such things as the capability to respond to accidents and medical assistance for treatment of radiological injuries. Where DOE's emergency plan is found to be inadequate, the NRC, if necessary, can impose license conditions that require DOE to correct any deficiencies. (See also response to Issue 3 below.)

Additionally, U.S. Federal Emergency Management Agency (FEMA) regulations, as well as DOE orders, require that DOE have an emergency response capability that is adequate to meet anticipated accidents, including potential radiological accidents. DOE is responsible for ensuring that the emergency treatment capability exists and is documented in its emergency plan, which is subject to NRC review in accordance with § 63.161.

Issue 2:
Will DOE's emergency plans be sufficiently comprehensive to include such scenarios as emergency evacuation procedures and responses to terrorist activity?

Comment.
Some commenters were concerned whether DOE would have adequate, effective, and sufficiently comprehensive plans and procedures to address most, if not all, potential accidents, incidents, and/or contingencies.

Response
. The rule requires DOE to have plans to cope with radiological accidents (emergency planning at § 63.161) and provide for physical protection (§ 63.21(b)(3)). These plans are required to address a number of criteria to ensure that DOE is prepared to respond, both on site and off site, to accidents, and that DOE has the capability to detect and respond to unauthorized access and activities that could threaten the physical protection of HLW. As noted in the previous response, NRC and FEMA regulations, as well as DOE orders, require that DOE have adequate plans and procedures in place to address any potential accidents and incidents. DOE's emergency plan and physical protection plan are subject to NRC review. The Commission believes that the requirements for DOE's plans for emergencies and physical protection expressed in the proposed part 63 are appropriate and has retained them in the final rule. In light of the terrorist attacks of September 11, 2001, the Commission has directed the staff to conduct a comprehensive reevaluation of NRC physical security requirements. If this effort indicates that NRC's regulations or requirements warrant revision, such changes would occur through a public rulemaking or other appropriate methods.

Section 63.161 requires DOE to develop an emergency plan based on the criteria of § 72.32 (i.e., criteria provided for an Emergency Plan for an Independent Spent Fuel Storage Installation (ISFSI)). The required Emergency Plan includes: Identification of each type of accident, description of the means of mitigating the consequences of each type of accident; prompt notification of offsite response organizations; and adequate methods, systems, and equipment for assessing and monitoring actual or potential consequences of a radiological emergency condition. If particular types of accidents require evacuation procedures to ensure the protection of public health and safety, they will be included in the Emergency Plan.

Section 63.21(b)(3) requires DOE to submit a detailed plan to provide physical protection of HLW in accordance with § 73.51 (requirements for physical protection of stored spent nuclear fuel and HLW). The requirements for physical protection include: (1) Capabilities to detect and assess unauthorized access or activities and protect against loss of control of the facility; (2) limiting access to HLW by means of two physical barriers; (3) providing continual surveillance of the protected area in addition to protection by an active intrusion alarm; and (4) providing a primary alarm station located within the protected area and have bullet-resisting walls, doors, ceiling, and floor. These requirements provide high assurance that physical protection of the repository includes appropriate measures to prevent and respond to unauthorized access and activities, including the potential for armed intruders (e.g., terrorist activity).

Issue 3:
Will Federal funding be available to upgrade emergency first-responders and emergency medical services so as to allow local communities to be better prepared to respond to potential transportation accidents?

Comment.
Counties in the Yucca Mountain region expressed concern with their ability to respond to medical emergencies resulting from a transportation accident involving nuclear waste. Local communities suggested that DOE be required to enhance local emergency capabilities for responding to transportation accidents.

Response.
Section 180(c) of the NWPA requires DOE to provide technical assistance and funding for training State and local governments and Tribes for safe routine transportation and emergency response. However, NRC's responsibility for oversight and review of DOE's emergency plans (see discussion under Issues 1 and 2) does not include responsibility for how DOE provides for technical assistance and funding. Additionally, under NEPA, the potential for (environmental) impacts due to transportation, including accidents, is the responsibility of DOE to assess and mitigate.

3 Requirements for the Postclosure Period

3.1 Postclosure Safety Assessment

Issue 1:
Can performance assessments be relied on as the sole quantitative technique for evaluating compliance with postclosure safety requirements?

Comment.
DOE and NEI supported the risk-informed, performance-based approach. Additionally, NEI supported requirements in proposed Part 63 intended to ensure that DOE conducts and documents a high-quality performance assessment (e.g., features, events, and processes (FEPs) be described; relevant conceptual models be considered) and NEI also expressed a need for the NRC to effectively and clearly articulate this approach in future regulatory efforts. However, other commenters indicated that, although performance assessment is a highly informative methodology, its capability to model complex, coupled geologic systems over extended time periods has yet to be demonstrated. Confidence in performance assessments could be improved through testing on actual geologic systems and conducting suitable, long-term studies.

Response.
Although repository postclosure performance is evaluated with respect to a single performance measure for individual protection, the NRC considers a broad range of information in arriving at a licensing decision. In the case of the proposed repository at Yucca Mountain, Part 63 contains a number of requirements (e.g., qualitative requirements for data and other information, the consideration and treatment of uncertainties, the demonstration of multiple barriers, performance confirmation program, and QA program) designed to increase confidence that the postclosure performance objective is satisfied. The Commission will rely on the performance assessment as well as DOE's compliance with these other requirements in making a decision, if DOE submits a license application for disposal of HLW at Yucca Mountain. The Commission believes the approach for performance assessment in the proposed rule is appropriate and it is retained in the final rule. However, requirements for QA, multiple barriers, and performance confirmation have been revised to clarify the Commission's intent for these requirements (see discussion under Quality Assurance, Multiple Barriers and Defense in Depth, and Performance Confirmation for more details).

The Commission believes that there have been significant advances in, and experience with, risk assessment in the

past 20 years (see Commission's white paper on Risk-Informed and Performance-Based Regulation, March 1999). The Commission continues to believe that a performance assessment, developed with sufficient credibility, is the best means to provide useful information to the Commission for making an informed, reasonable licensing decision. The Commission recognizes, however, the uncertainties inherent in evaluating a first-of-a-kind facility like the repository and in estimating system performance over very long time periods (i.e., 10,000 years). Thus, proposed part 63 contained requirements to ensure that: (1) Uncertainties inherent in any performance assessment are thoroughly articulated and analyzed or addressed; (2) DOE's performance assessment is tested (corroborated) to the extent practicable; and (3) there are additional bases, beyond the performance assessment, that provide confidence that the postclosure performance objectives will be met. For example:

1. Requirements for Addressing Uncertainty in Performance Assessment

Section 63.114 provides a number of requirements for DOE's performance assessment to thoroughly address uncertainty. Part 63 requires consideration of uncertainties in DOE's representation of the repository (uncertainty and variability in parameter values must be taken into account—§ 63.114(b)) and the events that can happen during the compliance period (consideration of potentially disruptive events with a probability of occurrence as low as one chance in 10,000 of occurring over 10,000 years—§ 63.114(d)) to be directly included in the quantitative estimate of performance. Additionally, DOE is required to provide additional assurances that uncertainty in the information (e.g., evaluation of site characterization data) used to develop the performance assessment have been evaluated by consideration of alternative conceptual models of features and processes that are consistent with available data and current scientific understanding (§ 63.114(c)); and the basis for inclusion or exclusion of FEPs that would have a significant effect on performance (§ 63.114(e) and (f)). (See discussion under Issue 2 for further details on uncertainty in performance assessment.)

2. DOE's Performance Assessment Is Tested (Corroborated) to the Extent Practicable

DOE must test or corroborate, to the extent practicable, the confidence in (validity of) the performance assessment models. Part 63 requires DOE to provide the technical basis for the models used in the performance assessment (§ 63.114(g)). Approaches for providing the technical basis would include comparisons of these models with information relevant to the conditions of geologic disposal and time periods of the assessment (e.g., results from detailed process-level models, field investigations, and natural analogs). Additionally, a performance confirmation program is required (part 63, subpart F) to confirm that the behavior of the barriers of the repository system is consistent with what has been assumed in the performance assessment (see discussion under Performance Confirmation for more details).

3. Basis for Confidence That the Postclosure Performance Objectives Will Be Met

As a basis for confidence that the postclosure performance objectives will be met, the Commission plans to rely on requirements in addition to that for the performance assessment. Specifically, part 63 requires a multiple barrier approach for the repository, and a QA program. A requirement that multiple barriers make up the repository system ensures that repository performance is not wholly dependent on a single barrier. As a result, the system is more tolerant of failures and external challenges such as disruptive events (see discussion under Multiple Barriers and Defense in Depth for more details). The required QA program enhances confidence in the design and characterization of barriers important to waste isolation.

In summary, any determination that the postclosure performance objectives will be met will be based on a comprehensive set of regulatory requirements. Thus, reliance on the performance assessment for assisting regulatory decisions is supported by a range of considerations. The Commission believes this comprehensive approach (i.e., requirements for addressing uncertainty, providing technical basis for models, and additional requirements, beyond expected performance, for increasing confidence that the performance objectives will be met) is appropriate and it is retained in the final rule.

Issue 2:
Should a requirement for the level of uncertainty and performance that is acceptable for performance assessment of the proposed repository be included in part 63?

Comment.
A number of comments were received concerning uncertainty in estimating postclosure performance of the repository. Commenters were concerned with the level or degree of uncertainty in performance calculations and approaches for analyzing uncertainty in performance calculations. Some specific concerns were: (1) The acceptable level of uncertainty should be clearly stated in part 63 (results that depend mainly on assumptions rather than actual properties are unacceptable); (2) the many orders of magnitude of uncertainty in performance projections are, and will continue to be, too high for assuring long-term safety; and (3) whether DOE is required to predict “actual” performance.

Response.
The first-of-a-kind nature of the repository and the evaluation over a very long time period result in significant uncertainty being included in the performance assessment. Part 63 not only requires DOE to account for uncertainty in its performance assessment but also contains a number of other requirements (e.g., use of multiple barriers, performance confirmation program) to compensate for residual uncertainties in estimating performance. The Commission will consider all these requirements in determining whether it has sufficient confidence (i.e., reasonable expectation) that DOE has demonstrated or has not demonstrated the safety of the repository. Specification of an acceptable level of uncertainty is neither practical nor appropriate due to the limited knowledge currently available to support any such specification and the range of uncertainties that would need to be addressed. The Commission believes the approach to performance assessment in the proposed rule, which includes the treatment of uncertainty, is appropriate and has retained this approach in the final rule.

The previous response under Issue 1, discussed the requirements for the performance assessment. Many of these requirements address uncertainty in the performance assessment. Some of these uncertainties will be directly included in the DOE's estimate of performance. For example, DOE is expected to conduct uncertainty analyses (i.e., evaluation of how uncertainty in parameter values affects uncertainty in the estimate of dose), including the consideration of disruptive events and associated probability of occurrence. Other uncertainties are not necessarily quantified but are considered during the development of the conceptual models for the performance assessment (e.g., consideration of alternative models, inclusion and exclusion of FEPs). If NRC were to specify an acceptable level of uncertainty, the specified value would be somewhat arbitrary because:

(1) Understanding of the site is evolving as site studies continue; (2) repository design options are still being evaluated; and (3) differences in the types of uncertainties (e.g., variability in measured parameters, modeling assumptions, expert judgment, etc.) complicate the specification. The approach defined in part 63, which requires DOE to fully address uncertainties in its performance assessment rather than requiring DOE to meet a specific level of uncertainty, is appropriate. The treatment of uncertainty in DOE's performance assessment will be an important part of NRC's review.

Regardless of the uncertainty in the performance assessment, part 63 contains additional provisions to increase confidence that the postclosure performance objectives will be met. These provisions include requirements for multiple barriers, a performance confirmation program, and implementation of a QA program (see discussion under Issue 1). However, it should be kept in mind that the performance assessment evaluates “potential” doses, not “actual” doses. For example, part 63 requires the performance assessment to assume for the next 10,000 years that the reasonably maximally exposed individual (RMEI) is a member of a community that: (1) Exists where it will intercept potential releases from the repository and (2) uses ground water but never tests the quality of this water nor treats the ground water to remove any contaminants. This specification is considered appropriately conservative for evaluating performance but most likely is not an “accurate” prediction of what will happen during the next 10,000 years (see discussion under RMEI Characteristics and Reference Biosphere for more information on the RMEI). Although the Commission does not require an “accurate” prediction of the future, uncertainty in performance estimates cannot be so large that the Commission cannot find a reasonable expectation that the postclosure performance objectives will be met (see discussion under Reasonable Expectation). At this time, the Commission is not aware of any information that suggests the uncertainties are so large that NRC will be unable to make a regulatory decision regarding the safety of a potential repository at Yucca Mountain.

Issue 3:
Do known conditions at the Yucca Mountain site and/or the potential for other adverse conditions make Yucca Mountain an unacceptable location for an HLW repository?

Comment.
Commenters expressed opinions/concerns regarding the impact of certain FEPs (e.g.; Yucca Mountain lies in an area that is seismically and tectonically active; volcanic activity in the recent geologic past; potential for fast ground-water pathways to the water table; the effect of heat and radiation on the surrounding rock; microbial-induced corrosion of the waste package; and the potential for a significant rise of the water table as the water table may rise and interact with the proposed repository) that could have a deleterious effect on repository performance. Given these concerns, many of the commenters recommended the Yucca Mountain site be withdrawn from further consideration as a potential repository.

Response
. Consideration of all FEPs, especially those with the potential to have an adverse effect on performance, is an important part of the evaluation of repository performance. Commenters have correctly identified a number of conditions that have been or are being considered by DOE in performance assessments for Yucca Mountain, such as seismic activity, thermal effects, volcanic activity, microbial-induced corrosion of th

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A01-27157. Public record. Not legal advice.