UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 

WASHINGTON, DC 20555 - 0001 

September 22, 2011 

The Honorable Gregory B. Jaczko 

Chairman 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555-0001 

SUBJECT: PROPOSED RULEMAKING TO INTRODUCE A SITE-SPECIFIC 

 PERFORMANCE ASSESSMENT AND HUMAN INTRUSION ANALYSIS 

 REQUIREMENT TO 10 CFR PART 61 

Dear Chairman Jaczko: 

During the 586th meeting of the Advisory Committee on Reactor Safeguards (ACRS), 

September 8-10, 2011, we completed our review of the staff’s proposed rulemaking on the 

Commission’s commercial low-level waste (LLW) disposal regulation. This rulemaking is 

intended to introduce both an explicit site-specific performance assessment as well as a human 

intrusion analysis requirement to 10 CFR Part 61. We were also briefed on this topic during our 

585th meeting, July 13-15, 2011. Our Subcommittee on Radiation Protection and Nuclear 

Materials discussed this matter during its meetings of June 23, and August 17, 2011. During 

these meetings we had the benefit of discussions with representatives of the NRC staff. We 

also had the benefit of the documents referenced. 

CONCLUSIONS AND RECOMMENDATIONS 

1. 10 CFR Part 61 should not be amended in accordance with the staff’s 

recommendations. Rather, the staff should develop a risk informed, performance based 

LLW site assessment methodology using realistic characterizations of disposed 

radioactive materials; the features, events, and processes that can disrupt disposed 

waste; natural and engineered barriers; environmental transport mechanisms; and 

subsequent human exposure scenarios. 

2. Implementation guidance for 10 CFR Part 61 should not specify an a priori period of 

performance. Rather, the performance assessment should develop a period of 

performance based on the features, events, and processes specific to the 

geohydrological features of a candidate site; the technologies used to isolate wastes; 

and the controls used to isolate wastes from the environment and humans. 

3. The approaches in Recommendations 1 and 2 are equally applicable to the disposal of 

depleted uranium (DU) as well as other LLW. 
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4. Compliance with performance objectives of the disposal system after the institutional 

control period ends, as well as the possible doses to hypothetical intruders, should be 

evaluated considering the natural features, events, and processes for a given site for a 

period of time commensurate with the risk for a specific facility and site. 

BACKGROUND 

The U.S. Nuclear Regulatory Commission (NRC) promulgated its commercial LLW disposal 

regulation in 1980. 10 CFR Part 61 sets forth the standards and criteria for the disposal of 

commercial LLW in near-surface facilities. To complement the regulation, the staff prepared a 

standard format and content guide for license applications (NUREG-1199) as well as a license 

application standard review plan (NUREG-1200) for 10 CFR Part 61. Neither NUREG-1199 nor 

NUREG-1200 makes reference to the use of performance assessments to demonstrate 

compliance with 10 CFR Part 61. Instead, those documents make reference to the use of 

“technical analyses” for the purpose of the requisite compliance demonstrations. 

In 1995, the Commission issued, “Use of Probabilistic Risk Assessment Methods in Nuclear 

Regulatory Activities,” encouraging the increased use of probabilistic risk assessment (PRA) 

methods in its regulatory processes. This policy statement sets forth the basis for the riskinformed, performance-based (RI/PB) regulatory principles used by the NRC in its regulatory 

decision-making. About the same time, the staff began to explore the use of performance 

assessment (a stylized type of PRA applied to the evaluation of waste management systems) to 

its national LLW program. In connection with these efforts, the staff developed a hypothetical 

test case to evaluate certain LLW design assumptions as well as the efficacy of the 

performance assessment methodology itself. The culmination of these efforts resulted in the 

identification of certain LLW performance assessment policy issues summarized in SECY-96-

103 and the ultimate publication of NUREG-1573, which documents the application of 

performance assessment methods to 10 CFR Part 61. 

In NUREG-1573, the staff states, “Finally, consistent with the Commission’s views regarding the 

use of probabilistic risk assessment, the application of the performance assessment techniques 

to LLW disposal facility designs outlined in the technical report should be tempered according to 

the complexity of the disposal system, uncertainties surrounding system performance, and the 

estimated risks due to the types and kinds of wastes being disposed.” 

DISCUSSION 

In commenting on this proposed rulemaking, there are three issues that merit discussion. What 

should the regulatory time period of performance (POP) be for a commercial LLW disposal 

facility under 10 CFR Part 61? Should DU be an acceptable waste form for disposal in a LLW 

disposal facility licensed under 10 CFR Part 61? How should the issue of hypothetical intruders 

into LLW disposal facilities be treated? 
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Period of Performance

A key element of a performance assessment conducted as part of regulatory decision-making is 

deciding on the duration (time span) of the calculation. During this period all the performance 

objectives for the facility, including dose limits to workers and the public, must be met. When 

determining a POP appropriate for 10 CFR Part 61, it is important to recognize that the 

magnitudes and durations of hazards posed by LLW are diverse. LLW consists of both shortlived and long-lived radionuclides in various chemical and physical forms. To provide licensees 

some flexibility in siting and designing disposal facilities, the current 10 CFR Part 61 LLW 

classification system is based on the half-lives and concentrations of those radioactive materials 

that can be expected in commercial facilities. Because of the long periods of time contemplated 

for the control of such materials, the regulation intentionally relies on passive rather than active 

systems to minimize and retard releases of radioactivity to the environment. 

As noted in the recent IAEA Safety Standard No SSR-5, “Disposal of Radioactive Waste 

Specific Safety Requirements,” Requirement 9: 

 “The disposal facility shall be sited, designed and operated to provide features that are 

 aimed at isolation of the radioactive waste from people and from the accessible 

 biosphere. The features shall aim to provide isolation for several hundreds of years for 

 short lived waste and at least several thousand years for intermediate and high level 

 waste. In so doing, consideration shall be given to both the natural evolution of the 

 disposal system and events causing disturbance of the facility.” 

The Advisory Committee on Nuclear Waste (ACNW) previously commented on whether the 

POP should be specified in 10 CFR Part 61 or whether the regulation should remain silent given 

the variable risk posed by commercial LLW. In a February 11, 1997, letter, the ACNW 

recommended a two-part approach for establishing a time frame over which compliance with the 

LLW disposal regulation would be demonstrated. The first part relied on a site-specific time 

span derived from a performance assessment to determine the time at which the more mobile 

radionuclides produced some peak dose to a designated receptor group. The second part was 

a qualitative evaluation, not requiring a specific measure of compliance, which identified any 

significant deficiencies in disposal system overall performance. 

The staff’s proposed amendments to 10 CFR Part 61 require that a detailed performance 

assessment be made demonstrating compliance with facility performance objectives (including 

protection of inadvertent intruders) for no less than 20,000 years. This major change to the 

existing rule is driven primarily by the intent to permit disposal of long-lived waste such as DU in 

LLW facilities. This time period is excessive and inconsistent with IAEA guidance cited above. 

It is also inconsistent with the practices of the Department of Energy (DOE) in their LLW 

facilities. DOE’s Office of Environmental Management commented on the proposed 

amendments to 10 CFR Part 61 in a letter of June 21, 2011, noting that their POP is 1000 

years. 
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There is an obligation to avoid the potential for catastrophic consequences from LLW disposal 

on future generations. This obligation has been articulated by the National Academy of Public 

Administration (NAPA) in its 1997 report, “Deciding for the Future: Balancing Risks, Costs, and 

Benefit Fairly Across the Generations” and by DOE, which stated, “The principles developed by 

NAPA suggest that when looking far into the future, the major concern should be to avoid the 

possibility of catastrophic consequences. Current disposal standards specify dose limits, which 

are equivalent to a few medical x-rays, to people in the vicinity (or to a single, reasonably 

maximally exposed individual)”. 

Avoiding catastrophic consequences for a facility, rather than complying solely with operational 

dose limits to hypothetical individuals, should be the focus of assessments designed to assess 

facility performance over a period longer than a few hundred years. 

We recommend that the POP be developed based on the approach outlined in the February 11, 

1997, ACNW letter, i.e., the POP should be a site-specific time span derived from a 

performance assessment to determine the time at which the more mobile radionuclides 

produced some peak dose to a designated receptor group. Beyond the POP, a qualitative 

evaluation not requiring a specific measure of compliance should be performed to identify any 

significant deficiencies in disposal system overall performance that could lead to catastrophic 

consequences. 

Depleted Uranium

DU waste from the nuclear fuels and weapons programs began accumulating in the early 

1950s. More recently, the DU inventory has increased as a result of commercial enrichment 

activities in the United States. 

The NRC staff included DU waste streams in its initial technical analysis during development of 

10 CFR Part 61 (NUREG-0738). The proposed 10 CFR Part 61 rule included waste 

classification Table 1, which set a maximum concentration of DU in Class C waste of 

0.05μCi/cm3

. The final 10 CFR Part 61 classification Tables 1 and 2 did not include a 

concentration limit for DU. The NRC decided that because there would not be a significant 

quantity of these wastes disposed at commercial shallow land facilities, no concentration limit 

would be needed. Thus, when it was decided that significant quantities of DU might be 

disposed in shallow land facilities, DU was, by default, classified as Class A LLW. 

In recognition of this designation, NRC’s principal LLW technical assistance contractor at the 

time, the Sandia National Laboratories (Sandia), performed a 10 CFR Part 61-driven 

performance assessment of a hypothetical LLW disposal facility with a waste inventory 

dominated by DU. The disposal scenario was based on a humid, near-surface setting. Two 

intruder analyses (at three different time intervals) were also performed using the same 

assumptions found in the 10 CFR Part 61 Draft Environmental Impact Statement. The Sandia 

analyses found that offsite doses to receptors, due to the inhalation daughters of radon, were 

conservatively estimated to be three rem after 1000 years. A very significant finding of the 

Sandia analyses is that the chemical toxicity of DU imposes a greater limitation on its disposal 

than radiological doses. Significant toxic effects to the kidney are observed even for 

contaminant intake levels that pose negligible radiological risk. 
-5- 

The Sandia analyses concluded that the acceptability of near-surface disposal for large 

quantities of DU depends upon the chemical form considered and the time frame applied to the 

analysis. Radiological risks associated with the disposal of DU will increase in proportion to the 

ingrowth of the progeny in the uranium decay series. Full equilibrium takes millions of years. 

The Sandia analysis found that truncation of the analysis prior to that time will not capture the 

potential peak doses. In this regard, the Sandia analyses did note that extrapolation of current 

conditions in a LLW performance assessment to 2 million years was of “dubious merit” for a 

near-surface facility owing to the uncertainties in predicting future system states. In particular, 

the Sandia analyses noted that the potential exists for other adverse conditions to manifest 

themselves apart from trying to determine the time at which the peak dose to a hypothetical 

individual from the radiological hazard occurs. 

In 2008, the staff was directed by the Commission to revisit the DU disposition issue to better 

understand the impacts of near-surface disposal of large quantities of DU, such as those 

expected to be generated at uranium enrichment facilities. The technical analysis, described in 

SECY-08-0147 addressed whether amendments to 10 CFR Part 61.55(a) would be necessary 

to assure that large quantities of DU could be disposed in a manner that meets the Subpart C 

performance objectives of 10 CFR Part 61. 

The analysis described in SECY-08-0147 focused on a hypothetical site located in an arid 

geographic setting. This analysis concluded that near-surface disposal of large quantities of DU 

may not be appropriate under all site conditions. Even in arid settings, the disposal depth needs 

to be “large” and a robust radon barrier installed. In this case, the staff found that the 10 CFR 

Part 61 Subpart C performance objectives could be met as long as the water supply was not 

potable. The staff’s SECY-08-0147 analysis also reached the same conclusions as the 1992 

Sandia analyses, namely, that the shallow disposal of large quantities of DU or disposal at 

humid sites with a potable groundwater pathway would likely result in the Part 61 performance 

objectives not being met. However, unlike the 1992 Sandia analysis, the SECY-08-0147 

analysis failed to evaluate the chemical risks associated with the disposal of DU in an arid 

geographic setting. 

We agree with the conclusions of SECY-08-0147 that under some circumstances DU can be an 

acceptable waste form for disposal in a LLW facility licensed under 10 CFR Part 61. The POP 

should be determined through a performance assessment based on the features, events, and 

processes specific to the geohydrological features of a candidate site; the technologies used to 

isolate wastes; and the controls used to isolate wastes from the environment and humans. 

 

Inadvertent Intruders

The use of overly conservative scenarios for inadvertent intrusion into presumably abandoned, 

unmarked, and unsecured LLW disposal facilities can change the focus of the facility design 

from the protection of the health and safety of the public during the period of operation of the 

facility (and a reasonable period thereafter), to the protection of hypothetical intruders many 

thousands of years in the future. During the period over which LLW facilities are in operation, 
-6- 

and for hundreds of years after closure, the many geotechnical and hydrologic, as well as 

climate and materials degradation variables that must be evaluated to assure health and safety 

are amenable to measurement and analysis. If the focus of current regulations is changed to 

the protection of inadvertent intruders many thousands of years in the future, great uncertainty 

is introduced into the performance assessment. 

A range of more realistic scenarios for inadvertent intrusion should be developed to avoid the 

introduction of needless burden and uncertainty. 

In summary, 10 CFR Part 61 should not be amended in accordance with the staff’s 

recommendations. We look forward to working with the staff on the development of a riskinformed performance-based framework for safe disposal of LLW. 

ACRS Member, Dr. D.A. Powers, did not participate in the discussions of the Sandia study of 

LLW disposal facilities. 

 Sincerely, 

 /RA/ 

 Said Abdel-Khalik 

 Chairman 

REFERENCES 

1. U.S. Nuclear Regulatory Commission, 10 Code of Federal Regulations, Part 61, 

 “Licensing Requirements for Land Disposal of Radioactive Waste,” 1982. 

2. U.S. Nuclear Regulatory Commission, “Site Specific Analyses for Demonstrating 

 Compliance with Subpart C, Performance Objectives,” 76FR24831, dated May 3, 2011. 

3. U.S. Nuclear Regulatory Commission, “Part 61: Site Specific Analyses for 

 Demonstrating Compliance with Subpart C, Performance Objectives: Preliminary 

 Proposed Rule Language” (ML111380658) 

4. U.S. Nuclear Regulatory Commission, “Technical Basis for Proposed Rule to Amend 10 

 CFR Part 61 to Specify Requirements for the Disposal of Unique Waste Streams, 

 Including Large Quantities of Depleted Uranium,” (ML111040419) 

5. U.S. Nuclear Regulatory Commission, “Technical Analysis Supporting Definition of 

 Period of Performance for Low-Level Waste Disposal” (ML111030586) 

6. U.S. Nuclear Regulatory Commission, “Standard Format and Content of a license 

 application for a Low-Level Radioactive Waste Disposal Facility,” NUREG-1199, 

 Revision 2, 1991 (ML022550605) 
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7. U.S. Nuclear Regulatory Commission, “Standard Review Plan for the review of a license 

 application for a Low-Level Radioactive Waste Disposal Facility,” NUREG-1200, 

 Revision 3, 1994 (ML061370484) 

8. U.S. Nuclear Regulatory Commission, “Use of Probabilistic Risk Assessment Methods in 

 Nuclear Regulatory Activities: Final Policy Statement,” 60FR12622, dated August 16, 

 1995 

9. U.S. Nuclear Regulatory Commission, “Regulatory Issues in Low-Level Radioactive 

 Waste Performance Assessment,” SECY-96-103, dated May 17, 1996 (ML003711482) 

10. U.S. Nuclear Regulatory Commission, “A Performance Assessment Methodology for 

 Low-Level Radioactive Waste Disposal Facilities: Recommendations of NRC’s 

 Performance Assessment Group,” NUREG-1573, 2000 (ML003770778) 

11. International Atomic Energy Agency, “Disposal of Radioactive Waste,” IAEA Safety 

 Standards, Specific Safety Requirements No. SSR-5, Vienna, Austria, 2011 

12. ACNW Letter, “Time of Compliance for Low-Level Nuclear Waste Disposal Facilities,” 

 Washington, DC, dated February 11, 1997 (ML091490047) 

13. U.S. Department of Energy, “Radioactive Waste Management Manual,” DOE Manual 

 435.1-1, Chapter IV, “Low-Level Waste Requirements,” 2001. 

14. Marcinowski, F., U.S. Department of Energy, Office of Environmental Management, 

 Letter to the Secretary, U.S. Nuclear Regulatory Commission, “Office of Environmental 

 Management Comments on the U.S. Nuclear Regulatory Commission's Preliminary 

 Proposed Rule, ‘Site Specific Analyses for Demonstrating Compliance with Subpart C 

 Performance Objectives,’ to Revise 10 CFR Part 61,” Washington, DC, dated June 21, 

 2011 (ML11178A096) 

15. National Academy of Public Administration, “Deciding for the Future: Balancing Risks, 

 Costs, and Benefits Fairly Across Generations,” June 1997 

16. Regnier, E.P. and A. Wallo, U.S. Department of Energy, “Intergenerational Decision 

 Making for Radioactive Waste Disposal, Policy and Science: Regulatory Protection 

 Forever?” Proceeds of the Waste Management ’06 Conference, Tucson, AZ, February 

 26-March 2, 2006. 

17. U.S. Nuclear Regulatory Commission, “Draft Environmental Impact Statement on 

 10 CFR Part 61, ‘Licensing Requirements for Land Disposal of Radioactive Waste,’” 

 NUREG-0782, Volumes 1 through 4 (ML052590347, ML052590350, ML052590353, 

 ML052590354) 
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18. Kozak, M., T. Feeney, C. Leigh, and H. Stockman, “Performance Assessment of the 

 proposed disposal of depleted uranium as Class A Low-Level Waste,” Sandia National 

 Laboratories, Final Letter Report submitted to F.W. Ross, U.S, Nuclear Regulatory 

 Commission, Albuquerque, NM, dated December 16, 1992 (ML101890179) 

19. U.S. Nuclear Regulatory Commission, “Response to Commission Order CLI-05-20 

 Regarding Depleted Uranium,” SECY-08-0147, dated October 7, 2008 (ML081820762) 
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18. Kozak, M., T. Feeney, C. Leigh, and H. Stockman, “Performance Assessment of the 

 proposed disposal of depleted uranium as Class A Low-Level Waste,” Sandia National 

 Laboratories, Final Letter Report submitted to F.W. Ross, U.S, Nuclear Regulatory 

 Commission, Albuquerque, NM, dated December 16, 1992 (ML101890179) 

19. U.S. Nuclear Regulatory Commission, “Response to Commission Order CLI-05-20 

 Regarding Depleted Uranium,” SECY-08-0147, dated October 7, 2008 (ML081820762) 

Accession No: ML11256A191 Publicly Available Y Sensitive N

Viewing Rights: NRC Users or ACRS Only or See Restricted distribution 

OFFICE ACRS SUNSI Review ACRS ACRS ACRS 

NAME DWidmayer DWidmayer CSantos EMHackett EMH for SAK 

DATE

OFFICIAL RECORD COPY 
Letter to the Honorable Gregory B. Jaczko, NRC Chairman, from Said Abdel-Khalik, ARS 

Chairman, dated September 20, 2011 

SUBJECT: PROPOSED RULEMAKING TO INTRODUCE A SITE-SPECIFIC 

 PERFORMANCE ASSESSMENT AND HUMAN INTRUSION ANALYSIS 

 REQUIREMENT TO 10 CFR PART 61 

ML# 11256A191 

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