STRATEGIES FOR EFFECTIVE

RADIOACTIVE WASTE MANAGEMENT

An operational strategy for implementing waste management policy in the USA involves the minimization of waste by requiring the licensees to reduce the quantity of waste generation from the source and by ensuring efficient and timely decontamination of facilities. Effective disposal strategies involve isolation of waste from the environment for a period of time appropriate for the hazard of the waste. This can be accomplished through appropriate characterization of the waste, adequate design and implementation of disposal technology, and realistic projections of disposal system performance over the period of hazard of the waste. Use of multiple barriers should be used to optimize the system. Also, the concept of defence in depth, consistent with the hazard of the waste, can be used to enhance confidence about the isolation of waste in the face of uncertainty. Passive safety designs for isolation of long lived waste are used, although institutional controls, including the periodic monitoring of on-site and off-site environmental media, such as soil, groundwater and air, are encouraged.

These strategies contribute to meeting the NRC’s strategic goal of preventing significant adverse impacts from radioactive waste on the current and future public health and safety and the environment, and promoting common defence and security.

6. CHALLENGES AND LESSONS LEARNED

Over the past decade, significant progress has been made in the disposal of radioactive waste in the USA. Near surface disposal of LLW continues to be a safe and viable option; intermediate level waste is currently being disposed of at the Waste Isolation Pilot Plant; DOE is proceeding toward submitting a HLW licence application to the NRC; and decommissioning of reactors continues without incident. Despite this progress, significant challenges remain in the areas of waste management and disposal. Important challenges remain with respect to making decisions in the face of uncertainty, public acceptance, and knowledge management.

A fundamental aspect of disposal is the estimation of potential radio-logical exposure in the future and, often, the far future (e.g. 1000 years and

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longer), based on an understanding of disposal site characteristics and the behaviour of engineered components such as the waste form and package.

Uncertainties exist in safety decisions, because of limits on the scientific under-standing of the future evolution of the site and engineered components, as well as limitations in the understanding of the behaviour and characteristics of future human exposure scenarios. Although it is generally accepted that speci-fication of a reference biosphere is an acceptable approach for addressing uncertainties in the exposure scenarios, such a stylized approach may not be appropriate for characterizing the complexities and variability of the hazard associated with the evolution of the post-closure environment. Uncertainties in the evolution of the site characteristics and engineered components should be addressed in a structured manner — involving a robust design, quantitative analyses, and monitoring and confirmation activities.

The defence in depth principle has served as a cornerstone of the NRC’s deterministic regulatory framework for nuclear reactors, and it provides an important tool for making regulatory decisions, with regard to complex facilities, in the face of significant uncertainties. The NRC also has applied the concept of defence in depth elsewhere in its regulations to ensure safety of licensed facilities through requirements for multiple barriers. For example, regulations for HLW disposal at Yucca Mountain specify that the repository is to be comprised of both natural and engineered barriers. A repository design made up of multiple barriers is expected to be more tolerant of unanticipated failures and external challenges. HLW represents a large potential hazard because of the magnitude of the inventory of long lived radionuclides. It would be expected that the need for defence in depth would vary, consistent with the variation of the level of the hazard and uncertainties over the spectrum of the waste management activities (see Fig. 2). Secondly, quantitative analyses can be used to achieve understanding of the potential effect of uncertainties with respect to overall performance of waste management facilities and the capabil-ities of safety barriers. Quantitative methods for addressing uncertainties associated with repository performance have matured significantly over the past two decades. Consistent with the level of the hazard and the uncertainties, quantitative methods can be used to evaluate the robustness of facility design and the impact of uncertainty on performance. Finally, the NRC uses its inspection programme as a means to further confirm, to the extent practicable, the safety attributes of the design components and site characteristics.

A second challenge is in the area of public outreach. Difficulties have been encountered in the siting of waste disposal facilities. Acceptance of waste management facilities requires public trust and understanding of the issues.

Certainly, the public should expect accurate and timely accessibility to

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information about the risks of waste management facilities. Access to information alone will go a long way toward building trust; however, trust alone does not provide for an understanding of the issues. Although scientists’

abilities to quantify and evaluate uncertainties have matured, additional improvements are needed in the ability to explain the analyses for all stake-holders. The information should be developed to be understandable to scientists and non-scientists, as well as to individuals outside of the immediate staff of the agencies responsible for developing and regulating the facilities. In this regard, the NRC continues efforts to improve its public outreach programme and communication tools to assist its explanation of risks. For example, a physical model of the potential repository at Yucca Mountain is being developed as a means to explain the behaviour of the repository without the need for charts and graphs, which can be somewhat abstract to many stake-holders with a non-science background. Primary goals of the outreach programme are to present objectively the results of scientific and engineering analyses (both NRC independent analyses as well as the analyses of others) as the basis for scientific judgements.

The NRC has gained significant experience in the development and application of performance assessments of waste management facilities and, more recently, in the development of methods and approaches for the commu-nication of performance assessment concepts and results. A final challenge is the management of this knowledge to ensure that staff benefits from, and will FIG. 2. An example of how the need for defence in depth (DID) can be related to uncertainty and potential hazard.

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be able to continue to build on, this valuable experience. A minimum requirement is to thoroughly document the technical basis for rules and guidance. In the high level waste programme, the NRC has consistently documented the development of its performance assessment capabilities, including the technical basis for performance assessment models, as well as the sensitivity and uncertainty analyses. Additionally, the NRC has documented technical analyses performed to develop the regulations for Yucca Mountain.

The international community provides another approach for enhancing staff knowledge. International peer reviews, research, safety evaluations and cooperative efforts provide opportunities for staff to learn and expand its knowledge of waste management issues and solutions.

7. SUMMARY AND CONCLUSION

Radioactive waste in the USA comprises five main categories, including:

SF, HLW, TRU, MT and LLW. The USA has well established policies and regulatory frameworks for radioactive waste disposal; they promote safety and ensure protection of the health and safety of workers, the public, the common defence and security, and the environment. The waste safety programmes maintain robust and effective oversight of large and diversified activities involving the management of spent nuclear fuel and radioactive waste. The policies and roles and responsibilities of the agencies are distinct and codified in a series of policy acts, by-laws, and regulations. The major agencies involved in radioactive waste management and regulatory oversight include: NRC, DOE, EPA and the Agreement States. A framework for the successful management of radioactive waste involves technical, societal and regulatory elements. Robust safety strategies include waste minimization, isolation, periodic monitoring, and defence in depth using multiple barriers.

For the past several years, the NRC, as well as other agencies, has made significant progress and gained extensive experience in regulatory oversight and management of radioactive waste. Lessons have been learned which have resulted in process improvements. However, challenges remain. For example, the NRC staff faces challenges with decision making in the face of uncertainties over long time periods as well as challenges in conducting an effective dialogue with the public on complex technical issues. While addressing these challenges, the NRC benefits from communication and collaboration with the interna-tional community. It is believed that continual learning, openness and worldwide cooperation will lead to additional advances in knowledge and public trust for radioactive waste management and disposal.

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ACKNOWLEDGEMENTS

The authors wish to acknowledge the help and support provided in reviewing this paper by NRC staff, J. Kennedy, L. Camper, J. Kotra, D. Cool and D. Diaz-Toro.

REFERENCES

[1] UNITED STATES OF AMERICA, The Nuclear Waste Policy Act of 1982, Public Law 97-425; 96 Stat. 2201, Washington, DC (1982).

[2] UNITED STATES OF AMERICA, U.S. Energy Policy Act of 1992, Public Law 102-486, Washington, DC.

[3] UNITED STATES OF AMERICA, Low-Level Radioactive Waste Policy Act of 1980, Public Law96-573; 94 Stat.3347, Washington, DC (1980).

[4] UNITED STATES OF AMERICA, Low-Level Radioactive Waste policy Act, Amended, Public Law99-240; 99 Stat.1842, Washington, DC (1985).

[5] UNITED STATES OF AMERICA, U.S. Code of Federal Regulations Title 10, Energy, Part 61, Washington, DC (2005).

[6] UNITED STATES OF AMERICA, Atomic Energy Act of 1954, Public Law 83-703, 68 Stat. 919, Washington, DC (1954)

DISCUSSION

W. HILDEN (European Commission): Is the radioactive waste resulting from nuclear power plant decommissioning in the United States of America being recycled or disposed of?

M.V. FEDERLINE (United States of America): We have a number of options that allow release, but most of the waste is being disposed of.

F