One Step at a Time: The Staged Development of Geologic Repositories for High-Level Radioactive Waste (2003)

The objective of this study is to advise the Department of Energy (DOE) on how to implement a staged geologic repository program for high-level waste.¹ The Nuclear Energy Agency has defined a staged approach to repository development as a process involving:

The staging concept embodies a more flexible approach to repository development, consistent with recommendations from a previous National Research Council report (NRC, 2001) on the disposition of high-level waste, and reflects current consensus in the international radioactive waste management arena (NEA, 1999a,b; EDRAM, 2002). The 2001 National Research Council report also emphasizes the enhanced learning opportunities available in a staged approach.

The statement of task is presented in Sidebar 1.1. Sections of this report addressing specific points of the statement of task are indicated in parenthesis. As requested, the committee focuses primarily on operational aspects of a geologic repository program; however, early in the committee’s deliberations the study’s scope was broadened. It was recognized that staging addresses the entire geologic repository program, beginning with siting and continuing to the post-closure phase.

The statement of task is broad, in that it requires the committee to examine policy and societal issues as well as science and technology matters. Given that managing the repository development process is a new challenge, with few or no past analogues, project management recommendations in this report are based upon the combined judgment and expertise of committee members rather than direct experience with implementation of staged approaches.

However, the committee believes that the approach recommended in this report will increase the likelihood of repository program success (see Section 1.2.2) because it is consistent with accepted principles of sound project management and engineering practices.

Recognizing the potential benefits of staging, DOE asked the National Research Council for advice on how to implement staging during the design, construction, operation, closure, and post-closure phases of a geologic repository program for high-level waste. To investigate the applicability of staging to generic geologic repository programs the National Research Council appointed a committee³ of 14 members (see Appendix A). The present report builds on the 1990 and 2001 National Research Council reports on geologic disposal of high-level radioactive waste and expands on this committee’s progress report released in March 2002 (NRC, 1990, 2001, 2002a).

When the committee began work in 2001, DOE was preparing to recommend the Yucca Mountain site in Nevada as a suitable site for a federal high-level radioactive waste repository. In February 2002, DOE submitted the site suitability recommendation to the President, who, in turn, submitted it to the U.S. Congress. Nevada subsequently vetoed the recommendation but Congress over-rode Nevada’s veto. In July 2002, the President signed a resolution allowing DOE to apply to the Nuclear Regulatory Commission for a license to construct a repository at Yucca Mountain.

The political debate and the concomitant public awareness heightened sensitivity to the issue of geologic disposal of high-level waste in general, and to the congressional decision in particular. It is important to emphasize the limitations on the scope of the committee’s statement of task (Sidebar 1.1). The statement of task does not direct the committee to comment on:

• the choice of geologic disposal as the preferred option for high-level waste management,

• the suitability of Yucca Mountain, Nevada, as a geologic repository site, and

• the specific siting decisions taken by DOE, the President, or the Congress.

As the statement of task requested, this study addresses a generic repository program with applications to Yucca Mountain, where appropriate.

The process leading to this report is summarized as follows. The delays (and rising costs) and impasses in the disposal of nuclear waste in nearly every radioactive waste management program has prompted various countries to reassess management approaches for the development of geologic repositories. One important concept emerged: A central feature of a new management approach might be to proceed in steps or stages (EDRAM, 2002; NEA, 1999a). This then became a widely shared informal hypothesis to be investigated and was suggestive enough that DOE asked the National Research Council for advice on how a staged approach might best be implemented. The committee’s work can thus be characterized as a rigorous, collective analysis to assess the feasibility of the hypothesis. In its approach to address the statement of task, the committee:

• elaborates the concept of staged development for repository programs (hypothesis);

• identifies and adopts terms to describe alternatives that represent two distinct management approaches:

  • Linear Staging: a single predetermined path, in which stages are defined primarily by milestones driven by program schedule, costs, and technical content, and

• Adaptive Staging: a flexible process based on incremental decisions, in which stages are predicated on the outcome of previous stages and are separated by structured Decision Points;⁴

• develops a list of attributes of Adaptive Staging;

• characterizes the decision-making process involved in the Decision Points; and

• addresses the following questions:

  • What type of project benefits from Adaptive Staging?

  • What rationale leads a repository program to use Adaptive Staging?

  • What potential benefits and drawbacks can result from Adaptive Staging?

As the committee addressed its task it quickly realized two things: first, given the large uncertainties and challenges of repository development, no management approach can guarantee a successful repository or a successful repository program as defined in Section 1.2.2. Second, again given the uncertainties and challenges, the development process needs to be resilient and incremental (i.e., adaptive). Therefore the committee suggests that as described in the following paragraphs, Adaptive Staging is likely to be more effective and less error-prone than Linear Staging or similar approaches.

Chapter 1 presents the study’s objective and task, the challenges of high-level waste geologic repository programs, and a definition of a repository program’s success. Chapter 2 differentiates two types of staging, Linear and Adaptive, and discusses criteria for their applicability in program management. The remaining chapters discuss Adaptive Staging for geologic repository programs. Chapter 3 describes activities involved in repository development phases as well as the institutional and societal context of high-level waste geologic disposal. The programmatic, safety, security, institutional, regulatory, and societal impacts of Adaptive Staging are addressed in Chapter 4, along with knowledge gaps. The statement of task directs the committee to focus mainly on operational details. Therefore, an in-depth study of the societal and institutional ramifications of staging was judged to extend beyond the statement of task. Given the time constraint, the committee only addresses the initial impacts and identifies knowledge gaps in societal and institutional domains. Chapter 5 discusses Adaptive Staging in the context of DOE’s Yucca Mountain Project and comments on the approach’s applicability to the U.S. situation. Chapter 6 presents the committee’s findings and recommendations, first for the generic case and thereafter specifically for Yucca Mountain. The appendixes elaborate on important issues raised in the main text. Appendix G provides a glossary of key terms.

A geologic repository program typically consists of the following phases:⁵

1. selection of specific geologic disposal option(s),

2. site selection and characterization,⁶

3. licensing,⁷

4. construction,

5. operation,

6. closure, and

7. post-closure.

The time frame for each phase varies considerably: from a few years to decades for selecting the geologic disposal option and the site; through several decades of operations, and up to centuries for the closure; and many thousands of years for the post-closure phase. Not all national repository programs include all these phases. The phases cited above are described in Chapter 3.

Compared to other large engineering projects,⁸ geologic repositories for high-level waste are peculiar undertakings because (1) they are first-of-a-kind, complex, and long-term projects that must actively manage hazardous materials during the operational phase; (2) they are expected, using natural and engineered barriers, to hold these hazardous materials passively safe for many millennia after repository closure; and (3) they are widely perceived to pose serious risks. These challenges are discussed briefly below.

• First-of-a-kind. There are no licensed geologic repositories for high-level waste in the world.⁹ This untested status of high-level nuclear waste disposal systems creates technical and societal uncertainties. The principal technical uncertainties arise from the complexity of the geologic system and the impossibility of demonstrating at closure the safety of the repository over tens of thousands of years in the future (see Sidebars 1.2 and 1.3). The prediction of long-term behavior of natural and engineered barriers must rely on modeling rather than operational experience. In the presence of such uncertainties, unexpected discoveries are inevitable.

• Complex. “Complex” means composed of many interconnected parts. More than in other objectively complex, large-scale, engineered facilities, such as

space programs or modern chemical processing plants, geologic repositories are heterogeneous systems with natural and engineered components that require timely integration of scientific, technological, institutional, and societal processes.

• Long-term. Repositories present two long-term challenges: (1) program development and (2) safety demonstration. Program development (i.e., siting, constructing, operating, and closing a repository) takes at a minimum, several decades. It is difficult, if not impossible, to plan clearly and reliably to the end of such a project. A future generation will be charged with ending the project.

SIDEBAR 1.2 Is Building a Repository Different from Building a Large Dam? FIGURE 1.1 On the left, a picture of a tunnel and the tunnel-boring machine in the Experimental Studies Facility at Yucca Mountain, the proposed high-level radioactive waste geologic repository site in Nevada, United States. On the right, the Hoover Dam, Nevada. Dams and repositories are both large public works projects that involve significant hazards. The two have selected challenges in common: They necessitate a cautious and prudent engineering approach to help ensure adequate safety. Both dams and repositories aim at a high degree of robustness, achieved in part through engineering over-design. They can result in major societal controversies, and increasingly do so. Dams were successfully built decades ago; today it is debatable whether a major dam could be built without controversy. Controversy also surrounds repository projects. There are also important differences between the new challenges presented by repository development and the more familiar challenges of dam building: Society has a long history and much experience in building dams. Society has no experience building and operating a geologic repository for high-level radioactive waste.

Although demonstrating repository safety over tens of thousands of years is impossible, a high level of confidence in future repository performance is essential because some radioactive waste remains hazardous for a very long time (up to millions of years).

• Risk. Handling high-level radioactive material entails risks. Two different aspects of risk influence implementation approaches: (1) the long life of radioactive waste means that a legacy of risk is passed on to future generations, and (2) the public perceives repositories as risky because of the well-documented public dread associated with nuclear technologies (Flynn et al., 1993).

• Negative public image. History and current events connect nuclear technologies with weapons and war. Nuclear fission, even before its use could be

harnessed and made practical, was viewed with deep ambivalence and great suspicion (Weart, 1988). Public distrust has expanded to the institutions managing nuclear technologies. This connection helps explain the negative public images associated with radioactive waste (Dunlap et al., 1993).

• Controversy. Many aspects of radioactive waste management are controversial, this controversy being often associated with the more general debate on nuclear energy. There is often little or no societal agreement on waste management goals, siting, disposing, transporting, securing, funding, and policy-making. All are issues on which strongly differing opinions are held. Controversy equally applies to ethical issues, such as societal values, institutional integrity, and inter- and intra-generational equity. The lack of agreement on program goals is a source of public skepticism or worse a basis for distrusting the institutions charged with formulating and implementing the specific policies (NRC, 2001).

A National Research Council committee previously addressed these technical and societal issues (NRC, 2001), that place special demands on the management approach. For example, the lack of precedent suggests the need for a management approach characterized by continuous learning and flexibility. Moreover, the decades-long development of a geologic repository requires a flexible approach that incorporates new knowledge as the program unfolds. An earlier report of the National Research Council on high-level waste management suggested a flexible approach that acknowledges the following premises:

In a flexible approach, confidence in the long-term safety of a geologic disposal system should be maintained or enhanced as the program evolves. This implies that assessing the impact on safety of any programmatic change becomes an important task to be performed iteratively throughout development. There is a developing international consensus (International Atomic Energy Agency [IAEA], 1997; NEA, 1999a, 2001a; NRC, 2002) that an appropriate “tool” for assessing confidence in the long-term safety of a geologic disposal system is preparation of a safety case, which is described in Sidebar 2.1.

Because of the first-of-a-kind nature and the controversy over goals, together with the real and perceived risks, the repository development program needs reversibility as long as feasible. Indeed, if alternative goals are to remain open as progress down a chosen path occurs, then reversibility is required for a program to be credible.

Similarly, a previous National Research Council Report emphasizes the importance of demonstrating reversibility of actions:

“Demonstrated reversibility of actions in general, and retrievability of wastes in particular, are highly desirable because of public reluctance to accept irreversible actions” (NRC, 2001, p. 3).

The complex framework of technical, societal, and institutional issues surrounding geologic repositories along with historical connections of radioactive waste to nuclear programs, often associated with secrecy and controversy, requires a management approach that demonstrates transparency, flexibility, integrity, responsiveness, and willingness to engage in a dialogue with all parties.¹⁰ The recent report on geologic disposition of high-level waste recommended:

What defines success for a geologic repository program? The repository implementer’s focus is often on disposing of a set amount of waste in a set time for a set cost or having all the waste underground in a sealed repository. These answers do not fully account for the technical and societal challenges mentioned above, the long times over which the program will be developed, or the much longer time required for waste isolation.

First and foremost, the ultimate measure of success of a repository is the extent to which it isolates the waste from the accessible environment for all future time during which the waste remains hazardous. In the committee’s view a more pragmatic and useful definition of success for the implementer focuses on a safe geologic repository that is also cost-effective,¹¹ follows an adaptable reference framework¹² rather than a rigid schedule, and is societally acceptable. More concretely and more measurably, the committee defines a successful geologic repository program as one in which:

• a geologic site and engineered system, judged to be technically suitable using the particular country’s accepted regulatory, public, and political processes, have been identified;

• operational and long-term safety aspects are made consistent with the current scientific understanding of repository systems; safety features are reviewed; and the necessary licenses are granted;

• an ongoing long-term monitoring and observation program designed to substantiate the current scientific understanding of the safety aspects of the repository system is in progress;

• sufficient societal consensus is achieved to allow operations to begin and continue;

• initial waste emplacement has taken place with plans for reversibility;

• all necessary safety and security measures are set up to emplace additional waste, if decided;

• procedures and funding arrangements¹³ are agreed to for either:

  • backfilling (if used), closing, and sealing the repository¹⁴ (if technical and societal confidence in its long-term isolation properties continues); or

  • maintaining capability for long-term control and monitoring, and capability for retrieving wastes, if waste retrieval is necessary for technical or societal reasons.

A successful repository program is different from a successful repository. Success of the repository itself will only be known far into the future, after thousands of years have passed without significant release of radionuclides into the accessible environment. The committee’s definition of a successful program emphasizes the goal of achieving the required degree of technical and societal consensus to begin waste emplacement and the incremental improvement of waste emplacement operations, rather than moving rapidly to full-scale emplacement. Repository implementers often view a fast ramp to full-scale emplacement and rapid waste emplacement until the repository is filled as a measure of success (since they may be under pressure to rapidly accept waste for disposal). This is consistent with Linear Staging but not with Adaptive Staging. Rather, with Adaptive Staging, a more deliberate, cautious, incremental (learn-as-you-go) set of intermediate goals is implemented on the way to the final goal of a successful repository.

This milestone of initial waste emplacement is important for the implementer to demonstrate the technical and societal viability of geologic disposal.¹⁵ A successful repository program is one that convinces the technical, regulatory, stakeholder,¹⁶ and policy communities that the repository will be safe enough to close, but that

arrangements have been made to monitor and continue to evaluate its safety over long time periods.

Although ultimate success will be known only in the far future, one can identify a number of requisites for the successful development of a repository program:

• recognition of future generations’ right to a safe and affordable nuclear waste disposal route;

• sufficient consensus on program goals (e.g., safety, cost-effectiveness, and societal acceptability);

• formulation of a reference framework for final disposal, with alternatives, and with the possibility to reverse the course of actions at any point in time;

• recognition that protecting public and worker health and safety at all times is the highest goal, taking precedence over minimizing the time or the costs for implementing disposal projects for radioactive wastes;

• deliberate incorporation of technical and societal input (including input provided by stakeholders) into the stages of the reference framework to maximize safety, cost-effectiveness, and acceptability;

• recognition of the need for regular examination and periodic revisions of the safety aspects of the repository system and of its underlying assumptions;

• recognition of the possibility that the reference framework may evolve using knowledge gained along the way;

• formulation within the reference framework of processes for implementing such potential changes;

• recognition of change as a positive experience and an opportunity to optimize the system; and

• acceptance of responsibility for and timely implementation of key decisions based on assuring safety at all times.

Adopting such a framework does not preclude the disposition of waste in a timely fashion. It does, however, place primary emphasis on the sequential and deliberate development of confidence in repository operations and ultimate performance, with emplacement consistent with such a staged approach.