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SUMMARY Since 1955, the National Research Council (NRC) has been advising the U.S. government on technical matters related to the management of radioactive waste. Today, this advice is provided by the Board on Radioactive Waste Management (BROOM or "the Board"), a permanent committee of the NBC. The conclusions presented in this position statement are the result of several years of discussions within the Board, whose members possess decades of professional experience in relevant scientific and technical fields. In July 198S, the Board convened a week-long study session in Santa Barbara, California, where experts from the United States and abroad joined BROOM in intensive discussions of current U.S. policies and programs for high-level radioactive waste (ELBOW) management. The group divided its deliberations into four categories: (1) the limitations of analysis; (2) moral and value issues; (3) modeling and its validity; and (4) strategic planning. A summary of the findings of these discussions, from which this position statement has been developed, follows the Summary. Current U.S. Policy and Program In the Nuclear Waste Policy Act of 1982 (NWPA), Congress assigned responsibility to the Department of Energy (DOE) for designing and eventually operating a deep geological repository for high-level radioactive waste. The repository must be licensed by the U.S. Nuclear Regulatory Commission (USNRC) and must meet radionuclide release limits, based on a generic repository, that would result in less than 1000 deaths in 10,000 years as specified in a Standard established by the Environmental Protection Agency (EPA) (40 CFR 191~. The U.S. program is unique among those of all nations in its rigid schedule, in its insistence on defining in advance the technical requirements for every part of the multibarrier system, and in its major emphasis on the geological component of the barrier as detailed in 10 CFR 60. Because one is predicting the fate of the HLW into the distant future, the undertaking is necessarily full of uncertainties. In this sense the government's HLW program and its regulation may be a "scientific trap" for DOE and the U.S. public alike, encouraging the public to expect absolute certainty about the safety of the repository for 10,000 years and encouraging DOE program managers to pretend that they can provide it. For historical and institutional reasons, DOE managers tend to feel com- pelled to do things perfectly the first time, rather than to make changes in concept and design as unexpected geological features are encountered and

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2 as scientific understanding develops. This "perfect knowledge" approach is unrealistic, given the inherent uncertainties of this unprecedented undertaking, and it runs the risk of encountering "show-stopping" problems and delays that could lead to a further deterioration of public and scientific trust. To- day, because of the regulatory requirements and the way the program is being carried out, U.S. policy has not led to satisfactory progress on the problem of radioactive waste disposal. Scientific Consensus on Geological Isolation There is a strong worldwide consensus that the best, safest long-term option for dealing with HEW is geological isolation. High-level waste should be put into specially designed and engineered facilities underground, where the local geology and groundwater conditions have been chosen to ensure isolation of the waste for tens of thousands of years or longer, and where waste materials will migrate very slowly if they come into contact with the rock. Although the scientific community has high confidence that the general strategy of geological isolation is the best one to pursue, the challenges are formidable. In essence, geological isolation amounts to building a mine in which `'ore" will be put back into the ground rather than taken out. Mining, however, has been and remains fundamentally an exploratory activity: be- cause our ability to predict rock conditions in advance is limited, miners often encounter surprises. Over the years, mining engineers have developed methods to deal with the vagaries of geological environments, so that min- eral extraction and construction can continue safely even when the conditions encountered are different from those anticipated. It is at this point that geological isolation of radioactive waste differs in an important sense from mining. In the United States, radioactive waste management is a tightly regulated activity, surrounded by laws and regula- tions, criteria and standards. Some of these rules call for detailed predictions of the behavior of the rock for the tens of thousands of years that the radioactive materials are to be isolated. Preparing quantitative predictions so far into the future stretches the limits of our understanding of geology, groundwater chemistry and movement, and their interactions with the emplaced material (radioactive waste package, backfill, sealants, and so forth). Although the basic scientific principles are well known, quantitative estimates (no matter how they are obtained) must rely on many assumptions. As a consequence, the resulting estimates are uncertain to some degree, and Hey will remain uncertain no matter how much additional information is gathered.

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3 Treatment of Uncertainty The character and implications of these uncertainties must be clearly understood by political leaders, program managers, and the concerned pub- lic. Engineers and scientists, no matter how experienced or well trained, are unable to anticipate all of the potential problems that might arise in trying to site, build, and operate a repository. Nor can science "prove" (in any absolute sense) that a repository will be "safe" as defined by EPA standards and USNRC regulations. This is so for two reasons. First, proof in the conventional sense cannot be available until we have experience with the behavior of an engineered repository system- precisely what we are trying to predict. The existence of uncertainties has prompted efforts to improve the technical analysis, but there will always remain some residual uncertainty. It is important to recognize, however, that uncertainty does not necessarily mean that the risks are significant. What it does mean is that a range of results are possible, and a successful management plan must accommodate residual uncertainties and still provide reasonable assurance of safety. Second, safety is in part a social judgment, not just a technical one. How safe is safe enough? Is it safer to leave the waste where it is, mostly at reactor sites, or to put it in an underground repository? In either case safety cannot be 100 percent guaranteed. Technical analyses can provide background for answering such questions, but ultimately the answers depend on choices made by the citizens of a democratic society. The EPA has not based its standards (which must allow for these choices by the citizenry) on social judgments derived from realistic consideration of these alternatives. Both of these important limitations of the analysis have been understated. The federal government must provide full public accountability as infor- mation about the risks changes with experience. This is not an impossible task: government and business make decisions every day under similar conditions of uncertainty. But a policy that promises to anticipate every conceivable problem, or assumes that science will shortly provide all the answers, is bound to fail. The public has been told too often that absolute guarantees can be provided, but most citizens watching the human frailties of their governments and technologists know better. A realistic and attainable- goal is to assure the public that the likelihood of serious unforeseen events (serious enough to cause catastrophic failure in the long term) is minimal, and that the consequences of such events will be limited. These assurances rest on the credible application of general principles, rather than a reliance on detailed predictions.

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4 Modeling of Geological Processes The current U.S. approach to developing a geological repository (with a mandated 10,000-year lifetime) for radioactive waste is based on a regula- tory philosophy that was developed from the licensing of nuclear power plants (which have a nominal 40-year lifetime). The geological medium, however, cannot be specified in advance to the degree possible for man- made components, such as valves or electronic instruments, nor can it be tested over its projected lifetime as can many man-made components. Commercial mining and underground construction both operate on the sound principle of "design (and improve the design) as you go." The inherent variability of the geological environment necessitates changes in specifications as experience increases. If that reality is not acknowledged, there will be unforeseen delays, rising costs, frustration among field personnel, and loss of public confidence in the site and in the program. Models of the repository system are useful, indeed indispensable. The computerized mathematical models that describe the geological structure and hydrological behavior of the rock are needed to manage the complex calculations that are necessary to evaluate a proposed site. Models are vital for two purposes: (1) to understand the history and present characteristics of the site; and (2) to predict its possible future behavior. Putting the available data into a coherent conceptual framework should focus attention on the kinds of uncertainty that persist. For example, the modeling of groundwater flow through fractured rock lies at the heart of understanding whether and how a repository in hard rock will perform its essential task of isolating radioactive materials. The studies done over the past two decades have led to the realization that the phenomena are more complicated than had been thought. Rather than decreasing our uncertainty, this line of research has increased the number of ways in which we know that we are uncertain. This does not mean that science has failed: we have learned a great deal about these phenomena. But it is a commonplace of human experience that increased knowledge can lead to greater humility about one's ability to fully understand the phenomena involved. Uncertainty is treated inappropriately in the simulation models used to describe the characteristics of the waste repository. As the quantity of information about natural geological settings grows, so too does our appre- ciation of their variability and unpredictability. This distinction has often been ignored. Indeed, the very existence of large databases and sophisticated computer models suggests, erroneously, that it is appropriate to design a geological repository as if it were a nuclear power plant or jet airliner, both of which have predictable attributes over their short lifetimes. That assumption of accurate predictability will continue to produce frustration and failure. Under the present program models are being asked to provide answers to

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5 questions that they were not designed to address. One scientifically sound objective of geological modeling is to learn, over time, how to achieve reasonable assurance about the long-term isolation of radioactive waste. That objective is profoundly different from predicting quantitatively the long-term behavior of a repository. Yet, in the face of public concerns about the safety of HEW disposal, it is the latter use to which models have been put. The Board believes that this use of geological information and analytical tools- to pretend to be able to make very accurate predictions of long-term site behavior is scientifically unsound. Its conclusion is based on detailed reviews of the methods used by the DOE and the regulatory agencies in implementing the NWPA. Well-known geophysical principles can be used to estimate or to set bounds on the behavior of a site, so that its likely suitability as a waste repository can be evaluated. But it is inappropriate to stretch the still-incomplete understanding of a site into a quantitative projection of whether a repository will be safe if constructed and operated there. Only after a detailed and costly examination of the site itself can an informed judgment be reached, and even then there will still be uncertainties. Many of the uncertainties associated with a candidate repository site will be technically interesting but irrelevant to overall repository performance. Further, the issues that are analytically tractable are not necessarily the most important. The key task for performance modeling is to separate the significant uncertainties and risks from the trivial. Similarly, when there are technical disputes over characteristics and processes that affect calcula- tions of waste transport, sensitivity analysis with alternative models and parameters can indicate where further analysis and data are required and where enough is known to move on to other concerns. It may even turn out to be appropriate to delay permanent closure of a waste repository until adequate assurances concerning its long-term behav- ior can be obtained through continued in-site geological studies. Judgments of whether enough is known to proceed with placement of waste in a repository will be needed throughout the life of the project. But these judgments should be based on a comparison of available alternatives, rather than a simplistic debate over whether, given current uncertainties, a repository site is "safe." Even while the detailed, long-term behavior of an underground repository is still being studied, it may be marginally safer to go ahead and store reactor waste there (in a way that permits retrieval if necessary), rather than leaving it at reactors. As a rule, the values determined from models should only be used for comparative purposes. Confidence in the disposal techniques must come from a combination of remoteness, engineering design, mathematical modeling, performance assessment, natural analogues (see below), and the possibility

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6 of remedial action in the event of unforeseen events. There may be political pressure on implementing agencies to provide absolute guarantees, but a more realistic and attainable- goal is to assure the public that the likeli- hood of unforeseen events is minimal, and that the magnitude of the conse- quences of such events is limited. Such an alternative approach, now being used in Canada and Sweden, promises to be far more successful in achieving a safe and practical waste disposal system. Moral and Ethical Questions Radioactive waste poses hazards that raise moral and ethical concerns. First, some of the radioactivity lasts for extremely long periods of time- the EPA standard for HEW calls for isolation of the waste for 10,000 years and more, a time longer than recorded human history. Second, the risks of high-level waste will be concentrated at a very few geological repositories. The neighbors of proposed waste repositories have understandably been alarmed at the prospect of hosting large quantities of a material that needs to be handled with great care. Ethical studies in this area underscore two points: (1) the central role of a fair process; and (2) the pervasive problem of promising more certainty than can be delivered. The need for a fair process is simply stated: people feel threatened by radioactive waste; and they deserve to be taken seriously in the decision- making process. The sense of threat is often ill informed, in a narrow technical sense, but when that occurs, it is the duty of technical experts and program managers to provide information and employ analyses that will be credible to the affected populations. Only with valid information that they believe can those affected parties negotiate equitable solutions. The primary goal of the program is to provide safe disposal; a secondary goal is to provide it without any gross unfairness. As a result, the mechanisms of negotiation, persuasion, and compensation are fundamental parts of any program to manage and dispose of radioactive waste not mere procedural hoops through which program managers must jump. The second ethical point is also important: the demand for accountabil- ity in our political system has fostered a tendency to promise a degree of certainty that cannot be realized. Pursuing that illusory certainty drives up costs without delivering the results promised or comparable benefits. The consequence is frustration and mistrust. For example, it is politically costly to admit that one has been surprised in exploring sites being considered for HEW repositories. Yet, this situation is self-defeating: surprises are bound to occur because a principal reason for exploration is to discover what is there. Instead of pursuing an ever-receding mirage, it is sensible to pursue an empirical exploratory approach: one that emphasizes fairness in the process

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7 while seeking outcomes that the affected populations judge to be equitable in light of their own values. This is not an easy course, but it is necessary. An Alternative Approach There are scientific reasons to think that a satisfactory HEW repository can be built and licensed. But for the reasons described earlier, the current U.S. program seems unlikely to achieve that desirable goal. The Board proposes an alternative approach that is built on well-defined goals and objectives, utilizes established scientific principles, and can be achieved in stages with appropriate review by regulatory and oversight bodies and with demonstrated management capabilities. The Board suggests an institutional approach that is more flexible and experimental in other words, a strategy that acknowledges the following premises: · Surprises are inevitable in the course of investigating any proposed site, and things are bound to go wrong on a minor scale in the development of a repository. If the repository design can be changed in response to new information, minor problems can be fixed without affecting safety, and major problems, if any appear, can be remedied before damage is done to the environment or to public health. This flexible approach can be summarized in three principles: · Start with the simplest description of what is known, so that the larg- est and most significant uncertainties can be identified early in the program and given priority attention. · Meet problems as they emerge, instead of trying to anticipate in advance all the complexities of a natural geological environment. Define the goal broadly in ultimate performance terms, rather than immediate requirements, so that increased knowledge can be incorporated in the design at a specific site. . In short, this approach uses a scientific approach and employs modeling tools to identify areas where more information is needed, rather than to justify decisions that have already been made on the basis of limited knowledge. The principal virtue of this strategy is that it would use science in the proper fashion. It would be similar to the strategies now being followed in Canada and Sweden, where the exploration and construction of an underground test laboratory and a shallow underground low-level waste repository have followed a flexible path. At each step, information and understanding developed during the prior stages are combined with experience from other underground

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8 construction projects, in order to modify designs and procedures in light of the growing stock of knowledge. During operations and after closure of the facilities, the emphasis will be on monitoring and assuring the capability to remedy unforeseen problems. In that way, the possibility is minimized that unplanned or unexpected events will compromise the integrity of the facil- ity. This flexible approach has more in common with research and underground exploration than with conventional engineering practice. The idea is to draw on natural analogues, integrate new data into the expert judgments of geologists and engineers, and take advantage of favorable surprises or compensate for unfavorable ones. Natural analogues—geological settings in which naturally occurring radioactive materials have been subjected to environmental forces for millions of years— demonstrate the action of transport processes like those that will affect the release of man-made radionuclides from a repository in a similar setting. Where there is scientific agreement that the analogy applies, this approach provides a check on performance assessment methodology and may be more meaningful than sophisticated numerical predictions to the lay public. A second element is to use professional judgment of technical experts as an input to modeling in areas where there is uncertainty as to parameters, structures, or even future events. Such judgments, which may differ from those of DOE program managers, should be incorporated early in the process; a model created in this way might redirect the DOE program substantially. The large number of underground construction projects that have been completed successfully around the world are evidence that this approach works well. Implicit in this approach, however, is the need to revise the program schedule, the repository design, and the performance criteria as more information is obtained. Putting such an approach into effect would require major changes in the way Congress, the regulatory agencies, and DOE conduct their business. The Risk of Failing to Act Given the history of radioactive waste management in the United States, a likely alternative is that the program will continue as at present. That would leave the nation's inventory of high-level waste, indefinitely, where it is now: mostly at reactor sites at or near the earth's surface. By the year 2000, spent fuel is expected to contain more than 3 x 10~° curies, while High Level Waste is expected to contain another 109 curies.* This alternative is safe in the short term~n-site storage systems are safe for at least 100 *Integrated Database for 1988: Spent Fuel and Radioactive Waste Inventories, Projections,and Characteristics: DOE/RW-0006Revision4,Sept.1988.

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9 years, according to present evidence.* The at-surface alternative may be irresponsible for the long run, however, due to the uncertainties associated with maintaining safe institutional control over HEW at or near the surface for centuries. In judging disposal options, therefore, it is essential to bear in mind that the comparison is not so much between ideal systems and imperfect reality as it is between a geologic repository and at-surface storage. From that standpoint, both technical experts and the general public would be reassured by a conservative engineering approach toward long-term safety, combined with an institutional structure designed to permit flexibility and remediation. Waste Confidence Decision Review. 54 FR 39767 (Sept. 28, 1989)