7—
Uncertainty: An Obstacle to Geological Disposal
The authors of a recent U.S. Geological Survey study of the Yucca Mountain site, proposed as the first permanent high-level radwaste repository in both the United States and the world, warned that site "data are not sufficient to predict accurately rates of [ground]-water movement and travel times."[1] One question raised by the USGS warning is whether the Yucca Mountain predictions, although inaccurate, are accurate enough for us to build the repository. Indeed, this is the same question raised by the three previous chapters. Are the controversial methodological value judgments and questionable inferences in the repository risk estimates and evaluations significant? Or are the risk assessments nevertheless accurate enough to justify permanent geological disposal of high-level radwaste?
If no scientific result is ever certain or completely objective, and if no policy is ever perfectly just, a reasonable person ought fault neither science nor policy merely for uncertainty, subjectivity, or incomplete justice. The real issue is the significance of the apparent problems. How objective is objective enough? How certain is certain enough? How just is just enough? How ought one to interpret the revelations and accusations of the last three chapters? In this chapter, we argue (1) that, in the paradigm case of Yucca Mountain, the sensitivity and the precision of the risk assessments of the site are not adequate for existing, precise regulation; therefore, the facility ought not be sited anytime in the foreseeable future (the next century). Moreover, building on the analyses of the last three chapters, we argue (2) that scien-
tific uncertainties associated with any proposed site anywhere are so extensive and problematic that we ought not adopt permanent geological disposal any time in the foreseeable future.
We Cannot Adequately Guarantee Yucca Mountain Safety
Given the questionable methodological value judgments and inferences made in Yucca Mountain risk assessments (see chapters 4 through 6), as well as the knowledge that similar judgments appear to have contributed to problems at other DOE radioactive waste facilities (such as Maxey Flats, Fernald, Savannah River, Hanford, Idaho Falls, and Rocky Flats), an obvious question is whether the Yucca Mountain site itself is known well enough to guarantee long-term isolation of radionuclides and compliance with government regulations. Do the available data and site characteristics lead one to believe that QRAs of Yucca Mountain can be done with sensitivity and precision adequate to insure credible regulation and long-term safety?
Many risk assessors believe that the data and the site are adequate to insure excellent regulation and safety. They say that Yucca Mountain would comply with the regulations.[2] This methodological value judgment, however, is quite controversial given all the ways in which incomplete data, inadequate theory, uncertainty, and site heterogeneity threaten accurate knowledge of Yucca Mountain (see chapters 4 through 6). Even DOE assessors use language that suggests their largely qualitative and imprecise knowledge of the site is a problem. Note, for example, the DOE's use of the terms "estimate," "likely," and "significant" in the following claim:
[E]stimates of groundwater travel time along any path of likely and significant radionuclide travel from the disturbed zone to the accessible environment are more than 1,000 years. Therefore, the evidence does not support a finding that the site is disqualified.[3]
Presumably, if DOE officials were more certain about Yucca Mountain safety, they would speak of "calculations" or definite "probabilities" of given groundwater travel times and not of "estimates." Likewise, if their data were more accurate, presumably they would speak of threats posed by "any path of radionuclide travel," rather than of threats "along any path of likely and significant radionuclide travel." As the
DOE's own words illustrate, its claims of safety are laden with vague statements, with methodological value judgments, and with language that avoids assigning any probabilities to regulatory compliance. The DOE officially admits, for example:
The characteristics of the Yucca Mountain site and the processes operating there permit, and probably ensure, compliance with the limits on radionuclide release to the accessible environment.[4]
When one is considering a potentially catastrophic threat to health and safety, however, one requires a very high probability that the site in question will comply with regulations.
One of the main reasons why the methodological value judgment—that site knowledge is adequate for regulation and for safety—is questionable is that the various DOE probabilities allegedly associated with site characteristics are already very close to the limits of regulatory acceptability. Hence, given a variety of questionable inferences, assumptions, and value judgments made by assessors,[5] actual site characteristics might not comply with regulations. Changes of only 1 order of magnitude in some of the parameters dealing with fracture flow, infiltration, precipitation, or volcanic and seismic activity could initiate disastrous changes—such as flooding or unacceptably rapid groundwater transport—in the Yucca Mountain repository. As Amory Lovins warned, an error factor of 2 at each stage of a 20-step methodology permits a possible millionfold mistake.[6] For example, increasing the alleged percolation rate by only 1 order of magnitude could initiate fracture flow and speed groundwater travel time.[7] Such sensitive numbers, together with the 2 to 6 orders of uncertainty characterizing many risk assessments (see chapters 4 through 6), show that the margin for error at Yucca Mountain may be too slim to insure adequate government regulation and safety. Even the NAS noted that the DOE assumes, incorrectly, "that the properties and future behavior of a geological repository can be determined and specified with a very high degree of certainty." "In reality," said the U.S. National Academy of Sciences (NAS), "the inherent variability of the geological environment will necessitate frequent changes in the specifications."[8] But if geological variability necessitates changes in repository specifications, then there is question whether a facility like Yucca Mountain can meet the predetermined U.S. safety regulations.
As we already mentioned in chapter 4, porous flow alone would mean leachate could reach the water table at Yucca Mountain in ten
to twenty thousand years.[9] Fracture flow, however, could enhance transport of water and radioactive leachate, above the flux at Yucca Mountain, by as much as 5 orders of magnitude.[10] Assessors have confirmed that "fractures do exist of sufficient width to allow significant water flow in the unsaturated region."[11] Moreover, with a large fracture-flow rate, 99 C, 238 U, and 237 Np could get through to the water table in less than ten thousand years.[12] Hence, understanding fracture flow is a crucial determinant of site safety. Yet knowledge of fractured zones, particularly for unsaturated regions, is very limited. Likewise, the seismicity at Yucca Mountain, prior to 1960, is virtually unknown even though seismic failure is possible.[13] One wonders how a possibly seismic, fractured site, even in an arid climate like Yucca Mountain, could be acceptable if volcanism, intruding water, and seismic activity were not highly improbable during the life of the repository.[14] At Yucca Mountain, these conditions do not appear to be highly improbable.
A person who makes the value judgment that site knowledge is sufficient for regulation and for safety is in the questionable position of knowing that significant problems could occur with fracture flow, seismicity, and volcanism, yet not being able to predict any of them accurately—because of all the difficulties with modeling, sampling, extrapolation, and so on, already discussed. Even the Nuclear Regulatory Commission (NRC) officials recognized some of these problems when they complained that the Yucca Mountain risk assessments fail to recognize adequately the uncertainty in the data. Likewise, the NAS warned that "uncertainty is treated inappropriately" in the Yucca Mountain assessments.[15] Indeed, the NRC said that the environmental assessments of the DOE for its proposed radwaste facilities are, in general, "overly optimistic."[16] Such optimism often appears almost gratuitous, because it is not based on precise, quantitative predictions. For example, an official DOE document claims that the site can protect the safety of all future generations from radiological hazards:
The quality of the environment during this and future generations can be adequately protected. Estimates of radiation releases during normal operation and worst-case accident scenarios provide confidence that the public and the environment can be adequately protected from the potential hazards of radioactive-waste disposal.[17]
Equally gratuitous is the DOE claim that no future groundwater conditions will disrupt the site:
Currently available engineering measures are considered more than adequate to guarantee that no disruption of construction and operation will occur because of groundwater conditions at Yucca Mountain.[18]
Such assurances are highly questionable, given present uncertainties about basic hydrological and geological conditions at the site. For example, at Yucca Mountain "in most cases, hydraulic data are insufficient for performing geostatistical analyses,"[19] and "traditional flow path chemical evaluation does not directly apply to tuffaceous volcanic environments."[20] Likewise, there is "no known mechanical model that describes nonuniform corrosion well enough to use in performance assessment" of the waste canisters.[21] In areas of hydrology, geology, canister security, climate, volcanism, and seismicity, no techniques exist, at the present time, that are adequate for removing the uncertainties at Yucca Mountain or even for quantifying them.[22] Basic questions concerning the reliability of the studies remain unanswered.[23] Indeed, how could significant uncertainties be removed if one required precise predictive power and regulatory guarantees regarding the site for ten thousand years?
The long time period of storage is one reason that Yucca Mountain reviewers have claimed that "compliance with U.S. [radiation-dose] limits cannot be shown objectively by PRA [probabilistic risk assessment] methods."[24] One reason for this problem is that the precise, probabilistic standards of the Environmental Protection Agency for the management of spent fuel and high-level and transuranic radioactive wastes cannot be confirmed with current data. The standards set limits for releases when events have more than a 1 in 10 chance of occurring over the ten thousand years.[25] Such precise probabilistic standards cannot be guaranteed for so long a time, however, As one reviewer put it: "No assurance can be given that all significant factors have been examined here."[26] Other reviewers maintain that it is doubtful whether we can model or predict long-term behavior at all, given the heterogeneities and uncertainties at the site.[27] Still other evaluators, including those from the utility industry and the NAS, have proclaimed that the limits of environmental science have been exceeded by the goals set by the nation's radioactive waste program.[28] Perhaps the most significant analysis of how scientific uncertainties undercut assurances of repository safety is that of the DOE team of fourteen peer reviewers who in 1992 analyzed the DOE's Early Site Suitability Evaluation for Yucca Mountain. The "consensus position" of the fourteen DOE-selected peer reviewers is telling:
It is the opinion of the panel that many aspects of site suitability are not well suited for quantitative risk assessment. In particular are predictions involving future geological activity, future value of mineral deposits and mineral occurrence models. Any projections of the rates of tectonic activity and volcanism, as well as natural resource occurrence and value, will be fraught with substantial uncertainties that cannot be quantified using standard statistical methods.[29]
Because of all the uncertainties in the Yucca Mountain data and methods, assessors typically are not able to determine the degree of accuracy in their models.[30] They are able, for example, merely to say that there is a "high level of probability" that groundwater travel time to the water table will exceed ten thousand years.[31] In other words, the degree of uncertainty regarding groundwater travel time is very great. Likewise, the margin of safety necessary to prevent significant problems, such as fracture flow, is quite slim. Yet, despite this narrow "window," some persons appear to believe that Yucca Mountain will be predictably safe or in compliance with government regulations requiring a groundwater travel time greater than one thousand years.[32] There is also only a "narrow window," or slim margin, of safety because groundwater travel time is extremely sensitive to fracture flow, and fracture flow is extremely sensitive to percolation rate. If either fracture flow or percolation increase by even a small amount, then the travel time of leachate from the waste will increase significantly.[33] In the world of groundwater flow, where risk assessments "are highly uncertain,"[34] a factor of 10 as a window of safety is quite small. Indeed, in some of the simulated cases, water travel time from the repository to the water table is less than one thousand years.[35] Hence, the methodological value judgment that current and near-future knowledge about Yucca Mountain can guarantee safety and compliance with government regulations—for example, requiring groundwater travel time of more than one thousand years—may be questionable.
The value judgment about travel time is not only factually questionable but also inconsistent. One well-known group of assessors, for example, found that, according to their models, some calculated groundwater travel times are less than ten thousand years. They also admitted that hydraulic data were insufficient and that there has not been enough time to estimate cumulative radioactive releases.[36] Nevertheless, they concluded that the "evidence indicates that the Yucca Mountain repository site would be in compliance with regulatory requirements"[37] and that "no radioactivity from the repository will migrate even to the water table immediately beneath the repository for
about 30,000 years."[38] How do some migration values of less than ten thousand years translate to a migration time of "about" thirty thousand years? How can the same DOE assessors claim that the repository will be in compliance with government regulations[39] when they also assert that low flux "will probably limit flow velocities to the extent that no leachate will reach the water table for tens to hundreds of thousands of years"?[40] Such poorly grounded "probable" knowledge of something that may occur within tens to hundreds of thousands of years (a wide range) is hardly consistent with precise claims about safety and regulatory compliance! Likewise, how can the same DOE assessors conclude, with confidence, that no radioactivity will migrate to the water table for at least thirty thousand years,[41] and yet claim: "Because data and understanding about water flow and contaminant transport in deep unsaturated fractured environments are just beginning to emerge, complete dismissal of the rapid-release scenarios is not possible at this time"?[42] How is the thirty-thousand-year claim consistent with the assertion about not dismissing the rapid-release scenarios?
Assessors investigating the uncertainties in the Yucca Mountain hydrogeological data also have admitted that, for the unsaturated zone, uncertainties in groundwater velocities may be as much as 100 percent above or below the mean value.[43] They likewise claim that a change in percolation of a factor of only 10 is sufficient to initiate fracture flow, that groundwater travel time is extremely sensitive to fracture flow,[44] and that heat from the waste could cause fractures.[45] Given such admissions, how can the same DOE assessors consistently claim that fracture flow is not a credible process,[46] and that groundwater flow will be "well within the limits set by the NRC"?[47] Similar inconsistencies appear when the same assessors, after acknowledging (1) that they have incomplete data,[48] (2) that they had no time to estimate cumulative radioactive releases,[49] and (3) that they may "have underestimated the cumulative releases of all nuclides during 100,000 years, by an amount that is unknown,"[50] nevertheless draw a contradictory conclusion. They conclude that only one ten-millionth of allowable releases of radionuclides will reach the water table.[51]
Likewise, Yucca Mountain assessors admit that solubility limits and retardation factors are site- and (radioactive) species-dependent.[52] They also claim that they may have underestimated radioactive releases.[53] If the same DOE assessors do not know the degree to which they may have underestimated radioactive releases,[54] how do they know so pre-
cisely that only one ten-millionth of allowable releases will occur? Similar inconsistencies and unsupported extrapolations occur throughout the Yucca Mountain analyses, with DOE assessors confidently affirming that there will be "less than one health effect every 1,400 years."[55] A more precise and consistent appraisal, given the problems with the data and models at Yucca Mountain, might be that of the assessors who concluded: "Even though we have tried to use the best data and models available at this time, we make no claims that these results have any value in the performance assessment of the Yucca Mountain repository site."[56]
Instead of using such precise language, however, the DOE's final 1992 Early Site Suitability Evaluation (ESSE) for Yucca Mountain continues to formulate site risks in terms of words such as "likely" and "unlikely" rather than by using numerical probabilities.[57] Similarly, when DOE reviewer M. T. Einaudi complained that the ESSE had vaguely defined the "foreseeable future" as "the next few years to 10 years, and occasionally as long as 30 years,"[58] the DOE ESSE team responded by removing from the document all language mentioning the number of years. Next the team noted:
The evaluation and definition of the terms, such as "reasonable projections" and "likely future activities" will receive considerable attention in the future and is likely to utilize the review of a panel of experts.[59]
This response, however, does not solve the problem with vague language, both because the DOE team uses the language to argue for site suitability, and presumably such usage must have implications. Indeed, if the language did not have certain implications regarding future time periods, then it would not be part of an effective argument for site suitability. Hence, if the terms are used effectively, they must have some precise, implicit meaning. If they do not have a precise, implicit meaning, then it is arguable that they are not effective in supporting the site-suitability conclusions and ought not be used. Indeed, by using indefinable terms to defend conclusions about site suitability, the ESSE renders its conclusions nonfalsifiable and therefore ineffective, because vague claims cannot be falsified. And if the ESSE site-suitability claims are not falsifiable, then this suggests that they are a priori rather than empirical and scientific.
Another reviewer (of the 1992 ESSE), J. I. Drever, also complained about the failure of the ESSE to provide rigorous definitions of words such as "likely" and "significant."[60] Again, the final ESSE
document did not alleviate the difficulty. Instead the ESSE Core Team responded to Drever's criticism:
The terms 'likely' and 'significant' should be defined in the context of the overall postclosure performance objectives. Because the evaluations of system performance cannot be definitive at this time, the ESSE Core Team believed it inappropriate to define those terms precisely for this evaluations.[61]
This response by the DOE team, however, creates more questions than it answers. For one thing, to say that terms like "likely" should be defined in terms of overall postclosure performance is not coherent, because the term "likely," for example, is rarely if ever used in the context of "total system performance." Rather, it is used in radically different but specific contexts, such as probability of human interference at the site or the probability of a route of radionuclide transport.[62] Hence, terms like "likely" not only do not refer to "overall performance," as the DOE team claimed, but, second , they are not univocal. They clearly mean different things in different ESSE contexts. Third , although the ESSE team says that such terms cannot be defined precisely because the system evaluations are incomplete, this response is puzzling because the ESSE team obviously has already used the terms to mean something. Fourth , if the system-performance evaluations are not definitive enough to allow the ESSE team to define the very terms that it uses, then it is unclear why the system-performance evaluations are definitive enough to support a lower-level suitability finding, rather than an unsuitability finding, for Yucca Mountain. Fifth , contrary to the response of the DOE ESSE Core Team, the terms used by the team clearly presuppose some precise meanings, because words like "likely" are often used in precise regulatory contexts, such as "not likely to exceed a small fraction of [radiation dose] limits."[63] If such terms were not used somewhat precisely, then it would be impossible for the claims in which they are imbedded not to be false. Likewise, the ESSE Core Team claims, for example, that "although confidence is substantial, it is not yet sufficient to support the higher-level suitability finding for this qualifying condition."[64] Such a claim appears to presuppose some precise level or cutoff of confidence or likelihood. It appears to presuppose that lower-level findings are justified below this level, and that higher-level findings are justified above it. For all these reasons, there appears to be a mismatch between the science and the regulations discussed in DOE assessments such as the ESSE. Because of this mismatch, it is ques-
tionable whether the science discussed in repository assessments is adequate to the regulatory task.
Previous experiences at the Maxey Flats low-level radwaste facility show that similar problems with value judgments about hydrogeological accuracy—and the ability of QRA to meet regulatory guidelines—may have occurred there. Environmental Protection Agency (EPA) assessors believed that the knowledge of the Maxey Flats site was adequate to insure containment, credible regulation, and safety largely because "the general soil characteristics" at the facility have been "very impermeable."[65] Yet such general assurances failed to address the problem of leachate migration with sufficient precision and accuracy. Other EPA geologists noted that precise determination of hydraulic conductivity is impossible at a site such as Maxey Flats, which has fractures.[66] United States Geological Survey scientists claimed that the Maxey Flats hydrogeology, because of the fractures, was "too complex for accurate quantitative description."[67] Given the complexity and uncertainty associated with much information about Yucca Mountain, there is reason to believe that optimistic value judgments about the accuracy of site studies may err just as they did at Maxey Flats. Because inaccurate knowledge of the Yucca Mountain facility prevents scientists from being able to predict precisely migration rates of the waste thousands of years into the future, it also prevents them from guaranteeing that the proposed repository will comply with very specific U.S. radiation-dose limits. Because compliance with government regulations is unknown, and because the consequences of repository failure could be catastrophic, it is arguable that the Yucca Mountain facility ought not be built, at least not until there is significantly more knowledge about the future risks likely to be associated with the installation.
Extensive, Nonquantifiable Uncertainty at Yucca Mountain Argues against Disposal
United States National Academy of Sciences panelists said that perhaps the United States should delay closing any permanent radwaste facility until we have more knowledge about long-term repository behavior. Likewise, a major U.S. government commission, studying policy for dealing with high-level radioactive waste, concluded recently that Congress should reconsider the subject of interim [rather than permanent] high-level radwaste storage by the year 2000
so as to "take into account uncertainties that exist today and which might be resolved or clarified within 10 years." Indeed, said the commission, "despite the considerable time and money already expended to site a repository, none has been sited yet, and the date by which a permanent repository will be available is uncertain. . . . the most notable uncertainty" is the "date of opening a permanent repository" in the United States.[68]
At least some of the reasons for the commission's worries, it appears, are the scientific uncertainties associated with the proposed facility at Yucca Mountain, many of which have been outlined in the preceding section and in chapters 4 through 6. Moreover, to the degree that this nonquantifiable uncertainty precludes assurance that precise radiation-control standards can be met during the thousands of years of operation of the proposed Nevada repository, to that extent it is arguable that we cannot yet guarantee the safety of permanent waste disposal. And if we cannot guarantee the long-term safety of proposed repositories like Yucca Mountain, then the "dig now, pay later" approach of repository supporters is highly questionable. Part of the rationale for delay or avoidance of a permanent U.S. repository is a basic legal premise: res inter alios acta alteri nocere non debet , that is, no one ought to suffer from what others have done.[69] Unless we can guarantee that many others in the future will not suffer unreasonably from what we have done in building a permanent repository, then our scientific uncertainty may be sufficient to argue against building the Yucca Mountain permanent repository.
Why does our uncertainty about whether Yucca Mountain will lead to catastrophe in the future argue against the facility? Although later we shall say more on this point, Brian Barry has provided one of the simplest rationales for the claim that the possibility of causing future catastrophe is a decisive reason for not acting in the present. He argues that (1) in the case of an individual making a possibly lethal choice that affects only himself, we should regard anyone who chooses the potentially fatal action—who claims that uncertainty makes it premature to decide against the action—as crazy. Likewise, says Barry, (2) when we change the case to one that involves millions of people and extends over many centuries, the same reasoning applies with increased force. Barry's rationale for (1) is that no rational person gambles with his own life except to gain a comparable benefit, to save it. Rock climbers, sky divers, and other risk enthusiasts, however, might claim that they are skilled and well trained and hence not gambling
with their lives since the probability of death for such a skilled person is low. Risk enthusiasts probably would also argue that they gain great benefits from their activities. Both Barry and these enthusiasts would likely agree, however, that as the benefits decreased and as the probability of death increased, the risky actions become more foolish. Hence, (1) is reasonable. Barry's rationale for (2) is that because the numbers of persons potentially at risk of death are larger, the impetus for choosing against the risk is likewise even greater. Despite reasoning such as Barry's, official DOE documents have argued for permanent repositories on exactly the grounds that Barry says are most questionable. He claims that anyone in this position—who argues that uncertainty makes it premature to decide against a potentially catastrophic action—is "crazy." Yet, the DOE repeatedly has argued for such a claim, for example:
A final conclusion on the qualifying condition for climatic changes cannot be made based on available data. However, the evidence does not support a finding that the reference repository location is not likely to meet the qualifying condition.[70]
In other words, DOE officials have used uncertainty about climatic changes as an argument for the thesis that the repository ought not be disqualified. Such an argument, like the many appeals to ignorance documented earlier in this volume, is problematic on both logical grounds and for the ethical reasons outlined by Barry. Moreover, in cases of future catastrophic risk, Barry's reasons (1) and (2) likewise are compelling because a repository catastrophe presumably could wipe out an entire culture, not just many persons, and destroying a culture may be worse than merely killing many people. Also, in the case of our threatening future generations, the repository risk is imposed without the consent of the possible victims, and it is not confined to the beneficiaries—a point that we shall discuss in more detail in the next chapter. For all these reasons, scientific uncertainty argues against siting permanent radwaste facilities like Yucca Mountain.[71]
Uncertainty and Permanent Disposal
Because Yucca Mountain has been proposed as the first permanent geological repository for high-level radioactive waste anywhere in the world, the United States is spending billions of dollars to
study and engineer the site. Indeed, as of 1991, more than $2.5 billion has already been spent in the formalities of site study and selection,[72] and the U.S. government was nowhere close to final approval of a single site. Because of the scientific and financial preeminence of Yucca Mountain, it provides a paradigm case of the risks and benefits associated with permanent disposal. Hence, if there are fundamental uncertainties associated with Yucca Mountain, the focus of the most ambitious and expensive permanent disposal program in the world, then unless there is a geologically more suitable site somewhere, there are likely to be similar uncertainties associated with other sites—and hence potential problems with building any permanent high-level repository in the foreseeable future.
Indeed, the earliest date that the United States could have a permanent geological facility for storage of high-level radioactive waste is 2010.[73] That deadline has already been moved forward many times. No other country is moving so quickly to permanent repositories. Officials in other nations have openly admitted that they are proceeding more slowly with high-level radioactive waste disposal, precisely because of the scientific uncertainties involved. As the Board on Radioactive Waste Management of the National Research Council of the U.S. National Academy of Sciences put it:
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. . . . It may even turn out to be appropriate to delay permanent closure of a waste repository until adequate assurances concerning its long-term behavior can be obtained through continued in-situ geological studies. . . . There are scientific reasons to think that a satisfactory HLW repository can be built and licensed. But for the reasons described earlier, the current U.S. program seems unlikely to achieve that desirable goal.[74]
What can we learn about the likelihood of success in permanent geological disposal on the basis of activities in the various countries considering the repository option?
Uncertainty and Permanent Disposal: Other Countries
In eight of the nations with the most radioactive waste, uncertainties have forced the countries to postpone permanent geo-
logical disposal. In Canada, for example, although nuclear reactors supply about 13 percent of the country's electricity, there has been no decision about spent reactor fuel, even though Canada will have approximately 34,000 MTU by the end of the century. Because Canada has made no decision about permanent disposal, the earliest Canadians could have such a repository is 2010, even assuming that it wanted one.[75]
Similarly, the French plan to use interim storage for a minimum of twenty years before moving to permanent disposal. Nuclear reactors currently supply more than 70 percent of French electricity. The earliest a permanent facility could be ready in France is 2010. The French rationale for delaying decisions about permanent storage is that cooling the waste would reduce the thermal impact on the host rock where it might be stored. (See chapter 9 for discussion of cooling the waste, as a U.S. option.) In the Yucca Mountain studies, many problems have arisen because of the ability of the high-temperature wastes to induce thermal fractures in the host rock, thereby increasing the probability of fracture flow of the leachate. Given such difficulties, "the French believe that the period [of interim storage] could be extended as long as needed because of the safety of monitored storage."[76]
Nuclear reactors supply approximately 40 percent of electricity in Germany. Like France, Germany is building interim storage facilities for high-level radioactive wastes, although the Germans hope to use deep geological disposal at the Gorleben salt dome. Even if the German plans are not delayed, the earliest a permanent repository could be ready is 2008. The Gorleben facility was licensed in 1983, but litigation concerning safety and scientific uncertainty has, so far, prevented its use as a repository for spent fuel.[77] In Japan, approximately 32 percent of the nation's electricity is supplied by nuclear reactors. Despite this fact, the Japanese appear to be quite concerned about a premature leap to an inadequately tested technology for permanent waste disposal. They plan to store their vitrified waste for thirty to fifty years before considering deep geological emplacement. In fact, the Japanese do not plan even to try to develop regulations for siting a permanent repository until after the year 2000. Hence, if approved, the earliest date at which a Japanese repository could operate is 2030.[78]
Spain is following a strategy similar to that of its European neighbors. With 36 percent of its electricity supplied by nuclear reactors, the Spaniards plan to store spent fuel at the reactors for ten years and
then to use interim storage for another forty years. Sometime around the turn of the century, they plan to consider possible candidate sites for permanent geological disposal. Their explicit strategy is to gain more experience dealing with the wastes before deciding what to do with them.[79]
In Sweden, approximately 50 percent of electricity is supplied by nuclear reactors. Because of scientific uncertainties and because they want to achieve a tenfold reduction in radiation and heat output from the waste, the Swedes are storing their spent fuel for thirty to forty years in centralized interim storage facilities. They do not expect to have a permanent facility available until some time after 2020.[80] Like the Swedes, the Swiss plan to store their spent fuel in interim facilities for forty years. Approximately 38 percent of electricity in Switzerland is supplied by nuclear reactors. The earliest a permanent repository could be available in Switzerland is sometime after 2025. Like the Swedes, the Swiss have laws and regulations that make it impossible to site a new commercial nuclear plant unless operators can demonstrate safe disposal of spent fuel. As a result, no new plants have been sited in either country.[81]
The United Kingdom, with 17 percent of its electricity coming from nuclear reactors, has one of the longest periods of interim storage of spent fuel, fifty years. Using interim storage at Sellafield has been necessary, in part, because of opposition in the U.K. to permanent disposal and because of scientific uncertainties associated with deep geological facilities. The earliest date by which the British could have a permanent repository ready is 2030, although they have not begun the siting process.[82]
Although all eight countries just surveyed are some of the world's major users of nuclear electricity, and even though all of them plan to use permanent geological disposal of spent fuel in the future, none of them expects to do so as quickly as the United States. Indeed, the preferred alternative is to reduce uncertainties about behavior of the waste. As the U.S. review commission put it: "In general, deferred disposal is viewed as beneficial because it reduces the heat output of the wastes." As a result, centralized, monitored, interim storage facilities have been built or planned in all but one country, Canada, which intends to use at-reactor interim storage.[83] If the experience of eight major nuclear countries is correct, then one powerful argument for not pursuing permanent disposal at present and for postponing a decision about a geological repository is that no nation, except the United States, has plans for rapid permanent disposal of nuclear waste. If the
plans of most countries reflect a scientific consensus about our inability at present to handle the uncertainties associated with permanent disposal of high-level nuclear waste, then these uncertainties may undercut arguments for permanent disposal anywhere at present.
Uncertainty and Permanent Disposal: Faulty Inferences
But what is the nature of the uncertainties that argue against permanent disposal anywhere at present? As we mentioned earlier, the uncertainties are so extensive that they are not even quantifiable. The Consensus Position of the 1992 DOE peer reviewers for the Yucca Mountain Early Site Suitability Evaluation is:
Any projections of the rates of tectonic activity and volcanism, as well as natural resource occurrence and value, will be fraught with substantial uncertainties that cannot be quantified using standard statistical models.[84]
If uncertainties at any proposed site are so severe that they cannot be quantified, then it is arguable that they force those who favor a permanent repository, at present, into either begging the question or appealing to ignorance in defending site suitability. Indeed, as chapter 4 argued, anyone who maintains that there is at present a compelling scientific basis for permanent geological disposal is unavoidably forced to use incomplete and short-term data (on seismicity, volcanism, hydrogeology, and so on) as a basis for extraordinarily precise long-term predictions—tens of thousands of years—about site suitability. We are able to make general predictions about the future, of course, and geologists do so all the time. Precise predictions, however, are a problem. Because of the imprecision of our hydrogeological and climate models, we are at present unable to predict the geological and hydrological situation at Yucca Mountain with any degree of reliability and precision ten thousand years into the future. As a result, we cannot quantify the claim that we shall be able to meet current U.S. repository standards for safety ten thousand years from now. We cannot be reasonably assured that a permanent repository might not cause catastrophe hundreds or thousands of years into the future. Indeed, to claim the ability to predict very precise geological events ten thousand years into the future when one's precise, site-specific evidential base for doing so covers only tens of years has little scientific justification.
As we argued in chapter 4, to assume that incomplete, short-term data enable one to make specific and reliable long-term predictions is, in general, an uncertain methodological value judgment. Although we can reconstruct geological histories spanning millions of years, geology is primarily an explanatory and not a predictive science, as we argued earlier. Hence, it seems prima facie evident that one ought not base arguments for the safety of a permanent repository on an uncertain methodological value judgment about our ability to make precise geological predictions.
Another reason that it is difficult to know the distant future in great detail is that we humans and our institutions are not precisely predictable. Anyone who argues for permanent geological disposal must discount the effects (on repository safety) of human error and the social amplification of risk that might occur in thousands of years. Discounting these effects is problematic, as the Chair of the U.S. National Academy's overview committee (for the WIPP project for storage of weapons-related radwaste in New Mexico) noted before Congress:
[C]urrent feeling is that the WIPP site could probably meet EPA standards with the exception of the so-called "human-intrusion" scenario. This is the idea that sometime in the future somebody comes and drills directly into a repository.[85]
As we argued in chapter 4, dismissing the effects of human activities such as terrorism, sabotage, or ignorance tens of thousands of years into the future is highly problematic. Indeed, given the prevalence of flaws in humans and their institutions, it might be more reasonable to assume that terrorism or ignorance would be a major problem for a facility storing radiotoxic materials. As we argued in chapter 4, whether about climate and hydrogeology, or about human errors and institutions, precise predictions about the long-term future are highly questionable, at least at present, because our generalizations are built on such a limited empirical base.
Scientific uncertainty further undercuts the case for permanent high-level radwaste disposal because, as we argued in chapter 6, anyone who claims that geological repositories will be safe for tens of thousands of years is probably using at least two logically invalid inferences, the appeal to ignorance and affirming the consequent. If it is impossible to know the long-term future with great precision, then any claims to precision (as U.S. radwaste regulations require) about the long-term future must rely in part on ignorance. Yet, from igno-
rance about a particular claim, it is logically invalid to conclude that the claim is either true or false. From our ignorance about long-term repository safety, it is logically invalid to conclude that a repository would be either safe or unsafe. Like many scientific claims, conclusions about the safety of repositories—tens of thousands of years into the future—are uncertain. Based on data from the present or even from several decades, there can be no empirically compelling argument for the safety of such repositories in the distant future. The best our experiments can do is to confirm that if permanent repositories meet certain safety standards in the future, then our current experiments are likely to exhibit these same features. Because affirming the consequent (see chapter 6) does not invariably lead to valid conclusions, however, the reverse is not true. We cannot infer that because of the success of current short-term experiments, therefore repositories will avoid catastrophic releases of radionuclides and will meet safety standards thousands of years from now.
In summary, in addition to Barry's intuitive argument about reasonable persons avoiding uncertain situations with the potential for catastrophe (see the earlier sections of this chapter), there appear to be at least four compelling arguments, all related to scientific uncertainty, against permanent geological disposal of high-level radwaste anywhere at present. These arguments include (1) the scientific uncertainties, including lack of data, associated with Yucca Mountain (see chapters 4 through 6); (2) the reluctance of other countries to move rapidly into programs of permanent geological disposal; (3) the presence of highly questionable methodological value judgments in scientific or empirical arguments in favor of the safety of permanent geological repositories; and (4) the presence of logically invalid inferences (the appeal to ignorance and affirming the consequent) in official arguments in favor of the safety of permanent geological repositories.
Uncertainty and Permanent Disposal: An Objection
In response to these arguments about the scientific uncertainty associated with the safety of permanent geological disposal, a proponent of the repositories could argue that no science is ever certain and that scientific certainty is not always required before one acts. In other words, one could argue that reasonable assurance of safety,
not scientific certainty, is a precondition for ethically defensible behavior. On this view, one could argue that certainty is impossible and therefore that one need merely follow the best available scientific opinion or the course of action leading to the best estimated results.
The heart of this objection to our analysis is correct. One does not need certainty before one acts, because certainty is unattainable. Our argument, however, is not that permanent disposal requires certainty. Rather, the argument is that permanent disposal requires more certainty than we have now and that, at present, the uncertainties associated with permanent disposal are extreme. In subsequent chapters we shall also argue that the uncertainties associated with permanent disposal are more extensive and more threatening than those associated with other radwaste options. For now, we wish to raise the issue of what behavior is ethically defensible under conditions of uncertainty. Following Barry's insights, already mentioned, our presupposition is that, in cases of extensive scientific and probabilistic uncertainty—like those concerning precise geological predictions ten thousand years from now or like those concerning events whose uncertainty cannot be quantified—we ought to behave in an ethically conservative way. But what is ethically conservative behavior? On one view, ethically conservative behavior in a situation of uncertainty is behavior that does not reject the null (no-effect) hypothesis. That is, if we are uncertain about a catastrophic event in the future, for example, ethical conservatives do not assume there will be no effect. In other words, we ought to minimize type-II statistical errors. Although we shall not take the time to provide the arguments in full here,[86] there are a number of reasons for minimizing type-II error in situations of uncertainty, like those associated with permanent geological disposal of radioactive waste.
Uncertainty and Permanent Disposal: Type-II Error
In a situation of uncertainty, errors of type I occur when one rejects a null hypothesis that is true; errors of type II occur when one fails to reject a null hypothesis that is false. (One null hypothesis might be, for example: "The proposed Yucca Mountain repository will secure high-level radwastes so that only one ten-millionth of allow-
able releases of radionuclides will reach the water table over 100,000 years.")[87]
Given a situation of uncertainty, which is the more serious error, type I or type II? An analogous issue arises in law. Is the more serious error to acquit a guilty person or to convict an innocent person? Ought one to run the risk of rejecting a true null hypothesis, of not using the Yucca Mountain technology that is really acceptable and safe? Or, ought one to run the risk of not rejecting a false null hypothesis, of employing the Yucca Mountain technology that is really unacceptable and unsafe? The basic problem is that to decrease type-I risk might hurt the public, especially members of future generations, and to decrease type-II risk might hurt both present persons and especially those dependent on the industries promoting the permanent repository.
In the area of pure science and statistics, most persons believe that in a situation of uncertainty one ought to minimize type-I risks, so as to limit false positives, assertions of effects where there are none. Pure scientists often attach a greater loss to accepting a falsehood than to failing to acknowledge a truth.[88] Societal decision making under uncertainty, as in cases involving siting permanent radwaste facilities, however, is arguably not analogous to decision making in pure science. Societal decision making involves rights, duties, and ethical consequences that affect the welfare of persons, whereas purely scientific decision making involves largely epistemological consequences. For this reason, it is not clear that in societal cases under uncertainty one ought to minimize type-I risks. Instead, there are a number of prima facie reasons for minimizing type-II errors. For one thing, it is arguably more important to protect the public from harm (from possible catastrophic radwaste releases) than to provide, in some positive sense, for welfare (building permanent repositories), because protecting from harm seems to be a necessary condition for enjoying other freedoms.[89] Admittedly, it is difficult to draw the line between providing benefits and protecting from harm, between positive and negative laws or duties. Nevertheless, just as there is a basic distinction between welfare rights and negative rights,[90] so there is an analogous distinction between welfare policies (that provide some good) and protective policies (that prohibit some infringement). Moral philosophers continue to honor related distinctions, such as that between letting die and killing someone. It therefore seems more important to protect citizens from public hazards, like a catastrophic leak at a permanent rad-
waste facility, than to attempt to enhance their welfare, over the short term, by implementing a technology such as permanent geological disposal of radwaste.[91]
A second reason for minimizing type-II errors under uncertainty is that the public typically needs more risk protection than do the industry or government proponents of the risky technology, like Yucca Mountain. The public usually has fewer financial resources and less information to deal with societal hazards that affect it, and laypersons are often faced with bureaucratic denials of public danger. Certainly members of future generations are likely to have less information to deal with a permanent repository since, by definition (U.S. regulations), it will not be monitored. Hence, their needs for protection seem larger, and the importance of minimizing type-II errors appears greater.[92]
Third, it is more important to minimize type-II error, especially in cases of great uncertainty, because laypersons ought to be accorded legal rights to protection against technological decisions that could threaten their health and physical security. These legal rights arise out of the considerations that everyone has both due process rights and rights to bodily security. In cases where those responsible or liable cannot redress the harm done to others by their faulty decisions—as they cannot in the case of repositories' harming future generations—there are strong arguments for minimizing the public risk. Industrial and technological decisionmakers cannot adequately compensate or insure their potential victims from bad consequences in the case of permanent disposal because the risks involve death. Therefore, they are what Judith Jarvis Thomson calls "incompensable." Surely incompensable risks ought to be minimized for those who do not have the opportunity to give free, informed consent to them. Whenever risks are incompensable, (e.g., imposing a significant probability of death on another), failure to minimize the risks is typically morally unjustifiable without the free, informed consent of the victim.[93] In the next chapter, we shall discuss the problem of free informed consent in more detail.
A final reason for minimizing type-II error in cases of uncertainty is that failure to do so would result in using members of future generations as means to the ends of present persons. It would result in their bearing a significantly higher risk from radwaste than members of present generations, despite the fact that present persons have received most of the benefits associated with generating the waste. Such discrim-
ination (in this case, against future persons), as Frankena has pointed out, is justified only if it would work to the advantage of everyone, including those discriminated against. Any other attempt to justify discrimination fails because it would amount to sanctioning the use of some humans as means to the ends of other humans.[94]
In the next chapter, we shall give detailed arguments that discrimination against future persons would not work to the advantage of everyone. Because it would not, discrimination against members of future generations is not justified. And if it is not justified, then failure to minimize type-II errors, which cause such discrimination, is also not justified. Hence, in situations of uncertainty, such as those concerned with permanent radwaste disposal, the ethically preferable course of action is to minimize type-II, rather than type-I, error. This course of action, in a situation of uncertainty, requires us to run the risk of rejecting the null hypothesis, to run the risk of not using permanent high-level radwaste repositories, at least not until significant uncertainties are removed.
Conclusion
If the arguments of this chapter are correct, then permanent geological disposal of radwaste is highly questionable on both epistemological and methodological grounds. The epistemological grounds are the tremendous uncertainties associated with permanent disposal, uncertainties arising because of the ten-thousand-year time frame, the precision of safety predictions required by existing regulations, and our inability even to quantify these uncertainties. The methodological grounds are the imprecision of the methods currently available for assessment of proposed radwaste sites, some of which have been outlined in chapters 4 through 7.
Moreover, as chapter 6 argued, it is impossible to justify building a permanent radwaste repository, at present, without employing at least two logically invalid inferences: the appeal to ignorance and affirming the consequent. Policy based on questionable logical and scientific inferences is highly problematic. Hence, all those who support using permanent radwaste repositories at present appear to err in some of the same ways as DOE assessors. They appear to have abandoned conservative scientific assumptions and value judgments and, instead, to have "embraced with enthusiasm an unwarranted optimism."[95]