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A Review of the President's Recommendation to Develop a Nuclear Waste Repository at Yucca Mountain, Nevada
Subcommittee on Energy and Air Quality
Dr. Jared L. Cohon
Good
morning, Mr. Chairman and members of the Subcommittee.
I am Jared Cohon, Chairman of the Nuclear Waste Technical Review Board.
All members of the Board are appointed by the President and serve on a
part-time basis. In my case, I also
am president of Carnegie Mellon University in Pittsburgh, Pennsylvania.
I
am pleased to be here today to present the Board's technical and scientific
evaluation of the Department of Energy's work related to the recommendation of
a site at Yucca Mountain, Nevada, as the location of a permanent repository for
spent nuclear fuel and high-level radioactive waste.
The Board hopes that the Subcommittee and other policy-makers will find
its technical and scientific evaluation useful as you consider the various
issues that will affect a decision on whether to proceed with repository
development. With your permission,
Mr. Chairman, I will summarize the Board's findings, and
I request that my full statement and the Board's January 24, 2002,
letter report to Congress and the Secretary be included in the hearing record. As
you know, Mr. Chairman, Congress created the Board in the 1987 amendments to the
Nuclear Waste Policy Act. Congress
charged the Board with performing an ongoing independent evaluation of the
technical and scientific validity of activities undertaken by the Secretary of
Energy related to disposing of spent nuclear fuel and high-level radioactive
waste. The Board also reviews the
DOE's activities related to transporting and packaging such waste.
Since the Board was established, its primary focus has been the DOE's
efforts to characterize a site at Yucca Mountain in Nevada to determine its
suitability as the location of a potential repository.
Early
last year, Secretary of Energy Spencer Abraham indicated that he would make a
decision at the end of 2001 on whether to recommend the Yucca Mountain site for
repository development. As the Secretary's decision approached, the Board decided
it was important to comment to the Secretary and Congress, within the context of
the Board's ongoing evaluation of the technical and scientific validity of DOE
activities, on the DOE's work related to a site recommendation.
So, in November 2001, the Board met to review comprehensively the DOE's
efforts in this area. In December
2001, the Board sent a letter to the Secretary indicating that the Board would
provide its comments within a few weeks. The
Board conveyed those comments in a letter, which included attachments with
supporting details, that was sent to Congress and the Secretary on January 24,
2002. I
will now summarize the Board's review procedures and the results of the
Board's evaluation. The
Board's evaluation represents the collective judgment of its members and was
based on the following:
To
focus its review, the Board considered the following 10 questions for components
of the repository system and for the disruptive-event scenarios:
In
evaluating the DOE's work related to individual natural and engineered
components of the proposed repository system, the Board found varying degrees of
strength and weakness. For example,
the Board considers the DOE's estimates of the probabilities of volcanic
events and earthquakes at Yucca Mountain strengths, while the lack of data
related to corrosion of materials proposed for the waste packages under
conditions that would likely be present in the repository and the very short
experience with these materials are considered weaknesses. This
kind of variability is not surprising, given that the Yucca Mountain project is
a complex, and in many respects, a first-of-a-kind undertaking.
An important conclusion in the Board's letter is that when the DOE's
technical and scientific work is taken as a whole, the Board's view is that
the technical basis for the DOE's repository performance estimates is weak to
moderate at this time. The
Board made no judgment in its January 24 letter on the question of whether the
Yucca Mountain site should be recommended or approved for repository
development. Those judgments, which
involve a number of public-policy considerations as well as an assessment of how
much technical certainty is necessary at various decision points, go beyond the
Board's congressionally established mandate. Let
me explain in a little more detail, Mr. Chairman, the bases for the Board's
conclusion on performance estimates. The DOE uses a complex, integrated performance assessment
model to project repository system performance.
Performance assessment is a useful tool because it assesses how well the
repository system as a whole, not just the site or the engineered components,
might perform. However, gaps in
data and basic understanding cause important uncertainties in the concepts and
assumptions on which the DOE's performance estimates are now based.
Therefore, while no individual technical or scientific factor has been
identified that would automatically eliminate Yucca Mountain from consideration
at this point, the Board has limited confidence in current performance estimates
generated by the DOE's performance assessment model.
As I will discuss in just a moment, the Board believes that confidence in
the DOE's projections of repository performance can be increased. But
first let me clarify the comment I just made on the current state of knowledge
of technical and scientific factors that could potentially eliminate Yucca
Mountain from consideration. The
Board considers the very precise statement in its letter that at this point, no
individual technical or scientific factor has been
identified that would automatically eliminate Yucca Mountain from
consideration a necessary condition for a discussion of site suitability to take
place. But this threshold
condition, by itself, is not necessarily sufficient for a definitive
determination of site suitability. How
can confidence in the DOE's performance estimates be increased?
As noted in the Board's letter, the Board believes that a fundamental
understanding of the potential behavior of a proposed repository system is very
important. Therefore, if
policy-makers decide to approve the Yucca Mountain site, the Board strongly
recommends that, in addition to demonstrating regulatory compliance, the DOE
continue a vigorous, well-integrated scientific investigation to increase its
fundamental understanding of the potential behavior of the repository system.
Increased understanding could show that components of the repository
system perform better than or not as well as the DOE's performance assessment
model now projects. In either case, making performance projections more realistic
and characterizing the full range of uncertainty could increase confidence in
the DOE's performance estimates. The
DOE's estimates of repository performance currently rely heavily on engineered
components of the repository system, making corrosion of the waste package very
important. As the Board has
mentioned in many of its previous reports and letters over the last 11 years, we
believe that high temperatures in the DOE's base-case repository design
increase uncertainties and decrease confidence in the performance of waste
package materials. It is possible
that confidence in waste package and repository performance could increase if
the DOE adopts a low-temperature repository design.
However, the Board continues to believe that the DOE should complete a
full and objective comparison of high- and low-temperature repository designs
before it selects a final repository design concept.
Over
the last several years, the Board has made several other recommendations that
could increase confidence in the DOE's projections of repository performance.
For example, the Board recommended that the DOE identify, quantify, and
communicate clearly the extent of the uncertainty associated with its
performance estimates. The Board
also recommended that the DOE use other lines of evidence and argument to
supplement the results of its performance assessment.
Moreover, the DOE could strengthen its arguments about how multiple
barriers in its proposed repository system provide "defense-in-depth" (or
redundancy). Although the DOE has
made progress in each of these areas, more work is needed.
Other
actions that might be considered if policy-makers approve the Yucca Mountain
site include systematically integrating new data and analyses produced by
ongoing scientific and engineering investigations; monitoring repository
performance before, during, and after waste emplacement; developing a strategy
for modifying or stopping repository development if potentially significant
unforeseen circumstances are encountered; and continuing external review of the
DOE's technical and scientific activities. Mr.
Chairman, eliminating all uncertainty associated with estimates of repository
performance would never be possible at any repository site.
Policy-makers will decide how much scientific uncertainty is acceptable
at the time various decisions are made on site recommendation or repository
development. The Board hopes that
the information provided in this testimony and in its letter report to Congress
and the Secretary will be useful to policy-makers faced with making these
important decisions. Not
surprisingly, Mr. Chairman, people have drawn from the Board's January 24
letter the points that support their case. The Board is concerned, however, that lifting individual
statements from the letter and using them without context can be confusing for
policy-makers and the public. Therefore,
we urge those charged with making decisions about Yucca Mountain to consider the
full text of our 3-page letter. Thank
you very much, Mr. Chairman. I will be happy to respond to questions.
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