Management of Commercially Generated Radioactive Waste - U.S. ...

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The release rates used in the ground-water transport analysis In the
Radiologcal safety
main body of the report jump strangely from 100%/yr to O.l%yr. The
base case should clearly be for the low rates, but results for intermediate
release rates should be presented. The consequence analysis
should consider solubility limits of the various radlonuclides in the
ground-water system under consideration; the present analysis assumes
varying source terms for nuclide transport,some of which may not be
physically possible.
The draft statement employs a consequence analysis; events with the
worst possible outcomes are postulated and the subsequent radiological
health effects described. These effects are considerable for some
events, but the discussion tempers this outcome by introducing the
concept of risk. Serious consequences, it is argued, have a low
probability of occurring so the net risk (probability x consequence)
Is judged to be qualitatively small.
Long-term surface storage It should be noted that the risk need not be zero and will not be zero
(30-60 s ye e of e r e s d be c d
Long-term (30-60 year) surface storage of radwaste should be considered
in the final statement as a means of decreasing uncertainties of geologic
disposal. The final statement should discuss the utilization of
extended (30-60 year) surface storage of HLW prior to disposal as a
means of reducing major rock mechanics uncertainties created by the heat
pulse. Such storage would reduce the heat pulse by one-half to threequarters.
The omission of this alternative is surprising in light of
the extended discussion in section 3.2 of chemical synthesis which,
similarly, is a way to reduce geochemical uncertainty In geologic
disposal. We recommend the final statement consider long-term surface
storage as a viable alternative.
for any waste-management option or energy system. Also, It Is not necessary,
for the purposes of this statement, that a complete risk analysis
be presented--only that enough be understood about the risk to justify
continuing with the option. This GEIS can be considered adequate when
viewed in this light. It makes clear that the earth has a potentially
high retentive capacity and that properly sited and engineered reposi-
tories should lead to a relatively low risk. Whether this risk will be
acceptable (i.e., judged safe) is for society to decide.
Faulting
The value of 4xl0-ll/yr for the probability of faulting or fracturing
Multiple barriers
(Claiborne, H.D., and Gera, F., 1974, Potential containment failure
mechanisms and their consequences at a radioactive waste repository in
The multiple barrier concept and the systems approach to mined repositories,
elaborated in the IRG reports, do not occupy the central role envisioned
by the IRG in this EIS. Words that include these concepts appear in the
statement, but they are obviously last-minute additions and include major
errors in places. For example, on page 3.1.1, "multiple barriers" are
listed as one of six characteristics of conventional geologic disposal
when, in fact, three of the other five characteristics are themselves
important barriers to nuclide transport. Apparently, what is meant by
multiple barriers here is only the hydrologic systems beyond the host
rock. However, the desired properties of the hydrelogic system are not
necessarily the same as those of the disposal medium. Indeed, since
predictability of the system is important, it might be advantageous to
have part of the hydrologic flow system include a porous medium in which
transport is relatively well understood as opposed to a relatively
impervious medium subject to flow-through fractures,which is much less
well understood.
bedded salt in New Mexico: Dak Ridge National Laboratory, ORNL-TM-4639)
used in risk considerations is outdated and its uncritical acceptance is
a major shortcoming of the draft EIS. This is not to say that the values
for faulting or fracturing probabilities ultimately used for a site-
specific risk assessment will not be some low number such as this, but
these probabilities will have to be determined on a sound basis.
Research to do this should be identified in the section on research and
development needs.
Claiborne and Gera (1974) assumed that faulting would be random within
a given region and that the rate of fault initiation for the Delaware
Basin could be approximated by assuming a constant rate over post-Permian
time. Both assumptions are highly unlikely in the light of recent tectonic
thinking. It is now realized that most tectonic strain is taken up on
existing faults as long as the tectonic regime remains the same. When
the tectonic regime changes, existing faults will continue to take up
much of the strain; but new faults may form depending on the new stress
Clearly, the draft EIS has not given sufficient thought to the total
system of containment, but considers its components separately.
state and its relation to existing discontinuities. The new faults
probably form over a relatively short time as the new tectonic regime
Is established.