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

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Modeling of Groundwater Modelin Migration Mraton of Groundwater
We believe the comprehensive model used in the safety analysis is not
applicable on a generic basis. The modeling efforts of H.C. Burkholder
and his colleagues at Battelle are pioneering and comnendable. However,
in Appendix I the assumptions used in the model analysis are clearly
spelled out on page I.9. Among these assumptions are: a) that "the
of salt. Emphasis on these unlikely release mechanisms seems unbalanced
and could cause undue apprehension as to the risks involved. Ground-
water transport is treated at greater length in appendix I.but this
material clearly should be up front. Even appendix I does not analyze
for variation of key parameters such as retardation, porosity, and
permeability.
repository is located in a non-salt formation surrounded by a geology
with nuclide retention properties similar to those for a particular
Hanford Reservation subsoil;" and b) "the ground water flows into a
surface stream with a flow rate of 10,000 ft
There are additional reasons for laying more stress on release by moving
ground water in the main part of the statement. Although this is a
3 /sec (1/10 the flow rate
of the Columbia River near the Hanford Reservation) where the nuclides
are further diluted." This. flow is equivalent to the average flow of
the Delaware River at Trenton. With theTr and other simplifying
assumptions, the model predicts a benign outcome. However, the problems
are multiple.
First, although dilution of the radionuclide-bearing ground water by a
10,000 ft
generic statement and values for hydrologic parameters are site-specific,
the possible ranges of these parameters are relatively well known. A
credible consequence analysis would, therefore, show the effects of vary-
ing porosity, permeability, hydraulic head, path length, retardation,
release rate, etc., over reasonable ranges. For environments in granite,
basalt, and shale relatively rapid flow through fractures should be
included in the analysis. One of the key parameters to be considered
is retardation. The present analysis uses values for the Hanford subsoil--
3 /sec river is one plausible scenario for radwaste dissolved in
Hanford ground waters, aT6,000-fold concentration might occur in other
environments, for example, in areas where ground water flow is toward
marshes or wet playas. Second, what is the dose to man if the ground
water were tapped by a future town well-field upgradient from discharge
into the river? Third, the Kd's for Hanford subsoil are unlikely to be
applicable to fractured media.
Briefly, the model is acceptable for one HLW scenario in Hanford alluvium.
highly site-specific and uncertain, inasmuch as values determined by
various laboratories continue to differ by significant amounts. An
analysis that shows the effects of a range of retardation values is
therefore especially critical.
Another reason for stressing variation in hydrologic parameters in the
consequence analysis is that,while the ranges of these are known, the
probabilities of initiating events (with the exception of meteorite
impact) are much more uncertain. It will be argued below that the
It is unacceptable for other scenarios at Hanford, and certainly unacceptable
for any other rocks and waste types. It follows that the seemingly
comprehensive tables comparing health effects from radwaste disposal in
salt, granite, shale, and basalt are difficult to justify. The draft EIS
itself in several places follows the IRG in emphasizing the importance
of site-specific studies. Therefore, we suggest the presentation of
considerable numerical data in Section 3.1.5.2 is not warranted; this
should be resolved in the final statement.
Ground-water transport
If a systems approach is to be used in siting and engineering mined
repositories, we believe the consequence analysis should consist of a
systematic consideration of failure of each element in the system. It
has been stated many times (e.g., IRG Subgroup, 1978, TID-288/8, app. A,
p. 16) that transport by moving ground water is the most likely means by
which toxic radionuclides may reach the biosphere. The multiple barrier
approach is designed to avert this eventuality. Yet, the consequence
analysis in the EIS treats this possibility in less depth than four
other "worst case" scenarios--meteorite impact, diversion of a surface
or underground river into the repository, drilling, and solution mining
probability used for faulting is unsupported; and the probabilities
assigned to human activities sometime in the distant future are generally
conceded to be meaningless (IRG Subgroup, 1978, TID-28818, app. A, p. 50,
52). The most likely result of human intrusion (aside from serious
effects to a few individuals) is release to ground water, again emphasiz-
ing the need for analysis for all barriers to nuclide migration.
There is a danger that, like the consequence analysis performed by EPA
in its standard-setting procedure, the attempt to be "conservative" will
lead to acceptance of repository site characteristics that violate the
multiple
main body
barrier approach. The ground-water transport analysis
of
in the
the statement uses a path length of only 10 km, apparently
in an attempt to show that consequences would not be drastic. The inter-
agency effort to find acceptable sites now going forward will certainly
not consider sites with such a short path. The analysis ould use a
longer flow path for the base cases and discuss consequences of shorten-
ing of the path due to tectonic and/orclimatic change.