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

3-33
Comment Comment
Number ,lumber
3.h.22 Appendix I concentrations near or equal to that of the repository source activity."
Appendix I discusses the possibility of release of radionuclides to the This would appear to indicate unacceptable repository performance. An
biosphere through groundwater mass transport. The impression given is explanation should be given of how this will be remedied or why this
that container life will be about 1000 years and that no significant analysis is not believed to indicate a problem.
release is expected for one million years. This is in apparent contradiction
to results given in TM-36/21 (p. xiv, 8-5 and 8-6). What is the 3.h.25 Y/OWI/TM-36/21
expected rate of corrosion of the canister and the sleeve in salt brine or Y/OWI/TM-36/21 addresses only three host rock media - granite, basalt and
in fresh water? What are the values (or ranges) of effective hydraulic shale. No basis for the apparent conclusion that groundwater movement in
conductivity, porosity, retardation factors and hydraulic gradients of the salt is negligible has been presented in either GEIS or in TM-36. Note
rock mass surround the repository that were used to obtain Tables I.1 to also that the permeabilities of granite and basalt presented in the GEIS
1.12? (Table 3.1.1, p. 3.1.9) are nil and therefore the repositories in granite
and basalt could presumably be located at depths significantly less than
3.h.23 Y/OWI/TM-36/21 salt and shale.
Pages 4-7 assume that the effective vertical permeability of basalt between
the repository level and the alluvium near the surface (a thickness of 3.h.26 General Comment
600 feet) is 5x10l 8 cm/s resulting in a downward flow through this layer Measures of performance used in the GEIS and its supporting documents make
into the repository of approximatedly 150 gpm (216000 gpd). In addition a it difficut to judge statements that claim "no deleterious effects." For
maximum upward flow of 230 gpm into the repository is calculated. example:
The GEIS should address and discuss the following with regard to radionuclde 1. Dose received by maximum individual. This seems to be someone using
transport: Are repositories in granite, basalt, salt and shale expected a water supply separated by 10 miles of poros flow from the respository.
to have any water inflow after the last stages of operation? Note that fracture flow with its lower retardation factor is not
considered.
3.h.24 Y/OWI/TM-36/21
The results of simplified calculations given in Y/OWI/TM-36/21 show 99 Tc 2 Concentration at 3 miles from boundary. This was used in TM-36
exceeding acceptable concentrations 3 miles from the center of the reposi- volume 21. In this case, Tc-99 occurs near the surface at 400-600
tory 400-600 years after recharge. To quote from page 8-5: " 99 Tc, due to years and exceeds maximum permissible concentrations by one thousand
its long half life and unity retardation coefficient exists in all layers (Tm-36/21 pgs. xiv, 8.5-8.6).
of the generic stratigraphic columns studies (shale, granite and basalt)
at concentrations near or equal to the source activities. The maximum 3 27 General Comment
source activity for 99 Tc used in this study is approximately 0.2-0.3uCi/ml One of the assumptions that makes mined geologic disposal feasible is that
(section 7.0) which is at least 10 3 times greater than an acceptable radioactive sources placed in a hydrologic environment with slow-moving
level. The first arrival of 99 Tc occurs in the near surface layers between groundwater will take long periods of time to be transported to the biosphere.
400-600 years after repository decommissioning and resaturation and at Furthermore, retardation effects will slow down (relative to groundwater
velocity) the movement of certain species. This basic characteristic is
common to all forms of geologic disposal.
3-34