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

Response
110
CONSEQUENCE ANALYSIS
As noted the ground water transport analysis used only a 10 km path length. It had
been decided that because of timing only one case would be modeled and it was further
decided that the shorter length would receive less criticism than an overly long path length.
As suggested something of a sensitivity analysis on consequences versus path length would
have been useful.
Issue
The worst-case accident scenarios are unrealistic and should be reformulated.
Analyses of worst-case accident scenarios should be carried out on the assumption that
application of state of the art techniques will limit dissolution rate of waste forms,
including proposed packaging of spent fuel. The availability of a flow of 2.8 m 3 /second
of ground water through any site chosen for a repository is unrealistic. The pressure head
to drive such a flow would not be available. Even when underground rock formations become
saturated with water, the volume will be inconsequential, and flow rates will be generally
close to zero. (219)
Response
It is hoped that a flow rate of 2.8 m3/s (100 cfs) would indeed be unrealistic as a
ground water flow rate through any site chosen for a repository. This scenario was devel-
oped as an extreme case and while highly improbable is not believed impossible when viewed
as an occurrence over millenia, due to tectonic and/or climatic changes.
Issue
Accidents occurring soon after the repository is closed should be given more prominence.
A less dramatic but more likely failure occurring at an earlier time-such as the slower
but more extensive flushing of a saturated repository-should be examined with respect to
consequences and risk. An early chapter should describe the step-by-step process by which
the dose estimates are developed. The model should be illustrated diagrammatically and,
wherever possible, relevant source terms and rates should be indicated. (219)
Response
In most instances the consequences for accidents were calculated for a time just after
repository closure. A case was examined where a relatively large flow of water penetrated
the repository and the consequences presented. It is not believed credible that even a
saturated repository would contain significant amounts at an early time.
The size and organization of the EIS precludes putting all material in early chapters;
a relatively detailed presentation of dose models was presented in Appendix D.