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

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Issue<br />

108<br />

CONSEQUENCE ANALYSIS<br />

A question was raised as to whether or not the scenario <strong>of</strong> a nuclear attack on a geo-<br />

logic repository had been considered. (40)<br />

Another commenter suggested that such a scenario not be analyzed because the effects <strong>of</strong><br />

the bomb itself would greatly exceed the effects <strong>of</strong> any release from the repository. (17)<br />

Response<br />

As a previous comment points out, the effects <strong>of</strong> nuclear war (i.e. release <strong>of</strong> repos-<br />

itory contents) would be bounded by the meteorite strike scenario. Therefore, the effects<br />

<strong>of</strong> weapons strike were not specifically calculated.<br />

Issue<br />

One commenter noted that a more likely initiating event for water intrusion into a<br />

repository is exploratory drilling or shaft seal failure. (7)<br />

Another commenter felt that the effect <strong>of</strong> water intrusion where spent fuel elements are<br />

placed in steel canisters be given more extensive consideration. (219)<br />

Response<br />

The faulting and flood accident is a worst case scenario which would bound those sug-<br />

gested by the first commenter. The breach <strong>of</strong> a spent fuel repository followed by water<br />

intrusion is discussed in detail in Section 5.5. For purposes <strong>of</strong> identifying an upper limit<br />

with respect to consequences <strong>of</strong> such an event, no credit was taken for the presence <strong>of</strong> steel<br />

canisters. Multiple barriers (including steel canisters) have been suggested as being able<br />

to assume the lack <strong>of</strong> release <strong>of</strong> radionuclides to the repository proper for perhaps 1,000<br />

years. On that basis, the consequences suggested for a breach 1,000 years after closure<br />

would apply.<br />

Issue<br />

One <strong>of</strong> the assumptions that makes mined geologic disposal feasible is that radioactive<br />

sources placed in a hydrologic environment with slow-moving groundwater will take long per-<br />

iods <strong>of</strong> time to be transported to the biosphere. Furthermore, retardation effects will slow<br />

down (relative to groundwater velocity) the movement <strong>of</strong> certain species. This basic char-<br />

acteristic is common to all forms <strong>of</strong> geologic disposal.<br />

The GEIS and its supporting documents fail to analyze flowpaths other than porous flow<br />

through intact media. The possible creation <strong>of</strong> high velocity flow paths by mining opera-<br />

tions or fractures created by the thermomechanical response <strong>of</strong> the rock mass are not con-<br />

sidered. Fracture flow'driven by thermal convection deserves more attention than meteorite<br />

impact or nuclear war as mechanisms for establishing communication between the repository<br />

and the biosphere. (208-NRC)

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