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

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73<br />

CONSEQUENCE ANALYSIS<br />

These probabilities are for purely random events. They are completely in error for<br />

non-random events. (30)<br />

The draft states that the Poisson process is used to model the occurrence <strong>of</strong> geologic<br />

events, based on past observation. However, whether this table presents the probability<br />

that one event occurs for the "interval" <strong>of</strong> concern or, more properly, that one or more<br />

event occurs during this period is not clear. From P( ) = 3 (gQ)/x!, the probability <strong>of</strong> one<br />

or more events occurring is (1 - the probability <strong>of</strong> zero occurrences) = (1 - P(O)) = 1 - egQ.<br />

This formulation, however, produces somewhat higher probabilities than those listed in draft<br />

Table 3.1.3, e.g., for the "number <strong>of</strong> occurrence years" equal to 106 years, and an "inter-<br />

val" equal to 104 years, the probability that one or more geologic event occurs is 9.95 x<br />

10 -3 as compared to 6.9 x 10 -3 . Thus, more explanation <strong>of</strong> the probabilities in draft<br />

Table 3.1.3 is needed. (208-NRC)<br />

Response<br />

The probabilities listed in Table 3.1.3 are for random events. The discussion surroun-<br />

ding the use <strong>of</strong> this table relates to the possibility <strong>of</strong> geologic events that would disrupt<br />

the integrity <strong>of</strong> the waste repository. It is agreed that these probabilities would be in<br />

error for non-random events. However, it is felt that careful site selection to identify<br />

all potential containment failure mechanisms would preclude other than random geologic<br />

events with potential to cause a waste repository failure.<br />

Draft p. 3.1.68<br />

Issue<br />

One commenter suggested referencing the model calibration done by J. B. Robertson<br />

(1974, Digital Modeling <strong>of</strong> <strong>Radioactive</strong> and Chemical <strong>Waste</strong> Transport in the Snake River Plain<br />

Aquifer at the National Reactor Testing Station, Idaho: U.S. Geological Survey Open-File<br />

Report (AEC-22054)). (218-DOI)<br />

Response<br />

More recent references were added in the final Statement, Section 3.4.3.2 (Cole 1979<br />

and Robertson 1977)<br />

Draft p. 3.1.69<br />

Issue .<br />

The man-caused events listed should be discussed in depth. (114)

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