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

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Response<br />

71<br />

CONSEQUENCE ANALYSIS<br />

Consequence analysis is indeed not restricted to postulated worst cases. The text was<br />

changed accordingly (see Section 3.4).<br />

Draft p. 3.1.67<br />

Issue<br />

Since the long-term behavior <strong>of</strong> the parameters is uncertain, risk assessment should be<br />

based on upper estimate predictions as well as on "reasonable" predictions. (113-EPA)<br />

Response<br />

involved.<br />

It should be based on "reasonable" predictions plus an estimation <strong>of</strong> the uncertainties<br />

Draft p. 3.1.67<br />

Issue<br />

Are the probabilities in the first paragraph best estimate probabilities, upper bound<br />

probabilities, or what? (113-EPA)<br />

Response<br />

Issue<br />

accident.<br />

The probabilities referred to are best estimate probabilities.<br />

Several letters commented on the probability cited for the faulting and flooding<br />

Draft p. 3.1.67--Uncertainties and the method for determining them should be consis-<br />

tently included with probability and consequence estimates. Although uncertainties are dis-<br />

cussed in isolated cases, they are usually not included with point values, e.g., the<br />

probability <strong>of</strong> faulting through the repository is estimated at 4 x 10 - 11 per year (pp.<br />

3.1.67) with no indication <strong>of</strong> associated uncertainties. (208-NRC)<br />

Draft p. 3.1.155--The value <strong>of</strong> 4 x 10- 11 /yr for the probability <strong>of</strong> faulting or frac-<br />

turing (H.D. Claiborne and F. Gera, 1974, Potential Containment Failure Mechanisms and Their<br />

Consequences at a <strong>Radioactive</strong> <strong>Waste</strong> Repository in Bedded Salt in New Mexico: Oak Ridge<br />

National Laboratory, ORNL-TM-4639) used in risk considerations is outdated and its uncriti-<br />

cal acceptance is a major shortcoming <strong>of</strong> the draft. This is not to say that the values for<br />

faulting or fracturing probabilities ultimately used for a site-specific risk assessment<br />

will not be some low number such as this, but these probabilities will have to be determined

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