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

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Issue<br />

111<br />

CONSEQUENCE ANALYSIS<br />

One commenter noted that consequences <strong>of</strong> hypothetical events and resulting absolute<br />

doses are presented, but no quantified predictions <strong>of</strong> the probability <strong>of</strong> these events hap-<br />

pening are given. The U.S. Geological Survey recommendation to provide a candid assessment<br />

<strong>of</strong> the uncertainties associated with the spectrum <strong>of</strong> alternative out-comes <strong>of</strong> geologic con-<br />

tainment is an objective safety criterion. These probabilities and their limits should be<br />

given at 10, 100, 1,000, 10,000, 100,000, and 1,000,000 years for each <strong>of</strong> the barriers <strong>of</strong><br />

waste form and container, medium, and site geohydrology, that is, through to the time <strong>of</strong><br />

radioactive decay <strong>of</strong> the waste to natural levels <strong>of</strong> radiation density in the ground. (28)<br />

Response<br />

To the contrary, where available, predictions <strong>of</strong> probabilities were given in the draft<br />

and appear again in the final Statement (see Section 5.5). Some events do not lend them-<br />

selves to estimates <strong>of</strong> probability and the associated societal risks remains a more subjec-<br />

tive assessment. In a number <strong>of</strong> instances large errors in probability would not result in<br />

a conclusion that a serious societal risk would exist.<br />

Aside from multiplying the number <strong>of</strong> years times the probability per year little can<br />

be done at this stage to provide probabilities over time periods suggested.<br />

Reference to reduction <strong>of</strong> radiation levels to natural levels in the ground was also<br />

made by the commenter. This aspect is treated briefly in Section 3.4. However, the reader<br />

is cautioned that while such hazard indices provide perspective, a direct comparison <strong>of</strong><br />

waste nuclides and naturally occurring nuclides needs qualification.<br />

Issue<br />

222<br />

The release <strong>of</strong> 2Rn from soil and/or rock should be evaluated for a leaking repos-<br />

itory. The entrance <strong>of</strong> radon into homes through foundation walls or base slabs may be the<br />

most important source <strong>of</strong> future human exposure. (196)<br />

Response<br />

Issue<br />

222 Rn is not a significant contributor to human exposure.<br />

Several commenters stated that the Statement should clearly outline the sensitivity <strong>of</strong><br />

the parameters used in the calculations and to the extent possible how conservatism <strong>of</strong>fsets<br />

uncertainties in the analysis. (38, 43, 58, 97, 113-EPA, 124, 202-HEW)

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