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

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98<br />

CONSEQUENCE ANALYSIS<br />

rates to be expected in a repository. One <strong>of</strong> the possible shortcomings <strong>of</strong> the values in<br />

draft Figure 1.3 is that they are determined for unfractured monolithic cylinders <strong>of</strong> the<br />

various glasses.<br />

Draft p. 1.7<br />

Issue<br />

Draft Figure 1.4 appears to require a leach time <strong>of</strong> 100,000 years for "satisfactory"<br />

(less than 120 millirems per year) operation. This may not be possible for all contained<br />

nuclides, since some nuclides are geochemically mobile. (113-EPA)<br />

Response<br />

A confusion <strong>of</strong> terms appears in this comment. If the commenter refers to time when a<br />

nuclide is discharged to the biosphere, then a 100,000-yr water travel time is not unreal-<br />

istic. By dating methods groundwater has been shown to be millions <strong>of</strong> years old.<br />

Draft p. I.10<br />

Issue<br />

The notion that the dose from 22 6 Ra can be reduced by limiting the leaching <strong>of</strong> 238U<br />

is incorrect. That 238 U migration could be controlled over its half-life (4.5 billion<br />

years) is doubtful.<br />

We believe that the impact analysis is in a premature stage in this section. The anal-<br />

yses stated in Appendix I are divided into two categories: past work and present work.<br />

Since the present work is only partially complete, the results presented in the Statement<br />

may be revised when the present work is completed. This may change results in the stated<br />

conclusions in the Statement. We believe the present work should include an error analysis<br />

and sensitivity analysis.<br />

All the references to this appendix are from Battelle Pacific Northwest Laboratories<br />

work. Has any <strong>of</strong> this work been performed elsewhere? (113-EPA)<br />

Response<br />

There was no suggestion in Appendix I that 23 8 U could be contained for 4.5 billion<br />

years or more. Radon-226 is a relatively short lived daughter <strong>of</strong> 23 8 U. In many systems<br />

Ra is less mobile than U. Furthermore, in most cases analyzed up to date, Ra is released<br />

to the biosphere only because it is a daughter <strong>of</strong> a long-lived parent. Therefore, the Ra<br />

dose can be very sensitive to 2U leach characteristics.<br />

As noted in final Appendix L much <strong>of</strong> the work done with respect to nuclear waste man-<br />

agement has been conducted by Battelle Pacific Northwest Laboratories (PNL). With respect

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