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

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6.47<br />

radioactivity transport, movement <strong>of</strong> water would be considered as taking place both through<br />

permeable rock and by means <strong>of</strong> joints and cracks in low-permeability rock (Heckman 1978).<br />

The impacts <strong>of</strong> a ground-water breach <strong>of</strong> a rock melt repository are expected to be similar to<br />

those that would result if a mined geologic repository were breached by ground water<br />

(Bechtel 1979a).<br />

6.1.2.6 Cost Analysis<br />

Cost estimates for the rock melt concept do not have the benefit <strong>of</strong> a reference concep-<br />

tual design, nor <strong>of</strong> previous cost estimates for similar types <strong>of</strong> facilities. Therefore,<br />

these cost estimates are only approximate. They are based on the reference concept disposal<br />

<strong>of</strong> HLW from 5,000 MTHM/yr, for 25 years, requiring three cavities.<br />

All cost estimates are in 1978 dollars based on January 1979 dollar estimates (Bechtel<br />

1979a) less 10 percent.<br />

Capital Costs<br />

The capital cost <strong>of</strong> a rock melt repository with an operating lifetime <strong>of</strong> 25 years is<br />

estimated at $560 million.<br />

Operating Costs<br />

An allowance <strong>of</strong> 2 percent <strong>of</strong> the capital cost is assumed for the annual operating cost,<br />

which comes to $11 million a year.<br />

Decommissioning Costs<br />

The total decommissioning cost for the three-cavity rock melting concept is estimated at<br />

$21 million. In this estimate, final shaft sealing is treated as a decommissioning cost<br />

with an allowance <strong>of</strong> $2 million per cavity.<br />

6.1.2.7 Safeguard Requirements<br />

Because <strong>of</strong> the restrictions concerning the transportation <strong>of</strong> radioactive liquids, the<br />

fuel reprocessing plant would have to be colocated with the rock melt repository. There-<br />

fore, accessibility to sensitive materials would be extremely limited with liquid emplace-<br />

ment. If the waste were to be placed in a solid form (e.g., pellets), which could be<br />

emplaced in the subsurface cavity as a slurry, the fuel reprocessing plant could be located<br />

<strong>of</strong>f site but transportation related safeguards would then be required. The subsurface<br />

cavity would increase the difficulty <strong>of</strong> diversion and the liquid or slurry waste<br />

form would complicate the transportation and handling problems for potential diversion.<br />

However unlikely, retrieval by drilling and pumping is possible. This would eventually need<br />

to be considered for rock melt repository safeguards. Material accountability would be<br />

enhanced by ease <strong>of</strong> sampling and measurement, but gross accountability (i.e., gallons vs.<br />

canisters) would be slightly more difficult than for the mined geologic repository concept.<br />

For additional discussion <strong>of</strong> predisposal operation safeguards see Section 4.10.

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