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

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Response<br />

330.<br />

ALTERNATIVE DISPOSAL CONCEPTS<br />

The final Statement has attempted to develop an equal assessment treatment under a<br />

standard format to all alternatives, consistent with the state <strong>of</strong> knowledge available. The<br />

information in Section 6.1 is a factual presentation and Section 6.2 presents a comparison<br />

<strong>of</strong> the alternatives. In all cases an explicit comparison <strong>of</strong> advantages and disadvantages<br />

is presented.<br />

Draft pp. 3.4.1-22<br />

Issue<br />

Rock Melting Concept--Would not radioactive heat act as a "pressure cooker" and cause<br />

an eruption <strong>of</strong> radioactive material into the environment? (88, 121)<br />

Response<br />

Sufficient rock is removed during construction <strong>of</strong> cavity that expansion <strong>of</strong> heated/<br />

melted rock can be accommodated. The point is a valid issue that must be considered. The<br />

understanding <strong>of</strong> the role that water might play in the melting <strong>of</strong> the rock and its avail-<br />

ability to create high pressure steam is not well understood. For rock melting to be seri-<br />

ously considered as a disposal method, substantial R&D would be required to understand this<br />

phenomena and its associate operational difficulties. Some engineering features could be<br />

built into the rock melt repository to reduce the potential impact <strong>of</strong> such an event. The<br />

cavity itself can be excavated to a size such that thermal expansion <strong>of</strong> the rock can be<br />

accommodated, filtered vents can alleviate pressure buildup, cooling waste can assist in<br />

controlling temperatures <strong>of</strong> the mix, and waste can be added at a slow rate.<br />

Draft pp. 3.4.1-22<br />

Issue<br />

A shortcoming <strong>of</strong> the description <strong>of</strong> the rock melt alternative is that no mention is<br />

made <strong>of</strong> the need for or availability <strong>of</strong> the water that's necessary for this alternative.<br />

Provide an estimate and discussion <strong>of</strong> the water requirements. (208-NRC)<br />

Response<br />

If the rock melt repository is co-located with a fuel reprocessing plant, little or no<br />

additional water (over that required for reprocessing) should be needed. Actual water<br />

requirements have not been accurately estimated; clearly, water availability will have to<br />

be one <strong>of</strong> the factors considered in the site selection process.<br />

Section 6.1.2.2 <strong>of</strong> the final Statement indicates that the cooling water will likely be<br />

recirculated in a closed system where the steam driven <strong>of</strong>f from the waste would be condensed<br />

and recirculated to cool the charge in the cavity. The closed cooling system would prevent

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