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

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K.4<br />

For the other rock media, i.e., granite, shale, and basalt, a good basis for specifying<br />

maximum rock temperatures had not been established at the time <strong>of</strong> this analysis. It (the<br />

criteria) will probably be quite site-specific. For shale a 250°C maximum may be reasonable<br />

and for the hard rocks temperatures higher than 350°C may be acceptable.<br />

It must be emphasized that the limits shown in Table K.1.1 are based on the best avail-<br />

able data at this time. As such, they should be reevaluated as more data become available.<br />

In addition, these limits require evaluation on a site-specific basis.<br />

K.1.1 Calculation <strong>of</strong> Acceptable Thermal Loads<br />

For convenience, the thermal criteria, subsequent analyses, and results are classified<br />

into three categories: far-field, near-field, and very-near-field. The far-field refers<br />

to the formation at distances far removed from the repository. The near-field represents<br />

the region within the repository horizon in the vicinity <strong>of</strong> the emplacement rooms and asso-<br />

ciated pillars. The very-near-field refers to the waste package and the rock within a few<br />

feet <strong>of</strong> the canister.<br />

The heat induced into the repository and surrounding formation depends upon repository<br />

design and the thermal loadings <strong>of</strong> the repository. These loadings include: 1) the average<br />

waste loading <strong>of</strong> the repository (averaged over full waste emplacement area) that determines<br />

the temperature rise <strong>of</strong> the formation in the far-field; 2) the local thermal loading (aver-<br />

age amount <strong>of</strong> waste emplaced per unit storage area <strong>of</strong> the repository) that most directly<br />

determines the near-field rock thermal and thermomechanical environments; and 3) individual<br />

canister loadings that most directly influence the temperatures in the waste, the canister,<br />

and the rock in the immediate vicinity <strong>of</strong> the waste canister, i.e., in the very-near-field.<br />

For a given repository design, acceptable loadings can be determined once appropriate tem-<br />

perature and thermomechanical limits have been established.<br />

Thermal and thermomechanical analyses have been performed to determine acceptable ther-<br />

mal loading values for spent fuel repositories and HLW repositories in salt, granite, shale,<br />

and basalt. Thse studies use an iterative technique that integrates the waste and canister<br />

temperature criteria, room and pillar stability analyses, and far-field thermal and rock<br />

mass response analyses.<br />

For isolation <strong>of</strong> HLW, the following steps were followed in the iterative analysis:<br />

Step 1: Select thermal and thermomechanical criteria.<br />

Step 2: Propose a conservative room and pillar design without consideration <strong>of</strong> an<br />

imposed thermal loading.<br />

Step 3: Make near-field heat-transfer calculations to determine the areal thermal<br />

loading range <strong>of</strong> interest.<br />

Step 4: Make very-near-field heat-transfer calculations to generate very-near-field<br />

temperature pr<strong>of</strong>iles as a funcion <strong>of</strong> areal thermal loading and canister<br />

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