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

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4.3.4.2 Gaseous Radionuclide Recovery<br />

4.42<br />

Where recovery <strong>of</strong> gaseous radionuclides (i.e., 3 H, 14 C, 85 Kr, 1291) from airborne waste<br />

streams is required, processes other than filtration must be employed. Recovery <strong>of</strong> at least<br />

some <strong>of</strong> these gaseous radionuclides will be required if the spent fuel is processed to con-<br />

vert it to an alternative disposal form in the once-through case or to recover uranium and<br />

plutonium for recycle. In the example process <strong>of</strong> this Statement for the once-through case<br />

(the packaging <strong>of</strong> intact spent fuel assemblies), it is anticipated that no gaseous radionu-<br />

clide recovery will be required. This is because only small quantities are expected to<br />

escape from the fuel.<br />

Recovery <strong>of</strong> the gaseous radionuclides 14 C, 85 Kr, and 129 (but not <strong>of</strong> 3 H) is included<br />

in the example <strong>of</strong>f-gas treatment process used in this Statement for the reprocessing cycle.<br />

Most <strong>of</strong> this recovery takes place from the <strong>of</strong>f-gas stream leaving the dissolver, since these<br />

radionuclides volatilize when the U0 2 fuel is dissolved in nitric acid. Iodine recovery<br />

from the gas streams leaving the separations process equipment is also provided, since a<br />

significant fraction <strong>of</strong> the iodine may remain in the dissolver solution and then volatilize<br />

later. Figure 4.3.13 presents a flow diagram for this gaseous radionuclide recovery system.<br />

The possible use <strong>of</strong> the voloxidation process to recover tritium is indicated also but, as<br />

mentioned previously, tritium recovery is not included in the example process <strong>of</strong> this<br />

Statement.<br />

Tritium (3H) recovery is not included in this Statement because the technology is not<br />

believed to have been suitably demonstrated as yet. In the example process, the tritium<br />

present in the U0 2 portion <strong>of</strong> the spent fuel is released to the atmosphere as water vapor.<br />

The bulk <strong>of</strong> this release occurs when the excess water is vaporized and discharged.<br />

Methods <strong>of</strong> tritium control have been studied. The voloxidation process (Groenier 1977)<br />

has received the most development, but other alternatives have also been examined (Burger<br />

TRITIUM<br />

I RECOVERY* -<br />

I I<br />

I N EIODINE CARBON KRYPTON<br />

I RECOVERY RECOVERY RECOVERY<br />

I OFF GAS<br />

OFF GAS I TO<br />

I GFRP-APS<br />

I OFF GAS<br />

I OFFGAS IODINE<br />

-, VOLOXIDIZER -- . RECOVERY<br />

, - , SEPARATIONS<br />

FUEL SHEAR * DISSOLVER PROCESS<br />

EQUIPMENT<br />

*NOT INCLUDED IN THE EXAMPLE<br />

SYSTEM<br />

FIGURE 4.3.13. Flow Diagram for Gaseous Radionuclide Recovery

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