Based on these findings and conclusions, the committee offers the following four recommendations. They are directed primarily to the decision makers and research managers responsible for the cesium separation program:

  1. If small-tank TPB precipitation remains as a contending process for removing cesium from HLW supernates at SRS, considerable effort should be made to (i) identify TPB catalytic decomposition mechanisms, (ii) establish probable bounding rates for TPB catalytic decomposition, and (iii) address the other scientific and technical issues listed in finding 2 above.

  2. As part of its efforts to bound catalytic decomposition rates, SRS should develop robust testing protocols to process moderately sized samples of real waste from each of the tanks using MST and TPB. These protocols are needed to provide information that can be used to develop a predictive capability for process performance for TPB decomposition rates, temperature excursions, foaming, and filterability.

  3. Tests on moderately sized samples of real waste should be implemented as soon as possible under this protocol to help assess the viability of the small tank TPB precipitation option. By using real waste from different tanks with different compositions, this testing will allow process performance to be systematically established under conditions that bracket, with safety margins, the acceptable conditions of planned processing operations.

  4. If the small-tank TPB processing option is selected for implementation at SRS, samples of each of the waste batches to be processed should be subjected to the testing protocols described above. This will help ensure that unknown synergistic effects of waste blending from different tanks are better understood prior to full-scale processing.

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