Nuclear Technology / Volume 177 / Number 1 / January 2012 / Pages 63-72
Technical Paper / Fuel Cycle and Management
Erbia-credit super high burnup (Er-SHB) fuel offers a means to introduce >5 wt% 235U enrichment fuel; small amounts of erbia added to all the high-enriched UO2 powder can reduce the initial reactivity to <5 wt% enrichment level. By using this erbia credit, the new fuel can be treated as <5 wt% enriched fuel, and most modifications to the existing facilities and equipment can be avoided. One of the key issues for developing the Er-SHB fuel is to validate the criticality safety analysis tools for this fuel based on a series of experiments using fuel with small amounts of erbia in the entire core. For that purpose, a series of critical experiments have been performed at the Kyoto University Critical Assembly (KUCA). Four critical cores were constructed utilizing two different average enrichments, three different erbia contents, and four different H/U ratios. Numerical analyses have also been performed using several different cross-section libraries, and the results were compared with the measurements from the KUCA experiments. These results confirm the validity of the calculations and the cross-section libraries for determining erbia reactivity. This paper outlines the basic concepts of the Er-SHB fuel, the erbia experiments, and the analyses results.