Improvement of prediction accuracy for fuel fabrication system with erbia bearing fuel

The concept of a fuel fabrication system with erbia bearing high burnup fuel has been proposed. The erbia is added to all fuel with over 5% 235U enrichment to retain the neutronics characteristics to that within 5% 235U enrichment. There is a problem of the prediction accuracy of the neutronics characteristics with erbia bearing fuel because of the short of experimental data of erbia bearing fuel. The purpose of the present work is to reduce the uncertainty. A new method has been proposed by combining bias factor method and the cross section adjustment method. In the case of the blending machine (H/U=0) for the fuel fabrication process, the uncertainty reduction, which shows the rate of reduction of uncertainty, of the keff is 0.604 by the present method and 0.555 by the conventional bias factor method. Thus the prediction uncertainties are reduced by the present method compared to the bias factor method. (authors)