A Combined Cross-Section Adjustment and Bias Factor Method for Accurate Prediction of Fast Breeder Reactor Core Performance Parameters

A formula for the uncertainty of core performance parameters based on a combination of the cross-section adjustment and bias factor methods has been derived. The formula is compared with those derived from the cross-section adjustment method and the bias factor method used separately. When the method error correlation is strong between the critical assemblies and a target core, the combined method is superior to the cross-section adjustment method used alone. The combined method is, in general, superior to the bias factor method used alone. Numerical results are presented for the uncertainties of k_eff, the control rod worth, and the power distribution of a large fast reactor. The combined method yields a smaller uncertainty for the control rod worth calculated in dollar units than the cross-section adjustment method used alone.