Uncertainty evaluation of burnup properties of large fast reactors using data adjustment method

The burnup uncertainties of a fast-breeder reactor have been evaluated based on the cross section adjustment technique. A group cross section set, obtained using JENDL-2, was adjusted using experimental data of fast critical assemblies ZPPR and FCA. The adjusted cross section was applied to the neutronics characteristic calculation of a 1,000 MWe-class fast reactor, and the changes in neutronics characteristics and their uncertainties due to the cross section adjustment were evaluated. The burnup reactivity loss was found to increase by 23% when the adjusted cross section library was used. This value corresponds to a reactivity decrease of about 0.7%Δk at the end of the equilibrium cycle for a typical 1,000 MWe LMFBR of 1 yr operation cycle. The uncertainty in burnup reactivity due to the cross section error was found to decrease from 21% to 12% if the cross section adjustment method was employed. This brings the benefit of a reduction in control rod worth requirement by about 0.3%Δk. (author)