Methodology to Design Simulated Irradiated Fuel by Maximizing Integral Indices (ck, E, G)

Critical experiments are used for validation of reactor physics codes, in particular, to determine the biases and uncertainties in code predictions. To reflect all conditions present in operating reactors, plans for such experiments often require tests involving irradiated fuel. However, it is impractical to use actual irradiated fuel in critical experiments due to hazards associated with handling and transporting the fuel. To overcome this limitation, a simulated irradiated fuel, whose composition mimics the neutronic behavior of the truly irradiated fuel (TRUFUEL), can be used in a critical experiment. Here, we present an optimization method in which the composition of simulated irradiated fuel for the Canadian supercritical water-cooled reactor (SCWR) concept at midburnup (⁠$21.3MWdkg−1$ (IHM)) is varied until the integral indices $ck$⁠, $E$⁠, and $G$ are maximized between the true and simulated irradiated fuel. In the optimization, the simulated irradiated fuel composition is simplified so that only the major actinides (⁠$U233$⁠, $Pu238-242$⁠, and $Th232$⁠) remain, while the absorbing fission products are replaced by dysprosia and zirconia. In this method, the integral indices $ck$⁠, $E$⁠, and $G$ are maximized while the buckling, $k∞$ and the relative ring-averaged pin fission powers are constrained, within a certain tolerance, to their reference lattice values. Using this method, maximized integral similarity indices of $ck=0.967$⁠, $E=0.992$⁠, and $G=0.891$ have been obtained.