Measurement of local power peaking factors in heavy-water moderated plutonium lattices

Local power peaking factors (LPF) in the heavy-water moderated plutonium lattices were measured by a new method of γ-scanning of fuel pins using the calculated power correction factor of which accuracy was evaluated with the aid of foil activation method. Accuracy in measurement of the LPF was evaluated to be with 1%. By this measurement, behaviors of the LPF have been made clear concerning the differences in fuel materials, coolant materials and arrangement in fuel enrichments. Depression of the thermal power in the fuel cluster makes LPF in the plutonium fuel lattice larger than in the uranium lattice. This tendency is more remarkable in air coolant lattice than in H2O coolant lattice. The value of LPF for the plutonium fuel cluster of different enrichments is smaller than that of a uniformly enriched fuel cluster. The reduction of LPF is smaller in H2O coolant than in air coolant lattice. The values of LPF by WIMS-D code based on the transport theory and by METHUSELAH-II code based on the diffusion theory are in agreement with the measured ones, within 1.5 and 2.4% respectively. (author)