A series of critical experiments were performed using heterogeneous cores at the Static Experiment Critical Facility (STACY) of Japan Atomic Energy Agency (JAEA) in order to obtain systematic benchmark data concerning the dissolving process in a reprocessing plant. Focusing on the introduction of the burn-up credit, critical mass measurement was conducted for a combination of uranium dioxide fuel rods (5 wt% 235 U) and uranyl nitrate solution (6 wt% 235 U) poisoned with pseudo-fission-product (FP) elements-samarium, cesium, rhodium, and europium. Fuel rods were arrayed at a 1.5-cm lattice interval in the poisoned fuel solution in a 60-cm-diameter cylindrical tank. The uranium concentration of the solution was roughly kept at about 320 gU/L, and the FP element concentrations were adjusted to be equivalent to that in a burn-up of about 30 GWd/t. The result provides basic experimental data for validation of computational methods to evaluate the reactivity effect of each FP element, as well as benchmark criticality data for validation of neutron multiplication factor calculation for heterogeneous systems of spent fuel. In this report, the details of the experiments and benchmark models will be presented as well as the procedure and the result of separate reactivity worth evaluation for each FP element. The experimental results and the computational evaluation results will also be compared.

The second series of critical experiments with 10% enriched uranyl nitrate solution using a 28-cm-thick slab core have been performed with the Static Experiment Critical Facility of the Japan Atomic Energy Research Institute. Systematic critical data were obtained by changing the uranium concentration of the fuel solution from 464 to 300 gU/l under various reflector conditions. In this paper, the thirteen critical configurations for water-reflected cores and unreflected cores are identified and evaluated. The effects of uncertainties in the experimental data on k eff are quantified by sensitivity studies. Benchmark model specifications that are necessary to construct a calculational model are given. The uncertainties of k eff 's included in the benchmark model specifications are approximately 0.1% k eff . The thirteen critical configurations are judged to be acceptable benchmark data. Using the benchmark model specifications, sample calculation results are provided with several sets of standard codes and cross section data.

No abstract

A series of critical experiments were performed using heterogeneous cores at the Static Experiment Critical Facility (STACY) of Japan Atomic Energy Agency (JAEA) in order to obtain systematic benchmark data concerning the dissolving process in a reprocessing plant. Focusing on the introduction of the burn-up credit, critical mass measurement was conducted for a combination of uranium dioxide fuel rods (5 wt% 235 U) and uranyl nitrate solution (6 wt% 235 U) poisoned with pseudo-fission-product (FP) elements-samarium, cesium, rhodium, and europium. Fuel rods were arrayed at a 1.5-cm lattice interval in the poisoned fuel solution in a 60-cm-diameter cylindrical tank. The uranium concentration of the solution was roughly kept at about 320 gU/L, and the FP element concentrations were adjusted to be equivalent to that in a burn-up of about 30 GWd/t. The result provides basic experimental data for validation of computational methods to evaluate the reactivity effect of each FP element, as well as benchmark criticality data for validation of neutron multiplication factor calculation for heterogeneous systems of spent fuel. In this report, the details of the experiments and benchmark models will be presented as well as the procedure and the result of separate reactivity worth evaluation for each FP element. The experimental results and the computational evaluation results will also be compared.

No abstract