Calculation of the kinetic parameters for homogeneous fuel systems. MOX powder with zinc stearate and plutonium nitrate solution

This report represents the kinetic parameters for homogeneous fuel systems obtained in the cooperative study with the Institut de Radioprotection et de Surete Nucleaire (IRSN) in France which aims at the accumulation of the criticality safety data and the reliability improvement of the criticality safety calculation technique. The subject fuels for calculation are MOX powder mixed with zinc stearate and plutonium nitrate solution. The calculation systems are the critical cylinder system with a 2.5-cm-thick water reflector or the infinite system for MOX powder and the critical cylindrical tank APPARATUS-B at Valduc facility in France for plutonium nitrate solution. The calculated kinetic parameters are the fraction of delayed neutron, the effective decay constant of delayed neutron precursor, the prompt neutron lifetime, and the temperature coefficient of reactivity. The calculation is executed using the combination of TWODANT code and the cross section which is collapsed to 17 energy groups based on JENDL-3.3. As a result of the calculations, it was found that the kinetic parameters of MOX powder is dependent on plutonium enrichment and the neutron moderation, and is not dependent on the density of MOX powder and the geometry of fuel except for the prompt neutron lifetime. This tendency does not depend on whether the fuel system is the cylindrical geometry or the infinite system. It is also found that the effect of collapsing of cross section from 107 group to 17 group does not appear except for prompt neutron lifetime. The effect of collapsing on prompt neutron lifetime depends on the enrichment of plutonium. The kinetic parameters of plutonium nitrate solution depend on the concentration of plutonium and temperature; the temperature coefficient of which plutonium concentration is below 19 g/l is positive. (author)