Modelling of Noise Experiments for Verification of Kinetic Parameters Obtained Using the Sapfir_rf Code

Abstract

New multi-group neutron data libraries and a new scheme of fuel burnup have been developed on the basis of the modern ROSFOND evaluated nuclear data files. The upgraded version has a working title - the SAPFIR_RF code. Noise experiments for defining the ratio of total delayed neutron yield to neutron lifetime, βeff/l, were performed to verify the computational scheme of kinetics parameters implemented in the SAPFIR_RF. These experiments have been performed using the homogeneous assemblies with various isotopic composition of uranium-plutonium fuel. In order to analyze and interpret the experimental data correctly, numerical investigations simulating the experimental conditions and features of measurement results processing were performed; these investigations highlighted the need for systematic correction to be made for measurement results. Taking into account the correction, the calculation results are qualitatively and quantitatively in agreement with measurement data within the measurement accuracy of ±8 %. This paper draws on the modern data of Russian neutron data library, ROSFOND, as well as on G.R. Keepin’s kinetic parameters and evaluated nuclear data of the foreign libraries, ENDF/B-VI and ENDF/B-VII. Kinetic parameters obtained by G.R. Keepin and ENDF/B-VI library give two extreme evaluations of βeff/l ratio; the difference between them averages ~4,5 %. It should be noted that the calculation results received using Keepin's parameters are closer to experimental data in the most cases.