Massimo Pescarini

A Neutron Cross Section Evaluation for 232Th in the En <20 MeV Energy Range

The neutron interaction cross sections in the energy range below 20 MeV for 232 Th have been completely revised starting from both recent experimental data1), 2) and theoretical results given by an updated version of the CIRCE, PO- LIFEMO and PENELOPE3) chain codes for direct reaction, compound nucleus and direct scattering calculations. The angular distributions for inelastic scattering by the first three excited levels, taking into account the nuclear deformation up to the hexadecapole term, have been calculated and compared with experimental results. The new data set has been tested in calculations performed on the THOR fast criticality experiment. The transport calculations were carried out in spherical geometry through the XSDRNPM transport module of the SCAMPI Data Processing System. *The results were compared with the corresponding ones obtained with other 232Th data files (ENDFB VI-3, JEF-2.2 and JENDL-3.2).

SN Validation of JEF-1 Data on the PCA-Replica Shielding Benchmark

The results of a DOT 3.5-E/JEF-1 validation on the (H20/Fe) PCA-REPLICA (UKAEA winfrith) low-flux shielding benchmark are presented. The PCA-REPLICA experiment reproduces the ex-core radial geometry of a PWR and is closely related to LWR safety since it is dedicated to test the accuracy of the calculated neutron exposure parameters (fast fluence and iron displacement rates) in a pressure vessel simulator. The SN 1-D ANISN code is used to collapse cross sections from the VITAMIN-J (175 n) shielding library, based on the JEF-1 data, to a 28 group working library for 2-D calculations. A 3-D-equivalent synthesis (X,Y,Z) of 2-D and 1-D DOT 3.5-E SN calculations in plane geometry, gives the integral and spectral results for comparison with the respective experimental data. The underprediction of the in-vessel dosimeter measured activities depends probably on an overestimation of the Fe-56 inelastic scattering cross section in the JEF-1 natural iron file.