Measurement of Selected Differential Cross Sections in ²³⁵U Spectrum

This paper describes the measurement of ⁵⁵Mn(n,2n) and ¹²⁷I(n,2n) reaction rates in a well-defined reactor field in a special core of LR-0 reactor. The reaction rates were derived using gamma-spectrometry by measuring gamma activities of irradiated MnO₂ and NaI samples at a high purity germanium (HPGe) detector. The spectral average cross section (SACS) in ²³⁵U prompt fission neutron spectrum (PFNS) was experimentally determined to be 0.2393 ± 0.015 × 10⁻³ b for ⁵⁵Mn and 1.2087 ± 0.052 × 10⁻³ b for ¹²⁷I. These obtained results were compared with calculations by MCNP6 code using ENDF/B VII.1, ENDF/B VII, JEFF-3.1, JEFF-3.2, JENDL-3.3, JENDL-4, ROSFOND- 2010, CENDL-3.1, and IRDFF nuclear data libraries. In a case of ⁵⁵Mn, a good agreement with ENDF/B VII.1, JEFF 3.1, JENDL 3.3, JENDL 4, ROSFOND, and CENDL 3.1 nuclear data libraries was found, where C/E⁻¹ is 0.1%, while IRDFF underestimated by about 15.8%. In the case of ¹²⁷I, more significant discrepancies were found, where JENDL 3.3 and JENDL 4 overestimate the result by about 31.3%.