Measurement and Calculation of Leakage Neutron and γ Spectra from Bi Slab Sample

The leakage neutron and γ spectra from ²⁰⁹Bi slab samples with different thicknesses (30 cm×30 cm×5 cm, 30 cm×30 cm×10 cm and 30 cm×30 cm×15 cm) were measured by time-of-flight method at 61° and 119° using a D-D neutron source. A BC501A liquid scintillation detector was chosen to measure the leakage neutron spectra from 0.8 to 3.2 MeV, and CLYC (Cs₂LiYCl₆: Ce) scintillator detector was used to measure the leakage neutron spectra from 0.2 to 0.8 MeV and γ spectra. Theoretical calculations were carried out by Monte Carlo neutron transport code MCNP-4C, using the evaluated nuclear libraries of ²⁰⁹Bi from the CENDL-3.1, ENDF/B-Ⅷ.0, JENDL-4.0 and JEFF-3.3. The experimental results were compared with the corresponding calculated ones. From the comparison, it is found that the calculated results of neutron spectra with the CENDL-3.1 library are underestimated in the elastic peak region at 119°, and the results with JENDL-4.0 are overestimated near 1.5 MeV but underestimated in the 0.2-1 MeV range at both 61° and 119°. The γ spectra with the JENDL-4.0 and JEFF-3.3 libraries are significantly different from the experimental results, while those from CENDL-3.1 library well reproduce the experimental ones.