Experimental Study Of Macrographic Examination On Neutron Cross Sections Of Pb And LBE Samples

Lead based materials are ideal coolant materials both in Fast Breeder Reactor (FBR) and Accelerator Driven Sub-critical System (ADS). The accuracy of their evaluated neutron data are directly related to the design and safety of FBR and ADS. Therefore, it is necessary to perform integral experiments to validate the quality of the current evaluated neutron data for lead based materials.In this thesis, neutron leakage spectra from lead and lead bismuth eutectic (LBE) alloy samples have been measured on a pulsed neutron generator in China Institute of Atomic Energy. The neutron leakage spectra were measured by Time Of Flight (TOF) method with a BC501A liquid scintillation detector. Super Monte Carlo Simulation Program for Nuclear and Radiation Process (SuperMC) has been used to model the experiment. The calculated leakage spectra in Pb and LBE experiments were gained by using SuperMC with ENDF/B-Ⅶ.1, JEFF-3.1and JENDL-4.0libraries. The neutron cross section data of Pb and Bi have been evaluated by comparing the experimental results with the calculation ones. And the sensitivity analyses have been used to distinguish the channel of reaction which may cause the differences of the spectra between experiment and calculation.The analysis results show that, in Pb experiment, the calculations with three evaluated libraries agree well with the measurement, except small discrepancies in2.5-10.5MeV energy range. Through sensitivity analysis on each reaction channel, we find that the discrepancies may be caused by the values of the (n,2n) cross section of208Pb in ENDF/B-Ⅶ.1and JEFF-3.1and the continuum inelastic scattering cross section of208Pb in JENDL-4.0which have obvious effects on energy spectra. In LBE experiment, an obvious difference is found between the simulation of ENDF/B-Ⅶ.1and the experimental result, especially in the medium energy range of5.5-7MeV. By estimating sensitivity of the partial cross sections of209Bi in ENDF/B-Ⅶ.1, it is found that the (n,2n) cross section distinctly affects the neutron leakage spectra. After reading the cross section of this channel in the three libraries, we can basically confirm that the lack of (n,2n) neutron angle distribution data of209Bi in ENDF/B-Ⅶ.1is the reason that cause the discrepancy.