Measurement and Analysis of Fission Rate Distributions of ^<237>Np and ^<238>U in a Polyethylene System with a 65 MeV Neutron Source
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Fission rates of <SUP>237</SUP>Np and <SUP>238</SUP>U in a polyethylene (CH<SUB>2</SUB>) system were measured with a 65MeV quasi monoenergetic neutron source. Relative fission rate distributions dependent on polyethylene thickness up to about 70cm were obtained for both nuclides with the experimental error within 7%. The present experiment was analyzed by the NMTC/JAERI code that has been employed for designing accelerator-driven transmutation systems. The fission rates of both <SUP>237</SUP>Np and <SUP>238</SUP>U calculated by the NMTC/JAERI did not agree with the experimental ones. The C/E values for both were about 2.0 at 71.8cm of polyethylene thickness when both experimental and calculated values were normalized to 1.0 at 0.0cm of polyethylene thickness. A sensitivity analysis of the NMTC/JAERI was performed by changing cross sections and angular distributions of hydrogen and carbon and by employing three options of the intra-nuclear cascade/evaporation calculation of the NMTC/JAERI. The disagreement of the NMTC/JAERI calculation with the experimental values was partially improved by increasing the nonelastic-scattering cross section of carbon and by broadening the elastic-scattering angular distribution of carbon.
- Journal of Nuclear Science and Technology
Journal of Nuclear Science and Technology 35(3), 169-177, 1998-03-25
Atomic Energy Society of Japan