Measurement and Analysis of ^<241>Am Fission Rate Ratio Relative to ^<235>U Fission Rate in Thermal Neutron Systems Using Kyoto University Critical Assembly

概要

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Integral measurements of 241Am fission rate ratio relative to 235U fission rate were performed at Kyoto University Critical Assembly. The fission rates were measured using the back-to-back type double fission chamber at five thermal cores with different H/235U ratio so that the neutron spectra of the cores were systematically varied. The measured fission rate ratios, normalized to number of atoms, were 0.0144 to 0.0522, with a typical uncertainty of 2%. The measured data were compared with the calculated results using MVP based on JENDL-3.2, which gave the averaged calculated-to-experimental ratio (C⁄E) of 0.88. Obtained results of C⁄E using 241Am fission cross sections from JENDL-3/2, ENDF/B-VI and JEF2.2 showed that the latter two gave larger C⁄E values than those by JENDL-3.2 by about 2% and 7 to 9%, respectively. It has been found that the large difference between JENDL-3.2 and JEF2.2 arises mainly from the significant cross section difference at the vicinity of resonance at 0.576 eV, whereas the difference of thermal cross sections, especially in the range of 0.01 eV to 0.2 eV also has significant contribution for well-thermalized cores.
社団法人日本原子力学会の論文
2001-08-25