Measurement of fast neutron induced fission cross section ratios of pu-240 and pu-242 relative to u-235

Tomohiko Iwasaki, Momoru Baba, Shigeo Matsuyama, Hiroyuki Kimiyama, Naohiro Hirakawa, Fumitoshi Manbe

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Fission cross section ratios of240Pu and242Pu relative to2S5U were measured by using the 4.5 MV Dynamitron accelerator of Tohoku University. The measurement using mono-energetic neutrons was performed in the neutron energy range of 0.6~7MeV with the time-of-flight method. Prior to the measurement, a fast timing back-to-back fission chamber was developed with good time resolution to reduce the backgrounds due to a-particles and spontaneous fissions. Furthermore, we took account of the effect of the nonuniformity of fission sample thickness for accurate determination of fission cross section ratio. The uncertainty was estimated by analyzing the correlation between the error sources. The correlation matrix between the measured data was given. The overall uncertainty of the present results is about 2%. For both nuclides, the present results agree well with those by Meadows and by Kuprijanov et al. The JENDL-3 evaluation generally has good agreement with the present results. However, the evaluated data are slightly higher around 1 MeV and lower above 6 MeV than the present results.

Original languageEnglish
Pages (from-to)885-898
Number of pages14
JournalJournal of Nuclear Science and Technology
Issue number10
Publication statusPublished - 1990 Oct


  • Comparative evaluations
  • Correlation matrix
  • Errors
  • Fast neutrons
  • Fast timing fission chamber
  • Fission cross section
  • MeV range 01-10
  • Plutonium 240
  • Plutonium 242
  • Ratio measurement
  • Time-of-flight method
  • Uranium 235


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