Journal of Nuclear Science and Technology

ISSN: 0022-3131 (Print) 1881-1248 (Online) Journal homepage: http://www.tandfonline.com/loi/tnst20

Measurement of Fast Neutron Induced Fission Cross Section Ratios of Pu-240 and Pu-242 Relative to U-235 Tomohiko IWASAKI , Fumitoshi MANABE , Mamoru BABA , Shigeo MATSUYAMA , Hiroyuki KIMIYAMA & Naohiro HIRAKAWA To cite this article: Tomohiko IWASAKI , Fumitoshi MANABE , Mamoru BABA , Shigeo MATSUYAMA , Hiroyuki KIMIYAMA & Naohiro HIRAKAWA (1990) Measurement of Fast Neutron Induced Fission Cross Section Ratios of Pu-240 and Pu-242 Relative to U-235, Journal of Nuclear Science and Technology, 27:10, 885-898, DOI: 10.1080/18811248.1990.9731269 To link to this article: http://dx.doi.org/10.1080/18811248.1990.9731269

Published online: 15 Mar 2012.

Submit your article to this journal

Article views: 137

View related articles

Citing articles: 1 View citing articles

Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tnst20 Download by: [37.44.207.17]

Date: 24 January 2017, At: 10:56

Journal of NUCLEAR SciENCE and TECHNOLOGY, 27[10], pp. 885-898 (October 1990).

885

Measurement of Fast Neutron Induced Fission Cross Section Ratios of Pu-240 and Pu-242 Relative to U-235 Tomohiko IWASAKI, Fumitoshi MANABEt, Mamoru BABA, Shigeo MA TSUY AMA, Hiroyuki KIMIY AMA and Naohiro HIRAKAWA

Department of Nuclear Engineering, Tohoku University* Received November 29, 1989 Fission cross section ratios of 240 Pu and 242 Pu relative to 285 0 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 0.6-7 MeV with the time-of-flight method. Prior to the measurement, a fast timing back-to-hack 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 at. 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.

KEYWORDS: fission cross section, plutonium 240, plutonium 242, ratio measurement, MeV range 01-10, fast neutrons, uranium 235, fast timing fission chamber, time-of-flight method, correlation matrix, comparative evaluations, errors

I.

INTRODUCTION

Fission cross sections of actinide nuclides for fast neutrons play very important role, not only in the design of fast or high-burnup reactors, but also in the research related to the fuel cycle, e. g. nuclear transmutation, minimum criticality and shielding. According to WRENDA 87;ggcll, the accuracy required for plutonium isotopes is as high as 2% in the energy range of 0.1"-'10 MeV. However, the available data base is not sufficient to meet the required accuracy except for 239 Pu. Using the absolute and the ratio measurement techniques, eight and seven measurements have been reported since 1970 for 24"Pu c2J-c•J and 242Pu C4J coJ csJ c1oJ-c13J, respectively. However, the previous experimental data show discrepancies beyond the quoted experimental errors. For example, the dis-1

crepancy for 24"Pu is more than 15% between the fission cross section ratios measured by Frehaut et at. ' 2) and those by Meadows< 6 J. Also, for 242 Pu, the difference more than 10% is shown between the data by Behrens et al. c4J and those by Meadows' 1"J. Therefore, new measurements are expected for the fission cross sections of both nuclides to meet the required accuracy. In this study, we have measured the fission cross section ratios of 240 Pu and 242 Pu relative to 236 U as a part of a series of measurements for fast neutron induced fission cross sections of actinide elements