MEASUREMENT OF FAST NEUTRON INDUCED FISSION CROSS SECTION RATIOS OF 239Pu AND 242Pu RELATIVE TO 235UDepartment of Nuclear Engineering, Tohoku University Aoba, Aramaki, Sendai, Miyagi 980, Japan Fission cross section ratios of Pu-239 and Pu-242 relative to U-235 were measured in the energy range from 0.6 to 7 MeV using the 4.5 MV Dynamitron accelerator of Tohoku University. A fast timing back to back fission chamber was used to detect fission events. The measurement was carried out with time of flight (TOF) method. The corrections to the measured data were carefully applied and uncertainty was analyzed taking the correlation between error sources into account. The overall uncertainty of the present results was about 2 %. The present results for Pu-239/U-235 are slightly higher than other experimental data and JENDL-2. For Pu-242/U-235, the present data agree with those of Meadows and Kuprijanov et al. KEYWORDS: fission cross section, fast neutron, Pu-239, Pu-242, U-235, time of flight, back to back fission chamber |