Neutron spectrum shape study at 4,5 - 18,6 MeV on the horizontal channel N 10 of WWR-M reactor

Abstract

To clarify the issue of neutron excess in the high-energy part of 235U fission neutron spectrum the reactor neutron spectrum measurements in the wide energy range by differential recoil proton method have been carried out at the angles of scattering 30, 35, 40, 45 and 50°. Silicon detector sensitive zone widths were chosen thus, that obtained neutron spectra overlapped the same energy interval 6 - 18 МeV. The methods of measurements and apparatus spectra treatment were described. The neutron spectrum was approximated by Maxwell distribution Е ~ Е1/2 exp (-α E) from which the "statistical" error of the parameter α was determined. The measured spectrum is in a good agreement with 235U fission spectrum in the energy interval 6 - 12 МeV and it has the following parameters: α = (0,765±0,012) МeV-1, temperature Т = (1,307 ± 0,021) МeV and average energy Ē = (1,960 ± 0,032) МeV. The analysis of the high-energy range (above 12 МeV) of the measured spectrum indicates its harder character (the average energy Ē is within the limits of 2,72 - 3,01 МeV). The observed effect of neutron excess in high-energy part of the spectrum is in favour of the hypotheses on high-energy “scission” neutron emission in nuclear fission.