Neutron Fluxenergy Measurements at the McMaster Nuclear Reactor

Abstract

To use the neutron activation technique to study the neutron flux in a nuclear reactor,some cross-section processing must be done to convert measured activation rates to fluxes. The effective cross section – the mean value of the cross section weighted to thespectrum – is introduced to facilitate the experimental determination of energy integrated fluxes. During future experiments, the flux spectrum will be coarsely divided in to three energy groups: thermal (E < 0.2 eV), epithermal (0.2 eV < E < 0.8 MeV), and fast (E > 0.8 MeV). NiCr wire will be used to study the ⁵⁰Cr (n,γ) ⁵¹Cr and ⁵⁸Ni (n,p) ⁵⁸Co reactions, which are sensitive to the thermal and fast flux, respectively. Through a series of simulations, it was determined that σ_Cr,thermal = 13.73 b ± 0.36 %, σ_Ni,fast = 124.02 mb ± 3.05 % and σ_Cr,total = 9.58 b ± 1.1 %.