原子炉構造用鋼の中性子はじき出し断面積の簡易計算法

概要

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A simplified procedure is presented for calculating the neutron displacement cross sections for structural steels of nuclear reactors. The procedure differs from Doran's in the following matters : 1) Recoil kinematics of compound nucleus reactions are treated assuming that most of the recoil energy upon neutron capture is dissipated during the lifetime of compound nucleus. 2) The nuclear evapolation model is not used to estimate the kinetic energies of outgoing particles in the compound nucleus reactions of (n, n) at high neutron energies above 7 MeV, (n, p), and (n, a). However, the energies are approximated by the kinematics that Doran et al. have used for (n, n) reactions below 7 MeV. 3) For the secondary displacement model, the ionization threshold model is adopted, being revised so that at low PKA energies the number of displacements in a steel per PKA of a constituent element is independent of that the PKA belongs to the element. The displacement cross sections for Type 304 stainless steel are calculated in the range of neutron energy below 10 MeV by the procedure using ENDF/B-IV library data. The cross sections are compared with those calculated by Doran et al. for 18Cr-10Ni stainless steel. It is concluded from the comparison that the procedure gives the reasonable values of displacement cross sections for structural steels of definite chemical compositions at neutron energies below 10 MeV.
1985-01-30