COMPARISON OF CALCULATED HELIUM PRODUCTION IN STAINLESS-STEEL DUE TO NEUTRON-IRRADIATION WITH EXPERIMENT

It is well known that helium produced during neutron irradiation throu gh the (n, alpha) reaction affects the mechanical properties and the a mount of void swelling in nuclear reactor materials. In order to estim ate the amount of helium produced in a high alloy stainless steel, whi ch is used in fast reactors and is appropriate to be used in future fu sion reactor structural materials, calculations have been performed us ing the neutron interaction cross sections of the steel constituents. Two austenitic steel specimens of type 1.4970 with high and low boron content, respectively, for which some experimental results are availab le have been chosen for the present calculations. Predominant nuclear reactions like B-10(n, alpha)Li-7, and the two-step reaction viz. Ni-5 8(n, gamma)Ni-59(n, alpha)Fe-56, and the details of the neutron spectr um are taken into account. The cross sections for Ni-59, the major con tributor for higher irradiation times, are taken from the KEDAK-4 (Ger man) and the most recent ENDF/B-VI (American) Evaluated Nuclear Data L ibraries. The results show that the calculated and the measured estima tes differ by a factor of 2 to 3. This difference may be due to uncert ainties in the measurement as well as uncertainties in the reaction cr oss section, especially in the two-step reaction.