MEASUREMENTS AND ANALYSES OF DECAY RADIOACTIVITY INDUCED IN SIMULATEDDEUTERIUM-TRITIUM NEUTRON ENVIRONMENTS FOR FUSION-REACTOR STRUCTURAL-MATERIALS

To meet urgent requirements for data validation, an experimental analy sis has been carried out for isotopic radioactivity induced by deuteri um-tritium neutron irradiation in structural materials. The primary ob jective is to examine the adequacy of the activation cross sections im plemented in the current activation calculation codes considered for u se in fusion reactor nuclear design. Four activation cross-section lib raries, namely, JENDL, LIB90, REAC63, and REAC*175 were investigated in this current analysis. The isotopic induced radioactivity calculati ons using these four libraries are compared with experimental values o btained in the Japan Atomic Energy Research Institute/U.S. Department of Energy collaborative program on fusion blanket neutronics. The nine materials studied are aluminum, silicon, titanium, vanadium, chromium , MnCu alloy, iron, nickel, niobium, and Type 316 stainless steel. The adequacy of the cross sections is investigated through the calculatio n to experiment analysis. As a result, most of the discrepancies in th e calculations from experiments can be explained by inadequate activat ion cross sections. In addition, uncertainties due to neutron energy g roups and neutron transport calculation are considered. The JENDL libr ary gives the best agreement with experiments, followed by REAC175, L IB90, and REAC63, in this order. Clear suggestions for a future direc tion to improve the overall calculation accuracy are developed based o n the current experimental analysis.