Activation analysis for the reference low-activation vanadium alloy NIFS-HEAT-2

Abstract

• Activation analysis was performed for a NIFS-HEAT2 (V-4Cr-4Ti) sample. • The sample was irradiated in Japan Material Testing Reactor (JMTR) ~15 years before. • Detected impurities were 0.41 wppm Co and 0.71 wppm Nb. • Ag impurity concentration was estimated to be <0.034 wppm. • Results are supporting the superior low activation properties of NIFS-HEAT-2. Activation analysis of impurities was performed on a test specimen of the reference low-activation vanadium alloy NIFS-HEAT-2 (V-4Cr-4Ti) which has been irradiated in Japan Materials Testing Reactor (JMTR) ~16 years before. Since the radioactive nuclides from V, Cr and Ti are produced with short half-lives, intense peaks of 60 Co (T 1/2 = 5.27 years) were dominant in the measured gamma-ray energy spectra and peaks of 94 Nb (2.03 × 10 4 years) were also observed. The concentrations were evaluated to be 0.41 wppm and 0.71 wppm respectively from comparison with results of radioactivity calculation using the FISPACT-2005 code. In the analysis, detection of 108m Ag (418 years), which would have a considerable influence on the material recycling after the usage in a fusion reactor, was intense motivation. Although the peaks of 108m Ag has not been detected, the concentration of Ag was estimated to be <0.034 wppm from analysis of detection limit in gamma-ray peak count. Gamma-ray peaks originated from other impurity elements were not observed in the spectra, and the present analysis are supporting the superior low activation properties of NIFS-HEAT-2.