The importance of using the mixed neutron flux in activation analysis of D-3He fueled reactors

It is emphasized that the mixed neutron source should always be used in any activation and safety analysis performed for D-³He reactors. It is noted that performing any activation analysis by using the two components of the neutron source (D-D and D-T) separately leads to overestimating the induced activity. The overestimation is determined by the destruction rate of the parent atoms, the magnitude of the neutron flux, the reactor operation time, and the radionuclide half-life. The overestimation was found to be more pronounced for short and intermediate lived nuclides. In a typical D- ³He reactor, the overestimation in the calculated activity and decay heat was as high as 40% after 30 years of reactor operation. In the meantime, the offsite dose was overestimated by 27%