Use of delayed Gamma Spectra for Detection of Actinides (U,Pu) By Photofission

The development of non-destructive methods to inspect nuclear waste container is important for radio active waste management and non proliferation purposes. Among methods using nuclear radiation as a probe, instrumental photon activation analysis (IPAA) seems to be a promising way forward. We have previously developed an IPAA method to determine the mass of actinides in radioactive wastes sealed on concrete by counting the delayed neutron emission after photofission. This method does not determine the nature of the actinides detected. Such additional useful information may, however, be derived from analysis of the delayed gamma emission spectrum. The main topic of this paper is to show how the analysis of the delayed gamma spectra may overcome some of the limitations of delayed neutron analysis. In a previous paper we presented out first results on U238 and U235, these nuclides were irradiated with bremsstrahlung gamma rays produced by 16-MeV electrons from a linear accelerator. In this paper we present our study on Pu sample and we show how the evolution of the peak in the delayed gamma spectra could b used.