Preliminary proliferation study of the molten salt fast reactor

The molten salt reactor designs, where fissile and fertile materials are dissolved in molten salts, under consideration in the framework of the Generation IV International Forum, present some unusual characteristics in terms of design, operation, safety and also proliferation resistance issues. This paper has the main objective of presenting some proliferation challenges for the reference version of the Molten Salt Fast Reactor (MSFR), a large power reactor based on the thorium fuel cycle. Preliminary studies of proliferation resistance are presented here, dedicated to the threat of nuclear material diversion in the MSFR, considering both the reactor system itself and the processing units located onsite. The present study focuses on a specific threat: the diversion of ²³³Pa by the host state, exfiltrating it from the site, and processing it in a concealed independent installation, in view of producing nuclear weapons. Our main hypothesis is that the 2.6 MeV gamma radiation emitted by the decay from ²⁰⁸Tl to ²⁰⁸Pb allows the detection of any illegitimate handling of nuclear materials. With this hypothesis, we conclude that it would be impossible to divert nuclear materials directly from the salt circulating in the reactor but that it would be possible to do so by misusing the salt cleaning facility