Considerations on safety and proliferation-resistant aspects for the MSBR design

Abstract

Even though a molten salt reactor (MSR) design did not pop up on industrial scale such as the liquid metal fast breeder, it has been retained under the six reference concepts of Generation IV. Some states have definitely interest in it, in particular when considering the use of large Th resources in a U–Th fuel cycle. Japan, Russia and the US reported under the ITHSMO consortium a well-advanced development stage of the FUJI 100 MWe MSR. This paper recalls the reference-design of the Molten Salt Breeder Reactor of ORNL while focusing on two opposing aspects the breeding flexibility and the complex operation safety (in particular reactivity control). Contrary to the safety aspects, for which solutions were uncovered in the European MOST project, it was felt necessary for the safeguards aspects to complete a proliferation sensitivity study and to analyse innovative solutions for proliferation-resistance. The assessment of the Molten Salt Breeder Reactor (MSBR) to the proliferation-resistance criteria of Generation IV reactors leads to propose no Pa and U removal in the reprocessing of the fuel. This proposal exploits the activity level of U 232 as intrinsic barrier against nuclear material proliferation and showed that a 60 ppm U 232 impurity level, with a high impurity precursor level, would enable this. However, without the removal of Pa and U from the fuel mixture, the reactivity starts to fluctuate and needs compensation.