The effects of core zoning on the graphite lifespan and breeding gain of a moderated molten salt reactor

In the various one-fluid moderated Molten Salt Reactor (MSR) designs the ratio of the volume of the salt and the graphite is not uniform. This is usually realized by two or three zones in the core in which the volume ratio of graphite and salt is constant. This non-uniform salt distribution is used to increase the graphite lifespan or Breeding Gain (BG). However, it is difficult to assess the contribution of this non-uniformity to the final results of lifespan and BG based on the literature. In this paper, the effect of the variation of the salt distribution is investigated. As the aim of this study is to provide an insight to this single change of the core and to apply it to increase the lifespan of the graphite, the variations were performed only on the radial direction of the graphite–salt lattice in a cylindrical core. The obtained results were compared with a reference core in which the salt is distributed uniformly. It is possible to increase the breeding gain or the graphite lifespan by separating the core into two radial zones with different amount of graphite. On the other hand, it is only possible to increase one by the cost of decreasing the other one due to the change in the power distribution induced by the change in the core geometry.

► Material evolution calculations for moderated molten salt reactor.
► Zoning of the core to increase graphite lifespan and/or breeding gain.
► Zoned cores compared with a one-zone reference.
► Increase is possible in the lifespan or breeding gain.
► An achieved increase in one decreases the other.