MAXIMISING DISCHARGE BURNUP IN AN OPEN CYCLE MOLTEN SALT REACTOR

¹ Cambridge University Engineering Department Trumpington Street, Cambridge, CB2 1PZ, United Kingdom
² Wood Kings Point House, Queen Mother Square, Dorchester, DT1 3BW, United Kingdom

cc846@cam.ac.uk
ben.lindley@woodplc.com
gtp10@cam.ac.uk

Published online: 22 February 2021

Abstract

This paper discusses work done to find an estimate of the maximum achievable discharge burnup in an open cycle molten salt reactor (MSR). An in-development deterministic code (WIMS11) is used to create a model of a simple generic MSR, and the methodology employed is discussed. Some experimentation is done with regards to the internal set-up of the ‘unit cells’ within the core, which shows there is a strong link between this geometry and the achievable burnup. Work is done to quantify the effects of removing volatile fission products and implementing a two-batch refuelling scheme. Finally, an optimization process is carried out whereby the optimal proportion of graphite moderator within the core is found which balances power across the regions while maximising discharge burnup. Two fuels are tested, one which carries only ²³⁵U and ²³⁸U, and another which also carries ²³²Th. It is found that the maximum achievable discharge burnup is approximately 155 MWd/kg, which is considerably higher than modern PWRs, despite a lower enrichment and only two batches of fuel being used.