Development of simple method to incorporate out-of-core cooling effect on thorium conversion in multi-pass fueled reactor and investigation on characteristics of the effect. (July 2015)

• Record Type: Journal Article
• Authors: Fukaya, Yuji
• Is Part Of: Annals of nuclear energy. Volume 81(2015:Jul.)
• Page Start: 301
• Page End: 305
• Publication Date: 2015-07
• Subjects: Out-of-core cooling -- Thorium conversion -- Protactinium -- Molten salt reactor -- Pebble bed reactor; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2015.03.005
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: I proposed simple method based on analytical approach. I applied this method to MVP-BURN calculations without a code modification. I estimated conversion efficiencies based on this method. I compared the conversion efficiencies of MSBR and PBMR. Abstract: Development of a simple method to incorporate the out-of-core cooling effect on the thorium conversion in multi-pass fueled reactors and investigation on characteristics of the effect have been undertaken. For multi-pass fueled reactors, such as Molten Salt Breeder Reactor (MSBR) and Pebble-Bed Modular Reactor (PBMR), fuel moves in the core and exits from the core. The produced nuclides also decay out of the core, which should be considered for core characteristics when needed. In the present study, 233 Pa is selected to evaluate the thorium conversion accurately. To take the effect into account, in the present study, an effective decay constant is proposed to make equilibrium concentration of 233 Pa without out-of-core cooling equal to that with out-of-core cooling. With the effective decay constant, the out-of-core cooling effect can be incorporated even with the code system using macroscopic cross sections generated by cell burn-up calculations without any code modification. In addition, the characteristics of out-of-core cooling effect for the thorium conversion are evaluated for thorium fueled reactors MSBR and PBMR. It is concluded that the out-of-core cooling effect is suitable for MSBR to enhance thorium conversion because of the fast flow rate of fuel salt. On the other hand, the effect is neither important nor realistic to employ for PBMR because the in-core residence time of approximately 100 days is longer than the half-life of 233 Pa of 27.0 days, and the effect cannot improve the conversion ratio significantly.