Design studies on a large-scale sodium-cooled TRU burner

A large monolithic sodium cooled fast reactor for a TRU burning with a power ranging from 1,500 MWt to 3,000 MWt was designed and its safety analysis was implemented. For a TRU burner core design, two possible scenarios were considered: (1) transition of a breakeven core into a burner core; and (2) design of a dedicated burner reactor. In the first case, the design approach of a variable cladding thickness was investigated. For the second case, the so-called 'pancake design' approach was adopted. Both core designs used the design constraints related to the current technology database with a TRU enrichment limit (30.0 w/o) and a fast neutron irradiation limit (4.0 x 1023 n/cm 2). A single enrichment concept was adopted to flatten the power distribution and fuel pin designs of different cladding thicknesses were used for different core regions. For both core design concepts, three power levels of 600, 900 and 1,200 MWe were selected to investigate the dependency of the core performance parameters and the reactivity coefficients on the power level. The calculation results show that both core designs can be accomplished to have almost the same TRU consumption rate per power and a burnup reactivity swing of ∼3,000 pcm. The safety characteristics of the core with the quasi-static reactivity balance method show that both TRU burner designs are found to satisfy the inherent shutdown criteria and there would be no remarkable threat to a reactor safety during the anticipated transient without scram events. (authors)