Coolant Void Reactivity in Supercritical CO_2-Cooled Fast Reactors

摘要

It has been found possible to achieve small positive, zero, or even negative coolant void reactivity in 20 MPa S-CO_2-cooled GFRs by proper choice of geometry and composition; this is in contrast with helium at 8 MPa. Since the diameter was held constant in this analysis, the cores with small H/D ratios have smaller total core volume, require higher TRU enrichment, and therefore suffer a burnup penalty. In future work, moving to a larger core volume while preserving tolerable coolant void properties will be investigated. In this regard, it should be noted that the helium-cooled, (Pu,U)O~2-fueled General Atomics GCFR design in the 1970's had a void reactivity of+55￠.