Three-dimensional analyses of candidate blanket designs for the compact tokamak reactor concept

Abstract

Three-dimensional nucleonic analyses have been performed for five candidate blanket systems proposed for a compact tokamak fusion reactor. These analyses were carried out using the Monte Carlo code MCNP and the nuclear data ENDF/B-IV. It has been found that the ternary ceramic breeder LiAlO 2 does not meet the required tritium breeding goal (TBR=1.1) even when the best nonfissionable neutron multiplier and different design configurations were utilized. Liquid metal breeders have better nucleonic performance than the solid breeders. Liquid lithium is superior to Li 17Pb 83 in terms of nucleonic performance especially when no breeding in the inboard is utilized and when peneteration systems are considered. Complete elimination of inboard breeding and accounting for penetration systems resulted in breeding losses of 23.0%, 25.3%, 23.5% and 32.9% in blankets of Li 2O/H 2O/SS316L, Li 2O/He/SS316L, Li/Li/V15Cr5Ti and Li 17Pb 83/Li 17Pb 83/HT-9 respectively. A careful choice of limiter structure and coolant leads to less breeding loss. The effect of the RF-system on the TBR was small for all the blanket systems considered. When Li 17Pb 83 is used as a static breeder to minimize its circulation, and thus making MHD losses negligible, a separate coolant such as water, helium or sodium should be used. It has been found that when high 6Li-enrichment is used the effect of the coolant choice on the TBR and energy multiplication factor, EMF, is negligible. The TBR of the Li 2O blanket cooled with water and without inboard breeding can be enhanced to 1.28 which is large enough to compensate for the losses associated with penetration systems. The atomic displacement rate in the first wall of the Li 17Pb 83 blanket system is the largest followed by that of the Li-blanket, with rates in the solid breeder blankets about 10% lower than that of Li 17Pb 83. The helium production rate in the first wall of a LiAlO 2 blanket system is the largest and it is high in the structure of the front breeder zones of solid breeder blankets. The hydrogen production rate in the first wall and front breeder structures is also high for solid breeder systems.