Nuclear and Thermal Analyses of Supercritical-water-cooled Solid Breeder Blanket for Fusion DEMO Reactor.

Abstract

Within a design study of a fusion DEMO reactor aiming at demonstrating technologies of fusion power plant, supercritical water is applied as a coolant of solid breeder blanket to attain high thermal efficiency. The blanket has multi-layer composed of solid breeder pebbles (Li 2 O) and neutron multiplier pebbles (Be) which are radially separated by cooling panels. The first wall and the breeding region are cooled by supercritical water below and above the pseudocritical temperature, respectively. Temperature distribution and tritium breeding ratio (TBR) have been estimated by one-dimensional nuclear and thermal calculations. The local TBR as high as 1.47 has been obtained after optimization of temperature distribution in the breeder region under the following conditions: neutron wall loading of 5 MW/m 2 , 6 Li enrichment of 30% and coolant temperature at inlet of breeder region of 380 • C. In the case of the higher coolant temperature 430 • C of the breeder region the local TBR was reduced to be 1.40. This means that the net TBR higher than 1.0 could be expected with the supercritical-water-cooled blanket, whose temperature distribution in the breeder region would be optimized by following the coolant temperature, and where a coverage of the breeder region is assumed to be 70%.

Radioactivity of the vanadium-alloy induced by D–T neutron irradiation

“…We calculated the radioactivity for 2 years irradiation, which corresponds to the actual operation condition assumed in the DEMO blanket [10], with the following formula:…”

Development of Supercritical Pressure Water Cooled Solid Breeder Blanket in JAERI

“…The candidates of the breeder pebbles are Li 2 O or Li 2 TiO 3 , and Be or Be 12 Ti is applied as the neutron multiplier. The size of the pebbles will range from 0.2 mm to 2 mm in diameter [4]. The breeding layer is purged with Helium gas in order to recover Tritium.…”

Effects of lithium burn-up on TBR in DEMO reactor SlimCS

“…Consequently, the tritium production might be changed by decrease of the atomic densities and the change of the neutron spectra due to the lithium burn-up. Numerous studies have been reported on the evaluation of TBR [1][2][3][4][5][6][7]. El-Guebaly et al reported the impact of tritium burn-up fraction on tritium start-up inventory [2].…”

“…DEMO reactors require the net tritium breeding ratio (TBR) of more than 1.05-1.1 [1,2] and a lot of design studies have been conducted to meet the requirement [1][2][3][4][5][6]. SlimCS is a conceptual design of a tokamak DEMO reactor being developed by JAEA [4].…”