Neutronic performance of HYLIFE-II fusion reactor using various thorium molten salts

HYLIFE-II is one of the major inertial fusion energy reactor design concepts in which a thick molten salt layer (Flibe = Li2BeF4) is injected between the reaction chamber walls and the explosions. Molten salt coolant eliminates the frequent replacement of solid first wall structure during reactors lifetime by decreasing intense neutron flux. This study presents the neutronic analysis of HYLIFE-II fusion reactor using various liquid wall coolants, namely, 75% LiF-25% ThF4, 75% LiF-24% ThF4-1% 233UF4 or 75% LiF-23% ThF4-2% 233UF4. Neutron transport calculations for the evaluation of neutron spectra were conducted with the help of Scale 4.3 by solving the Boltzmann transport equation in S8-P3 approximation. The effects of flowing liquid wall thickness and type of coolant on the neutronic performance of the reactor were investigated. Furthermore, radiation damage calculations at the first wall structure with respect to type and thickness of liquid wall were carried out. Numerical results showed that using the flowing liquid wall containing the molten salt, 75% LiF-23% ThF4-2% UF4 with a thickness of ∼70 cm maintained tritium self-sufficiency of the (DT) fusion driver and extended the first wall lifetime to the reactors lifetime (∼30 full power years). In addition significant amount of high quality fissile fuel was bred through (n, γ) reaction of 232Th. Moreover, energy multiplication factor (M) was increased to ∼12 by high rate fission reactions of 233U occurring in the flowing wall. On the other hand, it was concluded that using the other two coolants, 75% LiF-25% ThF4 or 75% LiF-24% ThF4-1% 233UF4, as liquid wall did not satisfy the radiation damage and the tritium sufficiency criteria together at any thickness, so that these two coolants were not suitable to improve neutronic performance of HYLIFE-II reactor.