Neutron-induced dpa, transmutations, gas production, and helium embrittlement of fusion materials

• Published in: Journal of nuclear materials 2013-11, Vol.442 (1-3), p.S755-S760
• Main Authors: Gilbert, M.R., Dudarev, S.L., Nguyen-Manh, D., Zheng, S., Packer, L.W., Sublet, J.-Ch
• Format: Article
• Language: English
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2013.03.085

•Neutron irradiation conditions are calculated for a 2009 DEMO concept model.•Spectra and fluxes converted to dpa to highlight variation and limitations.•Inventory calculations are used to quantify the production of helium via transmutation.•Basic modeling of grain boundary embrittlement gives critical helium concentrations.•Critical time estimates for different materials from transmutation results. In a fusion reactor materials will be subjected to significant fluxes of high-energy neutrons. As well as causing radiation damage, the neutrons also initiate nuclear reactions leading to changes in the chemical composition of materials (transmutation). Many of these reactions produce gases, particularly helium, which cause additional swelling and embrittlement of materials. This paper investigates, using a combination of neutron-transport and inventory calculations, the variation in displacements per atom (dpa) and helium production levels as a function of position within the high flux regions of a recent conceptual model for the ‘next-step’ fusion device DEMO. Subsequently, the gas production rates are used to provide revised estimates, based on new density-functional-theory results, for the critical component lifetimes associated with the helium-induced grain-boundary embrittlement of materials. The revised estimates give more optimistic projections for the lifetimes of materials in a fusion power plant compared to a previous study, while at the same time indicating that helium embrittlement remains one of the most significant factors controlling the structural integrity of fusion power plant components.