Calculated Composition Changes of Some Refractory Metals in a Fusion Reactor Environment

Composition changes that occur during neutron bombardment have been calculated for the first wall of a hypothetical fusion reactor. The first wall materials studied are pure niobium, zirconium, molybdenum, and vanadium, and some of their binary alloys. Two integrated neutron flux intensities, 3.8 × 10¹⁴ n/(cm² sec) and 3.8 × 10¹⁵ n/(cm² sec) up to a fluence of 3.6 × 10²³ n/cm², have been used in the calculations of the first three materials. In addition, the composition as a function of fluence (maximum fluence =4.0 × 10²³ n/cm²) has been calculated for a vanadium wall. Graphs for each material have been plotted to show the variation of composition as a function of time and/or fluence. Rates of production of hydrogen and helium have been calculated for all four materials; comparisons for niobium and vanadium walls with literature values show agreement that it is not poor. Furthermore, mixture diagrams have been constructed for two binary alloy systems, niobium-zirconium and niobium-vanadium, to relate composition at constant irradiation time to the initial composition.