The Suitability of the Materials Test Station for Fusion Materials Irradiations

Los Alamos National Laboratory has completed the conceptual design of the Materials Test Station (MTS), an accelerator-driven neutron source for irradiating nuclear fuel and materials in a fast neutron spectrum. In many respects, the irradiation conditions in the MTS are quite similar to those experienced by the first wall of a fusion reactor. Calculated He-to-dpa (displacements per atom) ratios range from 35 down to 5 appm He/dpa, allowing for critical testing of helium effects on mechanical properties under fusion-relevant conditions. We present here a brief history on the assessment of spallation sources for fusion materials testing and discuss irradiation conditions in the MTS as they pertain to testing materials for fusion reactor applications. In particular, we examine the production of spallation residues in the MTS for the fusion reactor candidate alloy EUROFER97 and compare the concentrations of these transmutation elements to those predicted for a fusion reactor first wall. We show that predicted yields of phosphorous and sulfur in steel alloys irradiated to high dose in fusion-relevant regions of the MTS are below typical as-fabricated concentrations.