Design of spectrally tailored fusion reactor materials experiments in the HFIR [High Flux Isotope Reactor] RB [removable beryllium] capsule irradiation facility

Design of four spectrally tailored capsules to irradiate magnetic fusion energy (MFE) materials specimens in the new High Flux Isotope Reactor (HFIR) removable beryllium (RB*) facility at temperatures of 60, 200, 330, and 4000C, respectively, is described. These designs incorporate provisions for removal, examination, and reencapsulation of the MFE specimens at intermediate exposure levels en route to a target exposure level of 30 displacements per atom (dpa). With the exception of the 600C capsule, where the test specimens are in direct contact with the reactor cooling water, the specimen temperatures (monitored by 24 thermocouples) are controlled by varying the thermal conductance of a small gap region between the specimen holder and the containment tube. Hafnium shields are used to tailor the neutron spectrum to closely match the helium production-to-atom displacement ratio (14 appm/dpa) expected in a fusion reactor first wall. These MFE capsule irradiations will begin in early 1988