Uses for the RB* facilities have included the production of radioisotopes; High Temperature Gas-Cooled Reactor (HTGR) fuel irradiations; and the irradiation of candidate fusion reactor materials. The later type of experiment requires a fast neutron flux. A significant fast flux is present in addition to the thermal flux. For this application the capsules are placed in a liner containing a thermal neutron poison for spectral-tailoring. These experiments are carefully reviewed with respect to their neutron poison content and limited to certain positions to minimize their effect on adjacent neutron scattering beam tubes.