Gamma radiation sources are used for a multitude of applications, including nuclear medicine applications. The current study investigated the feasibility of a switchable radioactive gamma source for two applications: as a calibration source for SPECT gamma cameras; and as a blood irradiator. The source was based on a sequence of (α, n) reactions followed by (n, γ) reactions. MCNP5 parametric studies were performed to investigate the effects of different moderators (e.g., heavy water, deuterated polyethylene or high density polyethylene), neutron absorbers (e.g., Sm(natural) or Gd(natural)) and geometries, on the calculated gamma flux and dose rate for the proposed source design. The results show that, although technically feasible, the applicability of the proposed source for the two intended applications is not feasible because of cost constraints for larger source designs, and low gamma fluxes and dose rates obtained for smaller source designs.