A cryogenic irradiation facility in the Safari-1 reactor

Abstract A liquid helium cooled irradiation facility has been built and tested in the SAFARI-1 reactor (ORR-type). The distinguishing feature of this facility is the low refrigerative capacity at 4.4°K of only about 30 Watts coupled to a reactor of relatively high power (20 MW) and γ-heat (10 W/g). The γ-heat was reduced by placing a lead shield of 10 cm thickness against the pool-side experimental facility of the reactor. This reduces the γ-heat to about 0.1 W/g. A fast neutron facility can be established by surrounding the in-pile trunk with boral (flux 8 × 1012 n cm−2 s−1, E > 0.1 MeV). For irradiations in a thermal neutron spectrum, a heavy water tank can be inserted between the in-pile trunk and the reactor face (flux 6 × 1012 n cm−2 s−1, thermal). The ratio of fast to thermal flux can be changed by a factor of 104. An annealing facility for the application of square temperature pulses with a stability of 10−2° K has been built as an integral part of the irradiation facility.