Physics design aspects of a proposed fast neutron irradiation facility in Dhruva reactor

The available fast neutron (>1 MeV) flux in the 100 MW Dhruva reactor in typical irradiation positions is about 3.OE+12 n/sqcm/sec. For studying fast neutron damage in structural materials it is desirable to have high fast neutron flux values so as to complete the irradiation in a reasonable time. To this end two different designs of fast neutron transformer assemblies, (i) annular geometry and (ii) 6-pin cluster geometry were considered and studied in detail. The irradiation volume is at the centre of the assemblies. For a typical assembly operating at 800 kW it is estimated that the fast neutron flux will be enhanced to a value of about 2.OE+13 n/sqcm/sec. The paper summarises the design considerations and the method of calculation adopted for the purpose. (author). 4 refs., 2 figs