SHIELDING AND CRITICALITY ANALYSIS FOR SPECIAL NUCLEAR MATERIAL (SNM) VAULT IN FUEL REPROCESSING PLANT (FRP) OF FAST REACTOR FUEL CYCLE FACILITY (FRFCF)
Fuel Reprocessing Plant (FRP) which is a part of Fast Reactor Fuel Cycle Facility (FRFCF), under construction, will be dedicated to recover the unburnt and bred fissile material from fast reactor (Prototype Fast Breeder Reactor) spent fuels. The purified finished oxide product of FRP will be stored in its Strategic Nuclear Material (SNM) vault. The radiations emitted due to the inherent nature of the product and the residual fission products are to be shielded. These shielding requirements have been estimated using the 3D transport code MCNP4B (Monte Carlo N Particle Transport Code-version 4B). The SNM vault contains 18 cylindrical containers with each having 6 kg of PuO2.Each such container is kept in a concrete pit. Total dose rates (neutron & gamma) have been estimated at various locations inside and outside the SNM vault and to reduce it below 1 µSv/hr at all locations, 7 cm mild steel plus 3 cm polyethylene extra is required as lid for the pit. Near the single pit, additional 5 cm thick concrete is required near the surface facing inside. Criticality analysis carried out for SNM vault confirms that the present arrangement of 18 containers with shield is critically safe.