Experimental Modelling to Measure the Seat Leakage in Shutdown System of PFBR

In case of Safety Control Rod-Accelerated Movement (SCRAM) in Indian Prototype Fast Breeder Reactor (PFBR), the electromagnet gets de-energized and releases the Diverse Safety Rod (DSR) to fall under gravity and finally deposited on the dashpot of DSR Sub-assembly (DSRSA) to shut down the reactor. DSR contains Boron Carbide, which is a neutron absorber material and absorbs neutrons to bring down the neutron flux which is controlling the chain reaction. The maximum amount of heat that can be generated in DSR while absorbing the neutrons is estimated as 1 MWt. To remove this heat, a minimum sodium coolant flow rate of 3 kg/s is required to pass through the mobile DSR. This required flow rate through mobile DSR is 95% of the total flow rate of 3.18 kg/s, which is passing through the DSRSA when DSR is deposited on the dashpot. Therefore, only 5% of the total flow is allowed to leak through the DSR–dashpot interface. In this study, leakage through DSR–dashpot interface has been measured experimentally using water as simulant fluid in a simplified, full-scale model of DSR–dashpot interface region. This paper primarily focuses on the modelling techniques for such kind of experiments using geometrically similar models of particular zone of interest. The predictions for prototype from the experimental results are also discussed.