Natural circulation experiments in a non-uniform diameter lead bismuth loop and validation of LeBENC code

Experimental studies are carried out on natural circulation in a Lead Bismuth Eutectic (LBE) loop. The loop mainly consists of a heated section, air heat exchanger, valves, various tanks and argon gas control system. All the components and piping are made of SS316L. The dissolved oxygen in the LBE is monitored online by an Yttria Stabilised Zirconia (YSZ) oxygen sensor and controlled during the operation of the loop. In this paper the details of the loop and experimental studies carried out with heater power levels varying from 900 W to 5000 W are described. The temperature range of LBE during the experiments was 200 °C-500 °C. The maximum heat loss in the piping is kept less than 20% of the main heater power. Steady state experimental studies are carried out at different power levels and the LBE flow rate was found to be varying from 0.095 kg/s to 0.135 kg/s. The analysis and results of the performance of the heat exchanger with air and water as the secondary coolants are also discussed in the paper. Transient studies were carried out to simulate various events like heat sink loss, step power change and secondary side coolant flow rate change and reported in the paper. In the start up experiments, where the flow is started from stagnant condition of LBE, the time required for starting of natural circulation is found to be 600 s, 400 s and 240 s with power level of 1200 W, 2400 W and 3000 W respectively. The results are compared with available correlation and prediction of computer code LeBENC.