Experimental investigation on natural circulation characteristics of passive heat removal system in Hualong pressurized reactor
The residual heat in Hualong pressurized reactor can be removed passively via natural circulation during the event of feed line break or station blackout accident. The Emergency Secondary Passive Residual heat removal Integral Test facility (ESPRIT) was constructed to obtain the natural circulation characteristics of the passive heat removal system under various initial and boundary conditions. The height of ESPRIT is equal with that of the prototypical Hualong pressurized reactor and the scaling ratio of power/volume is 1:62.5. The stable experiments were conducted to study the effect of heat transfer area of the heat exchanger, steam generator liquid level and resistance coefficient on the natural circulation process. Transient experiments were conducted to evaluate the safety performance of the passive heat removal system. The results of the stable experiment reveal that the system temperature/pressure rises dramatically with the decrease of the heat transfer area of the heat exchanger when the heat transfer area is small. The steam generator liquid level has no significant effect on the natural circulation flow rate and system pressure. Both the system pressure decline rate and the condensed water flow rate decrease with the increasing resistance coefficient. The transient experiments reveal that the blowdown time through the SG release valve increases significantly with the increase of the resistance coefficients of the throttle devices.