Study On The Passive Refrigeration With High- Pressure Air For Main Control Room Of Nuclear Power Plant In Blackout Accident

The reason of the Fukushima nuclear accident is the loss of emergency cooling and electric which leads the failure of exporting heat, mainly caused by earthquake and subsequent tsunami. Thus it leads to the study of how to ensure the nuclear safety in the condition of blackout of nuclear power plant.Main function of the habitable air conditioning system in main control room of nuclear power plant is to provide a safe environment where the operators can keep the reactor and auxiliary system under control in normal times and close the reactor under abnormal conditions, it is helpful to avoid or mitigate the accident consequence, so as to protect the safety of the operators and the nuclear power plant. Therefore, how to ensure the habitability of main control room in nuclear power plant under station blackout accident, especially ensure the ventilation and refrigeration of the main control room with the use of passive technology, has become a key research issue related to nuclear safety.In this paper, the nuclear power plant emergency accident caused blackout as the background. In order to ensure habitability of the main control room, several passive refrigeration technology schemes are put forward in this paper, namely the ice storage refrigeration, the vortex tube refrigeration, throttling refrigeration and expansion refrigeration. Based on the analysis of the working principle and operation of the refrigeration systems, it compared the feasibility and advantages of several schemes and verified the throttling refrigeration and expansion refrigeration scheme by the performance test-bed, finally determined that the expansion refrigeration drove by the high pressure air expander is the most feasible way.In order to study the effect of expansion refrigeration, the performance test-bed of compressed air expansion refrigeration is designed. Although the effect of expansion refrigeration is very excellent, exhaust of the expander appeared with oil. A new type of oil free expander which is made with a series of oil free processing technology is developed, such as oil free bearing, LGM lubrication gradient material. The refrigeration system of oil free expander were studied with experiment and the experimental results showed that: Using the new oil free expander expand the high pressure air, the temperature of the air is much reduced and the cooling rate is fast, the total cooling capacity reached 3937 W, meet the demand of SBO cases of main control room of 3000 W. At the same time, the cooling air can be discharged into the main control room to supply breathing of the personnel directly, so it can ensure the habitability of the main control room for 72 hours under station blackout accident.