Computational Fluid Dynamic Analysis of the ESFR Reactor Pit Cooling System in Case of Sodium Leakage

The decay heat removal system (DHRS) for the European sodium-cooled fast reactor (ESFR) concept consists of three cooling systems, which provide highly reliable, redundant, and diversified decay heat removal functions. Two of the systems provide a strong line of defense, whereas the third system provides long term-heat removal. This third DHR system, DHRS-3, involves in separating oil, and water-cooled loops integrated in the reactor pit serves the purpose of the safety vessel. It is expected that the proposed DHR concept enables a robust demonstration of the practical elimination of the prolonged loss of the decay heat removal function. For its confirmation, detailed nwnerical analysis is needed as a basis for further investigation. Supporting this approach, the current evaluation with means of computational fluid dynamic (CFD) provides a preliminary thermal analysis of the capability of the oil cooling system in the reactor to be used for residual heat removal in the pit in case of emergency. For the evaluation, different heat flux values are assumed at the vessel wall to examine the range of the resulting temperatures. The temperature of the main vessel wall should be below 800 degrees C. Furthermore, a sodium leakage at 500 degrees C into the reactor pit is assumed. The concrete structure is below 70 degrees C.