Advanced passive residual heat removal system for high power pool-type research reactor

Highlights: • The advanced system is described and tested by experiments in the scale-down model. • The experimental, theoretical, and CFD simulation results are in good agreement. • The theoretical model can assist analysis and design of actual-sized system. - Abstract: A novel passive residual heat removal system is proposed to enhance the safety and cost effectiveness of open pool-type research reactor with high power. As the pool-type research reactors typically have forced downward flow through the reactor core, a stagnant coolant in the middle of flow transition from forced to natural circulation can cause damage to fuel bundles. The main strategy of the proposed system is to delay the flow inversion time by prolonging the core downward flow until the decay heat is significantly calmed down. A gravity core cooling tank is devised to drag the downward flow on by gravity. To demonstrate the new system with the gravity core cooling tank, experimental results from a small-scale facility were compared with results from theoretical analysis and CFD simulation. The theoretical prediction of a 15 MWt real scale system shows that the advanced passive residual heat removal system can perform as an intermediate heat removal system to natural convection by providing sufficient mass flow to remove decay heat from a high power research reactor.