Model development for the transient heat transfer in a corium pool

Abstract A distributed parameter model has been proposed for the transient heat transfer calculation of IVR in this paper. The model, composed by the free convection model based on empirical correlations and the isothermal solidification model based on the moving boundary method, has been verified with the LIVE-L5L experiment. The result deviations of key parameters, including the average temperature of molten pool, the heat flux distribution on boundary, and the growth rate of solidified crust, are evaluated by comparing with the experimental data. The validation indicates that, for LIVE-L5L experiment within the Ra’ magnitude of 10 12 - 10 14 , Asfia-Dhir formula is optimal to calculate the averaged Nusselt number ( Nu ¯ ). And the errors caused by using the empirical correlations to calculating the transient free convection are acceptable. Besides, the moving boundary method under the isothermal assumption is also applicable for calculating the dynamic solidification on the pool boundary. When the internal heat changes, both the thermal non-equilibrium on the solid–liquid interface and the pulse shape of the crust’s growth rate can be well simulated. And a stable result for interface tracking (or thickness change) can also be obtained. Next, to show the model performance, the work chooses an IVR scenario in SMR (220 MW thermal power) for test. The calculation results show that, the maximum estimation result for the molten pool’s internal heat ( Q m ) is 0.42 MW/m3. And the corresponding peak heat flux ( q m θ ) can reach 267.5 kW/m2. Even in the maximum heat load moment, the maximum temperature on inner wall ( T w , i n θ ) only reaches 1318.1 K. When the molten pool enters into the long-term cooling, the peak heat flux will remain around 170.5 kW/m2. Another, At the upper position with large circumferential angle, the higher heat flux will make the crust form thinner. Thus, the local wall temperature of vessel will be higher by this combined effect of large heat load and small thermal resistance. But it can’t destroy the integrity of the pressure vessel. Research of this paper can provide references for the safety design of SMR.