Rationality analysis of CEFR sodium temperature change velocity limit from structure heat transfer

It is required that the sodium temperature change velocity shall not exceed 30 ℃/h when elevating CEFR power. Both the theoretical analysis and ANSYS numerical simulation were used to investigate the transient heat transfer process of a plate under the condition of external sodium temperature change and the time needed for the plate temperature to reach a steady state, so as to demonstrate the rationality of the limit 30 ℃/h. The result shows that the convective heat transfer condition directly affects the time needed for the structure temperature to enter a steady state. The temperature change of structure follows closely that of sodium in the condition of good convection heat transfer. In the condition of poor convection heat transfer, the sodium temperature change velocity of 30 ℃/h can ensure that the structure temperature could reach more than 60% of the total temperature change amplitude when sodium temperature becomes steady. The 30 ℃/h basically ensures that the temperature change velocity of the structure being into steady state is the same to that of sodium, which can reduce the complexity for distribution and change of thermal stress and guarantee the uniformity of the actual temperature and the steady-state design temperature of structure. (authors)