Background:In the water-cooled passive heat removal system for molten salt reactor

the decay heat generated in molten salt can finally be transferred to the heat exchanger placed in water tank by natural circulation.Purpose:Based on the principles of high safety and simplification

there is a need to transfer the decay heat passively without using external power.Methods:The heat exchanger consists of a set of bundles submerged into the water tank with a tube header at each side.Based on the flow process

corresponding numerical model was constructed in the code of C++.Then the total heat exchange coefficient is got and the heat transfer area is calculated.Continually iterate the heat transfer area until the iteration stopping criterion is met

after that the dimensions of water tank are figured out.Results:While the decay power is 100 kW in the initial of the operation

the power of heat exchanger reaches the maximum value of 130 kW due to the low-temperature water in water tank.Then it drops quickly for the decrease of heat exchanger pressure and the rise of water temperature in water tank.When the heat exchanger pressure begins to rise

the heat exchanger power drops slower than before.The heat transfer ability begins to decrease quickly as the temperature difference between inside and outside of heat exchanger tubes lowers.Then it drops gradually as a result of the slowly changed pressure.During early operation

the heat exchanger pressure decreases because the steam generation rate is lower than the steam condensation rate.Then the condition varies as the heat exchanger power declines gradually.When boiling happens inside the water tank

the steam condensation rate raises due to the increasing heat transfer ability which makes the pressure of heat exchanger drops quickly.Afterwards

the heat exchanger pressure changes very slowly as the steam generation rate is approximate to the steam condensation rate.The mass of water in water tank remains unchanged essentially until the water begins to boil

then it starts to evaporate as the heat is transferred.The variation trend of the mass flow of condensate is similar to the heat exchange power of condenser.It decreases first and rises when the water reaches saturation.Then it lowers as the condenser pressure declines.Conclusions:The parameters of heat exchanger are calculated and the result shows that it can meet the requirements for heat exchange and has the self-regulation to some extent.The water tank can transfer the heat for a long time.Meanwhile the power can be adjusted by changing the water level in water tank.