A passive decay heat removal system for emergency draining tanks of molten salt reactors

Abstract A passive decay heat removal system is proposed that is actuated by the phase change heat transfer method (latent heat of fusion and evaporation) for an emergency draining tank system of molten salt reactors. The emergency draining tank serves an evaporating tank, where the liquid fuel is mixed with an immiscible working fluid and later to vaporize this working fluid. The top header of the vaporizing tank is connected by pipes to a condenser. The resulting vapor pressure of the working fluid drives the vapor through these pipes to condensers, The condensers are located above the reactor, where the vapor condenses, releasing its latent heat of vaporization to a provided heat sink (air heat exchanger). The condensed working fluid flows at first in a Pythagorean cup type collector, which is located just below the condensers, the collected working fluid flows back, in batch, to the emergency draining tank by gravitational force. In this batch manner the working fluid can be strongly mixed with the liquid fuel to enhance the heat transfer between liquid fuel and working fluid without any mechanical or electrical assistance, i.e. a completely passive heat removal process. Therefore the system can passively transport the latent heat of vaporization of the working fluid from the emergency draining tank to the condenser section. This proposed decay heat removal system is described in more detail in this paper. The passive cooling of the liquid fuel to extract the residual heat has been studied.