Numerical Investigation of a Class of Accidents in the Generation IV Brest Reactor Involving the Formation of a Solid Phase in the Lead Coolant

The possible formation of a solid phase in the lead coolant in the BREST-OD-300 reactor, a problem common for reactors of such type, is numerically investigated. For modeling unsteady processes in the steam generator operating with a liquid-metal coolant under the conditions involving the occurrence of crystallization–melting phenomena, a procedure that makes it possible to take into account the process ambiguity depending on the state of the heat-transfer contact surface oxide layer was used. Accidents caused by a rupture of the main steam header and by failure of the regenerative feedwater heating system are considered. The influence of certain reactor parameters on the solid phase formation dynamics in such accidents is estimated. If loss of tightness occurs in the main steam header with simultaneous loss of power supply to the reactor and failure of the steam generators’ shutoff and control valves and also in the case of regenerative feedwater heating system failure with retaining the supply of feedwater to the steam generators, the solid phase fully blocks the flow section in all four loops of the primary coolant circuit. Depending on the state of the heat-transfer contact surface oxide layer, the flow sections of the steam generators themselves or those of the steam generator cavities in the concrete shell can be blocked. The main factor causing the lead coolant to become solidified in the case of steam header rupture is a sufficiently large amount of feedwater in the secondary coolant circuit pipelines and heat-transfer equipment at high pressure. At the same time, in an accident involving failure of the regenerative feedwater heating system, this volume is not of key importance for the solid phase formation dynamics in the lead coolant. The study results can be used in elaborating the designs of lead cooled reactors.