Simulating Method And Analysis Of The Sodium-Water Reaction Accident In The Sodium-Cooled Fast Reactor

With the development of nuclear power all over the world,the lack of nuclear fuels and difficulty of nuclear waste treatment have became the Achilles' heel of nuclear power field.Among those all solutions to these two problems,the fast reactor is the most attractive way which is because that the fast reactor can breed the nuclear fuels whiles it is under operating and purify the nuclear waste.Generally speaking,the liquid sodium is the common choice for the coolant of the primary loop of the fast reactor as that the excellent thermal properties and the low reaction cross section with Neutron.However,there are two major weakness for the sodium cooled fast reactor:the chemical property of sodium is too activity to let sodium exposure to air or water;the liquid sodium would destroy stainless steel through the chemical corrosion and stress corrosion.The leaking in the pipe of steam generator is an unavoidable phenomenon in the pressurized water reactor.But in the sodium cooled fast reactor,the leaking of steam generator caused by the corrosion of sodium is an unacceptable accident which is so called the sodium water reaction accident.Hydrogen would be generated by the reaction and the space would be occupied by the generated hydrogen when this sodium water reaction accident happened.During this accident,the leaked generator will lose its heat exchange capacity so that the refrigerating capacity of the secondary loop to the primary loop might decline,the reactor core might.And the pressure wave caused by the growing of hydrogen bubble will spread through the pipes to everywhere of the secondary loop,some of equipment might also be destroyed by this pressure wave.Because of these bad influence,the sodium water reaction accident has made the Monju reactor and the SuperPhenix reactor decommissioning,so that the safety performance of reactor under this the sodium water reaction accident came to the most important design criteria in the sodium cooled fast reactor.To figure out the safety performance of the Chinese Demonstration Fast Reactor(CDFR)under the sodium water reaction accident,this paper has designed the sodium water reaction numerical model based on the BN-600 reactor which is the prototype CDFR.Besides that,a numerical reactor model of the BN-600 reactor has been designed in the RELAP5 program.To make sure of that the RELAP5 program can meet the requirements of the veracity of simulating,a test of the steady state working condition of the numerical reactor model of the BN-600 has proceeded.By the redevelopment of RELAP5 program,the sodium water reaction model was implanted into the RELAP5 program,so that the numerical reactor model of BN-600 in RELAP5 program and the sodium water reaction model have been coupled together to conduct the simulating of the behavior and response of the BN-600 reactor in the sodium water reaction accident.This paper has successfully proceeded the coupled simulating of the sodium water reaction accident happened in the BN-600 reactor with the sodium water reaction model in the RELAP5 program,through the analysis of those simulating results,we can come to a conclusion of that:1.The emergency discharge system would work to discharge that contaminated liquid sodium from the leaking area and weaken the pressure wave caused by the growing of hydrogen bubble during the accident;2.The design of the multiple,parallel and low power steam generators of the secondary loop would help to take the power redistribution between accidental steam generator and those normal steam generators when the unevenness of cooling power caused by the accident happened,this design could avoid the meltdown of the reactor core happened in the sodium water reaction accident;3.The large volume of the sodium buffer could weaken the pressure wave caused by the growing of hydrogen bubble also,the pressure wave from the accidental steam generator might destroy others without the design sodium buffer.