Preliminary Research On Initial Events And Transient Safety Characteristic Of Lead-Cooled Fast Reactor

A lead-cooled fast reactor is one of the fourth-generation nuclear energy systems,which has a great potential due to its strong ability in sustainability,economics,safety and reliability,and proliferation resistance and physical protection.It has unique advantages in terms of safety performance.However,there are many safety problems,such as the corrosion and solidification of lead coolant.These are a great threat to the normal operation of the reactor,which need to be fully considered in the design and the security assessment of the reactor system.As a new type of advanced nuclear energy system,the relevant key technology of lead cooled-fast reactor is still in the stage of exploration and research.The transient safety analysis during the typical accident condition in LFR is one of the key issues to explore and study in the development of this new type reactor.In this article,the safety features of lead-cooled fast reactor are studied,based on the conceptual design of a 1000MWth driven circulation lead-cooled fast reactor.The main research work of this thesis is as follows:Firstly,the existing design scheme of 1000MWth forced circulation lead-cold fast reactor is briefly introduced,including the design of the overall structure and the special safety facilities.It provided an important basis for the research of initial events and transient safety characteristic and laid the foundation for the analysis of safety characteristics of lead-cold fast reactor.Secondly,on the basis of the design of 1000MWth driven circulation lead-cold fast reactor,the main logic diagram method(MLD)has been used to derive the initiating events.The core damage was chosen to be the top event,and the deductions are divided into three ways corresponding to the three physical barriers to the fission product and the external environment(fuel cladding challenges,RCS boundary challenges and containment challenges).Considering the relating experience of other liquid metal reactors,forty-three initial events were listed.There typical accidents with serious sequence and serious consequences in each category are selected for further transient safety analysis.Finally,based on the RELAP5 code,typical initial events that can lead to serious accidents were carried out to perform transient simulation,i.e.unprotected reactivity insertion(UTOP),unprotected loss of flow(ULOF),unprotected loss of offsite power(ULOF + ULOHS),and increase of feed water flowrate with all primary pumps trip.Then main safety characteristics of the innovative and safe lead cold fast reactor are summarized.The research results in this paper can provide experience and technical support for other research lead-cooled fast reactor in China,and help enhance the independent innovation ability in the field of lead-cooled fast reactor,which has important research significance and application value.