Effect Of Minor Actinide Transmutation On Safe Operation Of The Lead-cooled Fast Reactor

In China national 2021-2025 plan,the nuclear power needs to "develop actively and orderly under the premise of ensuring safety".The reprocessing of spent fuel is an unavoidable problem in the development of nuclear power,and we can effectively reduce its long term hazard through transmutation.Lead-cooled fast reactor is a reactor type suitable for transmuting minor actinide(MA)nuclides separated in spent fuel.At present,the international studies on transmutation MA nuclides in the lead-cooled fast reactor are mainly about the feasibility and transmutation rate,and almost no research on reactor safe operation.In this thesis,I use three different MA nuclide loading pattern to study characteristics of MA transmutation in lead-cooled fast reactor:MA cladding loading method;Mixed fuel loading method;Transmutation rod loading method.There are two schemes with different distribution in the transmutation rod loading method,so this thesis had four types of loading schemes in total.Using MCNP and SCALE codes simulate the reactor core model and calculate the results.then I study and analyze the influence of transmutation MA nuclides on the core effective proliferation factor(keff),core lifetime and power peaking factors in the core,as well as the change of fuel temperature coefficient during the reactor operation.In addition,this thesis designed three different distribution schemes to study the influence of the distribution position of transmutation rods on the core lifetime.The results denote that the addition of MA nuclides can affect the effective proliferation factor of the core,and decrease initial keff.The MA cladding loading method and the mixed fuel loading method prolong the core lifetime obviously.The nineteen rods one component distribution scheme of transmutation rod loading method reduces the core lifetime,and the six rods one component distribution scheme prolongs the core lifetime.Except for the nineteen rods distribution scheme of transmutation rod loading method,the other three loading schemes can reduce the core power peaking factor,which is beneficial to the safe power output of the core.The loading of MA nuclides causes the change of fuel temperature coefficients in the lead-cooled fast reactor.With the increase of MA nuclide loading amount,the fuel temperature coefficient deviates to a certain extent from core without MA loading,but it is always negative,which meets the needs of reactor safe operation.However,the fuel temperature coefficient simulation results under different burnup days show that the fuel temperature coefficients of the four loading schemes are similar at low loading amount(1%MA),and the nineteen rods distribution scheme of transmutation rod loading method has a higher absolute fuel temperature coefficient at high MA loading amount(5%MA).While loading MA nuclides in transmutation rod method,the distribution position of transmutation rod has a great influence on the core lifetime,when the transmutation rod concentrates in the core center,it can prolong the core lifetime greatly.My calculation results indicate that the three MA loading methods in this thesis are all feasible,but the transmutation rod loading method needs to pay attention to the position of transmutation rod,and the distribution scheme in which rods closely grouped together in one component should not be adopted.