In-Core Fuel Management Strategy Design And Optimization Research Of Lead-cooled Fast Reactor M~2LFR-1000

Core fuel management is an extremely important and complex work in the design of reactor,which directly affects the economics of the reactor.At present,there are many mature fuel management calculation methods for traditional thermal reactors such as pressurized water reactors at home and abroad.However,fast reactors are different from traditional thermal reactors in control methods and power distribution.Because of their hard energy spectrum and nuclear fuel proliferation ability,more systematic research have to be done on core fuel management of fast reactors.Based on the research and development of the forced circulation lead cooled fast reactor M2LFR-1000,which is independently researched and developed by the University of Science and Technology of China,according to the research on the fuel management research of pressurized water reactor and fast reactor at home and abroad,combined with the characteristics of fast reactor fuel management,fuel management schemes design and refueling optimization of M2LFR-1000 core were carried out in this paper,The OUT-IN-IN refueling scheme,low-leakage refueling scheme,mixed refueling scheme were given.Then the refueling schemes were evaluated by comparing the calculated results.Firstly,this paper analyzed the design method of M2LFR-1000 core fuel management seheme,including the introduction of equilibrium cycle design pseudo-equilibrium cycle analysis on the basis of equilibrium cycle analysis,and the summary of detailed process of core fuel management scheme design.At the same time,based on the M2LFR-1000 design plan and objectives,considering the safety,economy and technical feasibility of the reactor,the constraints and objectives of fuel management were determined.Secondly,according to the internal and external layout of M 2LFR-1000 core fuel assemblies,three batches of OUT-IN-IN refueling schemes were designed for the internal and external fuel assemblies respectively.The pseudo-equilibrium cycle analysis and optimization of refueling schemes were carried out.By optimizing the volume fraction of PuO2 in the outer zone to 19.9%.the core refueling cycle was extended to 18 months and the average burnup depths of discharge fuel were increased.Calculation and analysis of detailed initial cycle,transition cycle and balanced cycle were carried out further for the optimized feeding scheme.The calculated results of equilibrium cycle were compared with those of pseudo-equilibrium cycle.The cycle length both were 18 months,and the difference between the maximum discharge burnup depth and the average discharge burnup depth was not more than 0.2 GWd/tHM.Although the power peak factor was slightly different in the lifetime,it was still in a reasonable range,which verified that the pseudo-equilibrium cycle can be used in the preliminary analysis and optimization of core fuel management scheme,and reduces the calculation time in the design and optimization of refueling scheme.Then,the M2LFR-1000 core low-leakage refueling scheme design was carried out.Considering that the leakage of neutrons from the inner zone to the outer zone was not affect the core economy,three batches of OUT-IN-IN refueling scheme were still used in the inner zone,three batches of low-leakage refueling scheme was desigied for the outer area.According to the problems existed for the power distribution of fuel assembly,the refueling scheme was optimized by pseudo-balance cycle.Design and analysis of detailed initial cycle,transition cycle and balanced cycle were carried out for the optimized M2LFR-1000 core outer zone low-leakage refueling scheme.This paper also studied the M2LFR-1000 full-core low-leakage refueling scheme with only one enrichment in new fuel assembly,and carried out pseudo-equilibrium analysis and evaluation of the refueling scheme.It was found that this refueling scherne is difficult to flatten the core power distribution.Finally,the M2LFR-1000 core mixed refueling scheme design was carried out,and the M2LFR-1000 core mixed refueling scheme and balanced cycle core loading diagram were gven.The pseudo-balance cycle analysis and evaluation of the refi ueling core was carried out.The characteristics of the mixed refueling scheme were summarized.On this basis,the pseudo-equilibrium cycle analysis results of the three refueling schemes were compared,and their safety and economy were comprehensively evaluated from the aspects of new fuel enrichment,reactivity coefficient and shutdown time during refueling.In general,the M2 LFR-1000 core should be given priority in a mixed refueling scheme,followed by the OUT-IN-IN refueling scheme,and the use of low-leakage refueling scheme in outer zone should be cautious.The M2LFR-1000 core fuel management scheme design and optimization research carried out in this paper had achieved the objectives of extending the refueling time,deepening burnup of discharge fuel and reducing the peak factor of core power.The research results can provide more choices and important references for the core fuel management of lead-cooled fast reactor and even fast reactor.