Optimal Design And Th-U Cycle Performance Investigation Of Molten Chlorine Salt Fast Reactor

Molten salt reactor?MSR?,as the only liquid fuel among six candidate reactor type of the advanced Generation IV reactors which can be online refueling,it makes the reactor can operate with small excess reactivity,and it has obvious advantages in inherent safety,economics,coefficient of fuel utilization,nuclear nonproliferation and so on,it is an ideal type of reactor that can realize closed fuel cycle.In general,molten chloride salt fast reactor?MCFR?as one kind of molten salt fast reactor has high solubility of heavy metals,simple structure,superior neutron performance,hard spectrum and good fuel breeding ability and transmutation efficiency,it is suitable to achieve closed Th-U fuel cycle to solve the current challenges of nuclear energy development like low fuel utilization,large amount of minor actinides?MA?accumulation.However,realizing the large-scale deployment of MCFR also facing many challenges,the first challenge is to solve the problem of lacking of ²³³U source in nature,it is the start-up fuel in Th-U cycle,due to the the neutron energy spectrum in MCFR is more hard,the fission cross section in fissile material is smaller,it needs more fissile materials loading to realize initial critical,which further exacerbated the problem of the lacking of ²³³U.This work started from the optimization of breeding capability of MCFR in equilibrium state,a novel hybrid intelligent algorithm was applied for the optimization of MCFR in the equilibrium state under fixed total power.Then using currently available ignition fuel?LEU?Pu and TRU isolated from PWR fuel?to start MCFR based on the optimized model,at the Breeding and Burning?B&B?and Pre-Breeding and Burning?PB&B?transition mode,the effect on the neutron performance of the key parameters such as the type of start-up fuel salt,the reprocessing rate in transition state were researched and the performance of those cycle modes were assessed.Besides,the performance of Th-U cycle in the MCFR is compared with the Th-U cycle of the MFFR and the U-Pu cycle of the MCFR,which highlights the characteristics of the Th-U cycle in it.In this paper,the key problems of chlorine salt fast reactor are studied,and the pre-design scheme of MCFR is determined.Through calculation and analysis,NaCl which has good neutron economy and breeding capablility,low price and wide source was selected as the basic carrier salt.Then,the effects of ³⁷Cl enrichment on breeding performance,safety capability and harmful isotopes buildup were analyzed,and the anion of ³⁷Cl with 97%enrichment was determined.Finally,the reprocessing mode of MCFR was studied,and the fission products needed to be extracted during the reprocessing were determined by calculation and analysis.In this paper,the breeding performance of chlorine salt fast reactor at equilibrium state is optimized,and the optimal design of MCFR is completed.After calculation,nine variables including the core volume,power density and blanket thickness that have great influence on the breeding performance of MCFR are selected as the variables to be optimized,moreover,the ranges of the variables to be optimized are determined by calculation and analysis.To realize the rapid optimization of the MCFR in equilibrium state,we proposed a hybrid adaptive genetic annealing algorithm,which combines the global search ability of genetic algorithm and local search performance of simulated annealing algorithm,and joined the adaptive genetic operators,the test results show this algorithm with good robustness and search efficiency.Then,we coupled the HAGASA with the molten salt reactor fast search procedure MESA and SCALE critical calculation module,and develop the molten salt reactor equilibrium fast optimization program,and using it to realize the optimization of MCFR in equilibrium state to get the optimized MCFR design.In this paper,the neutron properties of Th-U cycle based on the optimized MCFR are researched in B&B and PB&B transition mode.In B&B mode,the reprocessing rate of 20L/day?40L/day and 200 L/day are selected as the research rate to perform the research;To solve the problem of ²³³U which acts as the starting fuel in Th-U cycle is inexistent in nature,the pure Th-U cycle is realized by adding ²³³U and ²³²Th online with the use of the LEU,Pu and TRU as the starting fuel.The results show that the three starting modes can successfully achieve the proliferation of ²³³U,however,²³³U need to be fed from the outside to maintain the critical thanks to the initial production of ²³³U can not meet the demand for critical,the²³³U required from the outside in LEU-started mode is the most,of which the demand at the reprocessing rate of 20 L/day reaches about 424 kg,which undoubtedly increases the difficulty of realizing the Th-U cycle.Furthermore,the core fuel doppler coefficient and fuel density coefficient corresponding to different start-up modes can maintain negative values during the whole 200 years operation,while the total temperature coefficient of reactivity?TCR?is below-8 pcm/K,which ensures the safety of the core.In PB&B transition mode,the results show that under the condition of slow post-processing?40 L/day?,LEU net production of ²³³U,Pu and TRU are almost same and its average annual net production of²³³U is 565 kg,the corresponding doubling time is about 13 years,but the replacement ratio in LEU started mode is far less than TRU and Pu start-up mode,which means to get the same production of ²³³U,LEU-started mode need more fissile fuel consumption.When the fuel reprocessing rate of the core exceeds 85 L/day,the LEU start-up mode will not be able to maintain critical performance during the whole operation in 200 years.For TRU and Pu start-up reactor,when the reprocessing rate is increased to 300 L/day,the annual output of²³³U is about 928 kg and 940 kg,and the doubling time is reduced to about 6.6 years.In the end,the Th-U cycle of chlorine salt reactor was compared with that of fluorine salt reactor Th-U cycle and chlorine salt U-Pu cycle under the same conditions.The results showed that MCFR was superior to MFFR in terms of breeding performance,reprocessing requirement,and accumulation of fission products and Minor Actinides?MA?.While the MCFR has a larger delayed neutron fraction?DNF?.Besides,the U-Pu cycle in MCFR has a larger breeding ratio?BR?and shorter doubling time than the Th-U cycle,but its constant value of TCR and the DNF is smaller.Moreover,it has more accumulation of MA,which results in the higher radioactivity.