Analysis Of The Temperature Reactivity Coefficients Of PB-FHR

As a new type of reactor, pebble bed-fluoride salt high temperature cooling reactors inherited many virtues and technical foundation of the previous generations of nuclear reactors. An evaluation of think it is considered as a good security, economic, sustainable and nuclear nonproliferation reactor. Its commercialization under the condition of the current technology has high feasibility. Its core features mainly including two points:(1) the use of fluoride salt for cooling (molten salt reactor);(2) the use of pebble fuel assembly which contains graphite-coated fuel particles inside. The development of PB-FHR which is one types of IV reactor enjoys broad prospect.The value of the reactor temperature reactivity coefficient marks the reactor reactivity changes on the reactor with the strength of the feedbacks which is brought in with the reactor material of temperature changed. As the requirements of reactor physics design, in order to prevent the reactor core damage or reactors shut down automatically and to assure the reactor operation safety, normal and effective, the designed reactor must have a negative temperature reactivity coefficient. In this paper, the temperature reactivity coefficient of PB-FHR was studied by using Monte Carlo code of SCALE which is developed by Oak Ridge National Laboratory of USA, based on the study of four factor formula, the temperature coefficient of reactivity is decomposed into five parts and through study on the influence on the temperature reactivity coefficient of five parameter, qualitative analysis was carried out on the temperature reactivity coefficient. This research contents mainly includes three work:First, we investigated the6Li molar concentration selection in LiF-BeF2of PB-FHR primary loop coolant, the impact of6Li molar concentration to the coolant temperature reactivity coefficient, the fuel and moderator temperature reactivity coefficient of infinite PB-FHR. Second, we analyzed the influence of different TRISO packing factor on temperature reactivity coefficient with inifine PB-FHR. Third, we analyzed the influence of different core volumes on temperature reactivity coefficient with PB-FHR model which core cross section is octagonal.From the results of our study, we can conclude that6Li molar concentration of LiF-BeF2 significantly effect on the coolant temperature reactivity coefficient. From the perspective of neutron effect and economic consideration,6Li molar concentration of PB-FHR coolant in LiF-BeF2is most suited to select0.005%. The coolant and moderator temperature reactivity coefficient is affected significantly when TRISO packing factors are changed from1.8%-17.5%. The coolant and moderator temperature reactivity coefficient is affected significantly by PB-FHR core volume that didn’t effect on the fuel temperature reactivity coefficient.