Analysis Of Coupled Dynamics On MSR Under Accident Conditions

This paper introduces the research progress of nuclear reactors, classification andcharacteristics of the four generations of reactors, and the fourth-generation reactors’ workingprinciple. In particular, the paper described the study progress and working principle of moltensalt reactors which is the only to use liquid fuel in the fourth-generation reactors in detail.Compared with other solid pellet fuel reactors, molten salt reactor has incomparable advantages ininherent safety, economy, nuclear resources for sustainable development and the prevention ofnuclear proliferation. However, the development of molten salt reactors faces problems andchallenges. This paper studied the analysis of coupled dynamics of molten salt reactors underseveral transient accident conditions.Under steady-state condition, because the fission chain reactions in the core of cause a lot ofheat, and the delayed neutron precursors in nuclear fission process flow with molten salt flow, sotemperature in the reactor core axial is rising. Also, because the flow rate of the molten salt ismuch less than the speed of the neutrons, which means that the convective term in the controlequation of the neutron flux in can be ignored. Therefore, it can be learned that the flow of the fuelsalt has smaller impact on the neutron flux. Delayed neutron precursors affected by the molten saltflowing move to the exit of core and achieve the maximum. In addition, the extent of delayedneutron precursors moves to the exit at movement reduced with the increase of the decay constant.By the analysis of molten salt flow rate changes, the calculated results can be concluded thatthe flow of the fuel salt has little effect on the neutron flux, but more significant impact on delayedneutron precursors. By the analysis of rods bounce and drop, the calculated results can be obtained:neutron density increases over time; the value of the neutron flux in the central region sharpdecreases when the control rods drop, and the value of the neutron flux in other regions isrelatively large. These results can provide some useful reference for further study of molten saltreactor safety analysis.