Dynamic Effect of the Delayed Neutron Precursor Distribution on System Safety Analysis in Liquid-Fueled Molten Salt Reactor

The liquid-fueled molten salt reactor (MSR) is one of the candidate reactors for the Generation IV advanced nuclear power systems, which utilizes flowing liquid molten salt as both fuel and coolant. In transients of liquid-fueled MSRs, the distribution change in the delayed neutron precursors (DNPs) in the primary loop has an important impact on system safety analysis. In order to analyze and evaluate this effect, the RELAP5-TMSR code with a 1-D DNP transport model was used to model the Molten Salt Breeder Reactor (MSBR), and several representative transient scenarios, including the loss of primary flow, increase in primary flow, loss of secondary flow, reactivity perturbation, and load change, were simulated and analyzed. The results show that the DNP distribution changes obviously during primary flow transients, especially during the loss of primary flow. Besides, the power response trends at different power levels during the loss of primary flow are different. The analysis results reveal the steady-state and dynamic characteristics of the DNP distribution, indicating that the DNP distribution, temperature feedback, and reactor power are strongly coupled, which has significant implications for the design and safety analysis of liquid-fueled MSRs.