A specialized code for operation transient analysis and its application in fluoride salt-cooled high-temperature reactors

Abstract

Fluoride salt-cooled high-temperature reactors (FHRs) include many attractive features, such as high temperature, large heat capacity, low pressure and strong inherent safety. Transient characteristics of FHR are particularly important for evaluating its operation performance. Thus, a specialized code OCFHR (operation and control analysis code of FHR) issued to study an experimental FHR’s operation behaviors. The geometric modeling of OCFHR is based on one-dimensional lumped parameter method, and some simplifications are taken into consideration during simulation due to the existence of complex structures such as pebble bed, intermediate heat exchanger (IHX), air radiator (AR) and multiply channels. A point neutron kinetics model is developed, and neutron physics calculation is needed to provide some key inputs including axial power density distribution, reactivity coefficients and parameters about delayed neutron precursors. For analyzing the operational performance, five disturbed transients are simulated, involving reactivity step insertion, variations of coolant mass flow rate of primary loop and intermediate loop, adjustment of air inlet temperature and mass flow rate of air cooling system. Simulation results indicate that inherent self-stability of FHR restrains severe consequences under above transients, and some dynamic features are observed, such as large negative temperature feedbacks, remarkable thermal inertia and high response delay.