A SENSITIVITY STUDY OF A COUPLED KINETICS AND THERMAL-HYDRAULICS MODEL FOR FLUORIDE-SALT-COOLED, HIGH-TEMPERATURE REACTOR (FHR) TRANSIENT ANALYSIS

摘要

A coupled model of reactor point kinetics and thermal hydraulics was developed to analyze the Mark 1 Pebble-Bed, Fluoride-salt-cooled, High-temperature Reactor (Mk1 PB-FHR) behavior during various transient scenarios. In this model, nuclear power was computed using point kinetics equations with six groups of delayed neutron precursors. The average coolant temperature was determined using a lumped capacitance model and the temperature profile inside the fuel pebbles was obtained using 1D, spherical, finite-volume heat diffusion equations. An uncertainty and sensitivity study was conducted to support safety analysis and provide guidance for future research. The maximum temperature that is reached during the transient is affected mostly by the Doppler feedback coefficient and the effective thermal conductivity of the fuel layer. The 95% confidence interval for the maximum temperature during a 1$ reactivity insertion transient was [862, 917] °C in the fuel and [745, 786] °C in the coolant. Coated particle fuels have the ability to maintain their integrity up to temperatures of 1600°C or higher. Accordingly, the peak temperature of an average unit cell in the core found by this analysis is well below the safety margin for fuel integrity.