Application of frequency response methods in separate and integral effects tests for molten salt cooled and fueled reactors

Molten salt cooled and fueled reactors can be distinguished from other reactor types by their low volatility liquid coolant, which remains single-phase under most operating and accident conditions, and by the substantial heat capacity of both the coolant and solid structures. Forced and natural circulation of the molten salt coolant provide the primary heat transport mechanisms under power and shutdown operation, but thermal coupling to solid heat structures has important effects on dynamic system response during transients. These characteristics make frequency response methods particularly suitable to characterizing and predicting system response to transients. Predicting the temperature of coolant boundary structures during transients, including accidents, is also important for assessing whether damage may occur due to thermal stresses or accelerated thermal creep. This paper discusses how frequency response methods may be used in separate effect and integral effect tests, particularly with simulant fluids to measure the thermal inertia and coupling properties of heat structures and to validate transient response models. The methodology is discussed, followed by examples for application. The scaling parameters developed in this paper can be expected to play a major role in the design of integral effect test facilities for FHRs and MSRs.