Lumped parameters analysis of coupled kinetics and thermal-hydraulics for small reactors

A useful model is presented that permits to predict with simple means the dynamic response of a small research reactor core. The model uses a lumped parameters approach for the coupled kinetics (point reactor) and thermal-hydraulics, with continuous reactivity feedback due to coolant and fuel temperature effects. The model predictions are qualified by comparing with results from detailed simulations of reactivity insertion transients reported in the literature. Satisfactory results have been obtained for various reactivity insertion rates, up to insertions as high as $1.5. A simple criterion on the applicability range of the model is suggested, namely, the model can provide reasonably accurate predictions as long as the exit coolant temperature remains below saturation, i.e. no bulk boiling occurs in the core.