Development of Local Heat Transfer Models for the Safety Assessment of High Temperature Gas-Cooled Reactor Cores—Part II: Prismatic Modular Reactors

This paper extends the work of Part I to be applicable to prismatic block fuel elements and presents a model developed for determining fuel compact and fuel block temperatures of a prismatic core modular reactor. The model is applicable both in normal operation and under fault conditions and is an extension of the multiscale modeling techniques presented in Part I. The new model has been qualified by comparison with finite element simulations for both steady-state and transient conditions. Furthermore, a model for determining the effective conductivity of the block fuel elements—important for heat removal in loss of flow conditions—is presented and, again, qualified by comparison with finite element simulations. A numerical model for predicting conduction heat transfer both within and between block fuel elements has been developed, which, when coupled with the above multiscale model, allows simulations of whole cores to be carried out, while retaining the ability to predict the temperatures of individual coolant channels and individual coated particles in the fuel if required.