Passive Safety Characteristics of Fuel for a Modular High-Temperature Reactor and Fuel Performance Modeling Under Accident Conditions

Abstract

The high fission product retention potential of coated particle fuel combined with inherently passive temperature controls guarantee almost complete fission product retention during an accident in a small modular high-temperature reactor. Extensive experimental results provide the basis for this claim to inherent safety.Models and codes have been developed to (a) predict realistic, or at least conservative, overall release rates from the primary circuit, (b) reduce the large number of experimental results to a small set of characteristic coefficients, and (c) predict release beyond experimental conditions. Conservative predictions of release from the core have been done using a traditional pressure vessel model for release from fuel particles and simplified diffusion models for fission product transport. This approach is based on experimental work that has been done on nearly all possible accident conditions and is limited by the finite number of experiments. Data reduction has been achieved with two different modeling approaches combined into a new model that is equally relevant to all volatile fission products.The safety design of the 200-MW(thermal) HTR-Modul is based on Kernforschungsanlage Jülich experimental results from fuel accident condition performance testing and the modeling effort has been applied to a safety review.