Safety functions are the actions, passive or active, that structures, systems, and components of a nuclear facility contribute to the safety of the workers, the public, or the environment. Well-defined safety functions are the foundation of a solid safety case for a reactor. For reactors that use tri-structural isotropic (TRISO)-coated particles, the TRISO fuel plays an important part in the safety case because of its ability to contain radionuclides in the fuel itself. This ability enables the use of a functional containment strategy for the reactor where radionuclide retention is the primary safety function supported by the safety functions of controlling reactivity control and controlling heat rejection.

This paper establishes at a deeper level the role that TRISO fuel plays in each of these safety functions and the associated quality assurance and testing requirements for TRISO particle manufacturing to ensure these safety functions. Safety limits necessary to protect these safety functions include manufacturing specifications, operational limits, time-at-temperature limits, and fission gas release activity limits. This approach demonstrates the role that specific aspects of TRISO fuel play in protecting the safety of workers, the public, and the environment.