Phenomenology, methods and experimental program for fluoride-salt-cooled, high-temperature reactors (FHRs)

• Existing literature for FHR-specific phenomena is summarized.
• System-level modeling work for FHRs and key code-development needs are listed.
• Validation basis for FHR models exists but must be completed by additional tests.
• FHR test reactor will provide ultimate validation data and proof of concept.
• International collaboration and benchmarking is key to FHR development success.

Due to their combination of high-temperature coated-particle fuel, molten salt coolant and related materials requirements, fluoride-salt-cooled, high-temperature reactors (FHRs) exhibit different thermal hydraulic, neutronic and structural mechanics phenomena compared to conventional and more extensively studied other advanced nuclear reactor concepts. This paper highlights key phenomena unique to FHRs, and reviews general issues for developing, verifying, and validating evaluation models for FHR technology that may apply to other advanced reactors. System response codes that are appropriate to predict the behavior of FHRs under steady-state operation and licensing basis events are identified, along with experimental data needs to validate these codes. FHR materials requirements are highlighted, and the missions and licensing program for an FHR test reactor, providing ultimate validation data and proof of concept before a commercial prototype is built, are presented. This review draws upon information compiled in a series of four white papers based on FHR experts workshops held in 2012 in the U.S.