Radiation safety and fuel performance of pebble-bed modular high-temperature gas-cooled reactors

Safety of nuclear reactors is of wide concern in the world, and inherent safety of the reactors is the goal that the nuclear energy field has been pursuing over the last several decades. How to quantitatively evaluate the inherent safety, as well as the reactor radiation safety, is a long-term important scientific and technical issue. This study focused on the 10 MW high-temperature gas-cooled experimental reactor (HTR-10), the only operational pebble-bed modular HTGR for testing that can operate at full power currently, measured its primary coolant activity, a key indicator of reactor radiation safety, and assessed its fuel element performance, directly affecting its inherent safety feature. A method for evaluating tri-structural isotropic coated fuel particle (TRISO CFP) failure fraction and uranium contamination share was established. The release-to-birth (R/B) ratio for fission gas nuclides was < 1 × 10⁻⁶, with a TRISO CFP failure fraction of 7.23 × 10⁻⁵ and uranium contamination share of 9.20 × 10⁻⁶. The TRISO CFP performance of HTR-10 surpassed that of previous HTGRs and irradiation tests conducted in the world, highlighting its excellent radiation safety and potential for large-scale commercial application of HTR-PM (that are related/based on HTR-10).