Molten salt reactor: source terms due to gas leakage and nuclide volatilization

This study investigated realistic source terms for molten salt reactors (MSRs) by analyzing the parameters influencing radionuclide release and the containment performance of a core cavity during severe accidents. The research focused on gaseous leakage, fission product volatilization, and the relationship between vapor pressure and salt temperature. Results show that containment pressures remain below safety limits under all scenarios, with major contributors being gaseous leakage and temperature-driven pressure rise. Salt temperature is identified as the dominant factor determining release magnitude: at 900 K, releases are minimal (I-131 = 1.5 * 10^5 Bq), whereas at 1500 K, volatilization significantly increases, producing up to 1.50 × 10^14 Bq I-131—comparable to the Three Mile Island event. The gaseous inventory, primarily tritium ( 1.76 * 10^15 Bq) and xenon (≈ 8.48 * 10^16 Bq), is fully released in any core damage scenario, though the low operating pressure results in a slow release over two years. A Hastelloy N core cavity can contain volatile nuclides effectively if structural integrity is maintained, preventing external release. Overall, the findings indicate that realistic MSR source terms are dominated by gaseous products at low temperatures and by fission product volatilization at high temperatures, emphasizing the critical role of temperature control and cavity integrity in mitigating environmental releases.