Thermal Aging Analysis of RNS-NR Neutron-Shielding Material for Long-Term Storage of Spent Nuclear Fuel

This study evaluated the long-term stability of a boron-loaded resin, RNS-NR, developed as a neutron-shielding material for dry storage casks. A laboratory-scale cask system with four stainless steel chambers was constructed to replicate dry storage conditions. The system integrated mass monitoring to track the thermal aging behavior under controlled boundary configurations, and the mass change of RNS-NR was continuously monitored for 2000 h at 170°C under sealed and open configurations.The experimental results demonstrated that the sealed configuration exhibited a lower mass change (−0.436 wt%) than the open configuration (−1.574 wt%). These results confirmed the influence of the chamber geometry on the release of water generated during thermal aging and other volatile species. The system included a high-temperature reference chamber and an ambient control chamber, which verified the stable operation of the platform during the long-term test.Regression modeling projected that RNS-NR in sealed configurations would reach only ~1 wt% mass loss after nearly 3 decades, which demonstrated improved long-term stability relative to the commercial benchmark NS-4-FR. The consistently low mass change rates observed under dry storage–relevant conditions indicated robust thermal aging resistance and supported the use of RNS-NR as a durable neutron-shielding material for long-term dry cask storage.