Evaluation of long-term thermal durability of neutron-shielding resin in dry storage casks

This study evaluated the long-term thermal durability of the neutron-shielding resin RNS-NR under long-term thermal exposure. RNS-NR was exposed to 170 °C in open-type and closed-type chambers, with weight loss monitored for 1,500 hours and material characterization conducted after 2,000 hours. TGA, XRD, and ICP-OES were used to evaluate thermal, structural, and compositional stability. After 1,500 hours, the weight-loss rate was 0.447 wt% in the closed-type chamber and 1.380 wt% in the open-type chamber, indicating greater volatile removal in the open configuration. TGA showed major decomposition at 262.54 °C, suggesting that the mass loss at 170 °C was dominated by moisture release rather than polymer degradation. XRD confirmed no detectable phase change of aluminum hydroxide after thermal exposure. ICP-OES analysis of the water-rich condensate collected from the closed-type chamber detected boron at 17.6 ppm and zinc at 188 ppm, while aluminum was not detected. These results indicated minor transfer of B and Zn into the condensate. Based on this observation, ICP-OES analysis of solid samples showed that the boron content decreased from 1.37 wt% to 0.60–0.30 wt% in the open-type chamber and to 0.48–0.31 wt% in the closed-type chamber, with retention dependent on sampling location.