Effects of irradiation and design basis accident conditions on thermal properties of epoxy coating system for nuclear power plant

In this work, the thermal properties of epoxy coating system on carbon steel liner in an atomic reactor container have been investigated in terms of irradiation and design basis accident (DBA) conditions. Two epoxy coating systems were irradiated by different dose rates, i.e. 1×10⁶ and 5×10⁵rad/h in a total dosage of 2×10 ⁸rad/h. And, DBA tests were applied to them based on the specification. The glass transition temperature (T_g) and thermal stability of the epoxy coating systems after tests were measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. As a result, the irradiation led to the fracture of internal structure in cured epoxy systems, resulting in significantly decreasing the thermal stability, as well as, the T_g. Also, the higher dose rate made a relaxation of epoxy resins to reduce the hardening of the network system. Whereas, the DBA test made an important role in the thermal stability in the epoxy coating systems, resulting in post-curing of the uncured epoxy resins. Consequently, it could be found that the thermal properties of the epoxy coating system were greatly influenced on the irradiation and DBA tests, which were probably due to the modification of internal network structure of the epoxy resins.