原子力発電所から撤去された FR-EPDM ケーブルの重大事故環境下における絶縁性能

The insulation performance of cables removed from an actual plant was investigated in a simulated severe accident (SA) environment. The cable insulated with flame-retardant ethylene propylene diene rubber (FR-EPDM) was a safety cable in the plant. A similar FR-EPDM-insulated cable was aged artificially to the degree equivalent to what the removed cable would have been suffered. These cables were irradiated with ⁶⁰Co gamma rays at a dose rate of 10 kGy/h for 50 hours at room temperature to simulate the radiation exposure during a SA. The cables were then exposed to a steam environment for 168 hours to simulate the SA. During the steam exposure, the insulation resistance of the cables was measured continuously. As a result, the minimum insulation resistance was about 10⁸ to 10⁹ Ωm in the two cables, indicating that both have sufficient insulation performance.