Derivation of occupational accident risk during nuclear power plant decommissioning

During the decommissioning phase of nuclear power plants, workers may be exposed to both radiological and non-radiological effects resulting from occupational accidents, requiring a safety assessment during the decommissioning planning stage. This study derived risk levels by comprehensively considering both impacts of occupational accidents that may occur during NPP decommissioning. Occupational accidents that may occur during decommissioning were identified. And non-radiological risks were derived using a risk matrix based on construction-industry occupational accident statistics provided by the Ministry of Employment and Labor in Korea, collected over a 10-year period from 2015 to 2024. Worker exposure scenarios linked to these accidents were established to assess additional radiological impacts, which were then combined with the non-radiological risks to derive the final risk levels. The non-radiological risk levels ranged from 8 to 12(out of a maximum of 25), showing similar results across all occupational accident types. Among the radiation dose results, the explosion accident during stainless steel cutting yielded the highest value at 0.54 mSv, while the collapse accident during stainless steel cutting and fire accidents during waste handling recorded negligibly low values of 1 μSv. Fire, explosion, and collapse accidents were commonly rated as high-risk across all decommissioning processes, as these events can cause additional radiological impacts beyond non-radiological hazards. The findings of this study can be utilized in safety assessments for future decommissioning planning.