Kansai Electric Revises Site Survey Plan for Additional Units at Mihama Nuclear Power Station

On September 9, 2026, Kansai Electric Power Company (KEPCO) announced a revision to its voluntary site survey plan for additional units at the Mihama Nuclear Power Station, extending the completion of the preliminary survey from March 2027 to March 2028, while the detailed survey remains scheduled for completion in 2030.

Kansai Electric stated that, for the potential additional units at the Mihama Nuclear Power Station, it resumed the voluntary site survey on November 5, 2025, which had been suspended since March 12, 2011. Under the original plan announced on September 17, 2025, Kansai Electric first conducted a broad preliminary survey both inside and outside the plant site, then selected a more advantageous area based on geological conditions, and implemented a detailed survey in that area.

The preliminary survey results to date indicate that bedrock of sufficient strength for the installation of reactor and other facilities exists in both the northern and southern areas of the Mihama site; additionally, no structures such as potentially active faults have been identified at this stage.

As the survey results obtained to date for the two areas are similar, Kansai Electric plans to add supplementary drilling surveys and expand the dataset to further assess which area is more suitable for the installation of reactor and other facilities from the perspective of geological and foundation conditions. Under the revised plan, 8 additional boreholes will be drilled in the northern area and 5 in the southern area, with the exact number subject to adjustment as the survey progresses.

Following the revision, the preliminary survey will be conducted from November 2025 to March 2028, with the detailed survey scheduled to commence in April 2028 and be completed by 2030. The preliminary survey includes drilling surveys, seismic refraction surveys, and surface reconnaissance; the detailed survey includes trial pit investigations, seismic refraction surveys, deep and shallow measurements, drilling surveys, and earthquake-related investigations.

Kansai Electric stated that the decision on whether to construct additional units will not be made solely based on the results of this survey, but will also take into account factors such as the progress of innovative light-water reactor development, regulatory policies, and the business environment necessary for investment decisions. The company expressed its commitment to continuing to prioritize safety in the safe and stable operation of its nuclear power plants, and to advancing its nuclear power business with the understanding of local communities and the public.