[en] Supplement 25 to the Safety Evaluation Report for Pacific Gas and Electric Company's application for licenses to operate Diablo Canyon Nuclear Power Plants, Unit 1 and Unit 2 (Docket Nos. 50-275 and 50-323) has been prepared by the Office of Nuclear Reactor Regulation (NRR) of the US Nuclear Regulatory Commission. This supplement reports on the staff's inspection and evaluation efforts on the matter of piping and piping supports as related to the seven technical license conditions in an Order Modifying License issued by NRR on April 18, 1984