Unit 2 at Pacific Gas and Electric Company's (PG&E) Diablo Canyon Power Plant was shut down yesterday after an electrical disturbance occurred in equipment that supports moving power to the state’s electric grid.
Unit 1 continues to safely generate power.
Results from the preliminary investigation indicate the electrical disturbance was a result of a flashover event on a lightning arrestor located on the non-nuclear side of the plant. The flashover occurred during routine maintenance that involved pressure washing, known as “hot washing,” of electrical insulators near the lightning arrestor. Upon sensing the disturbance, the unit performed as designed and automatically went off line to protect equipment.
Unit 2 remains in a safe condition and will return to service after the cause is fully understood and the equipment is tested. PG&E has informed the U.S. Nuclear Regulatory Commission and appropriate local and state officials.