LOS ANGELES (AP) — A senior federal nuclear expert is urging regulators to shut down California’s last operating nuclear plant until they can determine whether the facility’s twin reactors can withstand powerful shaking from any one of several nearby earthquake faults. Michael Peck, who for five years was Diablo Canyon’s lead on-site inspector, says in a 42-page, confidential report that the Nuclear Regulatory Commission is not applying the safety rules it set out for the plant’s operation. The document, which was obtained and verified by The Associated Press, does not say the plant itself is unsafe.