"For 57 days last year and early this year, one of the nuclear reactors at the Palo Verde Nuclear Generating Station west of Phoenix kept running after an explosion knocked a backup generator out of service.
Experts at the Nuclear Regulatory Commission disagreed strongly over whether the plant should have been allowed to keep running during the repairs, according to documents leaked to the Union of Concerned Scientists, a watchdog group.
The NRC usually allows a nuclear plant 10 days to make such repairs. In this case, the agency granted the plant's operator, Arizona Public Service Co., two extensions. NRC officials said the decision came after a careful review of the risks."