Motion sensors at San Onofre Nuclear Power plant were switched off in March amid concerns that the sensors would fail in the event of a simultaneous blackout and earthquake. The sensors now under review were in use at the plant for more than 30 years and pose the latest problem to the now-shuttered plant that has critics questioning its safety. Vikki Vargas reports for the NBC4 News on May 30, 2012.
New challenges to the now-shuttered San Onofre Nuclear Generating Station arose this week which may increase the plant’s chances of staying offline for the summer air-conditioning season.
The viability of motion sensors, which are designed to trip emergency power sources and keep the reactors from overheating, was questioned.
Those sensors were switched off in March amid concerns that the sensors would fail in the event of a simultaneous blackout and earthquake.
"The sensors have been deactivated and all contingency emergency response actions that ensure the diesel generators operate after an earthquake are still in place,” Southern California Edison officials said in a statement.
According to the Nuclear Regulatory Commission, there are batteries that should supply power for four hours. Experts say the power could also be turned on manually.
After Tuesday night's Malibu earthquake, a 4.0 magnitude temblor that struck near the Channel Islands, some people continue to question San Onofre's earthquake readiness.
"They don’t know what would happen," said Shaun Burnie, a consultant with the nuclear power watchdog group Friends of the Earth. "Their assurances that these sensors may not trip and therefore they would have diesel is not credible."
The sensor issue at San Onofre follows the earlier discovery that tubes in a steam generator were wearing down after just two years of use. Why that is happening is still under investigation.
The sensors that are now under review were in use at the plant for more than 30 years. Now they are part of an ongoing review that has raised new questions about when or if the facility will reopen.
Whatever happens, Edison says the latest developments only prove that safety is the company's top priority.