LOS ANGELES (AP) — The utility that runs California's idled San Onofre nuclear power plant faced sharp questions Tuesday from federal regulators about a retooled monitoring system for its damaged steam generators.
Southern California Edison said in its October proposal to restart the Unit 2 reactor that the redesigned system, which relies on sensitive monitors to detect unusual vibrations, could help operators learn if any parts broke loose in the huge generators.
An NRC staff memo dated Dec. 10 said Edison wanted to upgrade the system, in part, to help detect a possible break in a tube that carries radioactive water. Each generator contains nearly 10,000 alloy tubes that carry heated water from the reactor.
Excessive tube wear has been at the heart of problems at San Onofre, which hasn't produced electricity since January, after the plant was abruptly shut down after a tube break released a trace of radiation. Investigators later found excessive wear on hundreds of tubes in the virtually new generators.
Edison officials fielded a range of questions about the monitors at a Nuclear Regulatory Commission panel meeting in Maryland, where an NRC official argued that the equipment could not do the job described by the company or provide additional safety if the plant is restarted.
"The instrumentation that you're proposing ... does not appear to be capable of detecting the conditions that would lead to actual tube wear," said Richard Stattel of the agency's instrumentation branch.
Stattel said the company depicted the equipment in its restart plan as an important safety measure "but it doesn't appear to do that."
The NRC staff "doesn't understand where that adds an additional safety margin" as proposed by the company, he added.
Mike Short, an Edison consultant, told regulators that the company "had not intended" to characterize the system as an important safeguard, technically known as "defense-in-depth," or one of multiple layers of systems designed to prevent accidents or the release of radiation from a nuclear power plant.
Short said the data collected by the system could be used in future research examining vibrations picked up by the monitors. "It's our plan ... to make sure that's clear" he said.
The agency is in the midst of reviewing Edison's plan to rekindle one of two damaged reactors. The company wants to run Unit 2 at reduced power, a change that company engineers believe will reduce vibration that damaged tubes in the Japanese-manufactured generators.
A decision could come as soon as March. Critics of the nuclear industry have depicted twin-domed San Onofre, located between San Diego and Los Angeles, as a catastrophe-in-the-making.
The questions over the monitors underscored the complexity of the company's restart proposal, as well as the stakes for an agency that has promised to put public safety above every concern.