SAN ONOFRE -- Just a few months before it is scheduled to begin cutting a 28-foot hole in one of the San Onofre Generating Station's two reactor domes, Southern California Edison may be facing a new round of scrutiny at the federal level.

In a letter dated July 14, Sen. Barbara Boxer, D-San Francisco, is asking the chairman of the Nuclear Regulatory Commission to look into activists' requests that the pending operation be postponed in light of the commission's recent concerns about workers' performance at the seaside plant.

The agency has already denied a request by a group of anti-nuclear activists who want the reactor work postponed, but Boxer's letter may carry more weight because she chairs the Senate Environment and Public Works Committee.

Reached Monday, Zachary Coile, Boxer's communications director, said the senator has received no response from the NRC on her request. Coile declined to say whether Boxer is in favor of the postponement. Her letter simply asks the agency to review the concerns.

In a report released this spring, regulators were sharply critical of the workplace culture at San Onofre and said workers needed to improve their adherence to the plant's strict maintenance and safety procedures in order to head off potential problems. A previous inspection found that a contract worker at San Onofre had skipped fire-watch rounds for five years, then falsified records to cover his tracks.

Local nuclear activism groups, especially the Alliance for Nuclear Responsibility, have cited such incidents in asking that the NRC postpone San Onofre's upcoming retrofit project, which would replace two 640-ton heat exchangers inside each of the plant's two concrete containment domes.

The procedure, scheduled to begin in October, requires cutting large holes in the reinforced concrete structures because the components are too large to fit through normal access hatches.

"We're not asking for the moon," said Rochelle Becker, an alliance member. "We're just asking the NRC to delay this until they can go two straight quarters without the same human performance issues that they have already found."

It's an argument that Becker unsuccessfully made at San Onofre's annual safety meeting held in Dana Point on May 7.

At that meeting, Charles Casto, deputy regional administrator for the NRC, said delaying the operation, which would replace two 640-ton heat exchangers inside the dome, was not likely. Casto said the commission's concerns with worker performance were designed to prevent problems from developing in the future but were not an indication that the plant was unsafe.

"We have no indication that there is an unsafe condition at the plant that has caused a problem with the steam generator replacement program," Casto said.

Not satisfied with the response they received from the NRC's regional office, Becker and State Sen. Christine Kehoe, D-San Diego, took their concerns up the regulatory food chain, complaining directly to Boxer and to the commission's Office of the Inspector General, which provides separate oversight of the Nuclear Regulatory Commission.

A spokesperson for the Inspector General's office was not available for comment Tuesday.

Meanwhile, Gil Alexander, an Edison spokesman, said in a written statement Tuesday that the plant has taken the NRC's complaints seriously, even replacing the plant's senior leadership over the last 18 months.

The statement also noted that the NRC has said consistently that San Onofre has been operated safely, despite its concerns. Alexander did not directly address the call for the project's postponement, though Edison has said in the past that it must move quickly to replace the components or risk a shut down.

Call staff writer Paul Sisson at 760-901-4087 or psisson@nctimes.com.