LOS ANGELES — More than a year after California endorsed a proposal to extend the lifespan of its last nuclear power plant, disputes continue to swirl about the safety of its decades-old reactors, whether more than $1 billion in public financing for the extension could be in jeopardy and even if the electricity is needed in the dawning age of renewables.

Late last month, a state judge tentatively approved the blueprint to keep the Diablo Canyon Nuclear Power Plant operating for an additional five years, until 2030. The proposal, which could get finalized later this month, imposed several conditions, including that federal nuclear safety regulators greenlight the longer run and that a state loan supporting the extension is not canceled.

The twin reactors, located midway between Los Angeles and San Francisco, began operating in the mid-1980s. They supply up to 9% of the state’s electricity on any given day.

Environmentalists argue California has adequate power without the reactors and that their continued operation could hinder development of new sources of clean energy. They also warn that long-delayed testing on one of the reactors poses a safety risk that could result in an accident, a claim disputed by operator Pacific Gas & Electric.

Public Utilities Commission Administrative Law Judge Ehren D. Seybert’s proposed ruling did not directly address yet another question: Whether a past felony conviction against PG&E might pose an obstacle to the government financing for the extension.

California is the birthplace of the modern environmental movement and for decades has had a fraught relationship with nuclear power. In 2016, PG&E, environmental groups and plant worker unions reached an agreement to close Diablo Canyon by 2025. But the Legislature voided the deal last year at the urging of Democratic Gov. Gavin Newsom, who said the power is needed to ward off blackouts as climate change stresses the energy system.

PG&E says it wants to keep the plant open to “ensure statewide electrical reliability and combat climate change” at the direction of the state. But the plant has to clear a series of state and federal regulatory hurdles, and it remains in dispute how much ratepayers will ultimately have to pay to keep it open.

On Tuesday, the same day that PG&E submitted its application to the Nuclear Regulatory Commission to keep the reactors running, supporters and critics clashed in a state utilities commission hearing over whether the plan is a sound investment or a financially reckless gamble. The utility is seeking a 20-year extension, typical in the industry, but emphasized the state would control how long the plant runs.

PG&E Accused of Wanting a ‘Blank Check’

Matthew Freedman, an attorney with the advocacy group The Utility Reform Network, told regulators that PG&E was looking for a “blank check” from ratepayers.

The fight is playing out as the long-struggling nuclear industry sees a potential rebirth in the era of global warming. Nuclear power doesn’t produce carbon pollution like fossil fuels, but it leaves behind waste that can remain dangerously radioactive for centuries.

In September, environmental and anti-nuclear groups called on federal regulators to shut down one of Diablo Canyon’s reactors. Friends of the Earth and Mothers for Peace said in a petition filed with the NRC that tests and inspections have been delayed for nearly 20 years on a pressure vessel in the Unit 1 reactor. They also argued that the steel wall in Unit 1 might be deteriorating from sustained exposure to radiation and is becoming susceptible to cracking, a condition technically known as embrittlement.

The pressure vessels are thick steel containers that hold nuclear fuel and cooling water in the reactors. The NRC took no action on the request and instead asked agency staff to review it.

PG&E has maintained the plant is safe, an assessment endorsed by the NRC.

PG&E was expected to begin embrittlement testing on the vessel last month, with the plant shut down for refueling. But it told legislators that workers couldn’t remove samples inside the vessel because they did not have the correct equipment to access them.

PG&E has said workers would try again during the next refueling period, which could be as much as two years away. Once removed, evaluating the material can take another year. Under that scenario, it’s possible that information might not be available until after state reviews are completed and the NRC has considered the utility’s request for extended licenses.

State Sen. John Laird and Assembly member Dawn Addis, both Democrats, urged PG&E to determine if alternative testing can be used. In a letter to the utility, they lamented the lost opportunity to answer “allegations that the vessel is dangerously embrittled.”

Financing questions also have emerged.

In 2016, a federal jury found PG&E guilty of multiple felonies for failing to properly inspect gas pipelines before a 2010 blast that incinerated a neighborhood in San Bruno, south of San Francisco, killing eight people. Federal rules generally prohibit the government from entering into a contract with any corporation with a federal felony conviction, though exceptions can be made.

The Alliance for Nuclear Responsibility, an anti-nuclear group, has alleged that PG&E failed to disclose its conviction before it received conditional approval from the U.S. Department of Energy last year for $1.1 billion in funding for the extension.

Both the Energy Department and PG&E declined to answer directly when asked by The Associated Press if the conviction was disclosed to the department. DOE spokesman Chad Smith said in an email that “DOE is in active discussions” with the utility, without providing further specifics. PG&E said it is eligible for the money because it already received conditional approval last year.

The Biden administration gave preliminary approval for the Energy Department funding in November. The financing came through the administration’s civil nuclear credit program, which is intended to bail out financially distressed owners or operators of nuclear power reactors as part of the administration’s effort to cut planet-warming greenhouse gas emissions in half by 2030, compared with 2005 levels.

The alliance said that if a failure to disclose the conviction is confirmed, PG&E could see its hopes for a longer run at Diablo Canyon extinguished — and possibly expose the company to penalties. Also at risk could be a $1.4 billion, forgivable state loan authorized by the Legislature, the alliance said, which is expected to be paid back with the federal funds. ___ This story has been corrected to show the state senator’s name is John Laird, not Robert Laird.