Compromised Transfer Tubes Leave San Onofre Plant Idle

San Onofre steam generators: expensive and unsafe

A year ago, Southern California Edison announced the installation of four new steam generators at the San Onofre nuclear power plant, hailing it as a major boost to electricity production.

The $671-million generators, which will be paid for by rate increases to Edison and San Diego Gas & Electric customers, were supposed to save ratepayers $1 billion over the next decade and extend the life of the San Onofre Nuclear Generating Station.

But for the last two months, San Onofre has been shut down after officials discovered problems in the generators’ heat transfer tubes.

It’s the longest outage in San Onofre’s history, and federal regulators say the plant should remain idle until they are confident no more tubes will leak or rupture.

Officials said deteriorating tubes are a potential safety problem because they carry radioactive water, and if they rupture, radiation can escape into the atmosphere.

In January, a small amount of radiation was released from a leak in one of the tubes. Officials decided to close the plant out of concern that if numerous tubes were compromised, a rupture could lead to a much more serious situation.

David Lochbaum, director of the nuclear safety program with the Union of Concerned Scientists, said the water carried in the tubes also helps to cool the reactor core. A series of tube breaks could compromise the cooling system and lead to a potential meltdown.

It’s not unprecedented for newer tubes to show wear, said Nuclear Regulatory Commissionspokeswoman Lara Uselding. But the deterioration at San Onofre is “more than expected.”

Arnie Gundersen, a former nuclear industry executive and chief engineer of the energy consulting company Fairewinds Associates, who is frequently critical of nuclear plant safety, estimated that the tube wear is 10 to 15 times the normal rate.

Besides the cost of replacing lost power generation at San Onofre, Edison officials will have to figure out how to pay for repairs. It remains unknown how much the outage and fixes will cost, and officials said it’s too early to say whether ratepayers might be asked to cover part of the bill.

The four generators, manufactured by Mitsubishi Heavy Industries, were installed in 2010 and 2011. Edison assured regulators and the public that they would last until 2022, when San Onofre’s license expires, and possibly beyond that if the license is extended.

In a Feb. 29 filing with the U.S. Securities and Exchange Commission, Edison noted that although the steam generators are under a 20-year warranty, Mitsubishi is liable only for the purchase price of $137 million under the purchase agreement.

That doesn’t include other costs such as shipping, installation or procuring replacement power while the plant is offline. Mitsubishi did not return a call seeking comment.

NRC is investigating whether manufacturing defects contributed to the problem.

When the California Public Utilities Commission signed off on the steam generator replacement project in 2005, it agreed to allow rate increases to cover the costs. The commission created a $782-million ceiling for the project and agreed to review any costs exceeding $680 million, later lowered to $671 million. The funding approval did not include money for any possible repair costs, Edison spokeswoman Jennifer Manfre said.

CPUC spokeswoman Terrie Prosper said the commission has not determined whether ratepayers could be asked to foot the bill for costs related to the outage.

Ratepayer advocates said that if Edison attempts to pass the costs of the outage on to ratepayers, they will be facing a battle royal.

“Ratepayers shouldn’t be responsible for Edison’s mistakes, and they shouldn’t be responsible for the mistakes of the vendors Edison contracts with,” said Matthew Freedman, staff counsel to The Utility Reform Network.

Edison officials said they don’t know when the plant will go back online, and state power officials have begun drawing up contingency plans to avoid shortages if San Onofre remains closed during the heavy-use summer months. To do this, they are considering transmission upgrades, bringing back retired generating units at a natural gas plant in Huntington Beach and launching new conservation efforts, including flex-alerts to encourage customers to use less energy.

The problems began Jan. 31 when workers found a small leak of radioactive water in one of the plant’s thousands of steam generator tubes. The leak released a small amount of radioactive steam that officials said was harmless.

Additional inspections found problems with more of the tubes.

The Unit 3 reactor was taken offline and Edison began testing 129 tubes in that reactor that showed excessive wear. Since then, eight tubes have failed pressure stress tests, and the NRC dispatched a team to investigate why the newly installed tubes are wearing out so quickly.

Meanwhile, in Unit 2, Edison discovered unexpected wear and tear on more tubes. They plugged 192 that showed excessive deterioration—1% of all the tubes in the reactor.

Edison had said that without the new steam generators, San Onofre might have had to shut down in 2009 and it would have had to find ways to replace the 2,150 megawatts of energy produced by the plant, at a higher cost to consumers.

From the start, some questioned Edison’s estimates of the project’s $1 billion in savings for customers. Anti-nuclear activists and ratepayer groups argued that any number of unexpected events could turn the project into a major money loser.

The CPUC, although it found the project probably would be cost-effective, gave more modest estimates of the savings to ratepayers and forecast scenarios where they would lose money. Truman Burns, a program and project supervisor with the commission’s Division of Ratepayer Advocates, said part of the projected cost-effectiveness of keeping the plant open was also based on predictions of high natural gas prices that didn’t materialize.