Thursday, February 2, 2012

San Onofre Nuke Plant: Faulty Steam Generator Was Made by Mitsubishi Heavy Industries

The plant operator replaced all the steam generators at the plant in December 2010 with the steam generators (SG) made by Mitsubishi Heavy Industries. Unit 3 re-started in February 2011. Unit 2 is under regular maintenance.

From The Orange County Register (2/2/2012):

As workers began inspecting a leaky tube in one of the San Onofre nuclear plant's reactors Thursday, federal regulators said more than 800 tubes in a second, offline reactor showed wear and thinning, although they are less than two years old.

And plant officials confirmed that sensors showed a tiny amount of radioactive gas may have leaked out of a building next to the first reactor before the reactor was shut down late Tuesday.

All four of the plant's steam generators and their tubes are less than two years old, installed after being delivered to the West Coast by the Japanese manufacturer of the generators, Mitsubishi Heavy Industries.

Some 9,700 tubes carry water from the reactor and through each generator.

"They have inspected 80 percent of the tubes in one of the steam generators at unit 2," said Victor Dricks, spokesman for the Nuclear Regulatory Commission. "Two of the tubes have thinning so extensive that they need to be plugged and taken out of service. Sixty nine other tubes have thinning greater than 20 percent of the wall thickness, and a larger number have thinning greater than 10 percent of wall thickness."

The tubes with 10 percent thinning number more than 800, he said.

Gil Alexander, a spokesman for plant operator Southern California Edison, said he could not confirm Dricks's numbers Thursday because an assessment of the unit 2 tubes is continuing.

Dricks and Alexander, however, said that highly sensitive alarms were tripped in an building next to San Onofre's unit 3 reactor after the leak was detected about 5:30 p.m. Tuesday, indicating that at least some radioactive gas was present.

The building houses the turbine that generates electricity.


And while workers were able to begin inspecting the unit 3 reactor, which had cooled enough to allow them to enter, they had not yet been able to characterize the size or nature of the leak, he said.

Mitsubishi officials were on scene, he said, and he had no estimate of when the reactor might be started up again, though it will likely be several days.

“Mitsubishi is aware of the issue reported at the San Onofre Nuclear Generating Station and has been in contact with the customer, Southern California Edison," the company said in a statement released to the press. "The investigation of the incident is being conducted by our customer. However, as the manufacturer of the steam generators, we will do whatever we can to support our customer in resolving the issue.”

New details also emerged about an unrelated accident on Friday, when a contract worker slipped into a pool above the unit 2 reactor, now offline for maintenance, while trying to retrieve a flashlight.

The man, whose name Edison declined to release, was not injured, and did not suffer harmful radiation exposure, but might have ingested the mildly radioactive water, Alexander said. No internal contamination was found.

Normally, water that is heated by the reactor and flows through the tubes is kept separate from another loop of water, from another source, inside the steam generators.

Instead, the tubes are immersed in the water inside the steam generators, heating the water, which turns to steam that powers the plant's turbines to produce electricity.

But a small leak in one of the tubes could have allowed radioactive water circulating from the reactor to mix with the water in the steam generator.

If so, it could have resulted in the escape of a small amount of radioactive gas.

(Full article at the link)

From Enformable (2/2/2012):

It’s not clear what caused the pipe to fail, or whether the company was facing an isolated break in a single alloy tube or a manufacturing defect that might be at issue elsewhere in the massive plant tube system.

This might mean there is a now a worry about the possibility that San Onofre has purchased 4 faulty steam generators from Mitsubishi, and the financial costs to replace them might prevent the plant from restarting.

Southern California Edison said a manufacturing defect was reported by Mitsubishi before delivery of two generators from Japan — but that the equipment was retested by the manufacturer and plant operator and determined to be fine before installation at the southern reactor.


Anonymous said...

Warrenty? Just like Fukushima? Who has to have terrorism when you have 800 pipes in a new facility leaking radioactive material--even if not on purpose..result is the same. .

Anonymous said...

Someone needs to look at the contract and award for this work. There should be penalties for substandard materials, and the pipes should have been made to certain regulations. And then there is the person who OKAYED a faulty installation..or accepted the installation. By that one act, the shoddy work may be the responsibility of the CA govenment, NOT the contractor. And if the approval authority was a contractor --someone needs to look and see if payouts or other activity took place. A good IG investigation is clearly called for. Another "shovel" ready project..wonder under whose watch -- Clinton, Bush or Obama...and what approval organization...They will have to lift rocks to find the slimy scum responsible for this mess.

Anonymous said...

It's all safe - until something isn't working the way it should. Which shouldn't happen, of course.

Atomfritz said...

This is actually nothing special.
Heat exchanger tubes thinning out and fracturing is completely normal.

They just get welded shut when they start to leak too much of radioactivity. The reason for that is that too much leaking of radioactivity into the secondary circuit would make it more radioactive than necessary, complicating maintenance and making it more expensive.

So the radioactivity regularly gets released with the cooling water, as this is the cheapest "solution" and the release limits are ample, in the order of terabecquerels of tritium annually.

Abnormal is just this premature onset of the damage which indicates either low craftmanship quality or construction mistakes, or both.

Usually heat exchangers/steam generators get exchanged when so many pipes got weld shut that the reactor power would need to be reduced, as to compensate for the reduced number of functional pipes.

The increasing radioactivity emissions from such damaged steam generators are less of a factor due to the very generous release limits.

I think this matter will be quietly and inofficially settled between the operator and Mitsubishi.
Both don't want the matter discussed in the media headlines.

Darth3/11 said...

I for one am NOT reassured.

Morgaine said...

As usual, SCE leaves out an important part of the story...

There were issues with leaks in generator wall welds AFTER the units were delivered, including the one that is currently shut down because of a leak.

And the water is leaking through a crack in the generator wall.

The "auxiliary building" where the radioactive gas is being vented is one in which people enter and leave.

Morgaine said...

San Onofre NPP has a history of issues.
"San Onofre nuclear power plant workers fired, disciplined over safety lapses"

"Seven workers at the San Onofre nuclear power plant near San Clemente have been disciplined or fired in connection with a rash of safety and security problems uncovered by federal regulators last year, Southern California Edison officials said Tuesday....In one case, a fire protection specialist on the night shift falsified records for more than five years to show that operators had made hourly fire patrols when they had not. The other violations involved a radiation worker who failed to comply with a work permit; a failure by supervisors to oversee an unqualified technician whose work led to the temporary shutdown of a safety system; and two lapses in plant security...

Says Edwin Lyman, a senior staff scientist at the Union of Concerned Scientists: "But these fabrications went unnoticed by supervisors and managers for 5 1/2 years. This says something about the inadequacy of the NRC's inspection process."

...But Dan Hirsch, founder of Committee to Bridge the Gap, a nuclear policy group based in Santa Cruz, disputed the NRC's contention that the problems were not that important to the plant's safety. "A major fire at a nuclear reactor could release a thousand times the long-lived radiation of the Hiroshima bomb," Hirsch said. "Fire protection data is the last thing one should tolerate being fabricated at a nuclear power plant." Hirsch noted that the current violations were the latest of a number of problems at San Onofre. Earlier this month, NRC inspectors discovered the failure of an emergency generator during three tests in late December. The diesel generator is one of two that provide electricity to safety systems in the event of a power outage. Edison officials said the generator failed because of a faulty speed sensor, which was replaced...."

Morgaine said...

The tubes were less than two years old.

Anonymous said...

Funny how foreigners are fingerprinted at every airport because they are terrorists in the eyes of japanese, but yet their own government are the enemy within.... sick country is japan

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