San Onofre Nuke Plant: Southern California Edison Serves Mitsubishi Heavy Industries with a Notice Seeking Compensation over Faulty Steam Generators

From Wall Street Journal (7/18/2013; emphasis is mine):

Owners of San Onofre Nuclear Plant Press Mitsubishi Heavy
Losses at Shuttered Plant Could Total More Than $4 Billion

The operator of the San Onofre nuclear-power plant took the first legal step Thursday to try to collect billions of dollars from Mitsubishi Heavy Industries Ltd. over what it says was gross negligence in the design and manufacture of equipment that prompted the shutdown of the California plant.

Southern California Edison, a unit of Edison International of Rosemead, Calif., served Mitsubishi with a notice that it will seek compensation for the plant owners' losses through arbitration.Those losses include the value of the closed plant and other expenses and could total more than $4 billion.

SoCal Edison is majority owner and operator of the plant, which once produced enough power to light 1.4 million homes in Southern California and is located near the Pacific Ocean between San Diego and Los Angeles. The other owners are San Diego Gas & Electric Co. and the city of Riverside, Calif.

A Mitsubishi unit, Mitsubishi Nuclear Energy Systems Inc., designed and supplied the plant in 2010 and 2011 with the largest steam generators ever used at a U.S. nuclear facility, replacing older generators. But after the new equipment sprang a leak in 2012, SoCal found problems that it concluded were too pervasive to fix. Last month, it told U.S. nuclear regulators the owners had decided to retire the plant.

Frank Gillespie, a senior vice president of Mitsubishi's nuclear unit, said he believes the company's liability is limited to the $137 million value of equipment it supplied to San Onofre.

In an interview Thursday after reviewing the dispute notice, he said that Mitsubishi is sorry the owners decided to close the 2,200 megawatt plant. "Technically, it could have been fixed," he said. "But it could have been expensive."

SoCal Edison spokesman Janet Clayton said that although the contract between Mitsubishi and the owners limits liability, the owners don't think it applies because they think Mitsubishi is guilty of gross negligence, an accusation Mr. Gillespie disputed. SoCal Edison said Mitsubishi should have done more modeling and analysis of its steam-generator design to have anticipated problems and made corrections.

An arbitration panel will decide what level of compensation, if any, is due the plant owners.

The California Public Utilities Commission has opened an inquiry to determine what went wrong with the plant overhaul. Ultimately, the agency will decide whether to saddle customers of SoCal Edison and San Diego Gas and Electric with the cost of a plant from which they get no electricity or whether to assign some share of San Onofre's costs to the owners and to vendors like Mitsubishi.

Problems at the plant surfaced in January 2012. One reactor at the plant was shut down for refueling when the other reactor sprang a leak in a heat transfer tube—part of the steam generator system furnished by Mitsubishi—and was taken out of service.

Coming as it did after the accident at the Fukushima Daiichi plant in Japan, news that the leak involved the release of small amounts of mildly radioactive steam alarmed nearby residents. Many public officials called for the plant to be retired, not just because of the equipment problem but also because it sits near seismic faults that still are being mapped. The faults were unknown when the plant was built three decades ago.

Extensive tests ordered by the U.S. Nuclear Regulatory Commission in 2012 revealed a serious problem with unusual wear in several thousand of the plant's roughly 10,000 steam tubes, which carry heat from the reactor to the equipment that makes electricity, as a result of vibrations within and between the tubes. Both Mitsubishi and plant owners agree the plant developed a problem with fluid-induced vibration. Mitsubishi has said the type of vibration hadn't been seen before and therefore the company shouldn't be blamed.

(Full article at the plant)

Mitsubishi's defense is almost funny. Of course that type of vibration hadn't been seen before, because there had been no steam generator that big. The steam generators built for San Onofre were one of the kind with 10,000 tubes, instead of normal 3,000 to 4,000 tubes.

It's somewhat akin to TEPCO and the Japanese government's claim that the earthquake like that had never happened before (at least not in their lifetime or the last 100 years), therefore they shouldn't be blamed for the nuclear accident caused by the disaster.

If the US NRC's opinion back in June 2012 is still valid, then Mitsubishi screwed up the computer modeling in designing the steam generator, grossly underestimating the speed of the flow inside the tubes.

But then, SCE was the one who gave Mitsubishi the spec, and SCE was the one who approved and accepted the final products. Gross negligence may be equally applicable to SCE.

For the whole saga of San Onofre and its steam generators, see my posts.

Tweet

Southern California Edison to Close San Onofre Nuke Plant, Due to Uncertainty over NRC's Decision

Residents in southern California had better hope it will be cool summer.

From CBS News (6/7/2013):

Calif. utility to retire troubled San Onofre nuclear power plant

LOS ANGELES The troubled San Onofre nuclear power plant on the California coast is closing after an epic 16-month battle over whether the twin reactors could be safely restarted with millions of people living nearby, officials announced Friday.

Operator Southern California Edison said in a statement it will retire the twin reactors because of uncertainty about the future of the plant, which faced a tangle of regulatory hurdles, investigations and mounting political opposition. With the reactors idle, the company has spent more than $500 million on repairs and replacement power.

San Onofre could power 1.4 million homes. California officials have said they would be able to make it through the summer without the plant but warned that wildfires or another disruption in distribution could cause power shortages.

It wasn't clear how electrical production from the plant would be replaced permanently. The California Public Utilities Commission said it will work with governments to ensure Southern California has enough electricity, which will require increased energy efficiency and conservation during peak usage, as well as upgrades to transmission and generation resources.

The plant between San Diego and Los Angeles hasn't produced electricity since January 2012, after a small radiation leak led to the discovery of unusual damage to hundreds of tubes that carry radioactive water.

The plant "has served this region for over 40 years," Ted Craver, chairman of SCE parent Edison International said in a statement. "But we have concluded that the continuing uncertainty about when or if (the plant) might return to service was not good for our customers, our investors or the need to plan for our region's long-term electricity needs."

SCE had been seeking permission from the Nuclear Regulatory Commission to restart the Unit 2 reactor and run it at reduced power, in hopes of stopping vibration that had damaged the tubing.

"The Nuclear Regulatory Commission is aware of Southern California Edison's plans to permanently shut down San Onofre, but we are waiting for formal notification of their decision," Victor Dricks, spokesman for NRC, told KNX1070.

Edison's stock price was up slightly in midday trading.

Friends of the Earth, an advocacy group critical of the nuclear power industry, praised the decision to close it.

"We have long said that these reactors are too dangerous to operate and now Edison has agreed. The people of California now have the opportunity to move away from the failed promise of dirty and dangerous nuclear power and replace it with the safe and clean energy provided by the sun and the wind," the group's president, Erich Pica, said in a statement.

Democratic U.S. Sen. Barbara Boxer of California, chairman of the Environment and Public Works Committee, said she's also relieved.

"This nuclear plant had a defective redesign and could no longer operate as intended. Modifications to the San Onofre nuclear plant were unsafe and posed a danger to the eight million people living within 50 miles of the plant," she said in a statement.

"Now that the San Onofre nuclear plant will be permanently shut down, it is essential that this nuclear plant be safely decommissioned and does not become a continuing liability for the community."

The problems center on steam generators that were installed during a $670 million overhaul in 2009 and 2010. After the plant was shut down, tests found some generator tubes were so badly eroded that they could fail and possibly release radiation, a stunning finding inside the nearly new equipment.

The four generators at San Onofre — two per reactor, each with 9,727 alloy tubes — function something like a car radiator, which controls heat in the vehicle's engine. The generator tubes circulate hot, radioactive water from the reactors, which then heats a bath of non-radioactive water surrounding them. That makes steam, which is used to turn turbines to make electricity.

Edison has argued for months that the Unit 2 plant could be safely restarted, but Craver recently raised the possibility of closing the plant because of lingering uncertainty about the future. The company had said little about the future of the heavily damaged Unit 3 reactor.

Questions arose over changes to the replacement generators — they were different than the originals, 23.6 tons heavier and hundreds of additional tubes were added as part of design changes.

San Onofre is owned by SCE, San Diego Gas & Electric and the city of Riverside. The Unit 1 reactor operated from 1968 to 1992, when it was shut down and dismantled.

I don't think SCE has agreed in any way that the reactors are too dangerous to operate, as Friends of the Earth (who invited former prime minister Naoto Kan as guest of honor in the recent anti-nuclear event) alleges. The company simply hates the uncertainty, particularly for the investors, over how the NRC decides. It is a financial decision.

Asahi Shinbun reports that SCE will sue Mitsubishi Heavy Industries for damages, but I don't see any mention of that in the US news. SCE is in no position to sue MHI, who built the steam generator in question. The specs were by SCE, and it was SCE that accepted the final products.

Asahi also says 1100 workers will be laid off.

(UPDATE) Asahi probably didn't read the local news well enough. KPBS reports (6/7/2013):

Ted Craver, Chairman and CEO of Edison International, parent company of SCE, ...said the company is pursuing efforts to get cost recovery from Mitsubishi, the Nuclear Industry Insurance Program and California ratepayers. Shareholders will cover the rest.

For whatever reason or unreason, the Japanese media is all abuzz about Mitsubishi Heavy Industries being sued for damages.

Mr. Craver also says the decommissioning fund for San Onofre is about $2.7 billion, about 90% funded.

$1 billion per reactor...

Tweet

San Onofre Nuke Plant: "Mitsubishi Heavy failed certain requirements", Says NRC

NRC says Mitsubishi Heavy Industries failed to meet requirements related to the mock-up and testing of re-designed components for the steam generators.

So-Cal Edison wants to restart Reactor 2 in March. It says independent experts from Areva, Westingshouse/Toshiba, and Intertek/Aptech conducted the operational assessment.

SCE insists the company didn't rely on Mitsubishi (as if it is a good thing; maybe it is...).

For more on the Mitsubishi-made steam generator problems at San Onofre, see my posts (here and here).

From Reuters (12/19/2012; emphasis is mine):

SCE's Calif. San Onofre restart plan didn't rely on Mitsubishi

* NRC says Mitsubishi Heavy failed certain requirements

* SCE wants to restart Unit 2 at San Onofre

* NRC may approve of San Onofre 2 restart in March

* San Onofre reactors shut in January

Dec 19 (Reuters) - California power company Southern California Edison (SCE) said it did not rely on testing by Japanese engineering firm Mitsubishi Heavy Industries Ltd to develop its restart plan for Unit 2 at the San Onofre nuclear plant in California.

Both reactors at the 2,150-megawatt (MW) San Onofre plant shut in January due to tube wear problems in the units' new steam generators. Mitsubishi Heavy built those steam generators and installed them in 2010 and 2011.

The U.S. Nuclear Regulatory Commission (NRC) said in a letter posted on its website that Mitsubishi Heavy failed to meet certain requirements related to the mock-up and testing of re-designed components for the steam generators that may be used to repair the San Onofre steam generators.

But in a statement Tuesday night, SCE, a unit of California power company Edison International, said it did not consult or rely upon the Mitsubishi testing under review by the NRC to create the utility's plan to restart Unit 2.

The NRC is also reviewing SCE's plan to restart Unit 2 and may issue a decision on that plan in March. The reactor cannot restart without the NRC's approval.

SCE's plan to restart Unit 2 includes preventive plugging of tubes in the steam generators and operating the 1,070-MW unit at 70 percent power for a five-month period.

San Onofre is one of the biggest power plants in California and its shutdown since January has caused reliability challenges for the Southern California power grid.

INDEPENDENT EXPERTS

SCE said its team of experts conducted three independent operational assessments of tube wear. The assessments were done by units of nuclear engineering firm Areva SA of France, the Westinghouse Electric unit of Japan's Toshiba Corp , and international testers at Intertek/Aptech.

SCE said none of its experts based their review and recommendations on testing by Mitsubishi. SCE said this was confirmed Tuesday at an NRC public meeting in Rockville, Maryland.

SCE submitted technical information to the NRC in October in support of its proposed restart plan for Unit 2. That plan did not include a restart for Unit 3 in part because the steam generators in Unit 3 suffered more tube wear.

The company shut Unit 2 on Jan. 9 for a planned outage. Unit 3 shut on Jan. 31 after station operators detected a leak in a steam generator tube.

SCE operates San Onofre for its owners: SCE (78.21 percent), Sempra Energy's San Diego Gas & Electric (20 percent) and the city of Riverside (1.79 percent).

I think NRC's letter mentioned in the article is this. It's more a report than a letter, dated November 30, 2012. So NRC staff made a trip to Kobe, Japan to inspect Mitsubishi Heavy Industries' noncompliance. Interesting.

Addressed to the Quality Assurance Manager Mr. Otake, NRC says:

From October 9-17, 2012, the U.S. Nuclear Regulatory Commission (NRC) staff conducted an inspection at the Mitsubishi Heavy Industries, Ltd (MHI) facility in Kobe, Japan. The purpose of this reactive inspection was to assess MHI’s compliance with the provisions of Title 10 of the Code of Federal Regulations (10 CFR) Part 21, “Reporting of Defects and Noncompliance,” and selected portions of Appendix B, “Quality Assurance Program Criteria for Nuclear Power Plants and Fuel Reprocessing Plants,” to 10 CFR Part 50, “Domestic Licensing of Production and Utilization Facilities.”

This reactive inspection evaluated MHI’s quality assurance activities associated with the mock-up and testing of re-designed anti-vibration bars that may be used as a long-term repair of both Unit 2 and Unit 3 San Onofre Nuclear Generating Station (SONGS) steam generators. The inspection will assist the Nuclear Regulatory Commission (NRC) when and if modifications are installed at SONGS. The design and installation of the modification will require that the NRC conduct an independent review of the modification and possibly approval of the design change. The inspection evaluated if MHI’s design, manufacturing, preparation, and testing of the mock-up and testing of re-designed anti-vibration bars meet the applicable requirements of Appendix B to 10 CFR Part 50, 10 CFR Part 21, and American Society of Mechanical Engineers Code Section III, “Rules for Construction of Nuclear Facility Components”. The enclosed report presents the results of this inspection. This NRC inspection report does not constitute NRC endorsement of MHI’s overall quality assurance (QA) or 10 CFR Part 21 programs.

During this inspection, the NRC inspection team found that the implementation of your quality assurance program failed to meet certain NRC requirements imposed on MHI by its customers or NRC licensees. Specifically, MHI: 1) failed to verify the tube outside diameter straightness, tube bending radius, and total tube length conformed to the requirements identified in the purchase order and purchase specifications to Sumitomo Metal Corporation for the alloy 690 seamless tubes used to construct the steam generator u-tube bundle mock-up; and
2) failed to perform dedication of the commercial calibration services provided by Tokyo Sokki Kenkyujo Co., Ltd. The enclosed Notice of Nonconformance (NON) cites these nonconformances, and the circumstances surrounding them are described in detail in the enclosed inspection report. Even though the NRC inspection team did not identify issues in all areas reviewed, in the response to the enclosed NON, MHI should document the results of the extent of condition and determine if there are any effects on other associated QA activities.

Please provide a written statement or explanation within 30 days from the date of this letter in accordance with the instructions specified in the enclosed NON. We will consider extending the response time if you show good cause for us to do so.

The letter is followed by the notice of nonconformance and the detailed inspection report.

Quick check on MHI's website, and there is still no mention of the accident.

Tweet

San Onofre Nuke Plant: Tube Wear Caused by Vibration and Settling of Support Equipment, Says SCE

In mid June, NRC said the cause of the excessive wear of the tubes in the steam generators at San Onofre Nuclear Power Plant could be a faulty computer modeling by the manufacturer, Mitsubishi Heavy Industries, which underpredicted the velocity of the steam and water.

Mitsubishi Heavy Industries sold 4 replacement steam generators to Southern California Edison. Each has over 10,000 tubes, instead of 4,000 or so for a standard steam generator that the company manufactures. Mitsubishi Heavy Industries is one of the top manufacturers of steam generators in the world.

From 10News.com (7/13/2012):

Tube Wear At San Onofre Blamed On Settling, Vibration
SoCal Edison Says Wear On Steam Generator Tubes Did Not Reach Federal Limits

SAN ONOFRE, Calif. -- The wear in the walls of steam generator tubes that forced the shutdown of the San Onofre Nuclear Generating Station earlier this year was caused by a settling of support equipment and vibrations, Southern California Edison announced Friday.

A leak from a tube forced the utility to take Unit 3 off-line in January, and thinning was found in a large number of them, which are less than two years old.

The plant's other unit had already been closed for routine maintenance. Neither has been returned to service.

SCE reported to the Nuclear Regulatory Commission last week that most of the wear in the tube wall was less than 20 percent, below the federal safety threshold of 35 percent. A tube over the limit must be plugged.

The cause of the wear on the tubes was vibration, which is unusual, and settling of the support structures, which sometimes occurs, SCE spokeswoman Jennifer Manfre said. She said the number of tubes affected by the settling was higher than normal.

"We're using this information and additional detailed data collected through testing to develop our repair plans according to best practices and industry standards, particularly the data on the unexpected tube-to-tube wear," said Pete Dietrich, senior vice president and chief nuclear officer.

SCE reported that in Unit 3 -- where the leak occurred -- 1,806 tubes showed wear of some type and 807 tubes were ultimately plugged. Of those, 381 tubes were plugged for wear of more than 35 percent and the rest as a precaution.

In Unit 2, 1,595 tubes showed wear of some type and 510 tubes were ultimately plugged. Six were for showing wear of more than 35 percent and the rest for preventative measures.

The units each have thousands of steam generator tubes.

An anti-nuclear group called Friends of the Earth released a statement Thursday, claiming that the utility and the NRC were down-playing the extent of damage. The FOE statement calls the steam generator problems at San Onofre the "most severe" of any nuclear plant in the United States.

San Onofre has more than three and a half times the number of steam tubes plugged as a safety measure than at 31 other similar U.S. reactors combined, according to the group. They contend that the number of tubes plugged in Unit 2 -- which did not have a leak -- is nearly five times that of any other reactor.

The San Onofre plant generates about 20 percent of the power for San Diego Gas and Electric. The utility is importing power to cover for the San Onofre shutdown, much of it coming over a transmission line from Imperial County that recently began operating.

Well, if each unit has two steam generators which have 10,000 tubes each, there are 20,000 tubes. If the number of tubes plugged in Unit 2, 510, was five times that of any other reactor in the US, what I'd like to know is the total number of tubes in the steam generator(s) in a typical PWR in the US.　(Does anyone know? I'm being lazy on weekend...)

And yes, the tubes got worn out in 2 years instead of 20...

Tweet

Faulty Steam Generators at San Onofre Nuke Plant in CA Caused by Mitsubishi Heavy Industries' Faulty Computer Modeling, Says NRC

The information was disclosed in a public hearing.

Mitsubishi Heavy Industry's computer modeling underpredicted the velocity of steam and water by a factor of 3 to 4.

According to the NRC who conducted the pressure test, it was "the first time in the history of the nuclear industry that more than one tube at a plant has failed". 8 tubes failed in the Unit 3's steam generators.

From LA Times (6/18/2012; emphasis is mine):

San Onofre's issues appear to be result of faulty computer modeling

The unusual equipment issues that have shut down the San Onofre nuclear power plant appear to be the result of faulty computer modeling by manufacturer Mitsubishi Heavy Industries, officials from the U.S. Nuclear Regulatory said Monday.

The agency used a public hearing in San Clemente to present the preliminary results of its inspection of the plant, which has been out of commission for more than four months after a steam generator tube sprang a leak, releasing a small amount of radioactivity. That led to the discovery that tubes were vibrating excessively and rubbing against each other, leading them to wear out more quickly than normal for equipment that had been operating for less than two years.

The NRC ordered plant operator Southern California Edison to keep the plant shut down until operators fully understand the wear and how to fix it.

Eight tubes in the plant's Unit 3 failed pressure testing, which NRC officials said Monday was the first time in the history of the nuclear industry that more than one tube at a plant has failed.

"This is a significant, serious safety issue," said NRC Regional Administrator Elmo Collins. "This is a very difficult technical issue, and to be honest, it's not one we've seen before."

NRC officials said it appears that simulations by Mitsubishi underpredicted the velocity of steam and water flowing among the tubes by a factor of three to four. The rate of flow caused the tubes to vibrate and knock against each other.

There were also issues with support structures intended to prevent vibration in Unit 3, but apparently not in Unit 2, officials said.

Mitsubishi did not have any representatives at the meeting and couldn't immediately be reached for comment. Collins said, however, that even though Mitsubishi did the computer modeling, the ultimate responsibility lies with Edison.

NRC and Edison officials did not give a timeline for restarting the plant, saying there are still unanswered questions and more inspections that need to be done.

Tweet

San Onofre Nuke Plant: 1,300 Tubes in Steam Generators Found Bad

There are 4 steam generators made by Mitsubishi Heavy Industries, two each for 2 reactors at San Onofre Nuclear Plant. 1,300 tubes represent about 3% of the total number of tubes in the steam generators.

For more on the SG problems at San Onofre, see my previous posts.

Mitsubishi Heavy Industry's English website doesn't have anything on the current problem. The last press release about the SG is about the delivery to San Onofre. It is the same with their Japanese site.

From ABC News (5/8/2012) citing AP:

More than 1,300 tubes that carry radioactive water inside the San Onofre nuclear plant in Southern California are so damaged that they will be taken out of service, the utility that runs the plant said Tuesday.

The figures released by Southern California Edison are the latest disclosure in a probe of equipment problems that have kept the coastal plant sidelined for more than three months.

At issue has been the integrity of tubing that snakes through the plant's four steam generators, which were installed in a multimillion-dollar makeover in 2009 and 2010.

A company statement said that as of Monday, 510 tubes had been plugged, or retired from use, in the Unit 2 reactor, and 807 tubes in its sister, Unit 3. Each of the generators has nearly 10,000 tubes, and the number retired is well within the limit allowed to continue operation.

The statement comes just days after an Edison executive said the company hopes to restart at least one of the twin reactors next month. The company is drafting a plan under which the reactors would run at reduced power, at least for several months, because engineers believe that will solve a problem with vibration that the company believes has been causing unusual wear in the alloy tubing.

Government regulators say there is no timetable for a restart, which would require federal approval.

A joint statement issued Tuesday by Edison and the agency that operates the state's wholesale power system, the California Independent System Operator, said the possible June dates are for planning and subject to change.

"There is no timeline on nuclear safety," Edison President Ron Litzinger said.

Activists viewed the new figures as another alarming sign following a tube break in January, which prompted Edison to shut down the Unit 3 reactor as a precaution. Traces of radiation escaped at the time, but officials said there was no danger to workers or neighbors.

Unit 2 was taken offline in January for routine maintenance, but investigators later confirmed accelerated wear on tubing in both units.

"It seems that these new steam generators are falling apart and Edison doesn't know why. It would be foolhardy to restart, even at reduced power, under the current circumstances," said Daniel Hirsch, a nuclear watchdog who lectures on nuclear policy at the University of California, Santa Cruz.

Ted Craver, chairman of SCE parent Edison International, told investors in a phone call last week that unusual wear was found in about 1 percent of nearly 39,000 tubes in the steam generators.

(Full article at the link)

Tweet

California's San Onofre Nuke Plant Unit 2: Steam Generator Tubes Showing "Many, Many Years" Worth of Wear

even though they are only 22 months old.

Overload, most likely. Mitsubishi's design flaw?

From LA Times (2/3/2012):

San Onofre nuclear plant radiation leak, worn tubes raise concerns

A week of problems at the San Onofre nuclear power plant has raised new safety concerns among some activists.

Officials of Southern California Edison, which operates the facility and is a majority owner, insist that the plant is perfectly safe, but others say the mishaps are one more sign of problems.

The situation is "further evidence that California should move beyond nuclear power. California should plan for the orderly phase out of ... aging nuclear power plants, including San Onofre, and shift to clean-energy alternatives like energy efficiency and renewable power," Bernadette Del Chiaro, director of clean-energy programs for the advocacy group Environment California, said in a statement.

Nuclear regulation officials said Thursday that extensive wear had been found on tubes inside a unit at the San Onofre nuclear plant.

Another unit at the plant was taken off-line after a small radiation leak earlier this week.

Dozens of relatively new tubes that carry radioactive water in a steam generator showed "many, many years" worth of wear, even though the tubing is 22 months old, said Victor Dricks, a spokesman for the Nuclear Regulatory Commission.

Nearly 70 tubes, made from a metal alloy and formed into a U-shape, had 20% of their interior lining worn off, while hundreds more had 10% of the lining deteriorated, Dricks said. More than 9,000 tubes are in the generator.

Dricks said that some of the tubes will require repair, while others will probably have to be replaced.

But Edison officials say it's too early to make any determination on a course of action, and that additional tests will be conducted. The unit was off-line for a scheduled maintenance period of several months to deal with technology upgrades and fuel replacement, said Gil Alexander, an Edison spokesman.

It is unclear why the tubes are showing so much wear.

The NRC's findings come on the heels of a leak in a tube Tuesday, prompting operators to shut down a reactor. However, officials said, the amount of radiation released was minuscule and did not endanger the public.

"San Onofre has had such a troubled history in terms of the safety culture that each of these incidents shakes me further,” Daniel Hirsch with the group Committee to Bridge the Gap told the Orange County Register.

As for the Unit 3 that was tripped (scrammed) after a minute radiation leak was detected in the turbine building, the inspection won't be done until middle of next week due to the still high temperature (105 degrees Fahrenheit) in the building, according to San Francisco Chronicle.

Mitsubishi Heavy Industries' SG, as it was getting ready to be moved into the reactor building of Unit 2 in 2009 (from The Orange County Register):

Tweet

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.

Tweet