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.
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6 comments:
As the Americans should try to learn the lessons of Fukushima, the Japanese who use Mitsubishi Heavy products should try to learn the lessons of San Onofre, preferably before San Onofre syndrome actually causes an accident in Japan.
Amazing SONGS.
In March NRC originally intended to only test 129 tubes of #3 SG. And now we are at 800+ plugged tubes already.
This is 8 percent. At this pace the time will take no long until the 15-20 percent of plugged tubes NRC usually allows will be reached.
The SONGS "investors" that apparently believe the crap that Edison chairman tells them are, according to Wikipedia, the cities of San Diego and Riverside.
Probably Californians will have to pay sort of a nuclear tax soon like the Floridans, just to finance the upkeep of these crappy nuclear plants and the construction of even more nukes...
Maybe I'm just confused, but ... plugging the tubes doesn't resolve the problem that caused them to break in the first place. Running the reactor(s) at reduced speed guarantees that no further damage will occur? How do we/does Edison know that and can prove it? Somehow this isn't quite coming together in my head.
*mscharisma*
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@ mscharisma
Usually mass tube breaking as observes occurs when the acoustic stress exceeds a particular threshold.
This is very dependent on the particular reactor/SG combo.
This behavior is so complex that it cannot be modeled in advance using computer models. You can test this only by implementation.
By the way, the computer model shortcomings reveal very easily in the TMI accident, none (neither MAAP nor MELCOR) was able to produce a result that came near to what actually happened at the meltdown there. But this was discovered only many years after the accident, when the core remains were disassembled.
For example, the Soviet RMBK-1500s had to be downgraded to 1200 MWe because they'd have lasted only 12 instead of the scheduled 30 years if they'd have been operated at 1500MW.
Similiarly, most Japanese-origin ABWRs had to be downgraded to avoid the same.
(Just a side note, these downrates were motivated solely because of economical reasons, they didn't take into account the increased accident or contamination risk.)
I think it would be sensible to bet on a SONGS downrating by 20%.
What are the odds for this?
Do there exist any betting offices who take bets on such stuff?
@atomfritz: Thanks much for the info and explanation. But if I understand you correctly ("You can test this only by implementation"), then Edison's running at reduced power does not guarantee safe operation. Rather, the assessment is based on calculations and "reasonable" assumptions?
Especially given that SONGS doesn't exactly have a great record when it comes to safety issues and their correctly, I personally do not find this very comforting. Would be nice if the NRC stayed on top of this and didn't allow restart on a somewhat iffy basis.
*mscharisma*
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