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Sun Feb 5, 2012, 06:29 PM

Worn Pipes Shut California Reactors ( the pipes are relatively NEW!)

The two reactors at the San Onofre nuclear-power station near San Clemente, Calif., will remain shut down this weekend while federal safety officials investigate why critical—and relatively new—equipment is showing signs of premature wear.
The problem surfaced Jan. 31, when one of the units sprang a leak in a pipe called a steam tube, releasing small amounts of radioactive steam and tripping radiation alarms. Operators shut down the reactor four hours later.

http://online.wsj.com/article/SB10001424052970204662204577201343461828720.html

get this:
San Onofre was built in the 1980s. Its owners, Edison International and Sempra Energy, spent more than $800 million replacing nearly 40,000 steam tubes and four giant steam generators in 2009 and 2010, buying the equipment from Mitsubishi Heavy Industries. The tubes are made of a metal called Inconel alloy 690, a state-of-the-art material intended to address a prior problem with cracking in tubes made of a different alloy, experts said.

Steam-tube leaks aren't unusual in older plants, experts said, "but I think such rapid degradation is clearly unusual," said Edwin Lyman, nuclear expert for the Union of Concerned Scientists. He added that it suggests manufacturing defects or operational issues.

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Arrow 13 replies Author Time Post
Reply Worn Pipes Shut California Reactors ( the pipes are relatively NEW!) (Original post)
dixiegrrrrl Feb 2012 OP
madrchsod Feb 2012 #1
dixiegrrrrl Feb 2012 #2
madrchsod Feb 2012 #3
Sirveri Feb 2012 #4
Throckmorton Feb 2012 #5
Sirveri Feb 2012 #6
wtmusic Feb 2012 #7
Sirveri Feb 2012 #9
wtmusic Feb 2012 #11
Throckmorton Feb 2012 #8
Sirveri Feb 2012 #10
Throckmorton Feb 2012 #13
kristopher Feb 2012 #12

Response to dixiegrrrrl (Original post)

Sun Feb 5, 2012, 07:32 PM

1. it took 5 minutes on google to find where this pipe came from...

there are three manufacturers of 600-690,sweden,france,and korea. it seems the koreans have used the same material in thier nuke plants. i`m betting the us pipe came from korea.

http://www.iasmirt.org/SMiRT15/L02-5



i`m sort of a geek when it comes to metal since i`m a retired heavy metal worker.

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Response to madrchsod (Reply #1)

Sun Feb 5, 2012, 08:17 PM

2. Very impressive!

So what do you think about the story?

I am reminded that the crucial parts of the new Oakland Bay Bridge are built from chinese materials,
the state was so happy to save 400 million by outsourcing.

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Response to dixiegrrrrl (Reply #2)

Mon Feb 6, 2012, 12:16 AM

3. as a former steel worker who has watched his trade go overseas...

would`t trust chinese steel unless i watched every step of production. if it was`t for us and european firms china would still be 20 yrs behind the west

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Response to dixiegrrrrl (Original post)

Mon Feb 6, 2012, 02:55 AM

4. It's probably the fault of the water chem folks.

That's really the only way to get a U-tube piping failure that quickly other than as a material defect.

Screw up the pH balance in the water and those tubes basically dissolve in a matter of weeks. Other than that a manufacturing fault, or damage during installation could have done it too. But a primary side leak is more difficult since these tubes are double walled and the primary flows on the inside of the pipes as opposed to the steam generator feed water which is on the outside.

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Response to Sirveri (Reply #4)

Mon Feb 6, 2012, 08:21 AM

5. Dissolved Oxygen is also a major player.

We try to keep our primary and secondary Dissolved Oxygen content below 10 PPB.

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Response to Throckmorton (Reply #5)

Mon Feb 6, 2012, 09:49 AM

6. via the water chem guys adding H2 to the primary.

secondary has air ejectors which are used as gas scavengers (combined with the steam generator pulling all gasses out of solution should keep O2 levels quite low in that arena). Don't have those running and good luck maintaining a vacuum within tolerance.

But they said radioactive steam, which typically means failure of the primary side with leakage at the tube sheet since the tubes should be 'double tube' or tube within a tube meaning it would have to eat thru both sides. Though once accomplished the higher pressure primary would typically pass into the secondary, so I guess it's possible they screwed up the boiler chem and got sediment hideout which did the same thing.

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Response to Sirveri (Reply #6)

Mon Feb 6, 2012, 10:35 AM

7. Apparently 900 out of 4,000 pipes showed excessive wear

so it's unlikely it was installation damage.

What's the purpose of a "tube within a tube"? Do they use different alloys for the inside/outside?

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Response to wtmusic (Reply #7)

Tue Feb 7, 2012, 03:41 AM

9. basically if one tube leaks the leakage goes to a drainage spigot

Then you see that you have a problem, and start trying to figure out what's going on in the plant. Then you plug the failed tubes on the side that failed. Though in this case that's a pretty severe efficiency drop, so it's better to just shut down and rework. As far as I know the alloys are the same but it's possible that manufacturing techniques have advanced and they're using differing metals. Though that likely would add a cost they don't want to spend.

It could still be a manufacturing defect, especially if they got a bad batch of metal from their supplier. There will be hell to pay if that's the case.

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Response to Sirveri (Reply #9)

Tue Feb 7, 2012, 10:20 AM

11. If it was radioactive steam wouldn't that be a leak in the primary loop

Seems like double-walled tubing would be an inefficient way to transfer heat

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Response to Sirveri (Reply #6)

Mon Feb 6, 2012, 11:53 AM

8. We also add Ethanolammine to the condensate system,

to scavenge Oxygen that the Air Ejectors miss. Given that the SG's are only 2 to 3 years old, Im very interested in the Root Cause of these failures.

I dont know if San Onofre has seconday side N16 monitors, at my station, this type of tube leak will first show up there.

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Response to Throckmorton (Reply #8)

Tue Feb 7, 2012, 03:44 AM

10. They likely at least have air samplers.

A failure of 900 pipes on the primary side should cause that to alarm pretty quickly.

My guess is it's either a bad batch of metal because their supplier decided to cut corners or the water chem guys are blazing a lot of their logs.

For me I was a submariner, S6G plant, EM01, loved the science aspect of the job. For some odd reason that made me the odd man out on the boat though since most other people could have cared less, which I always found odd.

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Response to Sirveri (Reply #10)

Tue Feb 7, 2012, 02:38 PM

13. Our secondary detection scheme is radiation monitors on the air ejectors,

optimized to detect Krypton and Iodine. But the primary detection is N16 adjacent to the main steam lines inside containment.

S6G, In my misspent youth I built a few of those boats a EB.

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Response to dixiegrrrrl (Original post)

Tue Feb 7, 2012, 12:59 PM

12. k&r

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