San Onofre (SONGS)

[Fermi2]

Leak was 80 gallons per day (.065 gpm) and a rate of change of 30 gallons per hour.

Above the EPRI Limit for greater than Minor leakage and requires a Shutdown to less than 50% power within 60 minutes and be in Hotshutdown within the following 2 hours.

1. Reduce power to less than or equal to 50% power
within one hour and be in Mode 3 within the next 2
hours (total of 3 hrs).
2. Monitor radiation monitor readings every 15 min
and perform Appendix A.
3. Coordinate with Chemistry to identify leaking SG,
quantify leakage and determine leakage rate-ofchange.
4. Initiate actions to minimize spread of
contamination.
5. Evaluate need for additional resources in the
following areas: Operations, Chemistry, Rad
Protection, water processing, makeup water.


AND the Operations Staff decided it was bad enough they entered their SG Tube Rupture EOP which isn't something the NRC takes miildly.

Hardly a "minor" tube leak.

See the point?

[HydroDave63]

More than 800 tubes showed a 10 percent thinning in the tube wall, officials said. 69 others had at least 20 percent thinning. And two tubes needed to be plugged and taken out of service because a third of the wall was worn away.

With that much wear this soon, I'm thinking water chemistry or bad tube metallurgy at MHI...

[Already Gone]

Leak was 80 gallons per day (.065 gpm) and a rate of change of 30 gallons per hour.

Well, that changes the dynamic a bit.  .065 gpm vs. 30 gpm makes the leak rate lower than a tube rupture.  But, it is significantly worse than what you would expect on the first cycle.  Either one tube was on its way to a failure, or many of them were rapidly deteriorating. 
Combined with the tube wall thinning noted at Unit 2, this indicates a real problem.  I don't think the water chemistry could be the cause unless somebody was radioing the samples or ignoring the indications.  There had to be some contamination that was undetected or else it was a manufacturing defect.

Mitsubishi is going to blame the chemistry.  SONGS is going to blame the materials.  Time will tell who is right.

Still, it isn't something you should take in stride.  A primary to secondary leak that puts the unit at -15MW instead of full power is definitely not common.

[SloGlo]

Mitsubishi is going to blame the chemistry.  SONGS is going to blame the materials.  Time will tell who is right.

maybe m.h.i. didn't due things quite right in japan for it's n stamp.

[dirac]

See the point?

Never said there wasn't one. Just correcting the facts. 30 gpm and 30 gpd is a big difference and paints a different story.

[HydroDave63]

Never said there wasn't one. Just correcting the facts. 30 gpm and 30 gpd is a big difference and paints a different story.

But any guess as to root cause?

[Nuke of the North]

Not tube rupture.  Tube leak.  Very small.  Common in 1st cycle after replacement.  20,000 tubes in the unit.  Expect 1 or 2....................

T'is but a scratch...

[Brett LaVigne]

Not tube rupture.  Tube leak.  Very small.  Common in 1st cycle after replacement.  20,000 tubes in the unit.  Expect 1 or 2....................

1 or 2 or 900...something like that!

[MeterSwangin]

Not common at all. Incorrect. And 30 GPM is NOT a small leak.

You are misinformed.  Not 30 gpm.  80 gpd.  Very small.  See OE on replacement SGs for commonality.

[MeterSwangin]

But any guess as to root cause?

Eddy current testing 80% complete on Unit 2 (unit in RVH outage.)   Starts next week in U3 (tube leak unit.)  Much too early for conclusions.....although that appears to not dissuade media or some listers.

[Fermi2]

You are misinformed.  Not 30 gpm.  80 gpd.  Very small.  See OE on replacement SGs for commonality.

NOT very small. Large enough to cause a REQUIRED shutdown AND an entry into the EOPs.
I've checked OE and guess what, you're wrong. My source is the NRC event reports. I checked SG replacements against required shutdowns and trips. Found EXACTLY zero. Flat out you're wrong and an idiot.

[Already Gone]

You are misinformed.  Not 30 gpm.  80 gpd.  Very small.  See OE on replacement SGs for commonality.

"The amount of wear that we are seeing on these tubes is unusual for a new steam generator," said Nuclear Regulatory Commission spokesman Victor Dricks.

And that is in reference to the unit that is NOT leaking.  So, how can the leaking one be common?

Here is a little hint for ya -- NEW Steam Generators leak LESS than OLD Steam Generators.  That is the reason for buying NEW Steam Generators in the first place.  How much simpler does that concept have to be before you will understand it?

[OldHP]

Quote from: Already Gone on Yesterday at 23:23
Here is a little hint for ya -- NEW Steam Generators should leak LESS than OLD Steam Generators.  That is the reason for buying NEW Steam Generators in the first place.


Unless they are Westinghouse Model D-2/D-3 (or maybe? designed like them)!  The reported leak rate sounds like the leaks that occured in the D-2/3's due to no baffles in the secondary return lines.  Constant shaking resulting in heavy wear and eventual rupture at an upper support plate.

[tr]

NOT very small. Large enough to cause a REQUIRED shutdown AND an entry into the EOPs.
I've checked OE and guess what, you're wrong. My source is the NRC event reports. I checked SG replacements against required shutdowns and trips. Found EXACTLY zero. Flat out you're wrong and an idiot.

Could the EOP entry have been needed to allow performing the steps to isolate the SG, as it took place after the trip?

My understanding is that pretty much every SG, at every plant, is inspected each outage.  This includes the pre-service inspection of replacement SGs.  The expectation is ALWAYS that an SG can run the full cycle without leaks or failures (which is why tubes that have so much wear that they could possibly fail are plugged prior to cycle startup).

This was a significant leak (obviously, they had to shut down), but below the 400+ gpm you would get in an actual tube rupture.

[Already Gone]

Isolation of a S/G in a commercial nuke like SONGS requires that the unit be cooled down and de-pressurized below the relief valve setpoints.  You can do that by dragging and venting steam from the unaffected S/G while the leaking one is taken out of service.  Shutting the MSIV, feedwater isolations, blowdown isolations and blocking the safety valves is about all you can do to isolate it.  From there, you have to go to cold shutdown in order to drain it as there is no way to isolate it from the reactor.

[Starkist]

quick question, arent these things hydro'd before installation???

[Higgs]

quick question, arent these things hydro'd before installation???

That does nothing to predict tube wastage.

[tr]

So,it seems like any claim that the SG was "isolated" upon discovery of the tube failure was BS.

Not true.  "Isolation" really refers to isolating it from the outside environment (no steam or water releases from the affected SG), thus stopping any radioactive releases to the environment.   That happens once the steam isolation valve is closed, steam generator blowdown is isolated, and SG pressure is low enough that any open steam safety valves re-close.

Also, the NRC is being quoted as saying St. Lucie found similar tube thinning in their replacement SGs.

[hamsamich]

And I thought all the SGRs were over!!   

[HydroDave63]

Different plants, different S/G manufacturers....putting on my RootCauseWorker.com hat has me thinking this is the next Inconel-600 issue of the 21st century!

[Starkist]

That does nothing to predict tube wastage.

I am under the impression these were leaking from the get go?

Different plants, different S/G manufacturers....putting on my RootCauseWorker.com hat has me thinking this is the next Inconel-600 issue of the 21st century!

They should all be forced to use alloy 690! :p

[tr]

I am under the impression these were leaking from the get go?

Not true

[Starkist]

Not true

The more I look at it the more confused I become .

"The amount of wear that we are seeing on these tubes is unusual for a new steam generator," said Nuclear Regulatory Commission spokesman Victor Dricks.

 So its post install damage then?  Wall thinning is indicative of chemistry problems, no? Cant imagine inconel irroding like that. 

[GLW]

The more I look at it the more confused I become .

"The amount of wear that we are seeing on these tubes is unusual for a new steam generator," said Nuclear Regulatory Commission spokesman Victor Dricks.

 So its post install damage then?  Wall thinning is indicative of chemistry problems, no? Cant imagine inconel irroding like that.  

Stop crutching and do your research,...

Google steam generator tubes creep aerosol impingement wastage erosion sludge thinning,...

That should get you started,...

There's hundreds of pages of free stuff to read,...

The ANS papers will cost you, but they're very good,...

The best and most responsible answers will not translate well to an internet forum post,...

That or leave the chemistry to the ELT's, ChemTechs and engineers and keep yourself to spinning valves,...



Yep, we remember,.....

[Higgs]

The more I look at it the more confused I become .

"The amount of wear that we are seeing on these tubes is unusual for a new steam generator," said Nuclear Regulatory Commission spokesman Victor Dricks.

 So its post install damage then?  Wall thinning is indicative of chemistry problems, no? Cant imagine inconel irroding like that. 

They don't mean new as in just out of the box. They mean new as in installed within the last few cycles.