San Onofre steam generator tubes leaking - why?

[Hiddencamper]

Well, without actually being there there's no knowing what was the dynamic between the two outfits.

The Mitsubishi non-proprietary 'root cause' report at
http://libcloud.s3.amazonaws.com/93/92/5/2795/MHI_Root_Cause.pdf
has a couple interesting paragraphs in it:

I don't know what were the constraints.

Mitsubishi built steam generators for Ft Calhoun , pdf page 9 of 64



So, when they stuck to original CE physical design they were okay.

But they tinkered with the design:
Page 48 of 64 :


So do I think there was a push to avoid that 50.59 trigger ?

It's reading between the lines, but yes I do.
Phrases "close scrutiny"
and "optimal based on the overall RSG design requirements and constraints"
tell me somebody was worried but they yielded to schedule and contract pressures.

old jim

The 50.59 and other things are available here

http://www.nrc.gov/info-finder/reactor/songs/songs2/publ-avail-doc.html


Here is the direct link to the 50.59 http://pbadupws.nrc.gov/docs/ML1305/ML13050A189.pdf

proprietary stuff removed.

More than anything, There's a number of questions they answered "NO" to in the screening for adverse effect that I think are total horsegarbage (based on my experience as a qualified 50.59 engineer). Like the 50.59 screening is 15 pages...that's absurd. If you are using more than 4-5 pages for a screening you are doing it wrong (and it probably SHOULD be in the evaluation).

That said, I think based on what I do know, and the information they had at the time, that the evaluation for most of the changes would have been acceptable (the "no more than a minimal increase" sections).

 

[jim hardy]

The 50.59 and other things are available here



That said, I think based on what I do know, and the information they had at the time, that the evaluation for most of the changes would have been acceptable (the "no more than a minimal increase" sections).

Thanks for the links !

I don't disagree with the premise of like-for-like replacement under 50.59.
Just so it's done well .

For me, the question comes down to "...could anybody have reasonably forseen this vibration problem in the tubes? " .
That other computer codes found it so quickly in the followup investigation suggests to me that somebody might've.
But I'm an instrument maintenance guy not a fluids analyst.From: http://www.nrc.gov/info-finder/reactor/songs/ML12188A748.pdf

Both the NRC and Mitsubishi ATHOS results were reasonably consistent and strongly suggested that high velocities coupled with high void fraction were primary causal factors in the tube fluid-elastic instability and the excessive wear patterns observed in the Unit 3 steam generators.

From Root cause report , pdf page 51 http://pbadupws.nrc.gov/docs/ML1306/ML13065A097.pdf

Also MHI and SCE recognized that the SONGS RSG steam quality (void fraction) was
high and MHI performed feasibility studies of different methods to decrease it.
Several design adjustments were made to reduce the steam quality (void fraction)
but the effects were small. Design measures to reduce the steam quality (void
fraction) by a greater amount were considered, but these changes had
unacceptable consequences and MHI and SCE agreed not to implement them. It
was concluded that the final design was optimal based on the overall RSG design
requirements and constraints. These included physical and other constraints on the
RSG design in order to assure compliance with the provisions of 10 C.F.R. §50.59.
(underline mine- that was mid 2005 per http://pbadupws.nrc.gov/docs/ML1305/ML13057A014.pdf page 56 - jh)

Somebody was worried enough in '05 to want to reduce void fraction..
My guess is the utility wouldn't accept the changes it would have taken to accomplish that. This is how technology progresses, by building ever bigger machines, pushing designs, and seeing what goes wrong with them.
We low echelon guys have a saying "Murphy was an optimist"

Management science progresses similarly I suppose with their ever bigger organizations.

My old mentor used to say "Your evaluation is dandy but that power plant can't read."
I guess that's why the small things of the Earth still occasionally confound the mighty.
Who'd have ever thought the inside of a boiler could be too dry?

old jim

 

[Thermalne]

true enough



Not quite. ABB never had any part of Westinghouse.

In 1990, ABB bought Combustion Engineering (both the nuclear and fossil power businesses).

In 2000, ABB sold their nuclear businesses to Westinghouse Electric. Shortly after that, they sold their fossil equipment business (including the CE fossil interest) to Alstom.

WEC is the nuclear part of the "old" Westinghouse, which had been sold to BNFL when CBS broke the old Westinghouse into fragments around 1996. So if anything, BNFL is the one that "merged" CE nuclear into WEC (but even that is stretching things).

In 2006, BNFL sold Westinghouse Electric (including the previously absorbed CE nuclear) to Toshiba.

Interestingly, in the past Westinghouse and MHI had a good relationship (MHI built the PWRs in Japan originally following the W design under license). When BNFL sold Westinghouse, MHI was in the bidding, but Toshiba won out.

Anyway, Toshiba now owns the Westinghouse nuclear business, including the CE technology. Due to the Toshiba / MHI competitive dynamic it was never likely that they would cooperate on the SONGS RSG design.

Thank you! I did not know that!

 

[atyy]

The Economist has an item on this: http://www.economist.com/blogs/babbage/2013/06/nuclear-power .