San Onofre: Closer to the Truth, Further from the Bluster

This sounds serious:

[Sen. Barbara] Boxer (D-Calif.) said in a letter to Nuclear Regulatory Commission Chair Allison Macfarlane that a confidential report obtained by her office shows Southern California Edison and Mitsubishi Heavy Industries, the Japan-based company that built the generators, were aware of design problems before the equipment was installed.

Boxer, who chairs the Senate Environment and Public Works Committee, said the report written by Mitsubishi raises concerns that Edison and its contractor rejected safety modifications and sidestepped a more rigorous safety review.

A little mysterious, yes? This is about San Onofre, which has been off-line for a little over a year because of a steam generator problem. If Edison and Mitsubishi pressed ahead with a problematic steam generator, that would be very bad, but also rather inexplicable.

Just to get you up to date, here’s a refresher course on what happened at San Onofre:

Both of San Onofre's reactors have been offline for more than a year. The Unit 2 reactor had been taken down for routine maintenance early in January 2012, but on Jan. 31, 2012, a small leak of radioactive gas prompted the shutdown of Unit 3.
Inspections revealed unexpected wear among thousands of metal tubes that carry radioactive water inside the plant's four steam generators, two for each reactor.

Our friend Rod Adams over at Atomic Insights explains why the idea of a conspiracy is highly unlikely:

Aside from the fact that such an assertion was absurd – why on earth would any corporation take the risk of installing components known to be faulty into a vital, multi-billion dollar production facility capable of producing between $1-$10 million in daily revenue – it exposed a visceral dislike [by Rep. Boxer] of a power source that has been cleanly and safely supplying 20% of the electricity in the United States for several decades.

Let’s call that last bit an opinion – Sen. Boxer generally nuclear energy a fair shake in her committee, though she can be pretty tough. Let’s call that an opinion, too.

Rod also clarifies what the Mitsubishi report says:

After many months of investigation, tens of thousands of hours of analysis, and hundreds of millions of dollars worth of lost production time, it is now clear that the two steam generators installed in San Onofre Unit 3 contained a minor manufacturing feature that resulted in a “perfect pitch” harmonic. At just the wrong condition – 100% steam flow – a combination of relatively dry steam, precisely manufactured anti-vibration bars (AVB), and densely packed u-tubes resulted in a few hundred (out of nearly 10,000) tubes vibrating with a large enough amplitude to make contact. The unexpected vibration and contact resulted in accelerated wear and caused one tube to fail while the steam generator was operating.

That sounds a lot more plausible and certainly not an effort by Mitsubishi and Edison to shoot themselves in the proverbial foot – well, head really, as such a conspiracy would certainly do considerable damage to both companies. The entire Mitsubishi report can be found here.

Now, the report can make your head spin – it’s very dense and detailed. The estimable Will Davis over at Atomic Power Review takes a crack at it:

The root cause of this problem is essentially not a design flaw per se, nor even a miscalculation.  It is the basic, fundamental belief that in-plane fluid elastic instability in a vertical U-tube steam generator is not possible if out-of-plane instability has been guarded against.  This principle is described several times in the linked MHI material.

Well, I told you it was head spinning – and this is the simplified version. A little more:

What this means is that the designers of steam generators have essentially used a Maginot Line principle in preventing out-of-plane fluid elastic instability... which was supposed to inherently then preclude any chance of in-plane fluid elastic instability, which leads to serious tube-to-tube wear.  Singularly focused effort to prevent out-of-plane FEI has led to the situation in which in-plane FEI did actually occur through a set of very complicated circumstances which, when investigated, eventually implicates practices of manufacturing tolerances, fitting, calculation and even design variance between the two units' steam generators.

I’d probably avoid the word “implicates” as it often appears with the word “criminally,” but that’s not what Will means here. These are, rather, the elements that have to be looked at to understand how the problem occurred. This is a hard post to excerpt – you should read the whole thing. Here, for me, is the bottom line:

Now we can see clearly that MHI [Mitsubishi Heavy Industries] felt that it had developed replacement steam generators for San Onofre which were world-class in their design prevention of tube vibration, based on all the years of experience MHI has had in fabricating steam generators for PWR-type nuclear power plants.

This is completely believable. As Rod points out, the nuclear energy industry has a “squeaky clean” profile for manufacturing QA. It’s an industry that avoids – has to avoid - low-quality junk. N-stamps that validate nuclear equipment, a highly capable (and always present) regulator, a very strong safety culture – all these and more keep the vigilance against shoddiness very high. And Mitsubishi isn’t exactly Moe’s Steam Generators out in the valley, running a two-for-one sale.

I’m sure there will be more to say about San Onofre. But the public release of the Mitsubishi report takes a lot of the edge off the harsher statements made by a few politicians about the facility.
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Speaking of which, both Rod and Will are really furious at the politics around this and particularly about statements made by Sen. Boxer and Rep. Edward Markey (D-Mass.) over the last month. Both Boxer and Markey pulled unflattering bits out of the Mitsubishi report to highlight, but the report makes that possible for them. There are unflattering bits in there.

In my view, a report by the maker of flawed equipment would be inherently suspect, but this episode – and perhaps bluster from Capitol Hill - has put Mitsubishi’s reputation on the line. Consequently, Mitsubishi has produced what seems to me an honest assessment, with a lot of detail to back it up.

So why did some of the comments from Congress seem so intemperate? I don’t know. I do know that the motives of politicians, especially the experienced ones, are rarely singular.