Tuesday, October 9, 2012

Three independent groups of experts tell Edison/NRC: DON'T RESTART SAN ONOFRE UNIT 2!


Dear Readers,

It is to the nuclear industry's great advantage that their failures are odorless, colorless, tasteless -- in short, utterly undetectable to the human sense organs except in very high (and very poisonous) doses, when radiation first gives you a metallic taste in your mouth much like adrenalin might give you, then, at higher doses, skin burns, nausea, vomiting, organ deterioration, and death. And you might get all the rest without getting the metallic taste in your mouth. Lower doses cause cancer, heart disease, lowered IQs, and, of course, thyroid problems: 40% of Japanese children living near the crippled -- and still spewing -- Fukushima reactors now have thyroid problems, a harbinger of cancers in the community in the coming years.

You need sophisticated equipment to detect radiation -- equipment which, fortunately, has come down to the $150 price range, while increasing in sensitivity significantly too. Scintillators, which can tell you the energy level of the radiation as well as what type (alpha, beta, gamma) -- and thus can determine what isotope is emitting the deadly particles and rays -- are also coming out in similar price ranges.

I suppose it could be said to be an exciting time to detect radiation, thanks to Fukushima, Chernobyl, and a thousand other events.

But monitoring radioactive releases doesn't save lives nearly as well as not having the releases in the first place. San Onofre Unit 2 is in bad shape and should not be restarted in any case, but especially because of the problems it has right now.


Nuclear reactors heat water to create steam to turn a turbine to spin a generator to produce electricity. There are two types of commercial nuclear power plants in the United States. About 2/3rds of the 104 U.S. power reactors are Pressurized Water Reactors (PWRs), which have three coolant loops, and the rest are the Fukushima-style Boiling Water Reactors (BWRs), which have only two coolant loops. San Onofre Nuclear Generating Station's reactors are both PWRs.

In both types of reactors, assemblies of zirconium tubes filled with uranium oxide pellets the size of a pinkie-finger bone heat recirculating water in the primary loop. That water is very radioactive, mostly with short-lived isotopes but also with "fuel fleas" of plutonium and uranium and other "transuranic" elements which have broken off of the ceramic pellets and escaped the zirconium cladding. Fission products, which are the resultant parts of splitting each atom, have also leached into the primary loop. Fission products are nearly always radioactive, and biologically active, too. Although most of the radioactivity in the primary loop is from the short-lived isotopes, with half-lives measured in seconds, plutonium's half-life (the time it takes for half of a substance to decay) is 24,000 years. (Half of what is left will decay in the next 24,000 years, and so on for about 10 to 20 half-lives, until it's all decayed.)

Water is pressurized to ~1200 psi in a BWR, which is low enough so that it turns to steam directly in the reactor core. The steam is piped to a turbine in another building.

In San Onofre and other PWRs, the water is pressurized to ~2200 psi, so that it does not boil as it loops through the system repeatedly -- it just goes up and down in temperature. A second loop of recirculating water is flashed to steam by touching the other side of thin tubes which carry the pressurized water on the inside. Thousands of these tubes are bundled together inside of school-bus-sized containers known as Steam Generators (SGs).

In both types of reactors, the steam exits the containment area, spins the turbines, and then is condensed back to water by the second loop in BWR designs, and the third loop in PWR designs. The last loop might be lake, river, or ocean (salt) water. Salt water is, of course, particularly corrosive.

There are various disadvantages unique to each design. The BWR design places highly radioactive water outside the containment area, pretty much defeating the purpose of the containment in the first place. The PWR's most unique disadvantage is the SGs, which have proven to be troublesome throughout the nuclear industry.

Both designs run the risk of a fire of the zirconium cladding, releasing the fission products and resulting in a meltdown of the fuel (as apparently happened in Fukushima), or even a fire of the fuel itself (releasing everything -- the worst of the worst and far worse than Chernobyl OR Fukushima was). There are many other possible failure scenarios known as "Design Basis Accidents," which they have to plan for, and "Beyond Design Basis Accidents," which they don't have to plan for because they're considered too rare to bother about, and which are usually unstoppable if they do occur (asteroid impacts, or greater-than-DBA earthquakes are two examples of BDBAs).


There are 9,737 tubes inside each of the four failing SGs at San Onofre. Each is shaped like an upside-down U. The tubes are about 4/100ths of a inch in wall thickness and about the diameter of an average adult finger. Primary coolant flows through the inside of the tubes. Secondary coolant rises along the outside of the tubes and picks up heat through them, and turns to steam. At the top of the U, it was still supposed to be mostly water, which dampens vibrations of the tubes pretty well, but it turned out to be mostly steam, which doesn't. The tubes banged into each other.

San Onofre's replacement SGs were highly modified from the original design, and no wonder: The original SGs had performed very poorly, wearing out several decades early. When forcing the rate payers to pay for the new steam generators a few years ago, it was said they would last 60 to 80 years or more, because they would be made with the new alloy "690", instead of the old alloy "600".

Across the nation, everybody's switching over, we were told.

The NRC accepted the new SGs as "like for like" replacements for the old ones, thus avoiding a costly and delaying -- and possibly damaging -- public inquiry into the whole affair. Neither the NRC nor SCE, nor the SG manufacturer in Japan, Mitsubishi Heavy Industries, bothered to do a thorough, careful, critical analysis of the new SGs' ability to perform as intended. Mockups and scale models were not made. Instead, computer programs were fed various parameters of the new design, but they returned invalid values, which were not cross-checked in any meaningful way.

The "hydrodynamic" calculations are too complex to be done by hand, they have to be done by computer, and even the computer models are crude estimations of the actual flow patterns of all the millions of gallons of pressurized hot water, "cold" water, and steam.


This evening (October 9th, 2012) in Dana Point there is to be a special NRC public meeting about the problems with the steam generators. Edison has asked the NRC for permission to restart San Onofre Nuclear Reactor Unit 2 at 70% power.

The NRC has already stated they will need "months" to review Edison's restart proposal, but the NRC hasn't said whether it will hold full evidentiary hearings regarding the botched steam generator replacement project. Unit 2's two new replacement steam generators, which are not even two years old, have more wear than was expected to be seen in the 40- to 60-year extended life of the plant. Unit 3 is in even worse shape and there are no plans to restart it at the present time.


We were promised better steam generators and what we got was Fluid Elastic Instability (FEI). FEI is a synchronized swaying of these huge bundles of heat exchanger tubes in unison until something breaks. A single tube in Unit 3 ruptured on January 31st, 2012, spewing hundreds of gallons of radioactive water out from the primary (hottest, most pressurized side) to the secondary side, where it flashed to steam, went through the turbines, and was condensed, at which point radioactive noble gases were released and detected.

That was just one leak in one tube, but thousands of tubes were damaged and in subsequent pressure testing of selected tubes, 8 more burst, some at pressures below what they are required to handle, and all eight of them at less than 3 times the normal operating pressure. That is unacceptable even to the NRC. More than 800 tubes were plugged in Unit 3 while Edison attempted to convince the experts that Unit 3 was just "settling in" (their term). SCE's attempts to restart Unit 3 fell on deaf ears even among San Onofre's staunchest supporters -- the NRC. (Unit 1 was closed in 1992 for a variety of reasons.)

The replacement SGs at San Onofre suffered significant premature wear damage not just from FEI, but also from a more common -- but never THIS severe in any other reactor in the country -- problem known as Flow Induced Turbulence (FIT). Unlike FEI, FIT becomes chaotic, but also has damaged thousands of tube in the SGs of both reactors at San Onofre.


Edison wants the NRC to see Unit 2 as having completely different problems from Unit 3, even though Unit 2's SGs are identical in every way possible to those in Unit 3, and even though they are showing the same sorts of wear patterns, just not as severely. More than 500 tubes have been plugged in Unit 2 "as a precautionary measure" according to Edison. Two tubes in Unit 2's SGs -- and hundreds in Unit 3's SGs -- had "tube-to-tube" damage, which should never occur at all and almost surely indicates FEI in addition to FIT.

Edison claims that they can safely run Unit 2 for five months at 70% power and then take a look to see how much wear occurred. Although it's likely there won't be much additional wear, it's also possible that FEI will still set in, and it's ALSO possible that, since the "70%" figure is purely administrative, it will be exceeded. And a run-away power excursion might cause the operators to feel they have no choice but to run at full heat-removal capacity, despite the plan to run at 70% power.

And besides that, there is little evidence that FEI is necessarily less likely at 70% power, and in addition, other problems which have plagued the nuclear industry, such as crud buildup, are much more likely to occur at the lower power setting.

It's not a sound plan -- it's a desperate measure by Edison to stay in the nuclear energy business instead of being forced to allow renewable energy systems to hook up to the grid without excessive fees or delays. It's a plan to keep Edison from going out of business to be replaced by citizen-owned local utilities. It's a plan that puts Southern Californians at grave risk for corporate profits. There are better jobs in the renewable energy sector for the employees. Nobody needs San Onofre to restart.


Three groups of outside experts have each reached the same conclusion about San Onofre Unit 2: DO NOT RESTART IT.

Arnie Gundersen is a former nuclear industry engineer. With his wife, also a former nuclear industry executive, and other experts, Arnie's team, Fairewinds Associates, concluded that it would not be safe to restart Unit 2.

Dan Hirsch, founder of Committee to Bridge the Gap, with his own team of experts and students, researched every other steam generator system at PWR reactors across America and concluded the same thing -- that San Onofre is worse than anywhere else and should not be restarted.

And another independent team that was formed around a San Onofre employee who left the company this past August reviewed Arnie Gundersen's and Dan Hirsch's reports, as well as numerous other technical reports from all over the world, and also reached the same conclusion -- that restarting San Onofre Unit 2 is unsafe. (I am associated with this third group as a concerned citizen.)

The NRC says they'll take "months" to decide if Edison's restart plan is logical, which has taken Edison more than nine months to deliver since the shutdown. But the plan is utter folly and the NRC should be able to see that as easily as the independent experts have seen it. This is a no-brainer: Keep San Onofre shut forever. It's not worth the risk.

Ace Hoffman
Carlsbad, CA


Three Fairewinds Associates reports on San Onofre steam generators (July 2012, May 2012, April 2012):




Videos and much more about the San Onofre steam generators available at the Fairewinds Associates web site:


Committee to Bridge the Gap press release on San Onofre steam generators:

Committee to Bridge the Gap report on SanO:

Dan Hirsch of Committee to Bridge the Gap speaks about the steam generator report at Del Mar city council:

DAB safety team's collection of reports:


Ace Hoffman
Author, The Code Killers:
An Expose of the Nuclear Industry
Free download: acehoffman.org
Blog: acehoffman.blogspot.com
YouTube: youtube.com/user/AceHoffman
Carlsbad, CA
Email: ace [at] acehoffman.org


1 comment:

  1. I'm frankly stunned by what has happened at San Onofre. I was a senior operator at Arkansas Nuclear One -- Unit 2 -- during the period of time their two steam generators were replaced circa 2000. ANO-2 is a very similar Combustion Engineering design (we used to share information with SONGS 2 and 3 routinely), and I had the opportunity to get involved with our own steam generator replacement project from a number of different discipline perspectives. Our generators were designed and built through Westinghouse--which subcontracted the actual manufacture through a company in spain (the last domestically manufactured nuclear steam generators were finished in the mid-90's). Flow induced vibration and other premature wear mechanisms were all significant issues during design and startup.

    I can not believe what an incredible nightmare this must be for the engineers and operators at SONGS. To have a tube rupture at 2 years in service, and 8 more burst under test conditions is simply beyond belief. Somewhere in the design and/or manufacture process an engineer has cost SoCal Edison billions.



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