Circular cracks in reactor vessels (revisited)

From: "Russell D. Hoffman" <>
Subject: Circular cracks in reactor vessels (revisited)
Cc: "David Lochbaum -- UCS" <>

Editor, North County Times
September 6th, 2001

To The Editor:

The article shown below would seem to indicate that David Lochbaum, nuclear safety engineer at the Union of Concerned Scientists, would agree with my comments about the importance of circular cracks in reactor vessels, and would therefore agree that Ray Golden, PR guy at San Onofre Nuclear (Waste) Generating Station, either doesn't understand the laws of physics or lied to your reporter (or perhaps Mr. Lochbaum can think of another explanation).

The North County Times should publish a more reasonable article about this issue than the one you published on August 13th, 2001 (my previous comments about that article are shown below).  And puhleez stop falling for Ray Golden's malarky!

Russell Hoffman
Carlsbad, CA

attachments:  Article clipped from RADIATION BULLETIN, my previous comments on this issue, August 13th NCT article

08/31/01 ****     RADIATION BULLETIN(RADBULL)       **** VOL 9.210


Environment News Service: AmeriScan: August 30, 2001
AmeriScan: August 30, 2001

 WASHINGTON, DC, August 30, 2001 (ENS) - The Union of Concerned
Scientists (UCS) warns that many U.S. nuclear reactors could be
susceptible to the cracking found in a South Carolina nuclear
power plant this spring.

For 10 years the Nuclear Regulatory Commission (NRC) ignored a
deterioration problem that affects the reactor vessels of two
thirds of the nation's nuclear power plants, the UCS charges.
While France and Japan moved to correct the problem in their
plants soon after it first surfaced in 1991, the NRC has rejected
efforts to replace the equipment in U.S. plants, even though the
problem emerged this spring at a nuclear plant in South Carolina.

"The federal agency entrusted to ensure that our nuclear reactors
run safely should not turn a blind eye to a serious safety
problem," said David Lochbaum, nuclear safety engineer at the
UCS. "We're lucky an accident hasn't occurred." The
deterioriation problem, found in the nation's pressurized water
reactors, is in the joints between the reactor vessel and the
tubes that house control rods. These joints, or nozzles, are
subject to severe stress from heating and are susceptible to
cracking - as was found in a French plant in 1991.

If these cracks were to grow large enough, they could lead to an
ejection of the control rod, leakage of reactor cooling water,
and failure of emergency systems, which could lead to a reactor
meltdown, UCS said.

"Instead of a Band Aid fix, the NRC needs to follow the lead
other countries have taken in protecting public safety by
replacing the cracked reactor vessel heads." said Lochbaum.
"Anything short of replacing this broken equipment needlessly
endangers the public."

Cracks discovered this spring at Oconee Unit 3 in South Carolina
extended almost 45 percent of the way around two nozzles. With a
crack this large, the pressure in the reactor could result in a
catastrophic rupture, UCS charges.

In 1994, the NRC wrote a report on this type of cracking, based
on an inspection of a single U.S. nuclear plant, and claimed that
cracks as large as the one at Oconee were not likely. In
contrast, similar plants in Europe and Japan underwent aggressive
safety precautions when the problem was discovered. "Waiting a
decade until an expected problem crops up is bad enough,"
Lochbaum said. "Waiting until an accident occurs is worse." * * *


NOTE: In accordance with Title 17 U.S.C. section 107 this
material is distributed without profit or payment to those who
have expressed a prior interest in receiving this information for
non-profit research and educational purposes only. For more
information go to:
[end of article clipped from RADBULL]


To: Editor, North County Times
From: Russell D. Hoffman
cc: Office of Public Affairs/NRC, Governor Gray Davis
Re: Circular cracks in PWR reactor vessels are far more dangerous than linear ones!
Date: August 15th, 2001

To The Editor:

As shown by his statements published in your paper on August 13th, Ray Golden, public relations spokesperson for San Onofre Nuclear (Waste) Generating Station (known as SONGS because the W (Waste) is ignored), obviously doesn't understand the laws of physics.  Again.

The reason a circular crack in a Pressurized Water Reactor (PWR, like San Onofre's two units) is so scary is because it is unquestionably several orders of magnitude more likely than a linear crack would be to "announce" its existence by catastrophically failing (popping out like a champagne cork, but the bubbly will be far more deadly).

This is basic physics.  Yet somehow, Mr. Golden has fooled the North County Times' reporter, Phil Diehl, into thinking that linear and circular cracking is similar, with similar solutions.  This is shown in Mr. Diehl's August 13th front-page article on the new Nuclear Regulatory Commission inspection requirements.  The ill-logic goes as follows: Since San Onofre has equipment to detect leaks in their primary coolant system as low as several gallons a day, we need not worry about these new "circular cracks" that PWR reactor heads seem to get as they age.


The SON(W)GS reactors are already quite old, having come online in 1983 and 1984.  The power plants where circular cracks were recently found (two of three reactors at the Oconee nuclear power station in South Carolina) came online in 1974.  San Onofre's reactors are about 20% bigger than the Oconee reactors (more heat, more liquid, more vibration, etc.).

The Oconee experience is extremely relevant.  We need to look at this problem here at San Onofre now, not when it happens to be convenient (currently scheduled for as late as 2003).

The reason a circular crack is so scary -- what prompted the NRC requirement for inspections, no doubt -- is that if a circular crack completes its circle, the thing within the circle (here, any of about 100 ports into the reactor vessel) can be pushed out by the extreme internal pressure, violently and catastrophically.  That mustn't happen.  It's not like a similar blow-out of any other (non-nuclear) pressurized vessel, which is serious enough.  Enormous quantities of lethal radioactive substances would be released from a reactor blowout, with the potential for catastrophic consequences for the local community and for the health of the planet.  Tourism losses alone would cost California billions if this happens -- it would be known immediately as "the worst nuclear accident in the U.S. since Three Mile Island", and could easily be a whole lot worse than that was.  The explosive release of some part (probably weighing hundreds or even thousands of pounds), followed by spewing of the 90,000 gallons of extremely hot, extremely radioactive, highly pressurized water throughout the containment building may only be the ugly start of a far worse scenario: a meltdown.

Sure, maybe we'll be lucky and it will end before that happens.  But no ECCS has ever been tested.  And note this: the Primary Containment at another nuclear power plant -- Monticello -- was recently found to be inoperable after 30 years, because shipping bolts had been left on that were supposed to have been removed when the plant was constructed.  The system wouldn't have worked if it was ever needed.  (See NRC event report #38130.)

The whole idea in running a nuclear reactor properly is to never do anything which might cause you to need the ECCS or other emergency cooling systems in the first place.  San Onofre is flagrantly flaunting that policy.

And even a casual look at the actual evacuation plan for the area surrounding San Onofre should prove to anyone that if the reactor blows, we die.  Chances are you won't be going anywhere.  The roads out will all be crowded, first with slow-moving traffic, then with cars filled with dead people.  It depends on the winds.

Circular cracks are far more likely than linear cracks to fail catastrophically as their first sign of trouble.  Sure they might leak first.  But linear cracks on the other hand will almost surely begin to leak long before becoming catastrophic.  Circular cracks on the other hand will not necessarily leak substantially before failure, certainly not the gallons a day that Mr. Golden claims they can detect when such amounts are lost from the 90,000-gallon primary coolant system.  Personally I doubt they "detect" such small leaks exactly.  My guess is that leaks of that magnitude would be detected by an alternate means, for example, because radiation levels would go up in the area where the leak leaks into.

And lastly, what's with the title of the article -- "Plant to be checked / San Onofre reactor will be examined for new type of crack"?  That's backwards!  What the article actually said, if you follow it's implications, was that Ray Golden at San Onofre doesn't understand the laws of physics, and thinks that circular cracks can always be detected in time, just like linear ones.  And Southern California Edison, the majority owners of the plant, evidently using similar illogical thinking, isn't going to stop the plants and look for these cracks.  Instead they are going to wait until the next scheduled refueling outage, in May 2002 (Unit II) and January, 2003 (Unit III).  So the title should have been something like this: "NRC notifies San Onofre of a newly-discovered serious danger -- circular cracks / San Onofre doesn't understand the ramifications, and, at our peril, plans to ignore the NRC instructions until it won't cost them any money to investigate the matter along with other maintenance chores.  Your life just isn't worth stopping the money spigot which feeds the shareholders of SCE."

That would have been a much more accurate title, since that is what actually appears to be happening, based on the articles' contents.


Russell Hoffman
Concerned Citizen
Carlsbad, CA

NCT article available at the following URL is shown below:

San Onofre to be checked for new kind of crack

Phil Diehl
Staff Writer

SAN ONOFRE ญญ Federal regulators have instructed nuclear power plant operators, San Onofre among them, to examine their reactors for a newly discovered type of cracking that could release radioactive steam into the domed containment structures.

A Nuclear Regulatory Commission bulletin issued Aug. 3 asks nuclear power plant operators to look for circular cracks like those discovered recently for the first time in the heads of two reactors at the Oconee nuclear power plant in South Carolina, said Sue Gagner, a spokeswoman at the commission's headquarters in Rockville, Md.

San Onofre nuclear plant will be inspected for cracks that could lead to radioactive steam leaks.

"What made (the new cracking) unusual ... was that it was circumferential rather than up and down," Gagner said. Only linear, or "axial," cracks had been discovered previously in the nozzles that penetrate reactor vessels.

The new cracks were discovered in the welds around nozzles holding the control rods that slide in and out of the reactors. That makes the cracks more dangerous than other types because the nozzles are more likely to break loose from the vessel, she said.

None of the new circular cracks has been found at the San Onofre plant, a spokesman there said this week.

Nuclear reactors such as the two at the San Onofre nuclear plant along Interstate 5 between Oceanside and San Clemente have pressurized vessels about 40 feet tall made of thick steel that hold radioactive fuel rods submerged in water. Each pressurized vessel is penetrated by about 100 nozzles that hold control rods and other instrumentation.

The reactor's pressure vessel and its nozzles are within the concrete-and-steel dome built to withhold any radioactive release from the plant's primary coolant system.

The failure of a nozzle in an operating reactor would release large amounts of hot water that would flash to steam within the containment structure. Water from the primary system usually contains radioactive contamination. Federal regulators require nuclear plant operators to rehearse several times annually ways to handle any break in the reactor cooling system, though they say the chances of a large radioactive release are remote.

None of the circular cracks found so far at Oconee has allowed the penetration nozzles to break away, regulators said, though some water has leaked through the cracks.

"The problem is probably age-related," Gagner said. The Oconee plant began commercial operation in 1974.

Age-related degradation is one of the leading problems of the nuclear industry, according to critics such as the Nuclear Information Resource Service. Cracks are routinely repaired in reactor steam generators, and degradation has been found in other key components subject to extreme heat and pressure.

"The industry is plagued with age-related deterioration mechanisms unique to nuclear power operations," according to Paul Gunter, a researcher with Nuclear Information Resource Service, which regularly posts information at its Website at

"Chronic exposure to extreme radiation, heat, pressure, fatigue and corrosive chemistry are combining to cause embrittlement of metal, cracking, and erosion of components integral to the protection of the public's health and safety."

Nuclear industry officials have said problems such as cracking arise with age, but that those problems can be monitored and corrected with no significant risk to workers or the public.

San Onofre's operator, Southern California Edison Co., found and repaired linear cracks in reactor vessel nozzles in the Unit 3 reactor during routine refueling and maintenance work in 1997.

That reactor began commercial operation in 1984. The other operating San Onofre reactor, Unit 2, first went online in 1983.
The Unit 1 reactor, which operated from 1968 to 1992, is being demolished.
The reactor was retired to avoid the expense of costly additional safety upgrades required by federal regulators after the Three Mile Island accident in 1979 near Harrisburg, Pa.

Edison officials have not found cracks of any type in recent inspections of the reactor vessel, said plant spokesman Ray Golden.

"As a result of this (bulletin) we will do a more detailed inspection in the upcoming outages," Golden said, noting that Unit 2 is scheduled for refueling and maintenance next May, and Unit 3 is to start in January, 2003.

"Meanwhile, we normally monitor the entire system."

Detection systems within the plant allow operators to see a leak as low as two or three gallons per day in the 90,000-gallon primary cooling system, Golden said. That allows cracks to be identified before a leak becomes catastrophic.

The commission's bulletin went to the operators of all 69 commercial pressurized-water reactors in the United States. The pressurized-water reactors are designed to keep water in the primary coolant system pressurized so that it will not boil.

The primary coolant heats a secondary loop that turns to steam and spins the plant's electricity-generating turbines.

The country also has about 35 commercial boiling-water reactors, in which the primary coolant is allowed to turn to steam.

San Diego Gas & Electric Co. owns 20 percent of the two San Onofre reactors and distributes about 20 percent of the electricity produced there.

Contact staff writer Phil Diehl at (760) 901-4087 or
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First posted October 13th, 2001.

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