Davis-Besse scrutinized: Team seeks lessons in power plant's relapse

[kristopher]

Mar. 19--OAK HARBOR, Ohio -- Federal regulators want to know what, if any, lessons from Davis-Besse's latest relapse can be applied to the nation's 103 other nuclear plants, according to one of the key members of the special inspection team dispatched to the site by the U.S. Nuclear Regulatory Commission.

Jay Collins, a senior materials engineer at the NRC's headquarters in suburban Washington, said it will take some time before he and others on the inspection team discern what might be applicable to the rest of the industry and what is potentially unique to Davis-Besse, one of only seven plants with a Babcox & Wilcox design.

Since at least June of 2002, during a meeting of the NRC's Advisory Committee on Reactor Safeguards, the agency has known that the nation's Babcox & Wilcox plants typically operate hotter than others.

Davis-Besse, with an operating temperature of 605 degrees, was the nation's hottest in 2002. It typically operated 20 degrees warmer than the industry average of 585 degrees.

Mr. Collins said it ...
http://www.istockanalyst.com/article/viewiStockNews/articleid/3961818

[Statistical]

1. Glad to see NRC on the job as usual ...

keeping the largest source of emission free power in this country as safe as possible.

[kristopher]

2. How much of a "close call" was that big hole they found a few years ago there?

You know, the one they only discovered by chance...

[Name removed]

3. Deleted message

Message removed by moderator. Click here to review the message board rules.

[Kolesar]

4. Deflection is the tactic for those on the defensive...eom

[Statistical]

5. If by "chance" you mean periodic and routine inspection during refeuling

then you are right they discovered it by "chance".

[kristopher]

6. Do you really want to make such a dishonest and easily refuted assertion?

Through how many fueling cycles and routine inspections did that damage escape notice?

What was the time required to for the acid solution to eat through all that steel?

[Statistical]

7. Did they or did they not discover the corrosion durring a fueling outage & maintenance inspection.

Also they learned from that mistake. Now the control rod "nozzles" are inspected with ultrsound to allow inspectors to "see" inside the metal and discover damage before it is obvious.

That technique has worked very effectively at current Davis Besse fueling outage.

[kristopher]

8. Do you really want to make such a dishonest and easily refuted assertion?

Through how many fueling cycles and routine inspections did that damage escape notice?

What was the time required to for the acid solution to eat through all that steel?

[Throckmorton]

9. Well, the reactor head was replaced in 2003

So, I'd say 5 fuel cycles, tops.

[joshcryer]

12. Yeah, it was a major lapse, but the NRC did fine them tens of millions.

It's not like they got away with the bad behavior.

[Kolesar]

10. Statistical is acting like he does not know you are talking about the 2002 near-disaster

He is acting like the subthread is about the recent revelation of cracks in the "replacement" vessel lid.

[joshcryer]

13. Um, no, he pointed out specifically that that incident led to more robust inspections.

Don't be dishonest.

[kristopher]

14. Yeah, I know. Here are the bare facts as recited by the Nuclear Regulatory Commission

Overview of Reactor Vessel Head Degradation

On February 16, 2002, the Davis-Besse Nuclear Power Station in Oak Harbor, Ohio, began a refueling outage that included inspecting the nozzles entering the head of the reactor pressure vessel (RPV), the specially designed container that houses the reactor core and the control rods that regulate the power output of the reactor. Of these vessel head penetration (VHP) nozzles, the licensee's inspections focused on the nozzles associated with the mechanism that drives the control rods, known as the control rod drive mechanism (CRDM). Both the inspections and their focus were consistent with the licensee's commitments in response to NRC Bulletin 2001-01, "Circumferential Cracking of Reactor Pressure Vessel Head Penetration Nozzles," which the agency issued on August 3, 2001.

In conducting its inspections, the licensee found that three CRDM nozzles had indications of axial cracking, which had resulted in leakage of the reactor's pressure boundary. Specifically, the licensee found these indications in CRDM nozzles 1, 2, and 3, which are located near the center of the RPV head. The licensee reported these findings to the NRC on February 27, 2002, and provided supplemental information on March 5 and March 9, 2002. The licensee also decided to repair the three leaking nozzles, as well as two other nozzles that had indications of leakage but had not resulted in pressure boundary leakage.

The repair of these nozzles included roll expanding the CRDM nozzle material into the material of the surrounding RPV head and then machining along the axis of the CRDM nozzle to a point above the indications in the nozzle material. On March 6, 2002, the licensee prematurely terminated the machining process on CRDM nozzle 3 and removed the machining apparatus from the nozzle. During the removal, the nozzle was mechanically agitated and subsequently displaced (or tipped) in the downhill direction (away from the top of the RPV head) until its flange contacted the flange of the adjacent CRDM nozzle.

To identify the cause of the displacement, the licensee investigated the condition of the RPV head surrounding CRDM nozzle 3. This investigation included removing the CRDM nozzle from the RPV head, removing boric acid deposits from the top of the RPV head, and ultrasonically measuring the thickness of the RPV head in the vicinity of CRDM nozzles 1, 2, and 3.

Upon completing the boric acid removal on March 7, 2002, the licensee conducted a visual examination of the area, which identified a large cavity in the RPV head on the downhill side of CRDM nozzle 3. Followup characterization by ultrasonic testing indicated wastage of the low alloy steel RPV head material adjacent to the nozzle. The wastage area was found to extend approximately 5 inches downhill on the RPV head from the penetration for CRDM nozzle 3 and was approximately 4 to 5 inches at its widest part. The minimum remaining thickness of the RPV head in the wastage area was found to be approximately 3/8 inch. This thickness was attributed to the thickness of the stainless steel cladding on the inside surface of the RPV head, which is nominally 3/8 inch thick.

The investigation of the causative conditions surrounding the degradation of the RPV head at Davis-Besse is continuing. Boric acid or other contaminants could be contributing factors. Other factors contributing to the degradation might include the environment of the RPV head during both operating and shutdown conditions (e.g., wet/dry), the duration for which the RPV head is exposed to boric acid, and the source of the boric acid (e.g., leakage from the CRDM nozzle or from sources above the RPV head such as CRDM flanges).

http://www.nrc.gov/reactors/operating/ops-experience/vessel-head-degradation/images.html

[joshcryer]

11. The Conditional Core Damage Probability was .006.

Less likely than you getting killed today by driving to Church. Or if you're over 50, less likely than you dying for any reason whatsoever this very moment.

[kristopher]

15. That incident had assholes puckering all over the country.

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=237252&mesg_id=237533

[joshcryer]

16. Yes, when typical CCDPs are in the .00001's... .006 is shit your pants.

But still less likely than you dying right ... now, assuming you're over 50.

[kristopher]

17. That is a pathetic response...

The repair of these nozzles included roll expanding the CRDM nozzle material into the material of the surrounding RPV head and then machining along the axis of the CRDM nozzle to a point above the indications in the nozzle material. On March 6, 2002, the licensee prematurely terminated the machining process on CRDM nozzle 3 and removed the machining apparatus from the nozzle. During the removal, the nozzle was mechanically agitated and subsequently displaced (or tipped) in the downhill direction (away from the top of the RPV head) until its flange contacted the flange of the adjacent CRDM nozzle.

To identify the cause of the displacement, the licensee investigated the condition of the RPV head surrounding CRDM nozzle 3. This investigation included removing the CRDM nozzle from the RPV head, removing boric acid deposits from the top of the RPV head, and ultrasonically measuring the thickness of the RPV head in the vicinity of CRDM nozzles 1, 2, and 3.

Upon completing the boric acid removal on March 7, 2002, the licensee conducted a visual examination of the area, which identified a large cavity in the RPV head on the downhill side of CRDM nozzle 3. Followup characterization by ultrasonic testing indicated wastage of the low alloy steel RPV head material adjacent to the nozzle. The wastage area was found to extend approximately 5 inches downhill on the RPV head from the penetration for CRDM nozzle 3 and was approximately 4 to 5 inches at its widest part. The minimum remaining thickness of the RPV head in the wastage area was found to be approximately 3/8 inch. This thickness was attributed to the thickness of the stainless steel cladding on the inside surface of the RPV head, which is nominally 3/8 inch thick.

- NRC

Nuclear Regulatory Commission Chairman Nils Diaz told the newspaper that his agency will not tolerate having history repeat itself at Davis-Besse.... Dr. Diaz said Davis-Besse stands out as a "prime example" of what can happen when the NRC and the nuclear industry let down their guard.

The plant’s reactor head was so corroded that a pineapple-sized hole was found through six inches of carbon steel and only a cracked and buckling layer of stainless steel as thin as a pencil eraser had prevented a rupture that would have allowed radioactive steam into the reactor’s containment building.

Investigators determined that the emergency water supply system that was in place at the time to cool down the reactor was so poorly designed it might not have worked.

Davis-Besse’s close call "should not have been possible," Dr. Diaz told the conference attendees....

http://www.toledoblade.com/apps/pbcs.dll/article?AID=/20040311/NEWS17/103110139/-1/NEWS

But it was possible, and that is the entire point.

[joshcryer]

20. Yes, it was possible, about as possible as you dying right now if you're over 50.

Really, look at mortality tables. Over 50 is around .007 or higher. (The 100s approach 1.0.)

For the NRC it was a very very big deal. For reality? It was a big deal but not as dire as you make it out to be.

[kristopher]

19. No comment on posts 17 and 18?

Your claims regarding the statistical measure of safety for nuclear power seem sort of irrational when viewed against the numerous design and operations errors (see post 18) that almost resulted in a disaster at Davis-Besse, and that is the entire point.

Nuclear proponents want to create the impression that the actual risk of major problems is so low (0.0001) that it is absurd to worry about it happening; the implication being that the REAL level of risk is, for all intent and purpose, actually zero.

While it is reasonable to consider the statistics, it is also valuable to look at why they are pushed so hard with the intent of creating the impression of ZERO risk; which is obviously that the consequences of failure if it should occur are so horrific that only zero risk is a tolerable level in the mind of rational people.

Well, this incident (like TMI, Chernobyl and 2 space shuttle disasters) demonstrates that there is no such thing as ZERO risk in even the most rigorously designed and policed system.

[kristopher]

18. Davis Besse retrospective (Union of Concerned Scientists)

Davis-Besse Retrospective
Download: Davis-Besse Retrospective | Davis-Besse: The Reactor with a Hole in its Head

On March 6, 2002, workers repairing a cracked control rod drive mechanism (CRDM) nozzle at the Davis-Besse Nuclear Power Station in Ohio discovered a football-sized cavity in the reactor vessel head.<1> Their finding is linked to two other discoveries 15 years earlier. On March 13, 1987, workers at Turkey Point Unit 4 in Florida discovered that a small leak of borated water had corroded the reactor vessel head. Their revelation prompted the Nuclear Regulatory Commission (NRC) to require all owners of pressurized water reactors, including Davis-Besse, to take specific measures to protect plant equipment from boric acid corrosion.<2> On March 24, 1987, the NRC learned that control room operators at the Peach Bottom Atomic Power Station in Pennsylvania had been discovered sleeping while on duty. That revelation prompted the NRC to issue an order on March 31st requiring Peach Bottom Unit 3 to be immediately shut down.<3>

The three findings spanning 15 years are intertwined. Turkey Point demonstrated that a small amount of boric acid leaking onto the reactor vessel head corrodes carbon steel at a high rate. Had the FirstEnergy Nuclear Operating Company, the owner of Davis-Besse, remembered Turkey Point's lesson, the serious damage at Davis-Besse would have been averted. Peach Bottom demonstrated that a pervasive safety culture problem creates unacceptable conditions for operating a nuclear power plant. Had NRC remembered either Turkey Point's or Peach Bottom's lesson, they would have issued the order they drafted to shut down Davis-Besse. It would have been the first shut down order issued by the agency since the Peach Bottom order. But both FirstEnergy and the NRC forgot the past and relived the wrong event from March 1987 by having yet another reactor vessel head damaged by boric acid corrosion.

Many individuals, from both within and outside the NRC, have accused the agency's move towards risk-informed decision-making as the reason for its failure to issue the order to shut down Davis-Besse. On the contrary, the NRC's handling of circumferential cracking of control rod drive mechanism (CRDM) nozzles as reported by the Oconee nuclear plant in February 2001 was a successful demonstration of proper application of risk-informed decision-making ¾ with the sole and significant exception of its mistake in not issuing the shut down order for Davis-Besse. But even that mistake, as bad as it was, does not impugn the risk-informed decision-making process for the simple reason that the NRC deviated from that process. Had the NRC adhered to its risk-informed decision-making process, it would have issued the shut down order for Davis-Besse and capped off a stellar example of how this process can and should be used.

In February 2001, the NRC learned of a new aging mechanism, the circumferential cracking of stainless steel CRDM nozzles based on inspection results from Oconee. The NRC properly reacted to this finding by revisiting the nuclear industry's inspection regime for CRDM nozzles. It determined that the existing inspection regime did not provide adequate assurance that circumferential cracks would be identified and repaired. The NRC did not require all plant owners to immediately address this inspection shortfall, which would have imposed an unnecessary regulatory burden on those plants with low susceptibility for the problem. Nor did the NRC allow all plant owners to address the shortfall at their next regularly scheduled refueling outage, which would have imposed an unnecessary challenge to safety margins at those plants with high susceptibility. Instead, the NRC applied risk-informed decision-making by issuing Bulletin 2001-01 in August 2001 to all owners of pressurized water reactors. This Bulletin required the high susceptible reactors to resolve the inspection shortfall by December 2001, the medium susceptible reactors to resolve the inspection shortfall at their next regularly scheduled outage, and merely collected information from the low susceptible reactors.

Only two reactors with high susceptibility ...
http://www.ucsusa.org/nuclear_power/nuclear_power_risk/safety/davis-besse-retrospective.html



It is worth remembering the chortling of nuclear power proponents about how new regulatory regime concentrates virtually all regulatory oversight into the hands of the NRC, while at the same time unambiguously promoting the goal of a "nuclear revival" as being crucial to the continued existence of the industry.

Do you think the NRC is committed to seeing this industry not only continue, but grow? Is that the role of a regulatory agency that is charged with safety oversight an industry with such potential for calamity?

[joshcryer]

21. If a regulatory commission wants to continue existing, yes, it should help that industry grow.

A society without nuclear specialists would stagnate technologically and intellectually. I for one would prefer that will is spent building nuclear power that builds cleaner energy than one that solely exists for the creation of nuclear bombs. You get rid of clean nuclear power bombs are the only place nuclear specialists can go.

[Kolesar]

22. Alcohol, tobacco, and firearms...eom

[kristopher]

23. That is a problem with bureaucracies, it is not a feature of value.

We don't create regulatory agencies to perpetuate their existence, we create them to ensure the interests of the public are being managed properly.

The single largest FAILING of bureaucracy is that it tends towards a "my turf" mentality that results in bloat and perpetuation of programs and policies that do not meet basic standards of worth to the public.

The range of basic ideas you've demonstrated a need to brush up on grows with every post you make.

[joshcryer]

24. I suppose it's not up to the EPA to foster the development of clean technologies.

:rofl:

[kristopher]

25. What "industry" do they help "to grow"?

Aside from the fact that "industry" is in an antagonistic relationship with the EPA, not a symbiotic relationship, the EPA provides a wonderful example of how ineffective a bureaucracy can become when the administration (BushCo) is determined to allow the regulated industries free rein.

Now if that happens with the EPA, where the regulators are a fairly distinct career group than those in the industries they regulate; just imagine the potential for regulatory failure that the NRC and the nuclear industry represent. Hell, we don't have to imagine at all, all we have to do is examine the hole in Davis-Besse's reactor head to see the process in action.

What REALLY caused the hole in the reactor head?
Complacency on the part of the plant's owner and the NRC really caused the hole in the reactor head.

Evidence of complacency by the plant's owner includes:
● When problems with leaking CRDM flanges surfaced years agon, workers at Davis-Besse proposed a
modification that would enable better inspections of the reactor vessel head. Management approved this
modification, but then deferred its implementation.

● When boric acid crystals were repeatedly found coating the outer surface of the reactor vessel head,
workers at Davis-Besse merely tried cleaning them away. The plant's design required all components
coming into contact with reactor water to be made of corrosion-resistant materials or to be clad with a
protective layer of stainless steel. The outer surface of the reactor vessel head was neither
corrosion-resistant nor coated with stainless steel. Management tolerated a degraded condition prohibited
by the plant's design.


● Armed with knowledge about leaking CRDM flanges at Davis-Besse causing the outer surface of the
reactor vessel to be coated with boric acid crystals, about the high likelihood that one or more CRDM
nozzles would be cracked, and about elevated iron oxide levels within the containment building,
management begged the NRC in fall 2001 to allow it to skip the reactor vessel head inspection mandated
by the end of the year.

Evidence of complacency by the NRC includes:
● Less than two years after another similarly skipped inspection contributed to an accident at the Indian Point
2 nuclear plant, the NRC allowed Davis-Besse to skip the mandated 2001 year-end inspection.

● After CRDM nozzle cracking was reported at Bugey Unit 3 in 1991, the NRC initiated a research program
to examine the issue for US reactors. As the NRC research program was plodding along, Greenpeace
International petitioned the NRC on March 24, 1993, to require inspections of CRDM nozzles at all US
reactors and to make the inspection results publicly available. Greenpeace also sought to shut down all
reactors with cracked nozzles. The NRC denied Greenpeace's requests nearly two years later.<3>

● NRC denied Greenpeace's petition in large part because of a research report prepared by the Idaho
National Engineering Laboratory for the NRC. This report, released in October 1994, concluded "CRDM
nozzle cracking is not a short-term safety issue. All the detected cracks on the nozzle inside surface are
axially oriented. ...Some analyses have shown that short, circumferential cracks on the outside surface are
possible; however, these cracks are not expected to grow through-wall...." At the time of this conclusion, a
grand total of one (1) US nuclear plant (Point Beach Unit 1in Wisconsin) had been inspected for CRDM
nozzle cracking.<4>

● After large, through-wall, circumferential cracking was found on the outside surface of two CRDM nozzles
at Oconee Unit 3 in August 2001, the NRC asked plant owners to write them about inspections of CRDM
nozzles and the extent of identified cracking. In essence, the NRC only did part of what Greenpeace asked
eight years earlier.

● After a huge gaping hole was found in the reactor head at Davis-Besse, the NRC finally sought the
inspections that Greenpeace requested nine years earlier.


UCS -- Aging Nuclear Plants -- Davis-Besse: The Reactor with a Hole in its Head