Widespread problem: concrete degradation at nuclear plants

[kristopher]

NextEra and NRC to continue monitoring ASR degradation at Seabrook Station Nuclear Power Plan

Degrading concrete at a New Hampshire nuclear plant has prompted the Nuclear Regulatory Commission to alert all of its facilities and applicants to the same risk elsewhere.

The Seacost Online reported on a meeting this week between NextEra Energy, operators of the Seabrook nuclear plant, and the U.S. Nuclear Regulatory Commission on Monday in Bethesda, Md., in which the utility reported that the cause of concrete degradation at Seabrook Station is more pervasive than originally stated, has already brought some of the structures below licensing standards and could further delay the nuclear plant’s effort to extend its operating license to 2050.

The alkali-silica reaction (ASR, caused by the interaction of water and concrete) that has been identified as the reason for the degradation is “outside current licensing requirements, and was first noted at the plant in 2010,” according to Michael Collisions, design engineer manager for NextEra Energy.

Alkali-Silica Reaction-induced (ASR) concrete degradation, a slow chemical degradation process that occurs when alkalis—usually from cement—react with certain types of silica in the aggregate when moisture is present.

The reaction produces an alkali-silica gel that can absorb water and expand to cause micro-cracking of the concrete. Excessive expansion of the gel can lead to significant cracking....

http://enformable.com/2012/04/nextera-and-nrc-to-continue-monitoring-asr-degradation-at-seabrook-station-nuclear-power-plant/

[kristopher]

1. Looking for PhD student: Influence of Li on ASR degradation in concrete

PhD student: Influence of Li on ASR degradation in concrete
Degradation of concrete structures due to ASR is a complex mechanism, i.e., it is caused by a reaction between the hydroxyl ions in the alkaline cement pore solution in the concrete and reactive forms of silica in the aggregate. This Ph.D project is done in cooperation with Delft university. The project is part of the STW Program Perspectief IS2C (Integral Solutions for Sustainable Construction: www.is2c.nl

Function PhD-student
Departments Department of Applied Physics
FTE 1,0
Date off 15/05/2012
Reference numberV34.1424
Apply now Inform a friend

Degradation of concrete structures due to ASR is a complex mechanism, i.e., it is caused by a reaction between the hydroxyl ions in the alkaline cement pore solution in the concrete and reactive forms of silica in the aggregate (e.g; chert, quartzite, opal, strained quartz crystals). The gel which is produced in this reaction, increases in volume by taking up water and so exerts an expansive pressure, resulting in failure of the concrete. The underlying mechanisms are poorly understood and presently there is no good model for the development of damage. Lithium ions are known to positively affect the degradation process but the mechanism is not understood. This project aims to largely improve service life assessment and preservation of concrete structures with regard to ASR by elucidating the degradation process In this project we want to measure and model the effect of Li on ASR. This work should be a combination of experimental work and modeling.


This Ph.D project is done in cooperation with Delft university. The project is part of the STW Program Perspectief IS2C (Integral Solutions for Sustainable Construction: www.is2c.nl). This IS2C program is aiming to enforce new innovations in the current state of the art of service-life assessment and to set a new standard for sustainable construction and is a cooperation between universities and companies. ...

http://jobs.tue.nl/en/job/phd-student:-influence-of-li-on-asr-degradation-in-concrete-138163.html

[bananas]

4. The wear-out phase of the bathtub curb - compounded by the fact we're in uncharted territory.

Everything degrades.
Concrete degrades.
Rebar degrades.
Wiring degrades.
Plumbing degrades.

Even knowledge degrades.
The most experienced workers are retiring.

The utilities are not only running these things past their design life,
they're also uprating them to generate more power,
putting them under more stress - and more rapid degradation.

[backwoodsbob]

10. of course the most experienced workers are retiring

the OLDEST..most experienced workers are the ones that retire in ANY industry

[kristopher]

11. The nuclear industry identifies skilled labor shortage...

...as a major problem in all areas (construction, operations and maint) with about half of their workforce becoming eligible for retirement within 5-10 years IIRC.

[kristopher]

2. Good thing the NRC...

...wasn't really serious about the original design specs for the concrete (or any other aspect of the plants apparently) or we might conclude the spokesman for the company really wasn't sincere when he added the last word to this sentence:
"The alkali-silica reaction “has not, and will not, impact our ability to operate our plant safely".’’

"Markey, Tierney Seek Meeting on Seabrook Plant Safety"
http://www.boston.com/news/local/new_hampshire/articles/2012/04/19/markey_tierney_seek_meeting_on_seabrook_plant_safety/

[AtheistCrusader]

3. I take it they cannot plate the concrete with any sort of water-exclusion barrier

because it would interfere with inspection on the concrete itself?

[bananas]

5. The damage has already been done

The licensee believes that the waterproof membrane was damaged during original installation or backfill activities causing water intrusion that resulted in the ASR problems.

The meeting this week was focused on areas surrounding how the concrete has already been affected by the reaction, what effect the reaction has had on the rebar that supports the concrete, and the rate of degradation.

The strength of the concrete had been reduced by 22 percent compared to samples taken at the time the concrete was poured during construction in 1979.

[AtheistCrusader]

6. 22% through and through?

Welp. That will reduce the service lifetime of the reactor.

[kristopher]

7. That won't stop them from extending the operating licenses.

I believe the NRC is so firmly in the industry's corner that it is going to take a disaster here to get them to actually do anything that the industry doesn't want.

[AtheistCrusader]

8. There's probably an enormous margin of safety involved

but that didn't help at Fukushima Dai-ichi, because they under-planned for the size of a potential quake, and not only was the cooling system broken, but the building integrity was compromised.

No reason that couldn't happen here too.

You know I'm generally favorable of nuclear power, at least in theory, but this sort of thing is a major gut check, because nuclear power is expensive mostly to make it some specific level of 'safe'. When it turns out the cost was that high AND the level of safety expected for that price isn't actually there, well...

That starts casting it in a different light.

[kristopher]

9. The bathtub curve that bananas mentioned exists as a reflection of reality

We would do well to heed it.

Safety rules loosened for aging nuclear reactors
'We can't compromise on safety. I think the vulnerability is on these older plants,' says retired safety designer

LACEY TOWNSHIP, N.J. — Federal regulators have been working closely with the nuclear power industry to keep the nation's aging reactors operating within safety standards by repeatedly weakening those standards, or simply failing to enforce them, an investigation by The Associated Press has found.

Time after time, officials at the U.S. Nuclear Regulatory Commission have decided that original regulations were too strict, arguing that safety margins could be eased without peril, according to records and interviews.

The result? Rising fears that these accommodations by the NRC are significantly undermining safety — and inching the reactors closer to an accident that could harm the public and jeopardize the future of nuclear power in the United States.

Examples abound. When valves leaked, more leakage was allowed — up to 20 times the original limit. When rampant cracking caused radioactive leaks from steam generator tubing, an easier test of the tubes was devised, so plants could meet standards.

Failed cables. Busted seals. Broken nozzles, clogged screens, cracked concrete, dented containers, corroded metals and rusty underground pipes...

http://today.msnbc.msn.com/id/43455859/ns/today-today_news/t/safety-rules-loosened-aging-nuclear-reactors/#.T4Grue3N7dk


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