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NRC Steps Up Review of Problem Concrete

Monday, September 17, 2012

Federal regulators will conduct additional inspections and reviews to independently verify and assess work being done to address degrading concrete at the Seabrook Station Nuclear Plant.

Plant officials discovered cracking in the plant's control building in August. 2010. In December 2011, the Nuclear Regulatory Commission issued a general alert to all of its facilities and applicants regarding the risk of the same problem elsewhere.

Nuclear Regulatory Commission

Patterned cracking like this can be indicative of ASR-induced degradation. The Nuclear Regulatory Commission distributed the photo as a generic example from outside the nuclear industry.

NRC documents also now indicate the problem is affecting multiple structures at Seabrook.

ASR Degradation

The problem is known as 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.

Extra Reviews

On Friday (Sept. 14), the NRC announced the additional reviews—a deviation from the general Reactor Oversight Process—at New Hampshire’s Seabrook plant, which is operated by NextEra Energy Seabrook LLC.

Matthew Trump / Creative Commons

The Seabrook Station Nuclear Plant has found ASR-induced concrete degradation in multiple structures on site.

Although the agency’s process does not require the increased oversight, NRC’s “staff believes the additional inspections and assessments are needed to support the review of licensee commitments and planned large-scale concrete specimen testing by the licensee, the development of staff technical guidance, and stakeholder communications and outreach activities,” NRC Region I Administrator Bill Dean wrote in a memorandum to Executive Director for Operations William Borchardt.

That request for further resources has now been approved via a “Deviation Memorandum,” which refers to a deviation from the Reactor Oversight Process, the NRC said in a statement.

Safety Assured

The NRC continues to say that the problem does not threaten the structures’ integrity, but the agency is still investigating.

“While the extent of the problem at Seabrook is still being evaluated, the NRC has determined that the structures identified to be affected by ASR can perform their safety function when called upon,” the agency said in a statement.

Copies of the Deviation Memorandum and other documents related to the Seabrook ASR issue are available at www.nrc.gov. 

Comment from Chuck Pease, (9/18/2012, 11:14 AM)

Safety Assured The NRC continues to say that the problem does not threaten the structures’ integrity, but the agency is still investigating. “While the extent of the problem at Seabrook is still being evaluated, the NRC has determined that the structures identified to be affected by ASR can perform their safety function when called upon,” the agency said in a statement. WOW a claim by the NRC that ASR is not a issue with the saftey concerning structural integrity of concrete structures affected by ASR. Wonder what those folks are smoking!

Comment from Tom Schwerdt, (9/18/2012, 11:36 AM)

I'm shocked the NRC took this long to notice ASR exists. It has been a major, known problem in transportation for quite awhile. ASR susceptibility should always be a major consideration in concrete mix design.