Seabrook’s Concrete

The Story of Seabrook’s Concrete Concerns

I. Origins

Seabrook Station nuclear power plant was licensed in 1976 by the NRC. It was built by PSNH and a consortium of other companies on a design basis provided by the NRC. The portland concrete used to form Seabrook’s floor, containment building, and most of its structures was done by Parini and came from Maine. The entire plant was built from the same aggregate. Construction was completed in 1986. The plant went online in 1990 with a 40-year operating license. The current owner is NextEra Energy Resources.

Although the current license does not expire until 2030, in 2010 NextEra applied for an extension of Seabrook’s license till 2050.

II. Problems come to the surface

Flaws in Seabrook’s concrete began even during construction, as reported by several sources. Concrete was poured in below freezing temperatures contrary to procedure for proper solidification; cement which had been rejected by a safety inspector was poured anyway. There are reports of items such as beer bottles and cans tossed into the concrete, which could cause air pockets, and superficial patches were applied to cracks, resulting in improperly cured cement.

Settling of the structure caused cracking in the containment building before Seabrook began operating. The NRC told the owners to repair them with Vantex CP, which was known to be only a superficial solution, as stated by the dealer.  (Employees Legal Project, CMSEP Inc.,1986) This shows that cracking of the concrete has been a persistent problem at Seabrook. These  early repairs have not been re-examined.

In addition, steel rods designed to support the containment wall were improperly severed at the second storey level. In 1984 – during the construction process – an NRC report talks about groundwater infiltration into cracks affecting concrete and rebar, and stated a water-proofing membrane had not accomplished its purpose. Cracking of concrete could be heard by workers between the waste recessing building and the Diesel generator building, but this area was not inspected by the NRC.  The cooling tower concrete was poured in 2 layers which are not connected to each other.  The buildings have contained flaws and damages since before the plant went online, providing grounds for serious concern about the integrity and safety of the building and about the extent to which Seabrook’s owners care about the quality of the structure.

III. Concerns for safety proliferate

Here is a brief overview of safety concerns since Seabrook went online:

  • In 1999  a leak in the spent fuel pool  caused a build-up of  radioactive water in the space between the containment building and the containment enclosure building.
  • In 2005, concrete degradation was first identified at the Seabrook nuclear power plant. 84 areas requiring engineering evaluation were listed by the NRC. Below and above grade cracking was identified.
  • The groundwater was determined to be “aggressive” by testing results in 2008-9.
  • Heavy corrosion of the containment liner plate was determined in 2009.
  • In 2009 the NRC sent a relicensing team to Seabrook who evaluated the structures. Visual inspection revealed signs of alkali-silica reaction (ASR). Core samples were evaluated at a lab in Illinois, which confirmed ASR.
  • In 2010, the NRC reported they were without a technical basis or regulatory basis for ASR, the industry had no experience or knowledge of ASR concrete degradation, and ASR research was limited and no long-term studies on nuclear plants exists.
  • In 2011, the NRC reported that industry inspections must determine the extent and rate of ASR concrete degradation as it was an active, on-going form of degradation that was also not self-limiting and would continue to fail indefinitely.

*By this time ASR had been identified in 131 areas. ‘As of February 2012, there are safety concerns about concrete degradation at the plant. Concrete surrounding an electric control tunnel at the nuclear plant has lost almost 22 percent of its strength and is showing signs of an alkali–silica reaction (ASR) because of more than a decade of ground-water infiltration, according to an NRC inspection report released in May 2011.’(“Seabrook Station Nuclear Power Plant.” Wikipedia. Wikimedia Foundation, 1 Mar. 2015. Web. 14 May 2015.)

  • In 2014, the NRC and the National Institute of Standards and Technology (NIST) signed on a interagency agreement to  study ASR’s structural performance on nuclear power plants.

An NRC report portrayed the situation as follows:

“It was confirmed in 2010 that what is occurring at Seabrook is alkali silica reaction, or ASR. The result of the reaction is a gel, which can expand and may cause micro-cracks in the concrete. Graphics detailing the chemical reaction and the expansive gel can be viewed on slide 9 of the May 10, 2012 presentation titled, ‘Seabrook Station Safety in Light of the Alkali-Silica Reaction Occurring in Plant Structures….It was revealed  that Seabrook has ‘moderate-severe’ ASR in 4-5 safety related buildings, one of which already  ‘demonstrated a substantial reduction in compressive strength and a modulus of elasticity substantially lower than the expected value.’ “ (“Special NRC Oversight at Seabrook Nuclear Power Plant: ConcreteDegradation.” NRC:., 6 Apr. 2015. Web. 14 May 2015.)

Safety concerns of a variety of kinds have continued since before Seabrook’s beginning operations. In particular, ASR has the potential to create a situation which could endanger humans and other populations of surrounding ecosystems.

Since Seabrook sits on a marsh, water exposure is constant. This is especially true as climate patterns change and extreme weather events such as flooding become more frequent. In addition, the salt content of the water is elevated as the marsh borders on the Atlantic Ocean. While there are some techniques that may mitigate ASR, the reaction will continue to occur and spread. Moreover, the NRC and the concrete industry have no known solution for ASR. Indeed, when ASR was first discovered in Seabrook, the NRC had no protocols or standards for dealing with this problem, and it still does not. Seabrook is the first nuclear power plant known to have ASR. C-10 is asking that the NRC carry out its responsibility to ensure that NextEra do the appropriate testing to determine the extent of the problem in order to keep the public safe from leaks of radioactive nuclides.

IV. Re-licensing and Uncovering the Problems

When Seabrook filed to extend its license for 20 years from 2030 – 2050 in 2010, 20 years before the expiration of its current license, C-10 looked into the reasons for this unusual application. At a re-licensing hearing held at Seabrook, a member of the NRC panel mentioned ASR. An inspection report also mentioned the issue. C-10 began researching degradation in Seabrook’s concrete.

NextEra failed to include this adverse condition in their application. This was a violation of federal code. This concerned C-10. In September 2010, the NRC published the first public acknowledgement of the issue; after a year and a half of investigation, this resulted in a stay of the safety portion of the re-licensing procedure.

Persistent problems have included a lack of adequate inspections due to unqualified workers being assigned to carry out required steps. Water leaks have continued to occur as well.

V. C-10 Takes Action

As soon as ASR was first mentioned by the NRC, C-10 began to study concrete in order to better understand what ASR might mean for the safety of the Seabrook plant. What we found was grounds for serious concern. The NRC had no technical specs or regulations concerning  ASR. C-10 scoured industry reports and NRC reports.

C-10 formed a partnership with the Union of Concerned Scientists to promote further study of ASR. We needed scientists and a materials expert in concrete to educate us about the implications of ASR  at Seabrook. Ultimately C-10 located an industry expert to answer questions, help us understand further questions we need to ask about safety and radiation issues and possible impact on the public. He subsequently wrote a report on ASR (see link for further detail.)

C-10 requested hearings on ASR to be held in Seabrook because there was so much public concern. Several NRC hearings were held at Seabrook which were attended by hundreds of local residents.

C-10 then went to Washington in 2012 to attend meetings between the NRC and members of the concrete industry and participated as concerned members of the public. They presented the research and made requests for next steps. The NRC invited the expert we had retained to testify at hearings of the Advisory Committee on Reactor Safety.  Unrelenting pressure from C-10 helped hold the NRC accountable for following up on ASR concerns at Seabrook.

All this work has led to a delay in the licensing “until safety concerns are met.”  C-10 has done years of research to educate the NRC and the public and to ensure that the focus stays on ensuring public safety.  C-10 continues to diligently monitor the NRC’s work on Seabrook’s ASR and re-licensing application, as well as NextEra’s responses to the problems.

VI. Fom Seabrook to the Nation

It became clear that the NRC was dragging its feet in pressuring NextEra to do core sampling and testing of the concrete beyond visual inspections, which NextEra has been reluctant to perform, but which is considered critical in understanding the extent and rate to the ASR induced concrete degradation. C-10 realized that they had to up the ante on the NRC to fully analyze Seabrook’s ASR conditions and make a request that the NextEra would have to follow.

C-10 and its board had also realized that this issue is bigger than just Seabrook. Our nation’s nuclear fleet is built from concrete and that concrete gets damaged over time. That damage can be accelerated by conditions typically present in nuclear reactors: water seeping into the concrete, temperature changes, heat, and irradiation. No one seemed to have realized that the actual material out of which our plants are built might decay. There is a potential disaster not only in NH but across the nation.

Therefore C-10 wrote the following petition to the NRC to change its rules:


On September 25, 2014, C-10 submitted a petition for rulemaking requesting the NRC revise its regulation to require all nuclear plant owners comply with two existing industry standards for concrete inspections and evaluations.

In October 8, 2014 the NRC accepted the C-10 petition for rulemaking and assigned it as Docket Number PRM-50-109. This means the NRC has accepted that this petition is in line with its standards. The NRC will vote on whether to make the requested changes. View the petition here.

In February 2015, the Union of Concerned Scientists (UCS) submitted the attached comments by David Lochbaum, Director, Nuclear Safety Project on the C-10 petition for rulemaking.

He states that:

“1) existing inspections cannot be relied upon to detect ASR degradation,

2) that ASR degradation has adverse nuclear safety implications, and 

3) that the two measures sught by C-10’s petition are appropriate methods for properly managing ASR degradation.”

C-10’s petition has earned the approval and support of scientists and experts. C-10 is leading the way on evaluating concrete and the structural integrity of our nation’s nuclear power plants with the goal of keeping the public safe from radiation leaks.


VII. Seabrook’s Current Status 

– ASR issues at Seabrook are on-going. 131 locations in 19 buildings have been identified. Visual monitoring indicates that cracks are expanding.

– Seabrook is scheduled to perform testing on containment and spent fuel structures in 2015. The spent fuel structure has not yet been evaluated for ASR.

– The NRC has recently told NextEra that they need to “resolve all technical issues regarding ASR” and report on it by December 2015.

– Seabrook’s renewed license application is on hold. A decision is scheduled to be made in September 2016.

– THE NRC still needs to rule on the C-10 petition to require all nuclear plants in the US to conform to industry standards for concrete testing.

– Concrete at other nuclear power plants may be degrading as well.

– There is no known repair or solution for ASR.


Research and writing courtesy of Sarah Doenmez.

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