NEWBURYPORT — Nuclear watchdog group C-10 is asking the Nuclear Regulatory Commission to hold a public hearing on alkali-silica reaction, which is found in concrete at the Seabrook nuclear power plant.

Newburyport-based C-10 Research and Education Foundation announced in a press release it is filing for official intervenor status on the issue as it relates to a license amendment request filed by the plant’s owner, NextEra Energy, that concerns the concrete affected by ASR.

ASR was discovered by power plant staff in the walls of Seabrook Station and reported to the NRC before NextEra’s application on June 1, 2010, to extend its operating license from 2030 to 2050.

The slow chemical reaction can take years to appear and involves alkaline cement and reactive silica found in some concrete aggregates when moisture is present. It forms a gel that expands, causing microcracks that can cause concrete deformation.

Seabrook Station is the only nuclear power plant in the United States exhibiting ASR, although it is found in nuclear power plants elsewhere in the world. ASR is commonly found in dams and bridges.

The discovery of ASR at Seabrook Station brought increased monitoring by the NRC, according to Region I spokesman Neil Sheehan, as well as a lengthy study conducted by NextEra.

While assuring the public the plant is safe, NRC staff told NextEra the final decision on the license amendment depended on its plan to address the concrete problem as the plant ages to ensure public safety.

Sheehan said ASR is a unique and extremely complex issue, and the agency’s staff will likely take more than a year to review NextEra’s amendment.

Since C-10 first learned about the presence of ASR at Seabrook Station, it expressed significant concern to the NRC and general public about how the condition could affect the safety of those living in the area.

In its recent petition to the NRC, the organization gives 10 reasons why there should be further investigation and a public hearing, according to C-10 Executive Director Natalie Hildt Treat.

Among its reasons is C-10’s belief there is a “lack of transparency” concerning the testing results.

“We are concerned not only about the public health and safety implications of allowing the current operating license to stand given what we know about the plant’s concrete, but also about the precedent it would set for the entire U.S. nuclear industry,” Treat wrote in the press release.

C-10 board member Christopher Nord of Newbury states in the release that the organization wants the results of testing done on concrete core samples during the investigation of ASR at the plant.

“C-10’s concrete experts should be allowed to review the data,” Nord said.

Sheehan said a panel of three judges from the Atomic Safety and Licensing Board will decide if C-10 will be granted intervenor status and a public hearing. That decision will be based on the arguments made in C-10’s petition and whether it has legal standing as an intervenor.

Sheehan said it could take several months for that decision to be made.

C-10 is a nonprofit watchdog organization made up of people living within a 10-mile radius of the plant. It conducts field monitoring on the plant’s emissions under its contract with the Massachusetts Department of Public Health, and works to ensure the nuclear power plant is as safe as possible.

Angeljean Chiaramida can be reached at 978-961-3147, at achiaramida@newburyportnews.com, or follow her on Twitter @achiaramida1.