SEABROOK — Nuclear Regulatory Commission officials will soon travel south to the University of Texas to further investigate the concrete degradation problem affecting areas of NextEra Energy Seabrook nuclear power plant.
Alkali-silica reaction is a slow chemical reaction between water, the alkaline cement and reactive silica found in some aggregates used to make concrete. ASR forms a gel that expands, causing cracks that affect concrete properties, but which can take five to 15 years to show up.
More commonly found in transportation structures like dams, bridges and roads, where it has been successfully mitigated, Seabrook Station is the first nuclear power plant to discover and report the presence of ASR. It was found in an electrical conduit tunnel located about 40 feet below ground level, in one of the deepest sections of the plant. The tunnel contains wires that lead from the control room to the rest of the plant.
NRC officials have assured the public on several occasions that the presence of ASR in some walls presents no danger to the public and that they are confident the power plant is safe. The reason for their conclusion is the conservative safety factors built into the plant when it was constructed, such as the 2-foot thick walls reinforced with a lattice of steel bars — or rebar — that maintain the load-bearing capacity of the walls and meet federal standards.
Adding controversy to the discovery of ASR at the power plant is that NextEra Energy Seabrook is currently under review by the NRC for a 20-year extension of its operating license, extending it from 2030 to 2050. Agency officials have told the power plant’s owners that in order for the plant to gain approval for its license extension, proof must be provided concerning the impact ASR will have on the plant as it ages, as well as how to mitigate ASR in the plant’s concrete structures if necessary.
According to NRC senior reactor analyst William Cook, he and fellow members of the agency’s ASR team of experts will go to Austin, Texas, within the next few weeks for an extended visit to see for themselves the result of testing being conducted by the college on Seabrook’s ASR phenomenon. The University of Texas was commissioned by NextEra Energy Seabrook to research the effects ASR could have on the plant as it ages.
“We’ll go down to Austin and spend some time with the professionals working on the ASR testing because it’s the only way to gain confidence in their process,” Cook said. “We’ll be there while they’re testing the anchor bolts, doing destructive testing, which tests materials to determine what the breaking point is.”
Cook said anchor bolts testing will determine how well bolts in ASR-affected concrete retain their capacity to stay in the walls and not be pulled out.
The team will also watch as the scientist working on the project at the university fabricates concrete reinforcement beams in a manner that’s representative of the beams at Seabrook Station. The beams will again be stressed to judge their compressive and tensile strength.
Cook is one of about 10 NRC engineers on the team focusing on the ASR issue at Seabrook Station. He and four others were at an agency open house in Hampton Wednesday night, which offered an opportunity for members of the public to speak informally with the experts on issues related to Seabrook Station.
“I think we do our best work with the public when we are in this kind of informal setting, speaking with people one-on-one,” Cook said.