Southern Co. wants to amend its Plant Vogtle construction license after unforeseen settling of soil beneath the foundation for its new Unit 3 reactor created an uneven surface.
In a letter to the U.S. Nuclear regulatory Commission, dated March 30 and made public last week, the company said the concrete “mudmat” that lies atop compacted, load-bearing soil “is not as level as expected.”
The mudmat is the surface upon which the concrete “basemat” is to be built, after which nuclear buildings will be erected. The structures help protect against seismic damage.
The current license allows only a 1-inch variability in the levelness of the basemat, and the amendment would increase that leeway to 4 inches and allow engineers to use more concrete when the basemat is poured to ensure a level surface for the “nuclear island” buildings.
In the letter to the NRC, Southern Co. Regulatory Affairs Director Chuck Pierce wrote that the change will not affect safety standards for the new units and asked that pouring of basemat concrete – scheduled to commence in mid-June — be allowed to continue even if the license amendment remains under review.
Delaying such a determination, he added, “could result in an additional delay in the construction of the nuclear island basemat structure and subsequent construction activities that are dependent upon the completion of the basemat structure.”
The $14 billion project to add two new reactors calls for completion of Unit 3 in 2016 and Unit 4 in 2017. About 2,200 workers are employed at the Burke County construction site.
Steve Higginbottom, a Southern Co. spokesman, said the license amendment request is necessary because it involves a change in the design basis for the new AP1000 reactor. Although four of the units are under construction in China, the Vogtle project is the first site in the U.S. where the new reactors are being built.
“We anticipate the NRC will act in a very timely manner on our preliminary amendment request, and we don’t expect any delays based on this request,” he said.
The company has already filed notices of 32 license amendment requests it will file by 2014.
Environmental groups critical of the Vogtle expansion contend the foundation issue and other planned amendments to be sought could create delays and inflate the costs of the project.
Jim Warren, of the North Carolina Waste Awareness & Reduction Network, said federal regulators are obligated to thoroughly evaluate requested changes.
“The NRC simply cannot skip any steps in reviewing this fundamental safety issue just to accommodate the construction schedule, and a public hearing on the design change is warranted,” he said, in a press release.