There are no guarantees underground safety-related pipes can remain structurally sound under current regulations and standards, according to a report just issued by the federal General Accountability Office (GAO).
While the Nuclear Regulatory Commission (NRC) believes there is reasonable assurance the systems will remain structurally sound, the report said, “(P)ressure and flow tests NRC currently requires do not provide information about the structural integrity of an underground pipe (and) do not indicate the presence of degradation in a pipe that could hinder its future performance.”
The GAO review of the NRC’s oversight of underground piping systems was in response to leaks of tritiated water at nuclear reactor sites around the nation.
The GAO’s two teams of six experts reviewed leaks of tritiated water at Braidwood in Illinois, Oyster Creek in New Jersey and Vermont Yankee in Vernon in preparing the report.
One panel member said not having structural integrity information about safety-related systems “could create a very significant risk to public health and safety.”
“(L)imitations in the industry’s ability to measure wall thickness of an underground pipe without excavation prevent licensees from determining the structural integrity of underground piping systems,” according to the report. “In this context, licensees at nuclear power plants cannot assure that a safety-related pipe will continue to function properly between inspection intervals, thereby protecting the public’s health and safety.”
“We noted that, among other things, we agree with the report’s recommendations and have already established activities to address them,” said Neil Sheehan, spokesman for the NRC in its response to the GAO.
Licensees should follow American Society of Mechanical Engineers Code when it comes to buried components including piping, he said.
In addition, the NRC’s Generic Aging Lessons Learned program for license renewal reviews now addresses buried piping, Sheehan said.
“It spells out requirements for owners to excavate certain pipes and perform visual and other exams,” he said.
In 2009, the NRC reported as adequate its regulations to ensure buried piping can perform its safety function and in 2010 the NRC revised its aging management guidelines for preventing and mitigating corrosion of the inspection of underground piping systems in plants with extended licenses.
The GAO report registered concern about those plants in particular.
“The occurrence of leaks at nuclear power plants from underground piping systems is expected to continue as nuclear power plants and their piping systems corrode,” the report said. “While reported underground piping system leaks to date have not posed discernible health impacts to the public, there is no guarantee that future leaks’ impacts will be the same.”
Although those leaks have had “no discernible impact” on public health and though they are from systems not related to safety, “the leaks may affect people in the surrounding communities in a less tangible manner,” the report said.
Tritium has leaked from at least 48 of 65 nuclear sites, according to NRC records.
Leaks from at least 37 of those facilities contained concentrations exceeding the federal drinking water standard, up to hundreds of times the limit.
The industry has adopted two voluntary initiatives “to enhance public confidence in the operation and maintenance of their plants.”