The Nuclear Regulatory Commission will update by year’s end proposed guidelines for assessing the safe life span for nuclear reactors — a central issue for the nuclear industry, the nation’s future electric power supply and the Obama administration’s Clean Power Plan.
The new guidance is linked to NRC’s current judgment that there are as yet no "aging" issues with reactors’ structures and components that would prevent current plants from being licensed out to 80 years of age.
NRC’s Generic Aging Lessons Learned (GALL) Report will address four potential aging risks for reactors caused by decades of thermal shock, radiation and mechanical stress: metal embrittlement in pressure vessels, deterioration of cables, concrete and containment structures, and cracks in reactor components. The report will update inspection and assessment methods for aging issues.
"In general, there are no what we call showstoppers related to these four issues or any other potential aging issue," said Allen Hiser Jr., senior technical adviser for license renewal aging management in the Division of License Renewal.
Ongoing research and operating experience back up that conclusion, said Jason Remer, the Nuclear Energy Institute’s director of plant life extension, using Hiser’s terms. "No technical show-stoppers have been identified generically that would prevent plants from applying for second [operating] licenses" out to 80 years, he said.
However, research and inspection results will continue to feed into that assessment, NRC says.
"As the age increases, there will be more questions about aging management," said Jennifer Uhle, deputy director of the NRC Office of Nuclear Reactor Regulation, speaking last month to a joint meeting of the NRC and the Federal Energy Regulatory Commission. "If we thought there was a plant that did not meet our safety standards, we would shut it down immediately, no questions asked," she added.
With the grid facing an unprecedented, unpredictable transition over the next two decades, a crucial component is the future of nuclear power, its advocates say. Nuclear power supplies nearly 63 percent of carbon-free U.S. electricity supply.
Industry experts say plant aging tends to be a case-by-case story. But if aging issues did raise unmanageable technical or economic challenges across a cluster of similar plants, the challenges of grid transitions could turn sharply in the wrong direction.
The aging issue involving "passive" plant structures will be joined when U.S. reactors must seek renewed operating licenses. In 2030, near the end of the compliance period for power plant carbon reductions set by U.S. EPA’s Clean Power Plan, the average age of the 99 currently operating reactors will be 50 years. Most of the reactors were built in the 1970s and 1980s and were granted licenses to operate for 40 years. If they continue to meet safety standards, the plants can receive license renewals in 20-year increments.
As of the middle of this year, NRC had issued a first round of 20-year renewals for 78 reactor units at 47 sites (two of the units have since shut down), Uhle said. The first relicensing applications by plants seeking to go from 60 to 80 years are expected to arrive in 2029, after most expected coal plant retirements have occurred.
Nuclear’s role in Clean Power Plan
The role of nuclear reactors in meeting the Clean Power Plan’s goals is debated by nuclear energy’s supporters and critics, with advocates for renewable energy arguing that their sources can take on a much greater share of U.S. electricity needs.
The U.S. Energy Information Administration’s CPP assessment projects that while both natural gas generation and renewables will have to take up the slack of retired coal plants, nuclear power’s share of the power supply will remain essentially unchanged through 2030. The loss of a significant portion of the nuclear fleet would pressure industry and policymakers to expand support infrastructure for renewable power and natural gas; or to produce new technology breakthroughs; or plan, approve and built new reactors — a decadelong process.
Hiser said NRC’s experience to date doesn’t point to a possible timing shock. "Right now, we have sufficient data that we think predictions can be made very accurately, conservatively out to 70 years or more," he said. Now the goal is to take the assessments out to 80 years and beyond through more inspections and research. "That data will be developed over the next five to 10 years by the industry, well in time for the plants to enter the subsequent license renewal operating period" after 60 years, he said.
Jane Marshall, deputy director of the Division of License Renewal in the Office of Nuclear Reactor Regulation, added that NRC has tried to build in provisions in the aging review that are designed to lessen the impact of surprises. "We have positions that we think are conservative to address the potential uncertainties," she said.
"In the four major areas, I think we have sufficiently robust programs that the uncertainty should be accommodated within what we are proposing," Hiser agreed. "Based on what we know from 45 years of operating history, based on what we know from expert analyses and expert opinion, from people who have been involved in the industry for many of those 45 years, we think we have a good handle on what to expect in the 60- to 80-year period."
Hiser added, however, "As we get operating experience, other things may crop up that may require management."
Measuring aging risks
Debates may lie ahead on how aging risks should properly be measured, if a dispute involving Entergy Nuclear’s Palisades nuclear plant near South Haven, Mich., is a guide. Four citizen organizations — Beyond Nuclear, Don’t Waste Michigan, Michigan Safe Energy Future-Shoreline Chapter and the Nuclear Energy Information Service — oppose Entergy’s proposal for assessing the extent of neutron-caused embrittlement of the reactor, which could lead to critical failures.
As the NRC Atomic Safety and Licensing Board summarized the dispute, Entergy has proposed to use tests from "sister" plants with the same design as Palisades to determine the embrittlement issue at the Michigan plant. The citizens groups opposing Entergy claim the company should not be allowed to substitute those data for a direct examination of the Palisades reactor, using metal samples within the reactor that are called "coupons." The board has agreed to hear the dispute.
Aging has an economic side, too.
NEI points to recent decisions to close several nuclear plants in regions with power markets because the plants are losing out in competition with electricity from plants burning low-priced natural gas.
"Alarmingly, over the past three years, four reactors vital to regional economies and clean air efforts have been shut down prematurely already or will be retired prematurely within the next few years," NEI said. "If the United States is to substantially reduce carbon emissions, we cannot afford to prematurely close any more nuclear power plants because of flawed electricity markets. At the same time, new reactor construction — including development of small modular reactors and other advanced reactor technologies — should be pursued vigorously."
On Monday, Entergy announced a decision to close the James A. FitzPatrick nuclear power plant in Scriba, N.Y., when its current operating cycle ends in about a year. Previously, Entergy said it would close the Pilgrim Nuclear Generating Station in Plymouth, Mass., by the summer of 2019. In both cases, the company blamed low gas prices and electricity markets that don’t recognize the value of carbon-free power. But it says it intends to keep Palisades going.
Former EPA Administrator Christine Todd Whitman, who heads the pro-nuclear Clean and Safe Energy Coalition, also pointed to the gas price issue. "That’s what’s driving so many of these decisions, and so much of the thinking," she said recently.
"For a state that is looking at meeting their Clean Power Plan [targets], natural gas is a lot cleaner than coal; it’s still not nearly as clean as nuclear when it’s producing power. Right now, for the utilities — the economic modeling is not leading them to make huge investments in new nuclear," she said.
Aging issues could appear that don’t compel plant closing — provided that degraded components are replaced. But the replacement costs could potentially tip the balance against keeping the plant going, particularly if gas remains relatively cheap.
But that’s not an NRC issue, Marshall said. "We don’t look at the economics of whether or not the plant is profitable. That is up to the licensee. We just look at: Can it be operated safely?" Marshall said.
"It may be that certain cables, or large numbers of cables, would need to be replaced," for example, Hiser said. "That would assure safety. Whether plants choose to do that is not in our purview. If it’s necessary for safe plant operation, that would be required."
Could there be economic showstoppers? Remer was asked. "Absolutely," was his answer.
Reporter Elizabeth Harball contributed.
Correction: A previous version of this story incorrectly reported the percentage of carbon-free electricity provided by nuclear power in the United States.