US regulators look to license renewals to keep fleet active
Innovation, a tight decarbonization schedule and long-term operations cost data have helped build the case to extend the current U.S. nuclear fleet lifetimes for a second, and even the third, time, say experts.
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The vast majority of the operators of the U.S.’s 94 nuclear power reactors have made one license renewal since 1998, extending their lives to 60 years from 40 years.
However, the aging fleet is shrinking fast – there were over 112 reactors operating at the beginning of the nineties – and there are only two new reactors in construction in Waynesboro, Georgia, Vogtle 3 and 4, which are expected to be in service this November and next November respectively.
By 2030, the average age of all nuclear reactors in the United States will be 50 years, and with a dozen reactors scheduled to end their current licenses before the end of the decade, applications to the Nuclear Regulatory Commission (NRC) for extensions are increasing.
In the United States, four Subsequent License Renewals (SLRs) to extend the reactors’ lives to 80 years have been approved in the last two years, two are pending, two are under review and a further three are expected to apply later this year, according to the NRC.
In January, the NRC met to discuss potential technical issues that could arise if nuclear power reactors were licensed to operate for up to 100 years.
Second License Renewal Timeline
(Source: Nuclear Energy Institute)
A low cost bridge
The U.S. government is targeting zero carbon emissions by the electrical system by 2035 and net zero emissions by 2050 for the entire economy.
For nuclear to play a part in that, to provide a baseload as a backup to intermittent renewable generation, the current fleet will have to keep running until the new advanced reactors are commercially available to start taking the burden, sometime in the 2030s.
“If we fast forward to 2050, the energy system is going to be very different to the energy system we have today,” Director of Nuclear Innovation at the Electric Power Research Institute (EPRI) Heather Feldman said during the National Association of Regulatory Utility Commissioners (NARUC)’s Winter Policy Summit.
“There’s many net zero clean energy commitments that are being made today that are going to shape that future and the existing nuclear fleet is really a bridge to that future.”
Extending the lives of the plants makes good economic sense according to a recent study by the OECD Nuclear Energy Agency (NEA), the 2020 edition of “Projected Costs of Generating Electricity,” which examined data from 243 plants across 24 countries.
The report concluded that electricity produced from nuclear long-term operation (LTO) by lifetime extension was highly competitive with all forms for electricity generation, including fossil fuels and renewables, and not just low-carbon generation.
LTO, with limited project risks and with a significant pool of ‘shovel ready’ projects, has a levelized cost of electricity (LCOE) of $30-50MWh, the report said, comparable to natural gas combined cycle power plants.
Levelized Cost of Electricity against capacity and plant-life extensions
(Source: OECD NEA)
A nuclear power plant, like all long-term infrastructure and technology, is constantly being upgraded and renewed, with old parts stripped out and replaced and obsolete machinery updated. But extending a plant’s life to 80 years poses its own challenges.
“The NRC recognizes that the license renewal guidance would need to be updated,” said NRC Commission member David Wright during the NARUC meet ‘80 is the New 60: Decarbonization and Innovation Pace the Way for Second License Renewal for Existing Nuclear Plants.’
“(It must) address expected differences in aging effects and technical issues for extending operation from 60 to 80 years, such as neutron embrittlement, stress corrosion cracking related to pressure in the vessel, concrete and containment degradation and electrical cable qualification and conditioning monitoring,” Wright said.
Changing parameters
To keep the plants going, a collaborative effort across the industry conducted a systematic in-depth analysis to identify four areas that needed additional research and development, says EPRI’s Feldman.
Those were around the reactor vessel, inside the reactor, cables and concrete.
“These are the areas where we wanted to roll up our sleeves, understanding the bigger issues over time so we could put the appropriate mitigation and repair techniques in place,” she said.
Perspective over age management has changed over the last decade, she notes, from time to parameter-based guidelines.
Whereas 10 years ago, you might change the oil filter in your car every few months (time-based) now you change the filters when a sensor tells you to (parameter based).
“In the same way we’ve adapted our guidance to a point where we’re no longer time based but parameter based, and we’re monitoring the parameters that are very important to aging management,” she says.
Swapping out 80s technology of analogue dials and digital interfaces is also keeping the plants up to date.
“Nuclear plants are starting to install a wireless backbone, and that is a real enabler to many different innovations, for example, electronic work packages,” says Feldman.
Effective data collection that allows supervisors to spot problem areas and bottlenecks more easily, drones which keep essential workers off dangerous scaffolding and reduces inspection times, and data validation and reconciliation through sensors and the creation of digital twins all come together to bring a 40-year-old plant into the present day and future-proof it for the next 20 years of service.
Meanwhile, while tweaking and updating parts of the plant to bring them up to date is essential, components are routinely replaced to keep the reactors fully operational.
“Major components like the steam generators have been replaced in a number of plants, and that is because they are seeing the benefits of long-term operation,” says Niko McMurray, Nuclear Program Director at ClearPath and previously a materials engineer at the NRC focusing on new and advanced nuclear reactors.
“They are looking at the nuclear plant as a whole and understanding what needs to be replaced and what needs additional maintenance to continue operating.”
The refurbishing of large power plants through major component replacement is already underway in Canada, where nuclear power plant operator Bruce Power begun in January of last year a 13-year program for its 6.5 GW power plant to replace the remaining six of the plant’s eight reactors to extend its life by 30-35 years to 2064.
By Paul Day