JOIN USExtending lives of nuclear reactors by decades
Prospects for building new nuclear reactors may be sharply limited, but the owners of seven old ones, in Pennsylvania, Virginia and South Carolina, are preparing to ask for permission to run them until they are 80 years old.
Nuclear proponents say that extending plants’ lifetime is more economical — and a better way to hold down carbon dioxide emissions — than building new plants, although it will require extensive monitoring of steel, concrete, cable insulation and other components. But the idea is striking even to some members of the nuclear establishment.
At a meeting of the Nuclear Regulatory Commission in May, George Apostolakis, a risk expert who was then one of the five commissioners, pointed out that if operation were allowed until age 80, some reactors would be using designs substantially older than that.
“I don’t know how we would explain to the public that these designs, 90-year-old designs, 100-year-old designs, are still safe to operate,” he said. “Don’t we need more convincing arguments than just ‘We’re managing aging effects’?” He added, “I mean, will you buy a car that was designed in 1964?”
But the consensus of the commission staff and the industry is that with appropriate analysis and monitoring, the reactors can generate huge amounts of carbon-free electricity for additional decades. The commission itself has not yet approved a system.
“If you’ve effectively paid off the plant, this is very cheap power,” said Neil Wilmshurst, a nuclear engineer at the Electric Power Research Institute, a nonprofit utility consortium that has been researching how to keep old plants running. “The whole basis of license renewal is that the plants are being well maintained — that at the component level, things are being replaced when needed and maintained when needed.”
The leading candidates are Exelon’s two operating reactors at the Peach Bottom plant in Pennsylvania, 50 miles southeast of Harrisburg; Dominion’s twin Surry reactors, near Jamestown, Virginia; and Duke’s three Oconee reactors, near Seneca, South Carolina, all dating from the early 1970s.
“The preliminary analysis we’ve done is favourable,” said David A. Heacock, the chief nuclear officer of Dominion. Obtaining the extension would cost several million dollars, he said, and while Dominion is investigating just what would be needed, it has not decided yet to apply. But “it’s relatively inexpensive to relicense, compared to any new technology,” Heacock said. If the Environmental Protection Agency succeeds in setting a carbon dioxide emissions cap, he said, extending Surry’s life could save local consumers a lot of money.
Surry’s steel and concrete are in good shape, he said, and the company is already replacing much of the high-voltage cabling anyway.
The 100 operating power reactors, most of them completed by the late 1980s, were licensed for 40 years. In that era, new generating stations were expected to replace old ones within a few decades, but that turned out to be wrong for nuclear plants and coal-fired power stations as well. The nuclear industry now describes that 40-year period as an early estimate of the plants’ economic life, not physical viability.
As construction of new reactors tailed off to nearly nothing in the late 1980s, the Nuclear Regulatory Commission established a procedure in 1991 for 20-year license extensions, and it has now granted more than 70. Thus far it has not rejected any applications, although many are still under review.
The 1991 procedure allows for plants to receive additional 20-year extensions, but the commission is currently engaged in a major effort to determine the criteria it should set for years 61 to 80. It expects utilities to start seeking a second round of 20-year extensions by about 2018. The effort on reactors is part of a trend; airlines, highway departments, water system managers and others are all using major assets for longer than the builders imagined.
Exposed to decades of radiation, some metal parts grow brittle and are more likely to crack under stress. One potential source of stress is the emergency core cooling system; if the system sensed a leak in the piping, it could start up and dump huge volumes of cold water into a reactor, keeping it at operating pressure but at a far lower temperature. Engineers say that could lead to a condition called “pressurised thermal shock,” in which a reactor vessel would crack open.
Measuring embrittlement
To measure embrittlement, the plants use extra samples of the metal from which their reactor vessels were made, called coupons, stored for years in irradiated areas inside the reactors. These have been removed at various intervals and analysed for brittleness, in a test that usually destroys the coupon.
A few of the reactors have run out of these coupons, and engineers are trying to draw conclusions about their conditions by extrapolating from coupons in other reactors. In others, they have moved the coupons closer to the center of the reactor, to age them faster, so they have an idea of what the vessel’s metal will look like in a few years, not just its current condition.
Jim Riccio, a nuclear policy analyst at Greenpeace, said: “This isn’t about running reactors until they are 80. It’s amortising the large capital additions that the industry can’t afford right now.” The reactors, he noted, have been required to buy new hardware after the Fukushima Daiichi accident in 2011.
“The track record of this industry is a meltdown once a decade,” he said. “We have a concern that running reactors well beyond their economic lifetime and well into embrittlement is not sound.”
But Richard A. Reister, manager of an Energy Department programme for “reactor sustainability,” told the commission in May, “Our research has not yet determined any technical showstoppers to long-term operation.”
Utilities say they need advance notice of licensing rules to keep their plants running, because they must plan maintenance work, replacement of major components and even fuel supplies years in advance.
To win a license extension, the plants do not have to show that they will be safe for 80 years, only that they have monitoring programmes in place to promptly detect problems as they emerge.
Michael P. Gallagher, a license renewal specialist at Exelon, said the old plants were “important national assets.”
“Aging management is a continuum,” he said at the hearing. “We don’t see any cliffs in aging management.” Exelon acknowledged that it was looking into an extension for some of its reactors.
David Lochbaum, a nuclear engineer at the Union of Concerned Scientists, told the commission that nothing was inherently unsafe about running a reactor until it was 80, but that even now, when almost all the plants running are decades old, evidence of design errors continues to surface, sometimes causing plants to shut down.
“The bottom line is that compliance with current licensing basis requirements has never been shown to be valid at any nuclear plant in the country, not any plant at any time,” he said.