The Dilemma of Aging Nuclear Plants

October 20, 2009
Special Report: Energy

By PATRICIA BRETT
PARIS - From the time the world's first commercial nuclear power plants were switched on in the late 1950s, installed generating capacity rose rapidly over two decades. It leveled off in the 1980s as new building programs were scrapped in the wake of the accident at Three Mile Island, among other factors.
Contractors generally designed plants to last for 40 years - a standard enshrined in the United States in the adoption by the Nuclear Regulatory Commission, or N.R.C., of a 40-year licensing regime.
A large part of the world's installed nuclear power capacity is now coming to the end of that designed life span.
Caught between approaching retirement deadlines and public opposition to new plants, industry operators are pushing to extend the life of their plants to 60 or even 80 years - and this despite problems of premature aging of major components that have already obliged many to replace their plants' steam generators at heavy capital expense.
Running plants longer is one way to recoup the extra cost and raise returns on investment over the full life of the plant. But it has safety implications.
The 40-year life span was a design specification, said Guillaume Wack, director for nuclear plants at the Autorité de Sûreté Nucléaire, or A.S.N., the French nuclear regulator.
"It's like a car," Mr. Wack said in an interview. "The manufacturer says it will run for 100,000 kilometers" - 60,000 miles - "and last two years. That's the theoretical life. After that, it depends on how you run it. If you drive carefully with regular checkups, it could last much longer. If you drive recklessly and don't maintain it, it will wear out more quickly."
Extending plant life rests on the premise that operators run their plants abstemiously. But utilities, under pressure to maximize short-term profit, are constantly tempted to operate at high output, raising the burn-up of nuclear fuel.
Since the 1970s, regulators and operators have identified premature aging problems including vibrations in pipes, with consequent cracking, leaks and ruptures that in turn cause severe corrosion, leading to worse leaks and ruptures. Some of these result from high fuel burn rates, Mr. Wack said.
Stopgap measures like plugging some of the thousands of tubes in the steam generator are allowed by regulatory bodies. But no more than 20 percent can be plugged without impeding the circulation of the steam - and less in some cases - before the generator has to be changed.
The problem is further complicated by the fact that each reactor heats three or four generators. Anything done to one must also be reproduced on the others in order to avoid pressure imbalances: If one generator has to be changed, all the others must be swapped out, Mr. Wack said.
Most plants worldwide have, in fact, already replaced their generators, at a cost of around $50 million for each new generator, after operating for 20 years or less, according to Steve Kerkedes, press officer for the Nuclear Energy Institute, an industry lobby group.
While extending the operating life beyond 40 years may help to amortize that cost, it intensifies another problem - finding replacements for other components. Manufacturers are few, and the backlog for many parts is long. The French company Areva, the world's largest supplier of nuclear products and services, has, for example, traditionally supplied Électricité de France, the state-run utility that operates the world's largest nuclear park. But because of rising demand, E.D.F. is now going farther afield, ordering equipment from Mitsubishi of Japan.
Gérard Petit, a senior safety adviser at E.D.F., says this is more a business cost issue than a safety one: The reactor vessel in which the nuclear reaction takes place, like the containment building in which it is housed, is built to last, he says. "The problem is to keep everything else at the same level."
Still, there is no proof that the reactor vessel or the containment building is sufficiently robust to last beyond 40 years. Cracks in vessel heads, the lids that cover reactor vessels, were discovered in various reactors around the world as long ago as 1991, French and U.S. regulatory documents show.
That led E.D.F. to decide to change the heads on most of its reactor vessels - a replacement program that is ending just this year, Mr. Petit said. Each new head cost E.D.F. $5 million, Mr. Kerkedes said.
U.S. operators, on the other hand, did not systematically make the change. As a result, corrosion of a cracked lid at the Davis-Besse plant, in Ohio, came within a centimeter, or less than half an inch, of causing a serious coolant leakage accident in 2002, according to an N.R.C. report.
In addition, N.R.C. documents show, design flaws identified in 1991 raise the specter of possible long-term fatigue degradation in the reactor vessels themselves due to the heat and high radiation to which they are subjected. A leak in the reactor vessel would result in a core meltdown - the most serious accident possible - with an inevitable release of radioactive materials, Mr. Wack said.
This year, some plants in the United States will hit the 40-year mark but will continue to operate under licenses that have already been renewed.
An elaborate and complex U.S. license renewal program introduced by the N.R.C. in 1991 was scathingly criticized in 2007 by the commission's in-house safety auditor, the Office of the Inspector General, for lacking proper documentation and failing to independently verify operator-supplied data. In response, the review process was revised and expanded. But the license renewals of 52 plants - half the U.S. nuclear park - that were already processed before the revision will not be re-examined, said Travis Tate, a senior official in the commission's license renewal division. Reconsideration was not needed, Mr. Tate said, because the revisions merely "clarify the scope of the inspections and reviews necessary," without calling into question the adequacy of the previous process.
Also, Mr. Tate said, failure to implement an appropriate age management program would not be a ground for denying a new license. It would simply become a future operating issue, along with other commitments required by the N.R.C for license renewal.
As long as relicensed plants operate without accidents, the regulatory commission will have met its obligation to ensure that operators run their plants safely, he said.
This position has prompted some concern, not least because relicensing approvals have been granted in several cases as much as 20 years before the original licenses expired.
Public Citizen, a consumer advocacy group, in opposing the 2001 renewal of two licenses for the Catawba, South Carolina, nuclear plant, due to expire in 2024 and 2026, asked how the regulators could be certain that the plant would meet requirements that far ahead. In fact, the N.R.C. relies for its decisions on operator-supplied computer models and projections.
The problem with those, said Mr. Petit, the E.D.F. safety adviser, was that they might "look good on paper, but you never really know until you actually try it."
In France, which has 58 reactors, plants are submitted to relicensing inspections every 10 years. The first of the 30-year inspections began this year. The inspections, by the A.S.N., take two to three months compared with a typical one-month renewal inspection by the U.S. regulatory agency.
But even that does not necessarily mean that French plants operate more safely. Efforts by E.D.F. to cut costs by centralizing procurement have led to a years-long dearth of spare parts on the ground, said Pierre Wiroth, who until he retired in July was for seven years E.D.F.'s inspector general, or top safety official. E.D.F. reports around 750 minor "events" every year, classifying them according to an established grid, and a third are subsequently upgraded to a more serious level because they are recurrent, Mr. Wiroth said.
In addition to the slow replacement of worn and aging parts, obsolescence is a growing problem. Many control room commands - a nuclear plant's nerve center - rely, said Scott Burnell, press officer for the U.S. regulator, "on technology that society has moved beyond." The technology is typically analog rather than digital because "with analog, we have a lot of experience" and know how it functions, he said. But the downside of that is that graduates coming out of engineering schools are no longer familiar with analog technology.
Areva and other suppliers are pushing to replace analog with digital systems, perhaps partly because they can charge more for new technology, Mr. Wack said. But that also raises an issue of reliability, said Mr. Burnell. "With the digital system, instead of having dedicated wires going to a particular place, you can have a small-scale version of Internet where you can have a single set of wires going all around the plant." That could raise the risk of bugs in the system and complicate problem-solving, he said.
Meanwhile, as more and more nuclear engineers reach retirement age, finding replacements to run the plants is problematic. "When you've been trained on the latest technology, the idea of working on outdated equipment or retraining is unappealing," Mr. Wack said.
Retiring engineers are increasingly being replaced by outsourcing deals with subcontractors, whose qualifications and competence are less rigorously controlled, said Elizabeth Pozzi, an operating technician at the Dampierre nuclear plant, near Orléans, and a local union official. "In the field, it seems that keeping the plant on line is more important than safety," Ms. Pozzi said. A report by Mr. Wiroth last year warned E.D.F. that it should better plan, carry out and supervise subcontracted work.
E.D.F., said Ms. Pozzi, is "not doing anything illegal, but they're using every loophole to push the maintenance boundaries as far as possible. If that's already the case at 30 years, what will it be like at 60?"
In 2006, the attorney general of Connecticut, Richard Blumenthal, requested that the N.R.C. not renew the license for the Indian Point nuclear power plant, located 34 miles north of New York City, when it expired in 2013.
"At Indian Point nuclear power plant, operators have compiled an unacceptable record of abject, repeated, multiyear failure to effectively address vital safety and security issues," he said in testimony to Congress, a view shared by the regulator's own safety auditor in a 2000 report. Mr. Blumenthal also cited growth in the region's population since the plant opened as a reason to shut it.
Two months ago, the N.R.C. issued a safety evaluation report for the plant as part of the renewal process. Of the 87 parts of the reactor vessel and related elements examined, all but three showed aging damage, as did 39 out of 44 steam generator components and 57 of 59 structural elements. Still, the report concluded that Indian Point met regulatory standards for license renewal.