Science & Technology
HOTTER NUKES FOR COOLER RATES?
Utilities want regulators to let them push the envelope
Karen F. Cornwell drives a 1966 Mustang with 330,000 miles on it and insists that, with proper maintenance, "the car will last as long as I want it to." She feels the same way about nuclear power plants. As manager of plant-upgrade projects for General Electric Co., Cornwell says some nuclear reactors could safely run longer and hotter than permitted in their original licenses. She is helping utilities ask the Nuclear Regulatory Commission (NRC) for permission to turn up the heat and extend reactor lifetimes. If she succeeds, the result could be a boost for the utilities, a small reduction in certain electricity rates, and--critics charge--an increase in the risk of nuclear accidents.
With competition increasing among electric utilities, companies are eager to extract the maximum from their high-cost nuclear plants. A 1994 report from the Edison Electric Institute concluded that as of January, 1993, only 25% of U.S. nuclear plants produced power more cheaply than generators powered by natural gas, coal, and other energy sources. Yet utilities are reluctant to shut down their nukes, partly because shareholders don't want to take a huge hit against earnings for writing down the assets prematurely.
TASTE FOR POWER. Since shutdown is an unattractive option, many utilities hope to make the best of a bad situation by squeezing more electricity out of the plants. Turning up the rate of nuclear fission generates more electricity with only a small increase in the expenditure of uranium fuel--and perhaps some investment in new equipment. Running the plants for up to 20 years past their originally licensed 40-year life spans also improves their economics.
Utilities already are challenging the power limitations. As early as June, the NRC may receive an application from one GE customer, Northern States Power Co., to raise the thermal output of its 25-year-old Monticello (Minn.) nuclear plant by 6.3% above its designed maximum of 1,670 megawatts. Since Monticello was built before many of today's costly safeguards were required, it already is producing electricity relatively inexpensively. The "uprating" would make its output even cheaper, helping hold down NSP's electricity rates. The Minneapolis utility is optimistic about its request for an increase: In preparation for approval, it has replaced one turbine and most of another with higher-capacity units.
The NRC has looked favorably on a more modest form of power increase. In this one, plants that originally were licensed to operate at less than their design capacity are permitted to raise thermal output to the design limit. Such increases, usually 5% or less, have been granted to 36 of the nation's 110 reactors, with more pending (table).
But Northern States' request will mark the first time a utility has sought an increase for a plant already operating at its limit. If the request is approved, it likely will trigger others. GE is helping three other utilities prepare studies to justify producing heat beyond their design limits. Westinghouse Electric Corp. also is working with customers that want to extend the bounds. Says Cornwell: "They got their first taste of additional power, and they want more."
ANTIQUE. So far, fewer utilities have expressed interest in extending licenses beyond 40 years. True, it would add time in which to earn back the initial plant investment. But replacing parts in geriatric plants could get prohibitively expensive. And unlike a vintage Mustang, there's nothing charming about an antique nuclear power plant. Even Baltimore Gas & Electric Co., the utility that has done the most work toward a possible license renewal request, has "yet to decide if it's the right thing," says Barth W. Doroshuk, BG&E's principal engineer for life-cycle management.
Northern States considered seeking an extra 20-year lease on life for Monticello before backing off and pursuing an uprating instead. But GE's Cornwell says the two options can go hand in hand, because running a plant beyond 40 years would help utilities recover equipment costs associated with a power increase.
How safe is it to turn up the heat in a nuclear reactor? It's hard to know for sure. Higher temperatures and pressures place more strain on a plant and complicate matters in case of an accident. If coolant is lost and emergency cooling water can't be pumped in quickly enough, the cladding materials around the fuel rods could become too hot and crack, spilling radioactive substances. Or if the turbine suddenly stops, halting the flow of steam, safety valves need to open promptly to avoid a huge surge of pressure in the core that could spring a leak in the cooling system.
SHORTCUTS. The power increases worry James P. Riccio, a lawyer for Public Citizen's Critical Mass Energy Project, a Ralph Nader organization. He says they come at a time when utilities are tempted to take shortcuts on safety because of cost pressures and deregulation. He notes, for example, that the NRC has shortened by 40% the list of operating limits that, if exceeded, force a plant to shut down. Says Riccio: "The concept is supposed to be `defense in depth.' They've shrunk the safety barrier on both ends."
GE, Westinghouse, and the utilities all say that such critical items as pumps and valves were designed more conservatively than necessary, so there's plenty of room to operate at higher temperatures and pressures. Says Steven J. Hammer, superintendent of turbine system engineering at Monticello: "Design numbers are somewhat arbitrary numbers. We are showing [the NRC] that we have acceptable margins."
The NRC, meanwhile, says that detailed computer simulations and advances in the science of risk management make it possible to pare back regulations and still be confident that an acceptable safety margin remains after a power increase. And utilities are running their nuclear plants more safely and efficiently. The median U.S. plant generated 82.6% of its potential electricity in 1995, up from just 62.7% in 1980, according to the Institute of Nuclear Power Operations.
Still, in something as complex as a nuclear plant, it's never possible to be sure an accident won't happen when the heat is turned up. Says Gary M. Holahan, NRC director of systems, safety, and analysis: "It's fair to say that, in general, we're getting to the more difficult cases." For regulators, the issue comes down to this: a certain increase in cheap megawatts vs. a best-estimate increase in risk.By Peter Coy in New YorkReturn to top