Much like the baby boom generation, many of America's 103 operating nuclear power plants are already firmly entrenched in middle age.

That's the dreaded period when parts begin wearing out and things often start to go wrong.

The age-related damage found in March at FirstEnergy's Davis-Besse nuclear power plant illustrates how the graying of the nation's nuclear plants is both a safety and an economic concern.

FirstEnergy expects to pay $120 million or more in repairs and energy-related costs before it can be allowed to restart the Oak Harbor power plant.

And the Akron company's admission that it should have prevented the acid corrosion that damaged its reactor vessel head only intensifies the arguments of those who say nuclear power is dangerous. Davis-Besse raises the volume of the debate at a time when many in the industry are seeking permits to extend the life of those plants.

Critics of nuclear power say the older the plants get, the less safe they are, no matter what kind of inspections, maintenance and equipment replacement goes on.

Nonsense, say the industry and its federal overseer, the U.S. Nuclear Regulatory Commission.

There's a lot at stake as nuclear power plants enter the last half of their initial 40-year licenses to operate.

Nuclear power currently supplies about 20 percent of the nation's electricity. Despite the protests of nuclear energy opponents, the uranium-powered reactors are unlikely to shut down any time soon.

That's because demand for electricity is projected to grow for decades. Energy policy under the Bush administration calls for the use of nuclear power, though utilities now have no immediate plans to build any new nuclear plants.

Instead, FirstEnergy and most other plant owners expect to ask for an additional 20 years to keep existing facilities, including Davis-Besse, making power.

The NRC ties the application for the 20-year licenses directly to how well plant operators address aging.

The critics and industry do agree that parts wear out.

Constant bombardment by radiation over the years can cause metal to become brittle. Temperature fluctuations and high pressure take their toll on sophisticated systems and equipment such as steam generators. Concrete cracks.

Even such nontechy things as water or coolant pipes are susceptible to the ravages of aging.

And the plumbers can charge some pretty hefty fees to make things right.

Disagreement comes in determining what should be done.

David Lochbaum, a nuclear engineer who now works for the Union of Concerned Scientists, says he wants better assurances that nuclear power plants will become safer as they get older.

The experience with Davis-Besse shows that the industry and regulators can become complacent and still be surprised by unexpected events, he said.

Lochbaum testified before the NRC this week, offering a plan that he says will help regulators know if age-related problems are growing.

``Most plant operations have programs in place to deal with aging,'' Lochbaum said. ``There was a miss (at Davis-Besse) for some reason. You can never be infallible.''

The industry has gotten better at plant maintenance after new rules went into effect in 1996, he said.

But he estimates that from 1997 on, more than half of plant outages have been caused by age-related problems.

The Union of Concerned Scientists plan calls for the NRC to look at the reasons it sends special teams to nuclear power plants, he said. If the teams increasingly are created and sent out because of age-related issues, the NRC needs to take corrective action, he said.

``We're thinking there's evidence of more near-misses,'' he said. ``The companies are cutting back on inspections. It costs money.''

Anti-nuclear activist Paul Gunter of the Washington, D.C.-based Nuclear Information & Resource Service says he doesn't believe the industry when it says the aging plants will stay safe.

``The plants are going into a breakdown phase,'' he said. ``From toasters to nuclear power stations, the longer you run them the more likely they are to fail.''

The fact that FirstEnergy didn't detect boric acid leaks that created two cavities on top of the Davis-Besse reactor vessel head shows the problems inherent in keeping nuclear plants safe, Gunter said.

The Davis-Besse incident and others show that the Nuclear Regulatory Commission is asleep, he said.

``We have a retreat from regulatory oversight,'' he said.

Increasing energy efficiency using off-the-shelf technology and programs can make up for the closing of nuclear power plants, he said.

The industry says its statistics show plants are getting safer.

``I would disagree with (critics') contention that they get less safe,'' said Charles Welty, director of technology applications for the utility-funded nonprofit Electric Power Research Institute in California. ``It's my firm belief that they don't get any less safe.''

The industry has vigorous and extensive inspection and maintenance programs in place to keep plants running safely, he said. In addition, the plant operators can predict when any age-related damage will occur and head it off, he said.

``We know these things will age,'' Welty said. ``We can manage the aging.''

The Davis-Besse reactor vessel head corrosion is an aging problem that ``just somehow got ahead of them,'' he said. ``It doesn't appear to be a new damage phenomena.''

``I don't see any real significant issue with aging,'' said Alex Marion, director of engineering at the industry-sponsored Nuclear Energy Institute.

The NRC has already granted 20-year license extensions for eight plants, which he said shows that the industry is properly addressing age-related problems.

Those licenses don't get granted overnight.

It takes about three years for a company to get ready to submit a 20-year license renewal application, said FirstEnergy spokesman Richard Wilkins. FirstEnergy is making plans now to apply for a license extension in December 2004 that will keep the plant running until 2037. (Davis-Besse's operating license expires in 2017.)

It will take the NRC until 2006 to evaluate the application.

FirstEnergy has accepted responsibility for not preventing the acid damage at David-Besse and is moving ahead with its repair plans, Wilkins said.

``We did find that problem. And we found it before anything failed,'' he said. ``The question is, why didn't we find it earlier.''

David Baker, the acting director of life-cycle management at Davis-Besse, said in addition to doing aging-related maintenance and repairs at the plant, FirstEnergy is planning to make enhancements in the next couple of years that will increase Davis-Besse's electricity output by 100 megawatts. The plant, shut down since Feb. 16, generates about 880 megawatts.

The license renewal work involves looking at valves and other components, and even doing such things as analyzing the soil to mitigate any possible corrosive properties that could hurt underground piping, he said.

P.T. Kuo, the new director of license renewal at the NRC, said he is convinced his agency is properly addressing nuclear plant aging.

The initial 40-year license period was based on economic, not technological, considerations, he said.

``The track record of the industry suggests that as the industry as a whole gets older, they're operating more safely,'' said NRC spokesman Victor Dricks. ``The older plants were built with very wide safety margins. Aging is understood and managed.''