SHIPPINGPORT, PA. -- -- Twelve years after the first atomic bomb was dropped on Hiroshima, President Dwight D. Eisenhower dedicated the Shippingport Atomic Power Station as part of the Atoms For Peace program.

Today, the worn-out plant, the first U.S. nuclear reactor to generate electricity, is being torn apart chunk by chunk, pipe by pipe. In the process, the government hopes to demonstrate that reactors can be dismantled safely and affordably, providing a primer for utilities to use when their plants outlive their usefulness.

An army of 200 workers has reached the midpoint of the five-year project.

"We're about halfway there and accelerating," says John Schrieber, project manager for the Department of Energy, owner of the Shippingport plant.

"What we're trying to do is help others who will be dismantling nuclear plants in the future."

Shippingport, 25 miles west of Pittsburgh along the Ohio River, was the granddaddy of the nation's 84 operating reactors. But the 72-megawatt reactor, a dwarf to modern 1,000-megawatt furnaces, reached retirement age five years ago and was taken out of service Oct. 1, 1982.

"It was a demonstration plant," Schrieber says. "It had served its purpose. It's a dead fish now.

"It's like an old car. As it gets older, more and more parts break down -- the brakes, the transmission, the carburetor. You're running down to the repairman every six months. When it's new, all you have to do is put gas and oil in it and drive it."

Congressmen, government officials and utility executives around the world have come to observe the dismantling of Shippingport, seeking answers to the questions of radioactive waste disposal, cost, safety, time and demolition methods. A videotape is being made as part of a training film.

Since a nuclear plant is contaminated, it cannot be abandoned or leveled with a bulldozer at the end of its 30- to 40-year operating life. Dismantling means the complete removal of radioactive parts so the land can be returned to unrestricted use.

Shippingport is the largest nuclear plant in the world to be dismantled to date. Other plants have been mothballed or entombed, two ways of keeping them in safe storage until they are demolished.

Several reactors have been idled and will be decommissioned when adjacent reactors are shut down. These include Peach Bottom Unit 1 in Pennsylvania, Dresden Unit 1 in Illinois and Indian Point 1 in New York.

Fifteen U.S. plants will reach the end of their useful lives by the year 2000, according to the DOE. The number could grow to 53 by 2005 and 70 by 2010 unless their lives are extended by replacing critical parts that become brittle from neutron bombardment.

Worldwide, more than 350 nuclear reactors may be taken out of service in the next 30 years. Critics like the Worldwatch Institute, a Washington research organization, say no one is ready to deal with radioactive garbage.

"Not one of the 26 countries currently relying on nuclear power is adequately prepared for this undertaking," says Cynthia Pollock of Worldwatch.

But government officials disagree.

"Decommissioning is not the ugly monster people make it out to be," Schrieber says. "There's no buried dogs or hidden problems out there."

But because Shippingport is owned by the government, it enjoys options not available to private utilities that will be dismantling their own reactors.

For example, Shippingport's spent uranium was removed in 1984 and taken to a military dump in Idaho. There are no nonmilitary sites open that can handle high-level wastes, and a national repository for spent fuel will not be open until 1998 at the earliest.

Almost all of the 12,000 metric tons of spent uranium fuel from private reactors is now stored temporarily in water-filled utility holding ponds, according to Worldwatch.

The Shippingport dismantling will cost $98.3 million. That's about 12 percent of what it would cost to build the plant in 1987 dollars, according to the DOE.

It took three years and $120 million to build the plant, which went on line on Dec. 18, 1957. It generated 6.35 billion kilowatt hours of electricity.

The last of its three nuclear cores was a breeder system activated by President Jimmy Carter in 1977 in a test to show a reactor could produce more fuel than it consumes.

The most eye-catching part of the Shippingport project will be ferrying the 770-ton radioactive reactor vessel in one piece on a 7,800-mile barge trip to a federal burial ground in Hanford, Wash. Shippingport gets special treatment here, too. By law, new burial grounds must be open to take trash from dismantled private reactors.

The Shippingport vessel is 25 feet high and 10.5 feet in diameter with steel walls 8 inches thick. It is to be filled with concrete, lifted off its bolted platform by a crane and placed on a special barge in October 1988.

The cargo will go down the Ohio and Mississippi rivers to the Gulf of Mexico, through the Panama Canal, up the West Coast to the Columbia River.

The radioactivity is contained in the steel walls. Officials say a three-foot layer of concrete around the vessel will shield anyone from exposure.

"This really is an innocuous package," Schrieber says. "I'm seriously thinking of putting a patio table next to it when it sails. You could sit on it."

If it's not shipped in one piece, the vessel would have to be cut up for 80 cross-country truck trips to Washington, Schrieber says. The barge method will save $7 million, reduce radioactive exposure to workmen and save a year's work.

But critics say the one-piece method may not be suitable for larger, more radioactive vessels at privately owned plants.

"The strategies being used there are not replicable at larger plants," Pollock says. "I don't think it's going to be feasible to lift them in one piece.

"I think they're being very shortsighted. The most difficult task decommissioning crews of the future face is dismantling the pressure vessel and its contents."

The largest plant taken apart before Shippingport was a 22-megawatt test reactor at Elk River in Minnesota. The reactor vessel was cut up in 1974 and a parking lot was built at the site.

At Shippingport, workers guided by a 12-volume set of plans have processed 450,000 of the 500,000 gallons of coolant at the plant, which contained 20 miles of pipe.

The rust-colored, warehouse-like building is half-gutted. Deep in the plant's innards, 40 to 60 feet below ground, technicians scrub radioactive residue from walls.

When the job is finished in 1989, grass will be planted on the seven-acre site and the land returned to its owner, the Duquesne Light Co. The utility has built two 833-megawatt reactors near the original.

"The level of radioactivity will be such {that} there will be no restrictions on the use of the ground," says G. Richard Mullee of General Electric Co., the main contractor on the dismantling.

"It might be a neighborhood picnic ground."