The Achilles' heel of nuclear power.

In January 1993, Portland General Electric (PGE), Oregon's largest electric utility, closed its nuclear power plant, Trojan, after the cooling tubes had seriously corroded less than halfway through the plant's anticipated 35-year lifespan. PGE had also found inexpensive replacement power from California. It would be cheaper to close Trojan, said the utility, than to fix it.

What PGE didn't mention, however, was a discovery that could be the Achilles' heel of nuclear power. A space-age chrome-lead-nickel alloy called Inconel 600, used in Trojan's cooling tubes, had worn out almost 20 years sooner than expected, allowing radioactive gas to escape into the plant. And tiny, virtually undetectable cracks in the tubes, if present, could lead to a loss of coolant, which could, in turn, cause the worst-case nuclear nightmare--a core melt down. This danger reaches far beyond the lush Oregon forests surrounding Trojan; the same alloy is used in nukes all over the globe, including two-thirds of U.S. plants.

To deal with the potential danger, the Nuclear Regulatory Commission (NRC), the government agency responsible for nuke safety, is taking action--not to force utilities to fix the problem, but to ease the rules so the nukes can stay open without being repaired. "They're stripping away one of our defenses against nuclear accidents," says Oregon anti-nuclear activist Lloyd Marbet. "They're playing nuclear roulette with our lives."

In 1991, an NRC safety expert, Dr. J. Hopenfeld, wrote that it was "essentially impossible" to detect cracks in the corroded tubes. His internal memo was made public by the Boston-based Union of Concerned Scientists (UCS), But NRC dismissed the warning and instead began loosening its regulations. The relaxed rules, says UCS' Robert Pollard, have allowed at least four affected U.S. reactors--two in Alabama and one each in South Carolina and Michigan--to stay open. Others in Connecticut, Minnesota and Wisconsin now seek similar treatment. In all, NRC says, 71 of the 108 commercial reactors in the U.S. contain Inconel 600 tubes.

Rather than handling this issue nuke-by-nuke, as it has been doing, NRC wants to change its rules across the board. NRC spokeswoman Sue Gagner says that safety won't be compromised because conditions have changed since the rules were first issued 20 years ago. For one thing, she says, "changes in water chemistry" have made wall thinning less of a concern, "The concern is cracks," she says, "but the thinning of the walls is not causing cracks."

Pollard has his doubts. "Anytime there's an intractable problem," he says, "NRC drags its feet. That's why we call them |Nobody Really Cares.'"