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Archive for Wednesday, March 6, 1996

WOLF CREEK TESTS FIND WORN TUBES

March 6, 1996

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A Washington watchdog group dismisses tests at the state's only nuclear power plant as incomplete and inconclusive.

Tests conducted last week at the Wolf Creek nuclear power plant in Burlington didn't reveal cracks like those that have plagued similar U.S. plants, a plant spokeswoman said Tuesday.

But 16 of the plant's 22,504 steam generator tubes were permanently taken out of service because the tests revealed "wear," said the spokeswoman, Mona Grimsley.

A Washington anti-nuclear group criticized the tests as inadequate and unreliable because only two of the plant's four steam generators were examined.

The plant's tubes were first tested for cracks using an older, less-reliable method. If there were any indications of corrosion or cracking, a newer, more sensitive probe was used.

That left about 20 percent of the tubes within the steam generators being tested with the latest, most sensitive technique.

No further tests are planned for at least 18 months, until the fall of 1997. The plant is scheduled to resume generating power in early April.

"That essentially is flying blind," said Paul Gunter of the Nuclear Information and Resource Service in Washington, D.C. "If there's any sign of wear that they're turning up in their limited inspection, you can rest assured they've embarked on an 18-month fuel cycle with more wear that went by undetected.

"Now they're going to run those worn tubes another 18 months, subject them to that harsh operational environment, without really knowing the degree of deterioration."

Similarities

Steam generators are huge coils of finger-thick tubes that transfer heat from radioactive to nonradioactive water.

Wolf Creek's four steam generators each have 5,626 tubes, which, if stretched out, would extend more than nine miles.

At least nine other nuclear power plants in the country have been found with cracked and corroded steam generator tubes, leading to costly repairs in some cases and to the closure of a plant in Oregon in 1992.

Robert Pollard, a former engineer for the U.S. Nuclear Regulatory Commission, has warned that multiple ruptures of steam generator tubes could cause a catastrophic accident.

Tests last year at a nuclear power plant in Maine revealed extensive tube corrosion and cracking that was missed six months earlier by inspectors who used the older technique that was largely relied upon at Wolf Creek.

Also last year, tests at Wolf Creek's sister facility, the Calloway nuclear power plant near Fulton, Mo., about 100 miles west of St. Louis, revealed cracks in 29 tubes. Those tubes were plugged to take them out of service.

Calloway and Wolf Creek have nearly identical designs. However, Wolf Creek has heat-treated steam generator tubes that are believed to be less susceptible to cracking than the tubes at Calloway and other plants.

"We have never had a history of cracking," said Grimsley, of the Wolf Creek Nuclear Operating Corp., which manages the plant for its corporate owners. "We have a high degree of confidence in the tubes that we have."

Grimsley said the 16 tubes taken out of service suffered wear from the stress of anti-vibration devices which is unrelated to the corrosion and cracking that has forced costly repairs at other plants.

Different opinions

Grimsley said there was no reason to test all four of the plant's steam generators because the others were tested in 1994 and 1993.

"Had we seen any kinds of problems in the two steam generators we tested, we would have gone back and tested the other two," she said.

"The good news is we have no cracking," Grimsley said.

Gunter said that can't be known based on the tests conducted at Wolf Creek.

"The material is susceptible to cracking," Gunter said. "They've only done a very small sampling of the steam generator tubes. If you don't look, you won't find it. What the NRC is finding is that if you do look, you will find it."

Wolf Creek, about 55 miles south of Topeka, was shut down Jan. 30 because ice buildup in a cooling pond disabled a pump. Although the problem was quickly solved, plant operators decided to keep Wolf Creek closed and to start a routine seven-week refueling and testing shutdown about a month earlier than planned.

During a refueling shutdown, workers replace about a third of the plant's 193 uranium fuel assemblies and inspect various systems within the plant.

Wolf Creek began generating electricity in 1985 and is jointly owned by Kansas Gas & Electric Co., Kansas City Power & Light Co. and Kansas Electric Power Cooperative.

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