05/23/03

Officials at a Texas nuclear plant say testing has confirmed the presence of five small cracks in a location where such damage had never been seen before - in tubes that penetrate the bottom of the reactor.

The preliminary findings, released yesterday, show that one crack was completely through the inch-thick metal wall of one of the instrument tubes, allowing a tiny amount of the reactor's coolant to seep out.

In the month since the leakage was discovered during a refueling shutdown at the South Texas Project nuclear plant about 60 miles southwest of Houston, the utility has been using equipment to examine the reactor's bottom under the supervision of the Nuclear Regulatory Commission.

Neither the plant nor the NRC has enough information yet to say what caused the cracking or whether it poses a risk for any of the 68 other similarly designed reactors. Such cracks likely would take years to enlarge to a critical size, but a large enough rupture could cause a serious accident.

The NRC had thought bottom leaks so unlikely that it doesn't require inspections there.

One other plant, Ohio's Davis-Besse near Toledo, has found suspicious coolant residue on the bottom of its reactor, raising concerns about similar cracks and leakage on the underbelly of the massive steel vessel.

Davis-Besse already has had a pineapple-size rust hole in the lid of its reactor, the result of cracks and leaks in control rod tubes. Those upper tubes, which have cracked at several other plants as well, are made of the same alloy as the instrument tubes on the reactors' base.

Davis-Besse owner FirstEnergy Corp. suspects the rust traces on the bottom are remnants of cleaning, not leaks, but it is planning to bring the long-idle reactor up to its normal operating temperature and pressure for a week this summer to look for any further signs.

Davis-Besse still must deal with a question about the ability of its emergency coolant pumps to withstand debris that might be sucked in during an accident. The utility had planned to ask the NRC's permission to do the bottom-leak test before resolving the pump issue, but decided this week to alter its approach.

The plan now, pending NRC approval, is to truck the two high-pressure pumps to a contractor's facility to install internal strainers to keep debris from fouling the pumps' bearings.

"We believe the [modified] pumps can be back in place by mid-July," and the plant ready to be restarted in August, said FirstEnergy spokesman Todd Schneider. That's a month later than the company's last estimate. The NRC has final say, and identification of bottom leaks could substantially delay a restart.

The South Texas plant hopes to make repairs and be ready to resume power production in late summer, said general manager Ed Halpin. "We're committed to safety," he said. "If it takes longer, it takes longer."

The vertical cracks were found in one of the plant's two reactors. Ultrasonic probes identified them on two of the 58 instrument tubes. Repair involves cutting out the cracked section and replacing it with a more durable alloy tube. The work will be complicated by the high radiation level at the reactor's base.

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jmangels@plaind.com, 216-999-4842