09/17/03

Add another day, or days, to the restart calendar for the long- idled Davis-Besse nuclear power plant.

A faulty electrically operated valve forced engineers Monday to halt heating up the reactor for a crucial leak test.

With most major work completed at the Toledo-area plant, engineers must test the reactor and more than 1,000 valve, pipe and flange connections for leaks.

The delay - while the valve was examined and repaired and operators got another dose of training - lasted until yesterday afternoon.

The Nuclear Regulatory Commission's special panel overseeing FirstEnergy Corp.'s efforts to repair the plant is requiring that final leak checks be done over seven days with the reactor at its normal high operating pressure and temperature.

This so-called "heat-up" comes from running the reactor's giant coolant circulation pumps rather than from nuclear fission. Operators turned on two of the four 9,000-horsepower pumps a week ago and had hoped to begin the seven-day test by the weekend.

But valve problems - mostly mechanical valves that had not seated correctly when they were rebuilt during the last 19 months of plant renovations - stalled the heat-up while crews repaired them.

"These were minor valve issues, and they were expected," spokesman Todd Schneider said of the weekend problems. "There were no showstoppers. These [delays] will pay dividends when it comes to bringing the plant on line. We'll have a smoother restart."

The leak test, however, cannot officially begin until the reactor's internal pressure is 2,155 pounds per square inch and its temperature at least 532 degrees, according to the NRC.

By Monday, the temperature was 348 degrees and the pressure 620 pounds per square inch. That's when an operator switched on the power to a valve in a pipe connected to an emergency water tank.

The valve is supposed to open automatically in the event of a major leak and flood the reactor to keep the radioactive core covered and out of danger of melting.

But the valve opened as soon as it was energized, said Schneider.

The valve normally opens only when pressure falls. Engineers determined it opened Monday because pressure in the system is building much more slowly than during a normal start-up, when pressure builds up very quickly - in 12 hours - as the result of nuclear fission, Schneider said.

Operators yesterday were instructed - in a new procedure - not to electrify the valve until the pressure is significantly higher, and the heat-up resumed about 2 p.m.

Operators had managed to keep the reactor's temperature and pressure where it had been the day before when the valve opened, and by 5 p.m. the big pumps had pushed pressure to 674 pounds per square inch - about a third of the way to operating pressure.

The plant hopes to begin the seven-day run today, Schneider said.

By agreement with the NRC, which has a beefed-up inspection team at the facility, workers will walk through the plant about four hours after the test begins to look for any obvious leaks.

A second walk-through will happen after three days. After seven days, the plant will be allowed to cool down for several days before workers begin a more intensive inspection.

One area of concern is the bottom of the reactor, which is penetrated by 52 1-inch-wide tubes carrying instruments into the nuclear core. More than a year ago, workers found residue that appeared to be dried coolant near a couple of the tubes. The company believes the residue was washed down from the reactor's head, which was badly corroded and leaking.

The NRC wants positive proof that the bottom tubes are not leaking, especially since a South Texas reactor did find cracked and leaking bottom tubes earlier this year.

If leaks are discovered, repairs could take a month, the company has estimated.

To reach this Plain Dealer reporter:

jfunk@plaind.com, 216-999-4138