Operators safely shut down the Unit 2 reactor at the Susquehanna nuclear power plant near Berwick Wednesday night (9/13) to begin the unit's seventh refueling and maintenance outage.

The outage began two days earlier than planned after ventilation valves associated with the containment structure surrounding the Unit 2 reactor did not pass a required test, said Herbert D. Woodeshick, special assistant to the president for Pennsylvania Power & Light Co., the plant's operator.

"The valves cannot be repaired with the unit in service, so we began a deliberate, controlled shutdown in accordance with the plant's operating guidelines when we became aware of the test results," Woodeshick said.

The refueling and maintenance outage is expected to be completed within 45 days. About one-third of the unit's uranium fuel will be replaced. Major projects include an inspection of main turbine-generator components and replacement of a plant monitoring computer system.

Effective outages help ensure that Susquehanna safely generates the maximum amount of electricity at the lowest cost for PP&L customers, Woodeshick said.

Since its last refueling outage, in the spring of 1994, Unit 2 generated 11.7 billion kilowatt-hours. A kilowatt-hour is enough electricity to power a 100-watt light bulb for 10 hours. An average PP&L residential customer uses about 10,000 kilowatt-hours a year.

Unit 2's capacity factor since its last refueling was 94.9 percent. Capacity factor, a measure of reliability, compares a unit's output to the amount of electricity it could generate if it ran continuously at full power. The average capacity factor for U.S. nuclear power plants in 1994 was 78 percent.

Unit 2 combined with Unit 1 to set a world performance record earlier this year for two-unit boiling water reactors.

"The real measure of outage success," Woodeshick said, "is how well the unit performs after the outage. Unit 2 is completing a highly successful run. Unit 1, which had a 43-day refueling outage this spring, has been in service for 130 consecutive days since May."

PP&L schedules Susquehanna refueling outages in the spring and fall, when demand for electricity is lower. Each unit is taken out of service for refueling every 18 months.

The Susquehanna plant, located in Luzerne County about five miles north of Berwick, is owned jointly by PP&L and Allegheny Electric Cooperative Inc.