Unit 1 at the Susquehanna nuclear power plant returned to service early Thursday (7/16) following upgrades to instruments that monitor safety relief valves on the reactor vessel.

The unit was taken out of service July 8 after one of 16 acoustical monitors in the reactor vessel malfunctioned. The monitors are one of several indicators that operators use to determine whether the reactor's safety relief valves are open or closed.

"While there was a problem only with one of the monitors, we made a decision to improve all 16," said Herbert D. Woodeshick, PP&L, Inc.'s special assistant to the president for Susquehanna. "These modifications will improve the reliability of these monitors, which are one of several ways that plant operators get information about whether the safety relief valves are working properly."

Woodeshick said the unit could have been returned to service more quickly if the company had decided only to fix the problem with the one monitor, but such a decision is not in character with the way PP&L, Inc., operates the Susquehanna facility.

"People at Susquehanna are focused on long-term safety and reliability," said Woodeshick. "This long-term view has resulted in lifetime safety and production performance that is among the best in the nuclear industry."

The safety relief valves would release steam from the reactor to the unit's suppression pool in case of a sudden unplanned shutdown of the reactor. When the unit is shut down normally, steam pressure is reduced gradually,and the safety relief valves are not needed, Woodeshick said. The suppression pool, located beneath the reactor, provides water for emergency cooling systems.

While the unit was out of service, other maintenance work that can only be done while it is shut down was accomplished, he added. Susquehanna Unit 2 continues to operate at 100 percent capacity.

The Susquehanna plant, jointly owned by PP&L, Inc. and Allegheny Electric Cooperative, Inc., is located about five miles northeast of Berwick along Route 11.