Unit 1 at the Susquehanna nuclear power plant shut down automatically early Thursday morning (8/1) after sensors detected abnormal vibrations in the unit's turbine.

Herbert D. Woodeshick, Pennsylvania Power & Light Co.'s special assistant to the president for Susquehanna, said the unit shut down safely as it is designed to do when such vibrations are detected.

"The monitoring equipment in the turbine, which is on the non- nuclear side of the plant, detects even minor changes in vibration. When abnormal vibrations are detected, the turbine shuts down and that leads to an automatic shutdown of the reactor," said Woodeshick. "There is no early indication of any major problems with the turbine."

The shutdown occurred at 5:33 a.m.

Woodeshick said plant crews will investigate the cause of the vibration and make any necessary repairs. Crews also will perform some plant maintenance that only can be done while the unit is out of service. He said Unit 1 probably will be back in service within a week.

Unit 1 had been operating for 236 consecutive days before Thursday's shutdown.

Thursday morning, plant operators were making final preparations for returning Susquehanna Unit 2 to service. That unit has been shut down for 17 days to repair an electrical circuit breaker and complete an investigation of plant procedures related to backup diesel generators.

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