PP&L has implemented a wide range of operational improvements at the Susquehanna nuclear plant following a mid-July event in which a control knob on a diesel generator governor was found in the wrong position.

"When the incident was discovered, we took immediate actions that included putting the control knob back in the proper position, testing the affected diesel generator, placing plant Security on heightened awareness and checking other similar controls on the other four diesel generators and other equipment to ensure they were positioned and operating properly," said Herbert D. Woodeshick, PP&L's special assistant to the president for Susquehanna.

"We also conducted several investigations to review the incident and determine the cause."

The investigations identified three possible causes: mechanical failure, movement of the knob by someone by mistake or intentional tampering.

"Although the investigations have been inconclusive regarding the cause, PP&L has taken wide-ranging actions based on all the plausible causes," Woodeshick said.

Among the actions PP&L took to improve plant operations were:

• checking other similar plant components;
• installing special covers and clearly marking the correct position of the control knobs;
• initiating a periodic check of the knobs by plant operators;
• initiating a review of procedures for work on the diesel generators to simplify the process; and
• changing certain aspects of the security access control process.

As part of the investigations, the company also hired an independent investigator to specifically look at whether the cause was intentional tampering, Woodeshick said.

In his recently completed report, the investigator said: "It was concluded that based upon the evidence developed, that there was insufficient direct evidence to conclude that the unauthorized movement of the load-limit control knob was the result of intentional tampering."

The investigator noted, however, that it was his opinion that intentional tampering was the likely cause.

Commenting on this conclusion, Woodeshick said, "In formulating our response to this event, we have taken action to prevent all plausible causes, including possible tampering."

The Susquehanna plant has five diesel generators in an emergency system that would provide electricity for the plant if power to the site from both the primary and alternate sources in PP&L's transmission system were lost.

"With the control knob in the wrong position, the affected diesel generator would not be able to reach full capacity and it would automatically shut down," Woodeshick said.

"When events like this happen, we take immediate corrective actions that cover all the bases, even though there are redundancies built into safety systems like the diesel generator system to prevent a single failure from causing a problem," he noted.

PP&L has discussed the investigation findings with the Nuclear Regulatory Commission.

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.