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**UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555-0001**

August 28, 1998

**Addressees**

All holders of operating licenses for nuclear power reactors, except for those who have ceased operations and have certifiedthat fuel has been permanently removed from the reactor vessel.

**Purpose**

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert addressees to recent inspectionfindings related to configuration control of safety-related equipment. Although the examples discussed in this informationnotice are related to the emergency diesel generator (EDG) system, the potential exists for similar problems to occur inother systems. It is expected that recipients will review the information for applicability to their facilities and consideractions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice are not NRCrequirements; therefore, no specific action or written response is required.

**Description of Circumstances**

Recent inspections conducted by NRC inspectors have found a number of configuration control issues at various sites. Therelevant findings associated with these concerns are discussed below.

**Mispositioned EDG Output Breaker Control Switch**

During a routine plant walkdown at H. B. Robinson Nuclear Station, an inspector noted that the EDG output breakercontrol switch, located on the local EDG generator control panel, was in the PULL-OUT position, rather than the normalNEUTRAL position (Inspection Reports 50-261/97-09 and 50-261/97-10 [Accessions 9710100035 and 9711190153]).There were no alarms present at the EDG control panel or at the control room indicating the abnormal switch position. Inthe PULL-OUT position, the EDG output breaker was incapable of performing its design closing function, thus making theEDG inoperable.

The output breaker control switch is a four-position, spring return to normal, T-handle switch. When manipulated to theTRIP or CLOSE position, the switch is designed to spring return to the NEUTRAL position upon release of the handle. Bymoving the switch to the TRIP position and then pulling the handle outward from the switch face and moving it counter-clockwise, the switch can be placed in the PULL-OUT position. The licensee postulated that the switch may have beenmispositioned as a result of an inadvertent bumping of the handle. There were some maintenance-related activitiesconducted in the EDG room preceding the discovery of the mispositioned switch. The switch had been manipulated duringa scheduled surveillance test approximately two weeks before to the discovery of the mispositioning. However, proceduralcontrols were not in place to confirm proper switch position following these manipulations. The switch was not checkedduring periodic operator rounds, although the switch affected the operability of the EDG.

**Mispositioned Voltage Regulator Potentiometers**

In 1993, at H. B. Robinson, both EDGs were rendered inoperable during painting activities. During these activities, thevoltage regulator potentiometers for both EDGs were erroneously adjusted to approximately 440 volts from the required480 volts when painters bumped into them (Inspection Report 50-261/93-35 [Accession 9401040383]). As in the caseabove, there were no alarms indicating the inappropriate settings, and the potentiometers were not checked during periodicoperator rounds.

**Mispositioned EDG Fuel Oil Transfer Switches**

At Watts Bar Nuclear Plant, during a routine tour of the EDG building, an inspector discovered that the fuel oil transferpump control switches for an EDG were in the off, instead of the required automatic position (Inspection Report 50-390/97010 [Accession 9802040123]). The control switches had been manipulated earlier, during a required surveillancetest of the fuel oil transfer pumps. Further review showed that the test method used by the operators was not in accordancewith procedures, which may have contributed to the switches being left in the off position. With the switches in the offposition, the automatic fill capability to the EDG day tank would not have been accomplished following an EDG start,resulting in the inoperability of the EDG. There were no audible alarms indicating the abnormal switch position, but therewere indicating lights at the local panel. However, the switch positions were not periodically verified during operatorrounds.

**Discussion**

The configuration control errors discussed in this information notice resulted in mispositioned components that were notannunciated to alert the operators to their abnormal position, yet they could render the EDG inoperable. Further, theverification of the component's configuration was not specifically prescribed in the checklist for the non-licensed operatorrounds. The corrective actions taken by the licensees as a result of the problems discussed above, included installing aprotective barrier to preclude inadvertent bumps to switches; better procedural guidance on switch manipulations and post-surveillance-testing restoration verification, and inclusion of safety-related switches in the non-licensed operator rounds topositively verify position. Additionally, the licensees reviewed other safety-related switches to determine if other similarunmonitored control switches existed.

The preceding examples highlight the need for continued attention to configuration control for components that may rendera system inoperable, but that are not provided with alarms. Further, it illustrates configuration control vulnerabilities thatwere not identified by non-licensed operator plant tours, because the components were not specifically listed in theirverification checklists.

This information notice requires no specific action or written response. However, recipients are reminded that they arerequired to consider industry-wide operating experience (including NRC information notices) where practical, when settinggoals and performing periodic evaluations under Section 50.65, "Requirement for monitoring the effectiveness ofmaintenance at nuclear power plants," to Part 50 of Title 10 of the Code of Federal Regulations.) If you have any questionsabout the information in this notice, please contact one of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.

Attachment:  List of Recently Issued NRC Information Notices

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