05000336/LER-2005-003

LER-2005-003,

Docket Number
Event date:	05-19-2005
Report date:	09-20-2005
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3362005003R01 - NRC Website

1. Event Description On May 18, 2005, with the plant in mode 1 at 29% power, a non-safety related test instrument was discovered (MPS 2) "B" emergency diesel generator (EDG)[EK]. The subject test instrument is used while testing an inoperable EDG. The subject test equipment is not provided with a qualified isolation device used to provide the necessary separation from the safety related equipment. If the subject test equipment or associated leads shorted or grounded due to a failure or seismic event, it may have caused the subject potential transformer to fail rendering the "B" EDG inoperable. Although the test equipment was still installed, the "B" EDG was (incorrectly) declared operable while in Mode 5 at 2144 on May 13, 2005 following completion of testing.

TS 3.0.4 requires that entry into an operational mode or another specified condition shall not be made when the conditions for the limiting conditions for operation are not met and the associated action requires a shutdown if they are not met within a specified time interval. The "B" EDG is required to be operable by Technical Specification (TS) 3.8.8.1 during modes 1, 2, 3, and 4. MPS 2 entered mode 4 at 1504 on May 15, 2005, with the "B" EDG inoperable due to the installed unqualified test equipment.

The subject test instrument was subsequently removed.

Since the TS requirement was not met, this is a condition prohibited by the TS and is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B).

Additional consequential non-compliance with TS was also noted as a result of being in modes 1, 2, 3, or 4 without recognizing that the "B" EDG was inoperable. Affected TSs were TS 3.8.1.1 Actions b.1, b.2, and b.3, and TS Surveillance Requirements 4.0.5, 4.8.1.1.1, 4.8.1.1.2.a.2, 4.4.9.3.1.a., and 3.0.5.

2. Cause The cause of this event was determined to be human error. The test instrument was not removed from the "B" EDG because the Night Shift Work Control Reactor Operator (WCRO) was not aware of this responsibility to have the instrument removed, due to an inadequate turnover with the Day Shift WCRO.

3. Assessment of Safety Consequences There were no adverse consequences as a result of this event. This event is significant because either a failure of the test equipment or a seismic event may have adversely affected the ability of the "B" EDG to operate if required.

During the period that the test equipment was installed, the "B" EDG was capable of operation. The "B" EDG was successfully exercised on May 13, 2005, after the test equipment was installed. The potential that the test equipment could physically interact with other safety related equipment was also reviewed. Using the seismic hazard curve for Millstone in NUREG-1488, the probability of a seismic event capable of causing a loss of offsite power during a 5 day period is relatively low, estimated to be less than 6E-6. When crediting the availability of the redundant EDG diesel, the risk of core damage is less than 6E-8, which would be characterized as green in the NRC Significance Determination Process (SDP).

The operability of A.C. sources (including EDGs) ensures that sufficient power is available to supply the safety related equipment required for safe shutdown of the facility, and to mitigate accidents within the facility. Although the "B" EDG should have been considered inoperable, in accordance with the TS requirements, the "B" EDG was available and capable of performing its function. Additionally, procedures exist (and operators are trained) that provide the necessary guidance to mitigate accidents with less than the minimum required A.C. sources and distribution systems. Therefore, the safety consequences and implications of this event were minimal.

4. Corrective Action An investigation was conducted and appropriate corrective actions are being addressed in accordance with the Millstone Corrective Action Program.

The corrective actions to prevent recurrence of this condition were determined to be:

• The Dominion Nuclear Operations Standard, DNOS 0306, "Shift Turnover," will be reinforced with the Operations department and monitored via the station work observation program,

• The appropriate MPS 2 EDG Operations Forms will be revised to include test equipment restoration.

The corrective actions associated with this condition are being addressed in accordance with the Millstone Corrective Action Program.

5. Previous Occurrences No previous similar events/conditions were identified at MPS.

Energy Industry Identification System (EIIS) codes are identified in the text as [XX].