SVPLTR 10-0016, Response to Non-Cited Violation (NCV) of Very Low Safety Significance for Routinely Performing EDG Governor Oil Changes

Response to Non-Cited Violation (NCV) of Very Low Safety Significance for Routinely Performing EDG Governor Oil Changes

ML100740373
Person / Time
Site:	Dresden
Issue date:	03/12/2010
From:	Hanley T Exelon Generation Co, Exelon Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
IR-09-003, SVPLTR 10-0016
Download: ML100740373 (3)

Text

Exelon Generation www.exeloncorp.com Exeltnm Nuclear Dresden Generating Station 6500 North Dresden Road Morris, IL 60450-9765 March 12, 2010 SVPLTR: #10-0016 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-19 and DPR-25 Docket Nos. 50-237 and 50-249

Subject:

Response to NCV 05000237(249)/2005009-03

Reference:

Letter from M. Ring (NRC) to C. Pardee (Exelon Generation Company, LLC), "Dresden Nuclear Power Station, Units 2 and 3 Integrated Inspection Report 05000237(249)/2009005," dated February 10, 2010 In the referenced letter, the NRC identified a finding and associated non-cited violation (NCV) at Dresden Nuclear Power Station (DNPS) of very low safety significance (Green) for routinely performing EDG governor oil changes, on a six year frequency, prior to performing required Technical Specification surveillances.

In accordance with 10 CFR 2.201, "Notice of violation," EGG is contesting this finding and its associated NCV. The basis for contesting this finding is that although we agree with the general facts contained in the inspection report and that a perceived potential for preconditioning occurred with the replacement of the EDG governor oil on a six year frequency, EGC believes that the maintenance performed was acceptable in that it is required preventative maintenance (PM) performed at the vendor recommended frequency and was performed with no expectation to improve the performance of the EDG. Also, the PM would not have masked a degraded condition.

EGC would also like the opportunity to meet with the NRC to further discuss the potential generic impacts of this violation on other surveillance testing methodologies.

First, it is EGC's intent to meet the NRC guidance on preconditioning and we have reviewed our internal processes and identified enhancements that will minimize the possibility of unacceptable preconditioning. However, EGC has determined that this specific PM has no potential to mask a degraded condition existing in the EDG governor. This was demonstrated via the compensation settings being successfully tested at least twice since the last oil change PM approximately six years ago by the undervoltage testing that is performed during each refueling outage. As part of the PM, the EDG governor compensation setting is locked in place after the last compensation adjustment, and subsequent drifting of the adjustment has not been observed here at DNPS. As described in the Woodward UG-8 Governor Installation and Operational manual 03040D, the compensation needle valve and lever (pointer) are the only adjustable parts of the compensation system. Their settings directly affect governor transient response and stability. The Nuclear Governor Coordinator at the EDG vendor facility stated that compensation adjustment is not expected to change over time unless other parameters in the governor change such as oil viscosity/quality and governor internal clearances, and even then, the changes would not be

U. S. Nuclear Regulatory Commission March 12, 2010 Page 2 of 3 expected to be dramatic and would not affect operability. The DNPS's own experience confirms the vendor's position as a surveillance test failure has not been experienced due to compensation drift.

The absence of engine/governor instability and demonstration of proper transient response during past surveillances shows that the governor compensation settings do not unacceptably drift. With no evidence of general governor problems in previous monthly, quarterly or semiannual surveillances, and no concern of potentially masking a degraded condition, this PM activity is acceptable preconditioning.

Narrowly, the issue for EGC with regard to this violation is the ambiguity surrounding what constitutes routine PMs. The examples cited in Information Notice 97-16 are activities that were performed repeatedly prior to a required surveillance.

NRC Inspection Procedure (IP) 62707, Maintenance Observation provides a perspective on preventative maintenance:

"Preventive maintenance activities are not routinely being scheduled to "Precondition" equipment prior to performing surveillance tests in order to help ensure the test is passed satisfactorily.

Inspectors should examine the sequence of preventive maintenance (PM) activities to determine if the licensee routinely schedules PMs prior to a surveillance tests. This could mask an equipment deficiency which would inhibit its ability to perform its intended function." IP 62707 focuses on activities performed to help ensure the subsequent testing is successful. The purpose of the oil change and subsequent compensation adjustment was not to improve the performance of the EDG, nor would it mask a potential equipment deficiency. The compensation adjustment is performed following the governor oil change in order to ensure any air entrained in the governor oil system during the oil change is purged prior to returning the EDG to operable status. The subsequent undervoltage testing ensures that the compensation adjustment was performed properly following the oil change.

Generally, EGC's agrees that as-found testing should be scheduled prior to performing maintenance. However, it is our position that it is acceptable to schedule and perform PMs on a component prior to performing a surveillance when the PM is not routinely performed just prior to the surveillance (i.e., it is performed at an interval greater than the surveillance frequency). For example, when it is inappropriate or impractical and where past tests have been performed without prior maintenance activities for the majority of the time, (i.e., three quarterly surveillances out of four or in this specific case, the surveillance was successfully performed twice before the PM was executed), then the PM is not routine and the maintenance activity, with an appropriate evaluation, can be considered as acceptable preconditioning.

It is not practical to schedule an as-found performance of TS SR 3.8.1.10 (i.e., a largest single load rejection test) prior to the governor oil change/compensation adjustment and then re-perform an as-left largest single load rejection test as a post-maintenance test for the work. The largest single load reject test can only be properly executed during a refueling outage due to the design of Dresden's 4 kV distribution system, as the test requires the EDG to carry the emergency bus in isochronous governor mode. Performing this test is only feasible when in a refueling outage due to

U. S. Nuclear Regulatory Commission March 12, 2010 Page 3 of 3 the inherent instability of running an EDG in parallel with off-site power when in isochronous control. In addition to the work-process inefficiencies, the EDG would be subjected to an unnecessary perturbation which is adverse to long-term EDG reliability. Our existing practice appropriately balances the need for preventive maintenance with the need to ensure that the EDG will respond properly to a design-basis event after the work is complete. This practice is consistent with the theme of eliminating overly-harsh EDG operating practices first promulgated under NRC Generic Letter 84-15, and further eliminating unnecessary EDG testing that is advocated in Generic Letter 93-05 and NUREG-1366.

If you have any questions regarding this response, please contact Ms. Marri Marchionda- Palmer, Regulatory Assurance Manager, at (815) 416-2800.

Respectfully, 6/nle*

Site Vice President Dresden Nuclear Power Station cc: Regional Administrator- NRC Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station Director, Office of Enforcement, NRC