ML101580337
| ML101580337 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/04/2010 |
| From: | Pederson C Region 3 Administrator |
| To: | Pardee C Exelon Generation Co, Exelon Nuclear |
| References | |
| EA-10-056 | |
| Download: ML101580337 (8) | |
See also: IR 05000237/2009005
Text
UNITED STATES
NUCLEAR REGULATORY COMMISSION
REGION III
2443 WARRENVILLE ROAD, SUITE 210
LISLE, IL 60532-4352
June 4, 2010
Mr. Charles G. Pardee
Senior Vice President, Exelon Generation Company, LLC
President and Chief Nuclear Officer (CNO), Exelon Nuclear
4300 Winfield Road
Warrenville, IL 60555
SUBJECT: RESPONSE TO DISPUTED NON-CITED VIOLATION - DRESDEN NUCLEAR
POWER STATION NRC INSPECTION REPORT 05000237/2009-005;
Dear Mr. Pardee:
On March 12, 2010, Mr. Tim Hanley, Exelon Generation Company (EGC), LLC, Dresden Station
Site Vice President, provided a response to a U.S. Nuclear Regulatory Commission (NRC)
Inspection Report issued on February 10, 2010, concerning activities conducted at your facility.
Specifically, you contested a finding and associated Non-Cited Violation (NCV) contained in the
inspection report, namely Green NCV 05000237/2009005-03, regarding unacceptable
Preconditioning of the Unit 2 Emergency Diesel Generator (EDG) Prior to Performing Technical
Specification (TS) Surveillance Requirements.
On April 1, 2010, the NRC acknowledged your letter. We have completed our review and
determined that the Title 10 of the Code of Federal Regulations, Part 50 (10 CFR 50),
Appendix B, Criterion XI, Test Control violation occurred as stated in the inspection report. In
addition, we identified one additional aspect of unacceptable preconditioning related to the
maintenance activities discussed in the report. We consider this additional aspect of
unacceptable preconditioning to be an additional example of the subject NCV. The finding and
NCV will remain as documented in the inspection report.
In your March 12, 2010, letter, you indicated that:
- Your intent is to meet the NRC guidance on preconditioning;
- You agree with the general facts contained in the inspection report;
- You believe that a perceived potential for preconditioning occurred with the replacement
of the EDG governor oil on a 6 year frequency;
C. Pardee -2-
- 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;
(note - you have subsequently changed this position).
This was demonstrated by:
o The EDG governors compensation settings being successfully tested at least
twice since the last oil change PM approximately 6 years ago by the under
voltage testing that is performed during each refueling outage;
o 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 at Dresden. As described in the Woodward
UG-8 Governor Installation and Operational Manual, 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;
and
o The Nuclear Governor Coordinator at the EDG vendor facility stated that the
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 expected to be
dramatic and would not affect operability. Dresden's own experience confirms
the vendors position as a surveillance test failure has not been experienced due
to compensation drift.
- Narrowly, your issue is the ambiguity surrounding what constitutes routine PMs. The
examples cited in NRC Information Notice 97-16 are activities that were performed
repeatedly prior to a required surveillance;
- NRC Inspection Procedure 62707, Maintenance Observation, provides the following
perspective on PM: Preventative 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
PM activities to determine if the licensee routinely schedules PMs prior to a surveillance
test;
- When the maintenance activities are not routinely performed before Technical
Specification Surveillance Requirements (TSSRs), the preconditioning can be
considered acceptable if an appropriate evaluation is performed;
- It is not practical to schedule an as-found performance of TSSR 3.8.1.10 (i.e., 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
(PMT) for the work. The largest single load reject test can only be properly executed
C. Pardee -3-
during a refueling outage due to the design of the Dresden 4kV distribution system as
the test requires the EDG to carry the emergency bus in isochronous governor mode. In
addition to the work-process inefficiencies, the EDG would be subjected to an
unnecessary perturbation which is adverse to long-tem EDG reliability. EGCs existing
practice is consistent with the theme of eliminating overly-harsh EDG operating practices
first promulgated under NRC Generic Letter 84-15, and further eliminate unnecessary
EDG testing that is advocated in Generic Letter 83-05, and NUREG-1366;
- You would like an opportunity to meet with the NRC to further discuss the potential
generic impacts of this violation on other surveillance testing methodologies.
NRC Staffs Review:
We reviewed the information you provided to determine if the NCV was properly characterized.
The NRC staff members that reviewed your basis for contesting the NCV were independent of
the initial inspection effort. After careful consideration, we have concluded that the violation
occurred as stated in the inspection report. In addition to the example contained in the
inspection report, the staff identified that EGC did not consider an additional aspect of EDG
preconditioning. Specifically, the EDG governors oil had been changed prior to the TSSR test
without an assessment as to how the as-found oil quantity and quality would/could affect the
TSSR test results. For example, a change in oil viscosity would affect the governors response
to a load change. The underlying performance deficiency involved in these examples involved
preconditioning the EDG in a manner such that the as-found condition was not preserved and a
latent condition adverse to quality could have been masked or bypassed. Although it is
generally recognized that PMs are set up with a frequency that is adequate to ensure
component reliability, unexpected conditions adverse to quality occur. The purpose of a TSSR
test is to detect these latent issues that may have developed within the specified testing
frequency.
Below, we have addressed the information that you stated supported your basis for acceptable
preconditioning. Our conclusions were based on the requirements of 10 CFR 50, Appendix B,
Criterion XI, Test Control. Our NRC Part 9900 Preconditioning Technical Guidance provides
our inspectors with guidance on evaluating the acceptability of preconditioning Structures,
Systems, and Components (SSCs) before performing operability, surveillance, or conformance
testing. However, this guidance was not used in a deterministic fashion, but rather as a part of
our overall assessment. This Technical Guidance is publicly available and can be utilized by
licensees to ensure unacceptable preconditioning does not occur (NRC Manual Chapter
Part 9900, Technical Guidance, Maintenance - Preconditioning of SSC before Determining
Operability, dated 9/28/1998). We recognize that following this guidance is not mandatory.
- We understand your intent to meet the NRCs guidance on preconditioning. The staffs
current guidance is contained in the NRC Manual Chapter Part 9900 Technical
Guidance. NRC Inspection Procedure 62707, Maintenance Observation is not a
required baseline inspection and was not utilized by the inspectors that originally
documented the issue. However, this inspection procedure was reviewed and
considered by the inspectors after we understood you used it as a basis for your
position.
C. Pardee -4-
- We understand that you did not identify any factual discrepancies for the NRC to
reconsider.
- We understand that you had performed the work activities in concert with no
expectations to precondition the EDG. Our guidance recognizes that preconditioning
may be inadvertent, however, the nature of the performance deficiency was that you
should have had suitable test controls in accordance with 10 CFR 50, Appendix B,
Criterion XI, Test Control, to ensure that the TSSR tests properly tested the as-found
EDG condition.
- Through conversations with your staff, we understand you have changed your position
and now recognize that the PM could mask or bypass a degraded condition. We agree
with this conclusion. You concluded that the cause of the failed TSSR test was due to
maintenance activities involving a governor compensation that was performed incorrectly
just prior to the test. This testing failure (and review of the specific job steps)
demonstrates that the prior maintenance activity clearly changed the as-found
conditions. The PMT for the oil change involves starting the EDG, stroking the fuel rack
to full travel 10 to 12 times to remove trapped air from governor passages, and
performing an EDG governor compensation adjustment. A note in the maintenance
procedure describes: The objective of the compensation adjustment is to find the
particular setting for the compensation needle valve and compensation adjustment
pointer at which the engine will return quickly to speed after a speed disturbance with
only a slight overshoot or undershoot. The TSSR test, in part, tests how quickly the
EDG responds to this change of speed (i.e., load change). The true as-found condition
is, therefore, preconditioned following the governor adjustment. As a result, the TSSR
test is not testing the as-found condition, but rather testing the as-left maintenance
condition. In addition to the governor compensation, we identified a second example of
unacceptable preconditioning. The EDG governor oil is changed out without any
assessment of how the as-found condition of the oil would have affected the machines
performance (e.g., oil viscosity, oil quality, biological fouling, etc.). Although it is
generally recognized that PMs are set up with a frequency that is adequate to ensure
component reliability, unexpected conditions adverse to quality can occur. The
inspectors noted that a change in oil viscosity would directly affect the machines
response to a load.
- We understand your review that this preconditioning issue can be narrowed to the
ambiguity surrounding what constitutes routine PMs. We disagree that a decision on
preconditioning can be narrowed to a definition of routine PMs. Our view is that
non-routine preconditioning may be acceptable if an acceptable engineering evaluation
is performed. As noted elsewhere in this letter, we did not consider your evaluation
acceptable.
- NRC Inspection Manual Part 9900 Technical Guidance states, Except where there is a
need to protect personnel or prevent equipment damage, preventive maintenance
should not be performed before TS surveillance testing. To the greatest extent possible,
SSCs should be tested in the as-found condition in order to determine if they would be
capable of performing their intended function and to collect as-found performance or
C. Pardee -5-
condition baseline data. In the cases in which the licensee chooses to precondition
SSCs, the effects on equipment performance or condition should be documented in an
engineering evaluation. This engineering evaluation should be performed in advance of
the surveillance. Although the evaluation in the Technical Guidance is not an NRC
requirement, the licensee did not provide an adequate explanation (either documented in
the corrective action program, or verbally discussed with the inspectors).
- You did not perform an evaluation prior to the maintenance activity. During our review of
the contested NCV, you performed the evaluation, Evaluation of Preconditioning
Acceptability. This evaluation concluded that the maintenance practice does by-pass or
mask the as-found condition (i.e., EGC answered Yes to question 3 of 5 of the Part I
questions). Part II of evaluation concluded that this was acceptable based on the need
to prevent equipment damage. In addition, the governor compensator adjustment, if
improperly performed, will adversely affect the outcome of the surveillance test, but is
unlikely to improve performance of the surveillance test. We do not agree with this
conclusion. We concluded that a degraded governor could be enhanced by having its oil
changed and response tuned in accordance with the prescribed maintenance activities.
Comprehensively, the evaluation did not provide an adequate basis to justify the
maintenance activities preconditioning the TSSR test and did not provide an adequate
basis to conclude that the preconditioning was acceptable.
- You stated that the TSSR tests can only be properly executed during a refueling outage
due to the design of the Dresdens 4kV distribution system. Our staff has not implied nor
made any suggestions as to the Mode in which the TSSR tests are or will be performed.
Our expectation is that these tests and types of tests be performed in a safe manner and
in accordance with 10 CFR 50, Appendix B, Criterion XI, Test Control, and other
applicable licensing basis requirements. We concluded that your example of work
progress inefficiencies is not an acceptable basis to precondition the EDG.
- You had stated that performing an additional test would subject the EDG to an additional
perturbation and adversely affect long-term EDG reliability. Affecting long-term reliability
is not the standard of our guidance, but rather the standard is to protect equipment from
damage. ECG has not made an adequate case for protecting the equipment from
damage consistent with the examples presented in our guidance.
- You requested an opportunity to meet with the NRC to further discuss the potential
generic impacts of this violation on other surveillance testing methodologies. We now
understand that you no longer request this meeting, at this time, based on discussions
with your staff.
NRC Conclusion:
Technical Specification surveillance and American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code in-service testing (testing) are performed to verify that
operability and performance (or condition) characteristics of SSCs have not degraded below
specific acceptance criteria during a specified period. The NRC expects surveillance and
testing processes of SSCs to be evaluated in an as-found condition. However, we recognize
C. Pardee -6-
that preventive maintenance activities are sometimes performed immediately before testing, and
these activities may involve manipulations of the SSCs that would constitute preconditioning the
equipment rather than testing it in the as-found condition. Whether such preconditioning is
acceptable, depends on the circumstances.
We have concluded that the station unacceptably preconditioned the Unit 2 EDG by performing
preventative maintenance and post-maintenance testing activities prior to performing required
TSSR testing on November 13, 2009, as documented in NRC Inspection Report 05000237/2009005; 05000249/2009005. In addition, the staff identified that, in addition to the
example discussed in the inspection report, EGC unacceptably preconditioned the
EDG governor by changing the oil without ensuring the as-found testing condition was properly
preserved.
In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter will be
available electronically for public inspection in the NRC Public Document Room or from the
Publicly Available Records System (PARS) component of NRC's Agencywide Documents
Access and Management System (ADAMS). ADAMS is accessible from the NRC Website at
http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).
Sincerely,
/RA/
Cynthia D. Pederson
Deputy Regional Administrator
Docket No. 50-237; 50-249
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C. Pardee -6-
that preventive maintenance activities are sometimes performed immediately before testing, and
these activities may involve manipulations of the SSCs that would constitute preconditioning the
equipment rather than testing it in the as-found condition. Whether such preconditioning is
acceptable, depends on the circumstances.
We have concluded that the station unacceptably preconditioned the Unit 2 EDG by performing
preventative maintenance and post-maintenance testing activities prior to performing required
TSSR testing on November 13, 2009, as documented in NRC Inspection Report 05000237/2009005; 05000249/2009005. In addition, the staff identified that, in addition to the
example discussed in the inspection report, EGC unacceptably preconditioned the
EDG governor by changing the oil without ensuring the as-found testing condition was properly
preserved.
In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter will be
available electronically for public inspection in the NRC Public Document Room or from the
Publicly Available Records System (PARS) component of NRC's Agencywide Documents
Access and Management System (ADAMS). ADAMS is accessible from the NRC Website at
http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).
Sincerely,
/RA/
Cynthia D. Pederson
Deputy Regional Administrator
Docket No. 50-237; 50-249
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OFFICIAL RECORD COPY
Letter to C. Pardee from C. Pederson dated June 4, 2010
SUBJECT: RESPONSE TO DISPUTED NON-CITED VIOLATION - DRESDEN NUCLEAR
POWER STATION NRC INSPECTION REPORT 05000237/2009-005;
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