IR 05000285/1992022
| ML20125D114 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 12/09/1992 |
| From: | Beach A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Gates W OMAHA PUBLIC POWER DISTRICT |
| References | |
| NUDOCS 9212150002 | |
| Download: ML20125D114 (3) | |
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OR REGg UNITED STATES
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NUCLEAR REGULATORY COMMISSION k.
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DEC 9 1992 Docket No. 50-285 License No. DPR-40 Omaha Public Power District ATTN:
W. G. Gates, Division llanager Nuclear Operations 444 South 16th Street Hall Mail Stop 8E/EP4 Omaha, Nebraska C102-2247 SUBJECT: RESPONSE TO NRC INSPECTION REPORT 50-285/92-22 Thank you for your letter of November 23, I?
in response to our lettter and Notice of Violation dated October 22, 1992.
We have reviewed your reply and find it responsive to the concerns raised in our Notice of Violation. We will review the implementation of your corrective actions during a future inspection to determine that full compliance has been achieved and will be maintained.
Sincerely, A. Bill Beach, Director Division of Reactor Projects cc:
LeBoeuf, Lamb, Leiby & MacRae ATTN:
Harry H. Voigt, Esq.
1875 Cennecticut Avenue, NW Washington, D.C. ' 20009-5728 Washington County Board of Supervisors ATTN: Jack Jensen, Chairman Blair, Nebraska 68008 9212150002 921209
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-2-Combustion Engineering, Inc.
ATTN: Charles B. Brinkman, Manager Washington Nuclear Operations Ic300 Twinbrook Parkway, Suite 330
- Rockville, Maryland 20852 Nebraska Department of Health ATTN: Harold Borchert, Director Division of Radiological Health 301 Centennial Mall, South
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P.O. Box 95007 Lincoln, Nebraska 68509-5007 Fort Calhoun Station ATTN:
T. L. Patterson, Manager P.O. Box 399 Fort Calhoun, Nebraska 68023
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Omaha Public Power District-3-
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becLib!DMBI(IE01)N bec distrib. by RIV:
J. L. Milhoan Resident Inspector DRSS-ilPS Section Chief (DRP/C)
MIS System RIV File DRP RSTS Operator.
Project Engineer (DRP/C)
Lisa Shea, RM/ALF, MS: MNBB 4503
'DRS Section Chief (DRP/TSS)
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Senior Resident Inspector - Cooper G. F. Sanborn, E0 Senior Resident Inspector - River Bend J. Lieberman, OE, MS: 7-H-b
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Omaha Pub!)c Power District 444 South 16th Street Mall Omaha. Nebraska 68102-2247
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November 23, 1992 LIC-92-332 9?P
U. S. Nuclear Regulator Commission
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References: 1.
Docket No. 50-285 2.
Letter from NRC 22,1992 (A. B. Beach) to OPPD (W. G. Gates)' dated October Gentlemen:
SUBJECT:
NRC Inspection Report No. 50-285/92-22 Reply to a Notice of Violation (NOV)
The subject report transmitted a NOV resulting from an NRC inspection conducted August 30 through October 10, 1992 at the Fort Calhoun Station. Attached is the Omaha Public Power District response to this NOV.
If you should have any questions, please contact me.
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Sincerely,
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W. G. Gates Vice President - Nuclear i
Attachment WGG/grc
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LeBoeuf, Lamb, Leiby & MacRae J. L. Milhoan, NRC Regional Administrator, Region IV R. P. Mullikin, NRC Senior Resident Inspector S. D. Bloom, NRC Project Manager
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Attachment LIC-92 332 Page 1 REPLY TO A NOTICE OF VIOLATION VIOLATION During an NRC inspection conducted on August 30 through October 10, 1992, a violation of NRC requirements was identified.
In accordance with the " General Statement of Policy and Procedure for NRC Enforcement Actions," 10 CFR Part 2 Appendix C, the violation is listed below:
10 CFR Part 50, Appendix B, Criterion XVI, and the Fort Calhoun Quality Assurance Plan, Revision 3, Section 10.4, Paragraph 4.2.5, require, in part, that corrective actions associated with signific'nt conditions adverse to quality shall preclude repetition.
Contrary to the above, the licensee's corrective action to preclude the loss of 480-Vac busses during an abnormal electrical alignment failed to prevent recurrence.
On September 1, 1992, three 480 Vac busses were electrically tied together and supplied through one breaker, resulting in the breaker tripping open on an overloud condition. One of the corrective actions from a similar event, on April 12,1992 (monitoring the current on the busses), was inadequate in that the proceduralized maximum current monitored was the incorrect value to prevent a bus overload.
This is a Severity Level IV violation.
OPPD Response 1.
Reason for Violation A Root Cause Analysis (RCA) was completed by Omaha Public Pcwer District (OPPD) for this event.
The root cause was determined to be that the administrative current limit for the primary side of transformer TlB-4C was based on the Long Time Delay (LTD) design trip setpoint (2240 amps on the secondary side of transformer TIB-4C) for breaker 184C, while the LTD actual trip setpoint was calibrated using a nominal 1600 amps due to test equipment limitations.
As a
result of this inconsistency, the administrative current limit of 200 amps (primary side of transformer TIB-4C) was not low enough to preclude the breaker from tripping.
Either the administrative current limit needed to be lower or the breaker calibration needed to be performed using a higher test input current to ensure the LTD actual trip setpoint would be closer to the LTD design trip setpoint.
A similar event occurred on April 12, 1992 when power through 480 VAC breaker IB3A was lost while in an abnormal electrical lineup.
This event was described by NRC Inspection Report 50-285/92-09 and Licensee Event Report 92-15.
OPPD personnel reviewed this event in April 1992 and concluded that the breaker functioned properly and appeared to trip within the expected range. Therefore, deficiencies in the method of calibration were not suspected at that tim.- -
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Attachment LIC-92-332 Page 2 2.
Corrective Actions That Have Been Taken The administrative current limit i. procedure 01-EE-28 has been revised to 150 amps for the primary side of all six 4160/480 VAC transformers.
The basis for this change is the calibration input. test current of a nominal 1600 amps (corresponding to 173 amps at 4160 volts, providing a 23 amp margin prior trip) for the 480 VAC supply breakers.
This change should preclude overload bus tripping during abnormal bus alignments.
Operator training has been provided on the circumstances of this event and the new
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limitations in 01-EE-28.
Design Engineering evaluated the worst case Design Basis Analysis (DBA)
loading on the 480 VAC busses. For all breakers except 1830 and 1848, the load was calculated to be below 1500 amps and therefore was satisfactorily enveloped by the existing calibration method. Breakers 183C and 184B were determined to have a worst case Design Basis Analysis (DBA) loading of
approximately 1600 amps. Following the September 1,1992 event, breakers IB3C and 1848 were subsequently tested using the correct criteria.
The as-found condition verified that the trip points were above the projected DBA loads for buses IB3C and 1848.
The calibration procedures for IB3C and 1848 were revised to specify a 1900-2000 amp test input to ensure the LTD actual trip setpoint will be above the worst case DBA loading.
A generic implications analysis was performed and concluded that the 480 VAC breaker calibration problems revealed by this event do not extend to the 4160 VAC breakers.
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Corrective Actions That Will Be Taken
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Abnormal Operating Procedure A0P-32 has been revised to reflect the OI-EE-28 changes and will be implemented following completion of training. This will be completed by December 31, 1992.
A memorandum will be sent to desiga engineers and system engineers describing this event and the associated P,CA. The memorandum will discuss the need for using empirical or verified data versus unverified assumptions when performing analyses. This will be completed by December 15, 1992.
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Date of Full Comoliance
OPPD is presently in full compliance.
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