ML20035A402
| ML20035A402 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 03/19/1993 |
| From: | Linville J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Frizzle C Maine Yankee |
| References | |
| NUDOCS 9303260011 | |
| Download: ML20035A402 (3) | |
See also: IR 05000309/1992021
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liar 191333
Docket No. 50-309
Mr. Charles D. Frizzle
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President
Maine Yankee Atomic Power Company
83 Edison Drive
Augusta, Maine 04336
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Dear Mr. Frizzle:
SUBJECT:
INSPECTION 50-309/92-21
This refers to your February 24,1993 correspondence, in response to our January 26, 1993
letter.
Thank you for informing us of the corrective and preventive actions documented in your letter
regarding verification of engineering design reviews. These actions will be examined during a
future inspection of your licensed program.
Your cooperation with us is appreciated.
Sincerely,
Ull inal Signed By
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James C. f.inville
James C. Linville, Chief
Projects Branch No. 3
Division of Reactor Projects
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9303260011 930319
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OFFICIAL RECORD COPY
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Mr. Charles D. Frizzle
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cc:
G. Leitch, Vice President, Operations
P. L. Anderson, Project Manager (Yankee Atomic Electric Company) (w/cy of Licensee's
Response Letter)
R. W. Blackmore, Plant Manager
J. A. Ritsher, Attorney (Ropes and Gray) (w/cy of Licensee's Response Letter)
P. Dostie, State Nuclear Safety Inspector (w/cy of Licensee's Response letter)
Peter Brann, Assistant Attorney General (w/cy of Licensee's Response 12tter)
U. Vanags, Maine State Planning Office (w/cy of Licensee's Response 12tter)
C. Brinkman, Combustion Engineering, Inc. (w/cy of Licensee's Response Ixtter)
First Selectmen of Wiscasset (w/cy of Licensee's Response Letter)
Maine State Planning Officer (w/cy of Licensee's Response Letter)
Public Document Room (PDR) (w/cy of Licensee's Response Letter)
Imcal Public Document Room (LPDR) (w/cy of Licensee's Response Letter)
Nuclear Safety Information Center (NSIC) (w/cy of Licensee's Response Letter)
K. Abraham, PAO (2 copies) (w/cy of Licensee's Response Letter)
. NRC Resident Inspector (w/cy of Licensee's Response Letter)
State of Maine, SLO Designee (w/cy of Licensee's Response Ixtter)
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OFFICIAL RECORD COPY
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Region I Docket Room (with concurrences nnd IFS Forms)
J. Linsille, DRP
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W. Immms, DRP
C. Marschall, SRI - Maine Yankee (w/ concurrences and IFS Forms)
H. Eichenholz, SRI - Vermont Yankee
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ED:50N DA!VE - AUGUTA MA'NE M33C . ;2Ti 622-4359
February 24, 1993
MN-93-20
JRH-93-37
UNITED STATES NUCLEAR REGULATORY COMMISSION
Attention: Document Control Desk
Washington, DC 20555
References:
(a)
License No. DPR-36 (Docket No. 50-309)
(b) USNRC Letter to MYAPCo dated January 26, 1993 - Resident
Inspection Report 50-309/92-21
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Subject:
Inspection Report 92-21: Response to Notice of Violation Associated with
the Verification of an Engineering Design Review
Gentlemen:
The attacliment to this letter responds to the Notice of Violation contained in
Reference (b).
In this attachment, we have restated the violation, provided our
response, and have addressed our actions taken and planned to prevent recurrence.
Please contact us should you have any questions regarding this matter.
Very truly yours,
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JJames R. Hebert, Manager
Licensing & Engineering Support Department
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Attachment
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Mr. Thomas T. Martin
Mr. Charles S. Marschall
Mr. E. H. Trottier
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Mr. Patrick J. Dostie
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Notice of Violation:
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During an inspection from November 20 thrcugh December 31, 1992, a violation of NRC
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requirements was identified. In accordance with the " General Statement of Policy and
Procedure for NRC Enforcement Actions," 10CFR Part 2, Appendix C (1992), the
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violation is listed below:
A.
10CFR Part 50, Appendix 8, Criterion III, states, in part, that licensees shall
establish design control measures for verifying the adequacy of design reviews.
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Contrary to the above, in December 1989, Maine Yankee failed to properly verify
the adequacy of a design review of the Primary and Secondary Component Cooling
Systems.
As a result, Maine Yankee failed to ensure that the plant operated
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with adequate loss of coolant accident heat removal capacity between December
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1989 and December 1993.
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Maine Yankee Response:
Stone and Webster Engineering Corporation (SWEC) design basis flow calculations for
the component cooling water systems that were performed in 1989 assumed that
Secondary Component Cooling (SCC) flow through valve SCC-T-227 would be negligible
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when the valve closed in response to a Containment Spray Actuation Signal (CSAS).
When SWEC assembled the calculation inputs during 1989, a Maine Yankee engineer
reviewed the post loss of Cooling Accident (LOCA) SCC system lineup and verified that
SCC-T-227 would be closed. However, the engineer overlooked the assumption that SCC-
T-227 was leak tight.
When recent maintenance activities discovered flow through SCC-T-227 in the closed
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position, plant startup was delayed while the SWEC SCC flow calculation was revised
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to include this flow. Maine Yankee calculations determined that for flows through
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SCC-T-227 up to about 150 gpm, flows to the Residual Heat Removal (RHR) heat
exchanger would still be adequate to provide post-LOCA heat removal capacity. Since
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design flow through SCC-T-227 in the closed position is 65 gpm, no change to the
maximum allowable service water inlet temperature was required to incorporate the
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actual design leak rate for the valve. Therefore, the operating limits for maximum
allowable service water temperatures were adequate to ensure SCC heat removal
capacity from December 1989 to December 1992 because the design leak rate for SCC-T-
227 is bounded by the allowable leak rate.
However, the maintenance activities referenced above also determined that leakage
through SCC-1-227 was initially measured at about 400 gpm and could only be improved
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to about 225 gpm by making external adjustments. Therefore, a bounding calculation
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was performed which evaluated current system conditions and, as a result, Maine
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Yankee conservatively reduced maximum allowable service water inlet temperatures by
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20af as an interim measure to allow plant startup to proceed while formal
calculations to change to the SWEC thermal analysis were performed.
The formal
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calculations to change the SWEC thermal analysis are complete and the results require
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a 4' reduction in maximum allowable service water inlet temperature based on a total
leakage flow of 400 gpm to nonsafeguards components.
Operating procedure
restrictions are being revised accordingly.
Substantial margin exists between actual service water inlet temperatures and maximum
allowable service water temperatures.
Maine Yankee has reviewed service water
temperature history for December 1989 through December 1992 and determined that the
revised allowable temperatures based on a 400 gpm leak have not been exceeded.
Therefore, we conclude that the plant has operated with sufficient SCC system heat
removal capacity from 1989 to the present time as indicated in Section 4.2 of the
inspection report, Reference (b), which i^ attached to the NRC Notice of Violation.
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Immediate Corrective Action and Results Achieved:
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The SCC-T-227 leakage was discovered on December 13, 1992, while the plant was
preparing to start up.
Plant start up was delayed until engineering verified that
SCC system capability was adequate at current service water temperatures, which was
completed on December 14, 1992.
Corrective Action Taken to Avoid Further Violations:
The root cause of this violation was a failure to perform an adequate review of an
assumption in an engineering analysis.
Maine Yankee is revising Procedure 17-21-5, ENGINEERING CALCULATIONS / ANALYSES to
include additional guidance to prevent recurrence. This procedure revision should
be completed by March 31, 1993.
In addition, the procedure revisions will be
discussed at future Engineering Department meetings to assure full awareness of this
issue.
The procedure revision will include specific requirements for an engineer reviewing
engineering calculations to ensure that key assumptions and their bases are
identified and to ensure that the assumptions are reasonable.
Full Comoliance Date:
Full compliance for the measured flows through SCC-T-227 was ensured on December 14,
1992, when engineering completed a preliminary calculation showing that SCC System
capability would meet design basis requirements. The formal calculation which added
400 gpm leakage to the SWEC calculations was completed 01/08/93 and resulted in a 4*F
reduction of maximum allowable service water inlet temperature for SCC system
operability.
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