ML20078M361
| ML20078M361 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 10/17/1983 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8310250149 | |
| Download: ML20078M361 (2) | |
Text
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rm TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374ol 400 Chestnut Street Tower II
%tGBU97A p3gy BLRD-50-438/83-10 BLRD-50-439/83-07 U.S. Nuclear Regulatory Commission Region II Attn:
Mr. James P. O'Reilly, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303
Dear Mr. O'Reilly:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - P0hER FOR EMERGENCY AIR CLEANUP UNITS AFTER LOSS OF OFFSITE POWER - BLRD-50-438/83-10, BLRD-50-439/83 - FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector P. E.
Fredrickson on January 3, 1983 in accordance with 10 CFR 50.55(e) as NCR BLN BLP 8235. This was followed by our interim report dated January 28, 1983 Enclosed is our final report.
If you have any questions, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours, TENNESSEE VALLEY AUTHORITY V1.
L. M. Mills, nager Nuclear Licensing-Enclosure cc:
Mr. Richard C. DeYoung, Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Records Center (Enclosure)
Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 gyy1CI AL OU'N]
8310250149 831017 PDR ADOCK 05000438 S
PDR y-I (
1983-TVA SOTH ANNIVERSARY An Equal Opportunity Emphyer
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ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 POWER FOR EMERGENCY AIR CLEANUP UNITS AFTER LOSS OF OFFSITE POWER BLRD-50-438/83-10, BLRD-50-430/83-07 10 CFR 50.55(e)
NCR BLN BLP 8235 FINAL REPORT Description of Deficiency The emergency air cleanup units limit the nirtorne centamination in the main control room to acceptable levels anc the unito are started either automatically or manually during control room isolation. The Control Building Environmental Control System Design Criteria (N4-VK-D740) requires that all redundant safety-related components be automatically leacad as part of the accident loading sequence and the loss of power loading saquence. However, a recent drawing review initiated in response to NCR BLN 04B 8:01 has disclosed that, due to a design error, the present solid-state control system's (SSCS) controls will not allow the unit to be automatically loaded as part of the loss of power loading sequence in the event the unit had been operating before loss of offsite power.
The error was caused by a failure of the designer and checker to recognize all possible combinations of c9nditions.
Safety Implications As originally designed, the SSCS control circuit would function properly for either control room isolation without locs of offsite power or for control room isolation occurring after loss of offsite power. However, if an event which required control room isolation occurred and the emergency air cleanup units were activated and then there was a loss of offsite power the units would not be automatically loaded. This situation could then cause the loss of control room habitability which could adversely sffect safe plant operation.
Corrective Action TVA issued engineering change notice (ECN) 1690 to correct the control logic so that the clean-up units will be automatically lohded as part of the loss of power loading sequence, and this ECN has been implemented at the site. Also, additional review of this and all other safety-related systems has been concluded to provide additional assurance that functional control logic diagrams (FCLDs) are in compliance with design criteria drawings.
This design error occurred several years before the issuance of the Division of Engineering Design's (EN DES) Engineering Procedure (EP) 4.25. TVA believes that this EP, which requires a checker who is both technically qualified and independent of the designer, will prevent a recurrence of this type of problem.
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