ML20202D069
| ML20202D069 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 03/20/1986 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8604110495 | |
| Download: ML20202D069 (3) | |
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TENNESSEE VALLEY AUTHORITY SN 157B Lookout Place ba h b, k9 6 M
BLRD-50-438/85-25 BLRD-50-439/85-22 U.S. Nuclear Regulatory Commission Region II Attn:
Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323
Dear Dr. Grace:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - UNDERVOLTAGE OF THE 125V DC VITAL POWER DISTRIBUTION SYSTEM TO AUXILIARY FEEDWATER TURBINE PUNP ROOM COOLING FANS - BLRD-50-439/85-25, BLRD-50-439/85 FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector Al Ignatonis on August 6,1985 in accordance with 10 CFR 50.55(e) as Significant Condition Report (SCR) BLN EEB 8510. This was followed by our first interim report dated September 18, 1985.
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
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L. Gridley Manager of Licensing cc:
Mr. James Taylor, Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Conunission Washington, D.C.
20555 Records Center (Enclosure)
Institute of Nuclear Power Operations 1100 circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 8604110495 860320 PDR ADOCK 05000438 9
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An Equal Opportunity Employer SED 9
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ENCLOSURE 4
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 j
UNDERVOLTAGE OF THE 125VDC VITAL POWER DISTRIBUTION SYSTEM TO AUXILIARY FEEDWATER TURBINE PUMP ROOM COOLING FANS BLRD-50-438/85-25 AND BLRD-50-439/85-22
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FINAL REPORT 1
Description of Deficiency l
While doing the voltage drop calculation for cables on Bellefonte Nuclear Plant (BLN), it was discovered that the auxiliary feedwater turbine pump room cooling fans would not operate a full two hours after loss of AC power.
The design configuration of the 125VDC vital power distribution system (EU) 1 provides a 104.5VDC terminal voltage two hours after loss of AC power. This low source voltage, coupled with the existing cable voltage drop, results in insufficient voltage to the auxiliary feedwater turbine pump (AFTP) rooms cooling fan motors. The insufficient voltage reduces the cooling capacity of the fans and could result in a high temperature environment for the AFTP controls.
The apparent cause of this deficiency appears to be an isolated failure for BLN personnel to consider the effects of cable voltage drop in the design of DC feeder cable circuits. This deficiency was the only one of this nature discovered in the design review of cables at BLN.
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Similar deficiencies have been identified at other TVA plants; Browns Ferry Nuclear Plant (NCR BFN EEB 8505 R2), Sequoyah Nuclear Plant (SCR SQN EEB 8514), and Watts Bar Nuclear Plant (SCR WBN REB 8515 and SCR WBN EEB 8520).
j Safety Implications A high temperature environment could cause a failure of the AFTP controls and subsequently lead to the inoperability of the AFTP, Upon the loss of both i
motor-driven auxiliary feedwater pumps due to the loss of all electrical AC i
power, the AFTP is required to supply adequate feedwater to the steam generators to bring the reactor coolant system temperature down and maintain i
the reactor in a safe condition until electrical AC power can be restored.
i The subject condition could have resulted in misoperation of the AFTP control i
circuits and subsequently could have adversely affected the safe operation of the plant.
-I Corrective Action i
i Engineering Change Notices (ECNs 3379 and 3382) have been written to identify and track the corrective action.
TVA will install new conduit and cable in a more direct route, which will give a cable length that is much shorter.
t The voltage drop will be lower, allowing sufficient voltage for the fan motor to 4
operate.
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- In order to eliminate the possibility of the recurrence of this problem. TVA has issued voltage drop calculations for all safety-related cables at BLN and will maintain these documents in accordance with Office of Engineering Procedure (OEP)-07-Calculations.
All action to correct the deficient condition will be completed for unit 1 and unit 2 by six months before fuel load of the applicable unit.
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