ML20214G019
| ML20214G019 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 11/10/1986 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8611250525 | |
| Download: ML20214G019 (2) | |
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374ol SN 157B Lookout Place ll0ff f3 P /,. j 3 BLRD-50-438/84-28 NOV 101986 BLRD-50-439/84-27 U.S. Nuclear Regulatory Commission Region II Attention:
Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 i
Dear Dr. Grace:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - TARGET ROCK SOLENOID VALVES ON POSTACCIDENT SAMPLING FACILITY (PASF) DO NOT MEET BACKPRESSURE REQUIREMENTS -
BLRD-50-438/84-28 AND BLRD-50-439/84 REVISED FINAL REPORT 1
Our final report on the subject deficiency committed to complete all corrective action by June 30, 1986.
Due to the extended fuel load date and revised construction schedules, the corrective action will not be complete i
until six months before fuel load of the respective unit. As discussed with Joe Brady by telephone on November 4, 1986, enclosed is our revised final report.
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If you have any questions, please call D. L. Terrill at 615/751-3274 extension 265.
Very truly yours, TENNESSEE VA EY AUTHORITY A
R. L. Gridley,, Director Nuclear Safetyland Licensing Enclosure cc (Enclosure):
Mr. James Taylor, Director Mr. G. G. Zech Office of Inspection and Enforcement Director, TVA Projects U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Region II 101 Marietta Street, NW, Suite 2900 Records Center Atlanta, Georgia 30323 Institute of Nuclear Power Operations 1100 circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 l
i 8611250S2S 861110 PDR ADOCK 05000438 5
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An Equal Opportunity Employer
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- ENCLOSURE 2
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 TARGET ROCK SOLENOID VALVES ON POSTACCIDENT SAMPLING FACILITY (PASF)
DO NOT MEET BACKPRESSURE REQUIREMENTS BLRD-50-438/84-28 AND BLRD-50-439/84-27 10 CFR 50.55(e)
NCR BLN EEB 8403 REVISED FINAL REPORT Description of Deficiency During a generic review for Watts Bar Nuclear Plant (WBN) nonconformance report (NCR) WBN WBP -8410 (WBRD-50-390/84-10, WBRD-50-391/84-10), TVA determined that Target Rock process solenoid valves were also being used at Bellefonte Nuclear Plant (BLN) postaccident sampling facility (PASF) lines as containment isolation valves, and as at WBN, these valves would see a back pressure during a loss of coolant accident (LOCA) which would keep the valves from remaining closed. At BLN, the valves could see a backpressure of 25 lb/in2 g resulting in a differential pressure which exceeds the five Ib/in2 differential design limit of the valve. This was caused by a failure to recognize that, on "open ended" piping inside containment, a LOCA would result in a reverse differential pressure across the isolation valve.
Safety Implications Because these valves could not have performed their intended containment isolation function, a breach of containment could have resulted during a LOCA, and this condition could have adversely affected the safe operation of the plant.
Corrective Action Design drawing revisions have been completed and field modifications will be completed by six months before fuel load of the respective unit, through engineering change notice (ECN) 3237 to reorient the affected valves so that the vendor-recommended valve flow direction is opposite the system flow. This allows the inlet port of the valve to be connected to the downstream side of 2 d the process line.
In this configuration, the postulated 25 lb/in pressure caused by a LOCA will appear at the inlet port which is consistent with the valve design and will allow the valve to close and remain closed during containment isolation. This " reversed" configuration is functionally acceptable and will not adversely affect the valves during normal operation.
To prevent a recurrence of this problem, TVA has issued design standard DS-E18.3.5 which includes a data sheet specifically for procuring process solenoid valves. Valve backpressure design consideration is an entry on this data sheet and is required to be addressed by the originating organization.
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