ML20082T681
| ML20082T681 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 12/09/1983 |
| 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 8312160094 | |
| Download: ML20082T681 (2) | |
Text
TENNESSEE VALLEY AUTHORITY CH ATTANOOG A. TENNESSEE 37401 400 Chestnut Street Tower II no nr P Q Regeptt{r39, 1983 BLRD-50-438/82-79 oJov 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 UNIT 1 - DISRUPTION AND COLLAPSE OF S0DIUM HYDR 0XIDE STORAGE TANK - BLRD-50-438/82 FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector Paul Fredrickson on November 24, 1983 in accordance with 10 CFR 50.55(e) as NCR 2082. This was followed by our interim reports dated December 27, 1982 and June 20, 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 L. M. Mills, M 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 RhhCK05000438 09A G31209 S
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1983-TVA SOm ANNIVERSARY An Equal Opportunity Employer
ENCLOSURE BELLEFONTE NUCLEAR PLANT UNIT 1 DISRUPTION AND COLLAPSE OF SODIUM HYDROXIDE STORAGE TANK NCR 2082 10 CFR 50.55(e)
BLRD-50-438/82-79 FINAL REPORT Description of Deficiency During a l'illing operation for the sodium hydroxide storage tank, personnel discovered the following damage:
1.
The base plate for the supports was lifted from the foundation.
2.
The concrete foundation was broken.
'[.
- The sway struts at three locations around the tank were sheared in half.
At the time of these discoveries the tank was full of water and overflowing, resulting in the filling of the adjacent expansion loop with water. The tank wss drained and additional investigation revealed the tank had collapsed on three sides, and the associated piping was sprung. The specific cause of the NaOH tank damage could not be determined since there were many contributing factors which had a synergetic effect. Some of these contributing factors were:
1.
Restricted flow in the pressure and vacuum relief pipe.
2.
Filling procedure omitted the filling precaution found in B&W Technical Document No. 67-1003781-00.
3 Tank left in an unmonitored condition during filling operation allowing the overfill condition.
4.
Basic design of the system allowing such a phenomenon to develop.
5.
Failure to remove sump shoring.
A review of the actions leading up to and resulting in the Na0H tank damage reveals that the phenomenon would not have developed had the filling procedure specified the required level and the filling operation been closely monitored to assure that the tank was only filled to 1-he desired level. The accident could also have been prevented if the precautions in the B&W Technical Document had been followed.
B
)
Snfaty Implications Shearing of the tank from its piping or tank rupture during a seismic event due to the reduced stability of its supports (if uncorrected) could result-in air being introduced into the system. This air could in turn cavitate the reactor building spray pumps and decay heat removal pumps thereby preventing them from performing their intended safety function and adversely affecting safe plant opera tions.
Corrective Action A site investigation team was organized to determine the events leading to the collapse, the possible causes of the failure and the appropriate corrective action. The results of this investigation were provided by our second interim report on this 50.55(e) item. The con *. sts of this report summarized their findings.
Approximately 50 percent of the tank has been repaired by Richmond Engineering Company (RECo) as authorized by Nuclear Steam Supply System (NSSS) Change of Contract (C0C) No. 397. The tank support embedments have been inspected and the results sent to TVA's Division of Engineering Design (EN DES) for evaluation.
No damaged embcdments were discovered. All damaged foundation concrete has been removed and replaced according to TVA's Division of Construction (CONST)
Specification G-34.
TVA drawings have been revised as required to depict any necessary modifications. Engineering Change Notice (ECN) 3072 has been prepared which will provide fail-safe vacuum breakers for the sodium hydroxide tank. All remaining repairs will be completed by January 27, 1984.
To prevent recurrence of this deficiency, TVA has revised procedure BNP-CTP-6.1,
" Cleaning and Flushing of Systems," to include positive measures for monitoring levels in tanks, a specific prerequisite QC verification of protective device installation, and a check of design limits and precautions (e.g., checking the B&W Technical Document previously referenced).
In addition, EN DES has conducted an investigation to determine if there was a need to place a vacuum relief device on any safety-related tank which may be inadvertently overfilled.
The results of this investigation proved that the condition does not exist for any other Bellefonte system or TVA plant.
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