ML16148A459
| ML16148A459 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 08/23/1983 |
| From: | Elzeftawy M NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | |
| Shared Package | |
| ML16148A460 | List: |
| References | |
| TASK-AE, TASK-T330 AEOD-T330, NUDOCS 8309230230 | |
| Download: ML16148A459 (2) | |
Text
AEOD TECHNICAL REVIEW REPORT*
UNIT: Oconee 2 TR REPORT NO. AEOD/T330 DOCKET NO.:
50-270 DATE:
Auqust 23, 1983 LICENSEE: Duke Power Company EVALUATOR/CONTACT: M. El-Zeftawy NSSS:
Babcock & Wilcox
SUBJECT:
STEAM GENERATOR TUBE RUPTURE AT OCONEE UNIT 2 EVENT DATE:
September 18, 1981
SUMMARY
It was discovered (reference 1) on September 18, 1981 at 1030 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.91915e-4 months <br /> from increased readings on Condensate Steam Air Ejector (CSAE) off gas radiation monitor that the 2B steam generator had a tube leak of 0.03 gpm. Later on that day at 1529 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.817845e-4 months <br />, the leak rate had increased to approximately 25 gpm.
DISCUSSION Oconee 2 was operating at 94% full power when the CSAE off gas radiation monitor showed:.an increase.
A primary-to-secondary leak rate of 0.03 gpm was cal culated.
Approximately five hours later, the leak rate increased to 25 gpm..
A rapid unit shutdown was made and the reactor coolant loops were drained to stop the leak., The affected steam generator (2B) was isolated. The tube leak was caused by a circumferential crack as determined by eddy current testing. On September 19, 1981, the plant had cooled down so that the low pressure injection (LPI) system could be started. During initiation of decay heat cooling, (see reference 2), valve 2LP-2 failed to open electrically and it was opened manually using manual hoists.
During this period, stopping the steam generator tube leak was delayed.
INPO performed a complete analysis (Ref. 3) of this event. That analysis pointed out that approximately 70,000 gallons of primary coolant had leaked to the "B" steam generator and was drained periodically to the hotwell.
Such information was not mentioned in the licensee event report, indicating incomplete reporting by the licensee.
F I ND I NGS The cause of the once through steam generator (OTSG) tube leak was a circum ferential crack in one of the tubes at the fifteenth support plate where high velocity steam flow exists.
Some of the findings of reference 3 indicated that the difficulties encountered in this event were due to procedural, design, or equipment problems.
- This document supports on-going AEOD and NRC activities and.does not represent the position or requirements of the responsible NRC program office.
830923O230 830829.
PDR ADOCK 05000270.
S PDR
- 1
-2
'CONCLUS ION Circumferential fatigue cracks of steam generator tubes could have serious implications on plant operation. Combining this event with the inability to initiate decay heat cooling could result in a serious delay in reducing the reactor pressure during unit shutdown. The analysis and evaluation which was conducted by INPO and reported in reference 3 is comDlete and provides much more information than was reported in the LERs by the licensee. The actions taken by the licensee appear to be both appropriate and sufficient; however the licensee's reporting of the event was incomplete. I recommend that AEOD not perform any additional work on.this event since it was well covered in reference 3.
REFERENCES
- 1) Reportable Occurrence Report RO-270/81-16 from William 0. Parker, Jr.,
(Duke Power Co.) to James P. O'Reilly (NRC-Region II) dated November 13, 1981.
- 2) Reportable Occurrence Report RO-270/81-17 from William 0. Parker Jr.,
(Duke Power Co.) to Jaems P. O'Reilly (NRC-Region II) dated November 13, 1981.
- 3) INPO - Report 82-030, November, 82, "Analysis of Steam Generator Tube Rupture Events at Oconee and Ginna."