ML19327A040

Miscellaneous Nozzle Cracking:Brunswick Steam Electric Plant,Unit 2, Technical Evaluation Rept

ML19327A040
Person / Time
Site:	Brunswick
Issue date:	07/23/1980
From:	Prior J FRANKLIN INSTITUTE
To:
Shared Package
ML19327A028	List: ML19327A030 ML19327A040
References
CON-NRC-03-79-118, CON-NRC-3-79-118 TER-C5257-092, TER-C5257-92, NUDOCS 8008010093
Download: ML19327A040 (4)

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TECHNICAL EVALUATION REPORT MISCELLANEOUS N0ZZLE CRACKING: BRUNSWICK STEAM ELECTRIC PLANT, UNIT 2 FRC TASK NO. 92 NRC TAC NO. 06569

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Prepared by: J. E. Prior Performing Organization Franklin Research Center The Parkway at Twentieth Street FRC Project No.

Philadelphia, PA 19103 CS257

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j Sponsoring Agency Nuclear Regulatory Commission NRC Contract No.

Washington, D.C. 20555 NRC-03-79-ll8 This report was prepared as an account of work spoussred by an agency of the United States Government. Neither the United States Government nor any agency th- eof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, apparatus, product or process dis-closed in this report, or represents that its use by such third party would not infringe privately owned rights.

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REPORT OF TECHNICAL EVALUATION UNIT: BRUNSWICK STEAM ELECTRIC LICENSEE: CAROLINA POWER AND LIGHT PLANT UNIT NO.2 CO.

DOCKET NO 50-324 TAC NO.06569

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SUMMARY

Carolina Power and Light Co. reported that a six-inch crack was discovered during a routine inspection on December 27, 1976. The crack was in the 2A resi-dual heat removal (RHR) pump suction line adjacent to the suction line-to-weldolet veld. The veldolet was connected to a short, clean-out line. The crack was weld-repaired and the line was returned to service. Inspection of the other seven RHR pump suction lines revealed that no other cracks were present.

The cracking was believed to be the result of inadvertent overloading during installation, although no metallurgical investigation was conducted. In order to obtain additional information to resolve the cause of cracking, a survey of the suction lines was conducted in January, 1980. No cracking was noted during the three-year period since the veld repair. The amplitude of vibration during pump

• operation was found to be low.

It was concluded th3t the crack was caused by overloading during installation and was not the result of vibrational fatigue. This is considered to be an isolated, unique failure and not a generic issue.

2. INTRODUCTION

! It was reported (Licensee Event Report (LER) 2-76-161, dated January 26, 1977) that a six-inch crack was discovered in the 2A RHR pump suction line during routine inspection on December 27, 1976. The crack was adjacent to the suction line-to-weldolet veld. The weldolet was connected to a flanged, four-inch, clean-out line,

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two feet, three inches long. The crack was veld repaired, radiographed and hydro-statically tested before the line was returned to service. Visual inspection was conducted of the other seven RHR pump suction lines. No evidence of cracking was observed.

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According to the LER, initiation of the crack was believed to be due to inad-vertent overloading during piping-installation before issuance of the operating license. Subsequent thermal and pressure cycles during RER system operation are believed to have caused propagation of the crack with eventual water leakage. Since the cracked material was not available for metallurgical examination, no definite

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resolution of the cause of cracking was possible.

3. TECHNICAL EVALUATION In a letter, S. P. Carfagno (FRC) to G. Zech dated November 16, 1979, a survey of the eight RHR pump suction lines in the Brunswick Unit 2 plant was requested. In response to this FRC request, Carolina Power and Light conducted an inspection of the suction lines in January 1980. No evidence of any cracks or leakage was noted to have developed during the three years of operation since the initial crack was discovered and repaired.

Vibration tests, conducted on January 8, 1980, indicated that the vibrational amplitude at the flange was less than 0.001 inch when the pumps were operating.

i Carolina does not believe that additional line support is required based on service experience and the low amplitude of vibration in the line.

FRC is in agreement with Carolina Power and Light that the cracking wa's prob-ably initiated by an installation defect or da= age during plant construction caused by some undefined action. It is apparent that the weld repair has been effdctive in correcting the leak. Additional support will not materially aid in mitigating the small amplitude of vibration. In fact, a welded support may introduce areas of stress concentration not now present in the line. The extended trouble-free service, over a period of five years for seven of the welded joints and three years for the repaired weld, indicates that the problem was limited to one veld that has been cor-rected satisfactorily.

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4 CONCLUSION Based upon technical evaluation of all factors involved with the suction line cracking, it is concluded that this crack was an isolated case, possibly caused by an initial velding defect or other construction related incidental damage, and is not indicative of an inherent design defect. The satisfactory three-year service life since the veld repair indicates that crack initiation and growth adjacent to

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the weld has been eliminated for all practical purposes and should not be considered a generic problem.

Based upon recent visual inspection, measurements indicating low vibrational amplitude during pump operation, and three years of satisfactory service since the crack was weld repaired, FRC is in agreement that additional pipe supports should not be required on this line.

Stress risers caused by additional pipe supports, improperly welded, may actual-ly increase the possibility of failure. However, routine visual inspection of these suction lines should be continued as a precautionary measure.

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