ML20085H065
| ML20085H065 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 10/02/1974 |
| From: | Eric Thomas TENNESSEE VALLEY AUTHORITY |
| To: | Case E US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20085H060 | List: |
| References | |
| NUDOCS 8308300134 | |
| Download: ML20085H065 (3) | |
Text
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Mr. Edson G. Case Active Direetcr of Licensing Office of Regulatica U.S. Atccic Energy Cc==ission Washington, DC 20545
Dear l'r. Case:
TENNESSEE VALLEY AUTHORITY - ERCWUS FERRY UUCLEAR PIAIIT UNIT 1 -
DOCKET UO. 50-259 - FACILITY OPEEATIIIG LICEUSE DPR AEHORFAL OCCURRENCE REPCRT EFAC-50-259/7449W The enclosed report is to provide details concerning a 1-inch, stainless-steel recirculatien system flow sensing line which failed at the tce of a fillet weld where it attached to a 6,000-pound half coupling and is submitted in accordance with Appendix A to Reculatcry Guide 1.16, Revision 1, October 1973 This event occurred en Brcwns Ferry Nuclear Plant unit 1 on September 22, 1974.
Very truly yours, D
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ABITOR"AL OCCURREt!CE REPORT Report Iro.: BFAO-50-259/7h49W Report Date: October 2,1974 Occurrence Date:
September 22, 1974 Facility: Browns Ferry I!uclear Plant unit 1 Identification of Occurrence A 1-inch, stainless-steel recirculation system flow sencing line failed at the too of a fillet veld uhere it attached to a 6,000-pound half coupling. The half coupling was attached to the 28-inch recirculation line on "is" loop.
This instrument line is the static pressure tap for flow clement 68-5 on the "A" recirculation pu=p discharge line.
Conditions Prior to Occurrence The reactor was in the cold shutdown mode during a scheduled outage.
Description of Occurrence Conteninated water was found in the dryuell during an inspection of the "A" rceirculation purp discharge icolation valve bypass line. An investi ation revealed that the failure was leaking reactor unter from a 1-inch,ctainless-steel recirculation flow concing line adjacent to the fillet wcld at the hclf coupling. The water leak uns stopped by extern-11y applying prescure to the sencing line in a direction that closed the crach. Proper radiologic 1 cafety precautions vere taken to assure that personnel vorking inside the dryuell wald not receive unacceptable radiation dosages.
Designation o'.' Annarent Cause of Occurrence The lina war, i= properly supported and vibre. tion generated by the recirculation flow execc(cd the vibration fatigue limit of the line.
Analysis r,f Occurrence There was no da= age to systers, components, or structures as a recult of the crack. There vas no jeopardy to reactor safety as adequate saicty cyctecs were operable. There were no adverse effects on the health or safety of the general public, and no personnel injuries or abnormal radiation exposure vere experienced.
Corrective Action The leak was repaired by instelling a fixture consisting of a split sleeve fabricated fro: 304 stainless steel which encompassed the crach. The sleeve was TIG welded using 308 filler rod. The root pass and final pass were licuid-penetrant tested, cad a hydroctatic test at 1,326 psi uas successful 2y acco=aliched. A pipe hanger analysis was performed for all recirculation flou sensing lines to determine the henger adequacy. II nger modifications were m:a'c as required to provide proper support.
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~2-Corrective Action (continued)
During insulation renoval to inspect the censing lines, a second leak was I
discovered at a valve vent veld on recirculation valve 68-1.
This leak was repaired by renoving the 45 clbou and pipe where the lech had occurred end installing a new section of pipe.
The renoved section of pipe will be given thorough motsllurgical exc=ination to determine the nochenism of this failure.
After the discover / of this second leak, an extensive inspection program (which included cl1 instrument sensing lines, vent, drain, and packing leak-off lines on principcl piping isolation valves inside the dryvell) was performed.
The incpection included a liquid-penetrant exWnation of the instrument line volds there they connect to the principal piping; liquid-penetrcnt examinations of velds on valve vent, drain, and packing leck-off lines; and a design review of all these lines for proper support. Additional supports were installed as needed. I!ondestructive en-Mc.tions revealed discontinuities in three additional locations. A lack of fusion on the final pass of one weld in the bonnet vent velve line on valve I!o. 66-3,'tuo linear indications 1n one test connection on velve I!o. 74-65, end an incomplete veld in the drain line on valve lio. 63-1 vere discovered. Repairs were made by grinding out discontinuities cnd revelding. A sinilar inspection progrcm vill be performed on unit 2 when the unit is shut doun for the inspection required by RO Bulletin 74-10.
Failure Data There is no previous record of vibration fatigue failure on the recirculation systen.
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