ML20148N582

/01T-0 on 780617:water Leak Found in Area of B Recirculation Sys N2A Inlet Nozzle Caused by Wall Crack in Nozzle Safe End.Lab Analysis Will Be Performed to Determine Cause of Cracking

ML20148N582
Person / Time
Site:	Duane Arnold
Issue date:	06/30/1978
From:	Vansickel J IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT
To:
Shared Package
ML20148N579	List: ML20148N582
References
LER-78-030-01T, LER-78-30-1T, NUDOCS 7811270150
Download: ML20148N582 (2)

Text

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--o131 1 f the "B" recirculation system N2A inlet nozzle. Further investication I i

oi4II revealed the leak was the result of a throuch will crack in tha no rPl a I o Is1 I safe end acoroximately 4 to 6 inches in circumferential lencth. Radineran I i 1

.o is 1 I hic and UT exam revealed susoect indications in 5 nther inlat nn771a saf I j o lil I e ends none throuch wall . Two safe ends had no susoect indications. I o Ia 1 l Primary system structural intecrity recuirements in Toch Snec 1 6-G. I

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. F**lE ARNOLD CLERGY CZirzER *

- Icma Electric Light and Power Company LICENSEE EVCIT REPORT-Supplemental Data

.. Docket Number 030-0331 ,

t.icancoa Event Report Date: 063078 . .

Reportable Occurrence No: 78-030 Event Description -

On June 17, 1978 during weekly control valve testing an automa' tic reactor scram occurred due to reactor protection system relay problems (see R0 78-031) and the CV l I

testing.* After the plant was shutdown a drywell inspectior, was made to detemine the source of drywell unidentified leak of 3 GPM. Technical Specification 3.6-C limits unidentified leakage into the primary gantainment to 5 GPM. Water was found leaking from the shield blocks around the "B" recirculation system N2A inlet nozzle. The '

reactor was placed in a cold shutdown condition and the shield blocks removed for further inspection of the nozzle area. The . leakage was found to be the result of a through wall crack in the nozzle safe end approximately 4 to 6 inches in circumferential length. ,

Ultrasonic testing and radiographic examination were then begun to detemine the full extent of the cracking in the N2A nozzle safe end and to check for similar problems in the remaining 7 nozzle safe ends. The examinations revealed suspect indications in 5 other safe ends, none of which were through wall cracks. The remaining 2 nozzle safe ends had no suspect indications. Primary system structural integrity requirements are listed in Technical Specifications Section 3.6-G.

Causa Description _

The exact cause of the cracking has not been determined. Following removal, a laboratory analysis will be done on a cracked safe end to determine the failure mechanism. ,

Corrective Action ,

Current plans are to replace all eight safe ends with new safe ends of an improved design.

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