ML20085F618

AO AO-17-74:on 740828,letdown Flow Indicated Zero When Charging Pumps Running,Due to Cracked Letdown Line Vent Nipple.Apparently Caused by Matl Failure.Possible Contributing Cause Was Design Inadequacy

ML20085F618
Person / Time
Site:	Palisades
Issue date:	09/09/1974
From:	Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085F616	List: ML20085F612 ML20085F618 ML20085F621 ML20085F626
References
AO-17-74, NUDOCS 8308230067
Download: ML20085F618 (2)

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Vj u ~1 Directorate of Licensing 1, . r J Re: Docket 50-255 US Atomic Energy Commissio ' LiL ~8 License DPR-20 Wshington, DC 20545 o[ P Palisades Plant A0-17-Th Gentl emen :

Attached is the report for Abnormal Occurrence 17-Th. This re; ort covers the cracking of a letdown line vent nipple. We have sent this vent to our laboratory for examination and shall inform you of our findings.

Yours very truly, Ralph B. Sewell (Signed)

WGF/mel Ralph B. Sewell Nuclear Licensing Administrator CC: JGKeppler, USAEC fY t~0 -

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pJ 8308230067 DR ADOCK 741115 050002y 1b10G gpy SENT REGION-

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] ABNORMAL OCCURRENCE REPORT Palisades Plant

1. Report Number: A0-17-Th, Docket 50-255

2. a. Report Date: September 9, 1974.

b. Occurrence Date: August 28, 1974.

3. Facility: Palisades Plant, Consumers Power Company, Covert, Michigan.

h. Identification of Occurrence: Cracking of a letdown line vent nipple.

5 Conditions Prior to Occurrence: The plant was at 400 F and in the process of cooling down.

6. Description of Occurrence: At about 2030, it was observed that all charging pumps were running and letdown flow indicated zero. Inspec-

! tion of the charging pump liner disclosed that water was blowing from a 3/h-inch vent nipple. This nipple had failed by cracking over about 75% of its circumference, just above the veld to the letdown line. The letdown line was isolated immediately and no further

problem resulted.

7 Designation of Cause: The apparent cause was material failure and a possible contributing cause was design inadequacy. The failed pipe has been sent to our laboratory for examination. The results of this examination will be forwarded when they become available.

8. Analysis of Occurrence: The plant was in the process of normal letdown j cooling when the pipe broke. Its rupture did not damage any equipment or injure any personnel. Because of the location of the break, 'any release of radiation from the break was held within the containment.

9 Corrective Action: The vent was in a nonused portion of the letdown line and, therefore, could be removed completely. The remaining portion of the vent nipple was removed and a certified plug was welded into its position plugging the line. Inspection of the rest of the line disclosed no other similar piping configurations which

, could develop a similar problem.

10. Failure Data: No previous history recorded on the letdown system. ,

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