ML20085J848

Ao:On 740610,leak Discovered in Newly Installed Vibration Test Line Located on Reactor Feedwater Pump Discharge Header.Caused by Crack on Side of Nipple of Test Line.Unit Shut Down to Repair Leak

ML20085J848
Person / Time
Site:	Dresden
Issue date:	06/18/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085J852	List: ML20085J848 ML20085J853
References
439-74, NUDOCS 8310190138
Download: ML20085J848 (3)

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C mmmOgith Edis n pnal Piaza. Chicago. Illinois fS One First}

Address R6 ply to: Post Office Box 767

., 3 Chicago, Illinois 60690 -

BBS Ltr.f439-74 Dresden Nuclear Power Station )

i R. R. #1 Morris, Illinois 60450 0 Q June 18, 1974 8 .,s kf Rf(Ifp '-k 50-249 d D5737h ". f-i Mr. J. F. O' Leary, Director Directorate of Licensing U. S. Atomic Energy Consnission Washington, D. C. 20545 M,g

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SUBJECT:

_ LICENSE DPR-25. DRESDEN NUCLEAR POWER STATION, UNIT #3. REPORT 0F ABNORMAL CCCURRENCE PER SECTION 6.6.B.1.s OF THE TECHNICAL i SPECIFICATIONS.

NIPPLE FAILURE ON FEEDWATER PUMP DISCHARGE LINE.

References:

Notification of Region III of AEC Regulatory Operations Telephong: F. Maura, 1325 hours0.0153 days <br />0.368 hours <br />0.00219 weeks <br />5.041625e-4 months <br /> on 6/10/74 Telegram: J. Keppler, 1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br /> on 6/10/74

Dear Mr. O' Leary:

This letter is to report a conditian relating to the operation of

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personnel noted a leak in a 3/4 inch test line which was welded to the feedwater pump discharge line. The unit was shutdown to effect repairs.

The leakage associated with the failure fell directly to the turbine build-ing floor and flowed into a nearby turbine building drain from which it

• was pumped to Radwaste. No airborne radioactivity resulted and no personnel exposure was experienced due to the leak.

This malfunction is reportable according to section 1.A.5 of the Technical Specifications which defines an abnormal occurrence as an abnormal degradation of one of the several boundaries which are designed to contain the radioactive materials resulting from the fission process.

, PROBLEM

.I l The problem was discovered at approximately 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> on June 10, 1974, when station personnel noted water spraying from a newly installed vibration test line located on the reactor feedwater pump discharge header.

At the time, the unit was operating at 440 MWe. The carbon steel line was leaking through a crack in the 3/4 inch nipple which connected the feedwater header to the two valves in the test line. Af ter discovery of the crack, it was determined that the test line could not be isolated without draining the feedwater header line 3-3201-24". This action in turn necessitated a plant shutdown. The unit was shutdown in an orderly fashion with the turbine 8310190138  % PDR h9 ,

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4 if COPY SENT REGION

1 Mr. J. F. O'Lsc Juno 18, 1974 being taken of f-line at 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> on June 10, 1974. Af ter shutdown, the feedwater discharge line was drained and the leaking vibration test line was cut out of the feedwater line. A plug was welded in its place and the weld was dye penetrant tested. By 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> on June 11, 1974, the repairs were completed and preparations for the unit startup were begun.

INVESTIGATION 1

Visual inspection of the nipple showed the failure to be a crack in the nipple body itself, not in welds. The crack was located on the side of the nipple, was vertical in nature, and extended for approximately 1/4 inch. Very near the crack itself was a deep pit or gouge in the nipple.

This gouge was due to the welder striking his arc on the nipple before welding the two valves to the nipple. It is very probable that this weld strike arc is the site for the start of the crack and that the crack pro- ,

pogated under the surface of the nipple until it surfaced approximately

] 3/8 of an inch from the strike arc. The nipple will be sent out for tests

to confirm this.

Although the strike are was the primary cause of the failure, several other contributory causes were noted during the investigation.

These include:

1. The strike are gouge was in a heat affected zone of the nipple.

This further weakened the wet.1 in this arme. There was no post-weld heat treatment of the area.

2. The feedwater header was cold and level when the test line was installed. Upon operating conditions, the header moved downward by approximately 1 inch. Since the test line was secured to the ceiling by a pipe hanger, a large stress was induced in the test line.

3. The feedwater header was known to be vibrating vertically during startup and operational conditions. This induced,a second, cyclic stress on the test line.

_ CORRECTIVE ACTIONS Upon discovery of the leaking nipple, and determination that the leak could not be isolated without isolating the feedwater header, the unit was shutdown in a controlled manner.

The feedwater header was isolated af ter unit shutdown and the leaking test connection was cut out of the feedwater header. A plug was welded into the resultant hole and the weld was dye penetrant tested.

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,Mr. J. F. O' Leary O Juna 18, 1974 Similar test connections on the feedwater header were checked and none were rigidly held in place, independent of the feeduster line to which it was welded.

This occurrence did not jeopardize the safety of the plant or the public and resulted in no significant contamination problems.

The nature of the failure is such that in-service hydrostatic testing, as is accepted by the codes, is sufficient to prevent or minimize failures of this type on similar equipment. This type of hydrostatic test was performed on this test connection. Because of the nature of the failure, no corrective action can be affected to prevent repetition of the occurrence on this and other equipment.

Cumulative experience regarding contaminated water line leaks of this nature is minimal. For this reason, the corrective actions are con-sidered ef fective and satisfactory.

Sincerely,

. /

JYs /kJ B. B. Sge,phenson

.. Superintendent BBS:JMD:do l

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