ML20085J815
| ML20085J815 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 07/02/1974 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20085J812 | List: |
| References | |
| 481-14, NUDOCS 8310190100 | |
| Download: ML20085J815 (4) | |
Text
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[.I[A Commonwo (hl>W* 9?i_EuMPiO(h Edison lan Cncew. Woo 1 Q C. ~ Acer ns Dc.cly to PM Cfheo Box 707 w
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Mr. J. F. O' Leary, Director
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U. S. Atomic Energy Cornission Washington, D. C.
20545 SUEJCCT:
LIC'":US EPR-25. DPRSD"N WCIE.AR POVErt STATIO::, UNIT #3, RStonT 5' AP,K00%L OCCURRENCE PER SECTION 6.6.B.1 OF THF, TECHNICAL SPECT"I('Ii1053.
EITT"3 FEW'ATP.R LIIE VIBRATION._
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References:
- 1) Notification of Region III of AEC Regulatory Operations Telephone: Mr. F. ?! sura, 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br /> on Junc 25, 1974 Telegram: Mr. J. Ecppler,1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on June 24, 1974
- 2) Dresden Station Piping and Instrumentation Diercaw M14.
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Dear Mr. O' Leary:
This letter is to report a condition relating to the operation of Unit #3 at about 2214 hours0.0256 days <br />0.615 hours <br />0.00366 weeks <br />8.42427e-4 months <br /> on June 23, 1974. At this tiac, damage to the unit's feedwater piping was discovered.
FR03LEM At about 2214 hours0.0256 days <br />0.615 hours <br />0.00366 weeks <br />8.42427e-4 months <br /> on June 23, 1974, severe vibrations were experienced on unit 3 feedwater syste :. As a result of the vibrations the feedwater systen incurred damage to the feedwater regulation valves and several pipe restraints.
Prior to the occurrence, the unit was in the "Run" mode with thermal power at 2122 rnegawatts.
Electrical load at the time was approx-imately 630 megawatta. At the tiac of the occurrence, the unit was in the procces of increasing load from a lead drop in which weekly ' surveillance was performed.
s The following is a record of the events that occurred on June 23, 1974 at the tir:e of the incident:
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2-July 2, 1974 3
Time Event i
2214 3D feedwater regulation valve locked up.
(3A regulation valve was in service at the time of failurc).
3B service air compressor tripped.
2216 Feedwater heaters 3Dl, 3D2,.3D3, 3B1, 3B2, and 3C2 tripped.
2217 3A feedwater regulation valve locked up.
Feeduater flow and reactor level appeared steady for about 30 seconds then both decreased. Level dropped frcm 30 inches to 21 inches. Feed-water flou decreased from nbout 7 x 106 lbs/hr. to 2.6 x 106 lb/hr.
2218 Cican-up recirculation pump tripped.
2219 Reset 3A feedwater regulation valve. Feedwater flow increases to 12 x 106 lb/hr. and reactor level increases to 35 inches.
Shift foreman inspected area of feeduater regulation valves.
Reports that air line on 3B feeduater regulation valve had broken loose and that the minimum flow valve was damaged in the open position.
2240 Clean-up system back in service.
2246 Feecwater heaters reset.
0040 After a visual examination of the piping was made, a unit shutdown was ordered by Mr. B. Stephenson in order to make a more detailed examination.
0610 Unit off system.
0700 Unit cuberitical.
i INVESTIGATION
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f An investigation into the problem began humediately upon l
reaching shutdown. Following shutdown a visual inspection of the feedwater piping was perforned. During this inspection, the following equipment was found damaged.
1.
Low flow feedwater regulation valve found in open position and rotated I
approximately 30 degrees. All air lines and electrical feeds to the low flow valve uere found broken off and bent.
Upstream pipe support for low flow valve found broken off its pad with concrete base cracked.
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Hr.*J. F. O' Leary July 2, 1974 2.
"A" feedwater regulation valve upstream pipe, support pad pulled out of its cement base.
3.
"B" feedwater regulation valve air supply line found broken off its main header.
4.
All three reactor feed pump discharge line pipe supports showed signs of movement.
"A" feed pump had bent warming line.
"C" reactor feed pump discharge line flow element tap looked as though it may have been bent. Ilowever, the velds on this line were later tested and found to be satisfactory. Alco "A" pump ninimum flow to condenser had loose insulation.
5.
In the "D" heater bay, two pipe hangers on the heater outlet had tack welds broken. A heater line entering the "X" area had a displaced pipe support pedestal.
6.
In the turbine pipe way in the extraction steam piping, one pipe support pedestal showed a three quarter of an inch movement. Also ona line had the pipe support pad cement cracked.
i 7.
The reactor feed pump suction header under the hotwell, had three pipe support pedestal cement pads cracked.
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hring :1.c i...;gt iv.. vi Ge feedwnet piping, a check or rne "#
feedwater regulation valve was performed. The intent ~of the check was to verify that the "A" regulation valve would lock up on a loss of instrument air. The "A" regulation valve did operate as designed during tha check out.
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Also, to determine if the feedwater piping integrity was af fected,
~ the entire feedwater piping was tested. All welds were tested using either nagnetic partical or dye penetrant. The results of this testing showed no signs of failure.
In review of the chart recorders for feedwater flow, reactor water level, and condensate dcmineralizer differential pressure, it appears that the "A" fecdwater regulation valve went nearly closed. At this time, no reason has been determined to cause the valve closure. However, invest-igation into the problem is continuing, and any additional inforration will be transnitted to Region 111.
CORRECTIVE ACTION To correct the condition, the feedwater piping was inspected and repaired. All feedwater piping welds were tested using either magnetic partical or dye penetrant, with results satisfactory. The feedwater regulation valves were checked out for proper operation with special atten-tion given to "A" regulation valve lock up ability. The resulta of this inspection showed that the "A" regulation valve would lock up as designed, and failed to show a reason for its closure.
u Mr. J..F. O' Leary ( )
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July 2, 1974 In addition, two six point recorders will be placed on the feed-water control circuit in 'crder to deteruine if.any spurious signals exist.
i; At this tiee, the two six point recorders are being purchased and will be installed immediately upon their arrival on site. Also, during startup and until the recorders are availabic, the unit will operate in singic element control. An operating order has been written to insure that the unit j
operates in singic cicaent control, unicss prior approvat has been obtained from an operating engineer to go to three element control.
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't Also, the probicm is being investigated by General Electric and i
it is expected that a modification to the feedwater control system will result. Also, in regards to feedwater system vibrations, a task force has been organized to investigate the problem at Quad Citics Nuclear Power Station as well as at Dresden Station.
EVALUATION During the occurrence, the safety of the plant and public was not in jeopardy. Although damage to the fecduater system did occur, an orderly shutdown was pcrforced. Also, at the time of the occurrence, all emergency systems were operational, and primary containment was not com-promised.
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In regard to cumulative experience, this is the first time the feedwater system has experienced damage. llowever, approximately one year n y a feedwatus auxulativa vaive imo tona parrinley reneeo curing e,ec:stier.:
r in which a scram occurred. The inspection revealed a faulty component in the feedwater control system which uns then replaced.
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Sincerely,
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s B. B. Stephenson Superintendent DBS:TEL:do a