ML17252A518
| ML17252A518 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 07/02/1974 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | O'Leary J US Atomic Energy Commission (AEC) |
| References | |
| BBS Ltr. #481-74 | |
| Download: ML17252A518 (4) | |
Text
Commonwealth&son One First National Pl~Chicago, Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 BBS Ltr.#481-74 Mr. J. F. O'Leary, Director Directorate of Licensing U. S. Atomic Energy Commission Washington, D. C.
20545
SUBJECT:
LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT 113, REPORT OF ABNORMAL OCCURRENCE PER SECTION 6. 6. B. l OF THE TECHNICAL SPECIFICATIONS.
UNIT 3 FEEDWATER LINE VIBRATION.
References:
l) Notification of Region 111 of AEC Regulatory Operations Telephone:.Mr. F. Maura, 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br /> on June 24, 1974 Teleg~am: Mr. J. Keppler, 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 Diagram Ml4.
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 time, damage to the unit's *feedwater piping was discovered.
PROBLEM At ~bout 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 system. As a result of the vibration~ the feedwater system 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 megawatts. Electrical load at the time was approx-imately 630 megawatts. At the time of the occurrence, the unit was in the process of increasing load from a load drop in which weekly surveillance was performed.
The following is a record of the events that occurred on June 23, 1974 at the time of the incident:
REGULATORY DOCKET FILE COPll
!!~,.:.;. F. 0 '.Leary.. e July 2, 1974 Event
-~-
-~--
2214 2216 2217 2218 2219
- 2240 2248 0040 0610 0700.
INVESTIGATION 3B feedwater regulation valve locked tip.* (3A regulation valve was in.service at the time of failure).
3B service air compressor tripped.
Feedwater _heaters 3Dl, 3D2, 3D3, 3Bl, 3B2, and 3C2 tripped.
3A feedwater regulation valve locked up.
Feedwater flow and reactor level appeared steady for about 30 seconds then both decreased.
Level dropped from 30 inches to 21 inches.
Feed-water flow decreased from~.1about 7 x 106 lbs/hr. to 2.6 x 106 lb/hr.
Clean-up recirculation pump tripped.
Reset 3A feedwater regulation -valve.
Feedwater flow increases to 12 x ;106 *-lb/hr. and ~eactor-level increases to 35 inches.
Shift foreman inspected area of feedwater regulation valves.
Reports tha..t:, ~ir line.on 3B feedW8ter t~gu_lation yalve _had*
broken l.oose and *th8t; the.JninimUm,flow*,;va~ve. ~as~-'~g~(i in',.
the ope~
1,i>o~ition~- -, *
- _:.*
- f,;*,
-~
Clean-up system back in service.
Feedwater heaters reset.
After a visual examination of the piping was made, a unit shutdown was ordered by Mr. B. *Stephenson in order.. to make a mare detailed examination.
Unit off system.
Unit subcritt*cal.
An investigation into the pr-oblem began immediately upon reaching shutdoWn..
Following shutdown a visual inspection of the feedwater piping was perfonned.
During this inspection, the following equipment was found damaged.
- 1.
Low flow feedwater regulation valve found in open position and rotated*
.approx~tely 30.degrees. All air lines and electrical feeds to the low flow valve were found broken off and bent.
Upstream pipe support for low flow valve found broken off its pad with concrete base cracked.
- F. O '.IA\\ary, July 2, 1974
- 2.
"A" feedwater regulation valve upstream pipe support p~~---~u_!le~_~ut __ Q_f_ _______________ _
its cement bas_e_,, ___ _
=
J.. "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.
However, the welds on this line were later tested and found to
- be satisfactory. Also "A" pump minimum flow to condenser had loose insulation.
- 5.
In the_ "D" heater bay, two pipe hangers on the heate~ 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 q\\iarter of an inch movement.
Also one line had the pipe support pad cement cracked.
- 7.
The reactor feed puinp suction header under the hotwell, had three pipe
. support *pedestal ~ement pads.cracked.
During the inspection of 'die feedwater piping, _a chec_k of_ the uA" feedwater regulati~~-valvEf :~as~.per~ormec;r.*.,.T}le i~tenrof\\he. ~ch~ck :wa~:-*to verify that the "A r.eg1lla'Oon~valve would lock:'l,ip on.a'.l9ss*;of -instrument air.
The "A" regulation val.V,e: d'-id: o,pera'te: a,_:'cie~~gned *'during' :th~ check out.
Also, to determine if the feedwater piping integrity was affected, the entire feedwater piping was tested. All welds were ~ested using either*
magnetic parti~l 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 demineralizer differential pressure, it appears that the "A" feedwater. regula.tio~ yalve went nearly* closed.
At this time, no reason has been determined to cause. the valve closure. *However, invest-.
igation into the proble_m is continuing,. and any additional information will be transmitted t~ Region III.
CORRECTIVE ACTION
- -- * - * -To corr~ct 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 regulat-ion valves were checked out for proper operation with special atten-
- uon given to "A" regulation valve lock up ability. The results of this inspection showed* that the "A" regulation valve* would lock up as designed, and failed to show a reason for its closure.
- . July 2, 1974 In addition, two six point recorders wil~ be placed on the feed-water control circuit in orde~_t9_4-eJ:et'Dline_ if-any---:sput;~ious---signa-ls-exist-;- - - --** ------
-- --- -- ------At:=-:tlfiFf'lme-,-tlie--two si.X point recorde-rs are being purchased and will be installed immediately upon their arrival on site. Also, during startup and until the recorders are available, the unit will operate in single element control. An operating order has been written to insure that the unit operates in single element control, unless prior approval has been obtained from an operating engineer to go to three element control.
Also, the problem is be~ng inve~tigated by General Electric and it is expected that a modificati<in to the feedwater control system will result. Also, in regards to feedwater system vibrations, a task force has been organized to inves~igate the problem at Quad Cities.Nuclear Power Station as well as at Dresden Station.
- '1
- l 1
7, EVALUATION During the occurrence, the safety of the plant and public was not in.jeopardy.
Although damage to the feedwater system did occur, an orderly shutdown was performed. Also, at the time of the occurrence, all emergency systems were operational, and primary containment was not com-promised.
In regard,::to cumulative expet;ience, this is the first time the feedwater system has experienced damage.
Ho~ever, approximately one year ago a feedwater regulation valve had* gone partially _closed during operations in which a scram occurred.
- The inspection revealed a faulty C91DPonent in the feedwater control system whic~ was then replaced.
Sincerely~
BBS:TEL:do