ML17252B166
| ML17252B166 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 08/26/1974 |
| From: | James Keppler US Atomic Energy Commission (AEC) |
| To: | Brian Lee Commonwealth Edison Co |
| References | |
| IR 1974007 | |
| Download: ML17252B166 (12) | |
Text
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U. S. ATOMIC ENERGY COMMISSION
- . DIRECTORATE OF REGULATORY OPERATIONS.
- -----~-{-* ----"-- ----- -------------- --------------REGION. III - ---- - - ----- - --- - - Report of Operations Inspection RO .Inspection Report No. 050-249/74-07 Licensee: Commonwealth Edison Company P.O. Box 767 Chicago, Illinois 60690 Dresden Uriit 3 License No. DPR-25
. 'I Morris, Illinois Category: C Type of Licensee: GE, BWR, 809 Mwe Type of Inspection: *Special, _Announce.d Dates of Inspection: June 25, July 1, 2 and 10, 1974 Dates of Previous Inspection:. June 10-14, ~5 and 26, 1974 (Operations)
Principal Inspector: ~~~ f' /;)3b(
'(Dale)
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Accompanying Inspector:
....,c'~ lBrown 1
f,@317'/ (Dite) Other Accompanying Personnel: L. Beratan, RO:HQ R. Lofy, Parameter, Inc. R. Dean, Parameter, Inc.
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c:;6t'-c?~~c....-L.t::-l:'-l--*c.. ~k:_. Reviewed By: H. C. Dance, Senior Reactor Inspector Nuclear Support Operations Branch
SUMMARY
OF FINDINGS Enforcement Action: ___ None-------------------------------- Licensee Action On-Previously Identified Enforcement Items: Not Inspected Unusual Occurrence Feedwater System Hydraulic Shock. , Other Significant Findings A. Current Findings A hydraulic shock occurred in Unit 3 Feedwater System on June i3, 1974. The shock caused pipe movement-and e-quipment damage. *The licensee was performing a pipe and equipment inspection before restarting the Unit. B. Status Of Previously Reported Unresolved Items: None Management Interview The following subjects were discussed on the completion of the June 25,- 1974, inspection with Messrs. B. Stephenson, Station_ Superintendent; T. Watts, Supervi~ing Engineer; T. Lang, Engineer; G. Lampy, Engineer. A. The inspector stated that he understood that all the feedwater piping would be visually inspected and magnetic particle inspected at stres_s points. The licensee concurred. B. The inspector inquired as to the rest of the licensee's program before the Uni.t was restarted~ The licensee stated that a program was being developed by the C. E. Engineering group to check all the equipment and. piping in the system and then make required repairs~ The system would be checked for operation and completed program reviewed by C. E. Engineering before the Unit was restarted. -
- c. The inspector inquired into the desirability to perform a *stress analysis of the piping in question and determine if its useful life*
.... has been reduced, using the most conservative movement noted. The
*licensee stated that their Engineering Department and Sargent and Lundy Engineers had determined such calculations were not required.
D. The inspector stated that after reviewing the recorder charts it is apparent that the in_itiating cause was not the rupture of the control air lines of the low flow regulating valve, but the closing of the main 2 -
feedwater regulating valve. Closure of the main valve was probably caused by. spikes in the feedwater flow signal. The licensee stated the investigation will continue in* an effort t.o determine and cor-rect the problem.. _________________________ ---- ------- ---- ------------
-~-----*----
At the July 10,1974 meeting, (See Section II of this report) Com-monwealth Edison representatives agreed to conduct .a stress analysis of the affected systems and submit a summary of the findings to Regulatory Operations. *
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REPORT DETAILS
-*--~----- ___________________ ---~~-r:_ !_~r~~a_r~~~!--~*- H~ _Br_~~ __________ *--* ________.__ _
Persons Contacted B. S.tephenson, Dresden Station Superintendent T. Vatts, Dresden Supervisory Engineer, Technical Staff T. Lang, Engineer, Technical Staff G. Lampy, Engineer, Technical Staff D. Galle, Mechanical and Structural Engineer, CECO
*G. Kitz, Sargent and Lundy F. Spakoski, Sargent and Lundy E. Branch, Sargent and Lundy D. Sedgurck, Sargent and Lundy J. Muffett, Sargent and Lundy ~
J. Irish, Sargent and Lundy * *
- 1. Feedwater System Hydraulic Shock On June 23, 1974 at 2217 the feedwater system for Unit 3 experienced a hydraulic shock that caused displacement of equipment and piping. The
.Unit was operating .at 660 Mwe (79%) with two reactor feed pumps
*Operating. The movement caused damage to some concrete supports and i*.. -
several piping restraints.
*During the inspection conducted on June 25, the following recorder
-charts were reviewed:
Reactor Vessel Level Reactor Feedwater Flow APRM Reactor Pressure (Narrow Range) Turbine Steam Flow Condensate Demineralizer Lj P
- F~edwater Temperature The Shift Supervisor's log was reviewed with the following entries relating to the event.
3A feedwater regulating valve had been controlling feedwater at .the* time of the event. 2214 - 3B Feedwater regulating valve lockout alarm received. 2216 - Feedwater preheaters 3Dl, 3D2, 3D3, 3Bl, 3B2, and 3C2 tripped *
.2217 - 3A Feedwater regulating valve lockout alarm received.
2218 - Cleanup recirculating pump tripped. 2219 - Reset 3A Feedwater regulating valve lockout.
- 0
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*- Air lines to 3B Feedwater regulating valve and low flow regulating valve were reported damaged. ~,
2240~_<;],_~~Jl'Jp__ pump _restarted------ --- - --. - - - ----------2248 - Preheaters reset. . The key recorder charts showed the following changes at the time of the event. Reactor Feedwater Flow was indicat~ng about 7 x 106 lb/hr prior ~o the event tgen spiked down to 2.6 x 10 lb/hr and back to full scale of _ 12 x 10 lb~hr and held at 8.6 x 106 lb/hr for a short time then back
*to 7.0 x 10 lb/hr. The chart was marked at this point stating that 3A regulating valve was reset.
The APRM charts showed a maximum spike downscale of 7% and then* an upscale maximum spike of 5% from a ~minal 75% indicated reactor power level. The Condensate DemineralizerilP chart indicated a rapid decrease in differeµtial pressure across the demineralizer beds from 37 to 4 psid. The damage resulting from the shock included the following:
- a. The spring loaded pipe supports .for the discharge pipe of the
. two operating feedwater pumps, and one of the discharge lines from the high pressure preheaters were displaced.
- b. The concrete pipe support for the low flow regulating valve was
*.. i partially broken.
- c. The concrete grouting around supports for the high pressure heaters and the main feedwater regulating valves was broken loo.se.
- d. The pipe hangers on the discharge pipe of the high pressure pre-heaters had the pad tack welds broken and the hangers ~ere dis-placed.
- e. The air lines to the low flow regulating valve were broken which allowed the valve to go full open and the operator was rotated in its clamp approximately 30°. *
- f. One of the holddown bolts for the support on 3A feedwater regulating valve was sheared.
- g. 3A feedwater pump had been displaced en~ugh to bend the stack pins.
- b. The minimum flow line for 3A feedwater pump had sections of insu-lation broken off. ~
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At the time of the June 25, 1974 inspection. the licensee was con-
. ducting a magnetic particle insp.ec.tion of the feeqwater pipe. The
__ -*----- _______ !~~=~:::s~;:~::s~~~.~ ~-~~-t-~~~.~e~-~~~t~-~ _P_i~~~~~~~ -:-t~~ ~e--~~~pe~-~e.d_____ ._________ _ The initiating cause of this event is not know, but the system oscilations have been reduced by the licensee converting to a single element level control signal to the feedwater regulating system.
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**---- *-- :. .,)tEPORT' DETAILS -
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- - * - _____________________________________ !a~~--!I~ __:_ ____________ _ -- --- - - - - - - - - -- - - - - - - - - - - Prepared by:~+-~-.:o..~...x.._..:=.__,,4-4~:...._~c.........~~~~~~~~ L. L. Bera tan, J *or S true tural Engineer Technical Assi~ ance Branch
- Directorate of Regulatory Operations Dates of Inspection & Meeting: July 1, 2, and 10, 1974
- Reviewed by :_.L--..!..=.~:::........--l!..::....e:=::::::::::....~~~---------
-- K. V. Seyf ri t, Chi,,ef. Date *
*. Technical Assis tanc ranch Directo~ate of Regulatory_ Operations
- 1. Persons Contacted B. s*tephenson. Dresden Power Station G. A. Lampy, Dresden Power Station
. D. P. Calle, Commonwealth Edison Company G. Kitz, Sargent & Lundy '. **
F. Spak~ki, Sargent & Lundy C~ Brown, *RO: III . L. L. Beratan, RO:HQ R. A. Lofy, Parameter, Inc., AEC Consultant
2. Background
On *June 23, 1974, severe vibrations were experienced in the Unit 3 feedwater system. The vibrations caused damage to the f~edwater regulation valves *and several pipe restraints. The unit was at approximately 630 megawatts at the time of the occurrence and in the process of increasing load. The sequence of events reported
*by the licensee were as follows:*
- Feedwater reguiation valve 3B locked up. Service air compressor 3B tripped (3A regulation valve was in service at the time of failure) ; --
- Feedwater heaters 3Di, 302, 303, *3Bl, 3B2 and 3C2 tripped;
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2
- _ Feedwa ter regula :_~on -~a_l_ve _3_A _l_g<:~~g_ yp_. __ F'eedwa ter--flow--and-- ----- ---- ------
- .------------.- -- ---reactor--leve-1 appeared steady for- about 30 seconds, then both
---
- decreased; *level dropped fGom 30 inches -to 21 inches. Feedwater flow decreased from 7 x 10_ lbs/.hr to 2.6 x 106 lbs/hr; Cleanup recirculation pump tripped; Cleanup recirculation pump tripped; Reset 3A feedwater regulation valve. Feedwater flow increased to 12 x 106 lbs/hr and reactor level increased to 35 inches. The air line on the 3B feedwater regulation valve had broken loose and the minimum flow valve was damaged and remained in -the open position; Clean-up system back in service;
-* Feedwater heaters reset; A visual examination of the piping system was made and a shutdown was ordered to make a more detailed examination.
- 3. Findings of Detailed Examination*
The low fl9w feedwater regulation valve was found in the open position and rotated approximately 30 degrees. All air lines and electrical - feeds to the low flow valve were found broken off or bent. Upstream pipe support for low flow valve found broken off its pad with the concrete base cracked. The "A" feedwater regulation valve upstream _pipe support pad pulled out of its concrete base. The "B" feedwater regulation valve air supply line found broken off its main header. All three reactor feed pump discharge line pipe supports showed signs of movement. "A" feedwater discharge line had bent the warming line. The "C" reactor feed pump discharge line flow element tap looked as though it may have been bent. The welds on this line were tested and found to be satisfactory. The "A" pump* minimum flow to condenser had. loose insulation. 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. In the turbine pipeway in the extraction steam piping, one pipe support pedestal showed 3/4 inch of movement, and one line had the pipe support pad cracked. The reactor feed pump suction heater under the hotwell, had three pipe support pedestal cement pads cracked.
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- 4. Corrective Actions Taken
* - The feedwater piping was in~pg_i:ted_and-:I'epa-~red;- -A-1-1--feed\vate*r-piping __________
---'-'---*------------welds-were--restea-*using--either magnetic particle or dye penetrant, with satisfactory results* *The feedwater regulation valves were checked
- for proper-operation with .special attention given to the "A" regulation_
valve lock~up ability. .
- 5 *. Exit Meeting After completing an inspection of the damaged piping and support systems; it was the position of RO and our consultant that the magnetic particle and dye penetrant.examination was.not adequate to insure that the piping sys-tern had not been over-stressed and their useful life reduced. It was further suggested that the licensee. shou.ld-conduct a stress analysis of the affected sys.terns by imposing. upon 'the system the estimated movements encountered. The licensee wanted to study the problem and requested a.
meeting on July 10, 1974 in the offices of their consultant, Sargent & Lundy, to establish the parameters of -the stress analysis. This meeting was held as planned on July 10, 1974 irt the offices of Sargent & Lundy and. the parameters of the analysis.and techniques*discussed and agreed upon by the licensee, their consultant~ RO and our consultant, Parameter, Inc. *A list of* attendees of the July 10, 1974 meeting is attached~ It
.was agreed that Commonwealth Edison would submit a report to RO within 40 days. It was also agreed that an open. line of com.'llunication would be
.maintained between Sargent.& Lundy.and our consultant, Parameter Inc.,
in the event some technical question had to be reconciled. j I.
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*~~LX1 MEETING - JULY 10, 1974 CECO - M&S Engineer G. T. Kitz Sargent & Lundy' F. L. Spakoski Sargent & Lt.indy E~ B. Branch Sargent & Lundy D. J. Sedgurck Sargent & Lundy ,.
J. w. Muffett Sargent & Lundy J. D. Irish Sargent & Lundy
- c. H. Brown us AEC, RO:III L. L. Bera tan US AEC, RO:HQ R. A. Lofy Parameter, Inc., Consultant for AEC R. s. -Dean Parameter, Inc., Consultant for AEC e
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