ML20083L268

Forwards Response to 740111 Info Request 74-01, AOs in Piping Sys, Re Occurrences Resulting in Vibrations or Unanticipated Dynamic Forces to Specified Sys

ML20083L268
Person / Time
Site:	Quad Cities
Issue date:	02/14/1974
From:	Abel J COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
NUDOCS 8009220448
Download: ML20083L268 (7)

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'f / _--w a One FirsTn inat Plaza. Chicago ll! nois 2 y :o: Post Office Box 767

, ^30icis'h)nois Chicago. 60690 February 14, 1974 .

Mr. James G. Keppler . .

Regional Director '

Directorate of Regulatory, Operations - Region III  !

U.S. Atomic Energy Commission 799 Roosevelt Road . .

Glen Ellyn, Illinois 60137

Subject:

Response to Regulatory Operations Information

Request No. 74-1, " Abnormal Occurrences in

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Piping Systems" for Dresden and Quad-Cities S tions, SEC I) ts 50-10, 50-237, 50-249, 50-254 and 50-265 -

Dear Mr. Keppler:

This reply is submitted in response to your Information Request 74-1, dated January 11, 1974, which requested information on occurrences resulting in vibrations or unanticipated dynnmic forces to specified systems at Dresden and Quad-Cities Stations.

- Attached are reports submitted to this office from Dresden and . Quad-Cities Stations outlining six incidents which occurred in Class B piping systems. All these incidents have been reported to the AEC.

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f further information is required, please contact this offi'ce. .

Very truly.yours, w \,,

q J. S .s Abel Nuclear Licensing Administrator Boiling Water Reactors Att.

[0 cc Mr. Boyce H. Grier -

Assistant Director for O ' - '

I Construction and Operation  : -O Directorate of Regulatory Operations , "/ ' ,, l[1 7 s U.S. Atomic Energy Commission ( I1% '

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3NOR!1AL OCCURRENCES IN PIk ?G U

SYSTEMS AT DRESDEN STATION DRESDEN U!!IT 1 ,

No abnormal occurrences in piping systc=s DRESDEti U?lIT 2

1) May 29, 1970 The situation was discovered at 0050 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> Fay 29, 1970 while checking the HPCI system.in preparation for a test run.

The HPCI turbihe had been taken out of service at 0730 hours0.00845 days <br />0.203 hours <br />0.00121 weeks <br />2.77765e-4 months <br /> May 28 for '

, a steam strainer inspection. This work was completed and HPCI was placed back in service at 1623 hours0.0188 days <br />0.451 hours <br />0.00268 weeks <br />6.175515e-4 months <br /> May 28, 1970.

. During the outace a scram occurred following which water level rose to the HPCI steam nozzle which allowed uater to enter the stcam line up to the outboard isolation valve which was closed.

Khen HPCI was placed in service at 1623 hours0.0188 days <br />0.451 hours <br />0.00268 weeks <br />6.175515e-4 months <br /> the accumulated water was forced down the steam line causing unusual hydraulic forces on the steam line, particularly at the bends.

During the HPCI outage the inboard isolation valve located close to the reactor was not closed. The outboard isolation valve was closed along with the valve ahead of the turbine stop valve. This was the established

. procedure.. -

A revised procedure has been placed in effect which requires the inboard and outboard isolation valves to be closed when taking HPCI out of service. This, along with a steam line draining procedure for restoring the system to service will insure any collected water will be drained from the header before appling reactor pressure to the line.

2) March 29,1971 ,

- The unit had been shutdown for refueling and the core spray subsystem had been out of service for modifications ~to the logic circuitry. -

Upon completion of testing the modifications the core spray surveillance

'.' s, test was performed at 0330 hours0.00382 days <br />0.0917 hours <br />5.456349e-4 weeks <br />1.25565e-4 months <br /> Farch 29, 1971 to demonstrate operability.

At 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> during a routine operator inspection seismic restraints on the 2A core spray subsystem line 1403, exterior to the drywell, were J found damaged .

Further investigation revealed that three seismic restraints and one hanger on the 2A core spray subsystem line had been damaged. The 2C core spray subsystem line 1404 was also inspected and three seismic

, restraints and two hanners were found datared. Visual inspection -

I revealed no piping danane, although line 1404 app ared to be " sprung" one to two inches from its original position.

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Subsequent evaluation indicated that the damage was the result of a

" water hn=cr'. The core spray subsystem was idle for an c:dended period of time and leakage of uater through the core spray pump discharge stop check valve drained the core spray line. Subsequent operation of the pump resulted in accelcration of a " water slug" in the line causing a " water ha=cr".

To prevent recurrence of the " vater ha=cr" a " jockey" pump was installed that takes suction from the torus and discharges to the core spray and low pressure coolant injection lines to keep the line filled. A similar system was i:p:talled on unit 83.

3) Septc=ber 2h,1971

, At 2058 on 9/22/71 while at a load of 384 me and while surveillance testing was in progress for timing of the shutdown cooling system isolation valves a vibrational shock uas felt in the control rc~om. Simultaneously there was indications of effects on the reactor system, including "A" recirculating water pu p vibration alarm. The pump was shut doun and on the follouing morning a review was made of the situation at which time it was concluded that an inspection of the related systems inside the dryuell would be prudent.

The unit was taken off system at 1703 on 9/29/71 and the reactor placed in cold shutdcun condition, drprell de incrted and ecolod for inspection.

Visual inspection revealed about 8' of mirror insulation dislocated immediately upstream of penetration X 111B on the terbon steal line and dounstream of the shutdoun cooling isolation valve M021101 1B. Sub-

' sequent ca.nctic particle inspection of the tuo elbor welds at this location and stress analysis indicated no distress of this piping or related "A" recirculation pipint;. "A" recirculathg unter pump was subsequently operated at 28% (minimum) speed uhile taking vibration data with satisfactory results. The review of the entire situation by G.E.

and C.E. (SR3 and I?.B) concluded that no darage had been sustained by the primary system or the shutdoun cooling system inside or outside the drywell and that the reactor could be safely returned to service.

A review of the sequence of testine isolation valves could not explain e all of the indicated effects, however it was concluded that a water hammer must have occurred as a result of the testing. It was further concluded that the testing of these valves should be conducted in the g future only'with the reactor cooled down to nor=al shutdown system operating temperatures. -

s Plant startup was authorized after concurrence by the !!RB which required that all seven shutdown coolin: system valves be closed c1cetrically and then checked for proper seating. This was done and proper seating did occur on electrical operation. AEC Compliance was informed of our intent to restart after a discussion of the findbgs and had no objection.

EVESTIGATION FOR POSSIBLE DA" AGE a.. On 9 29-71 a thorough visual inspection was made of the shutdown cooling system piping, equipment, piping supports, insulation j

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and connections to LPCI piping and drywell penetrations (which were also leak tested). In all testinc and inspections there was no visible distress with the execption of the 2A heat exchanger which showed the hold down bolts bent to the south and a small corner segment of the concrete cupport ( 6" x 4" x 3") cracked but still in place. 'The crack did not appear to communicato with the holdown bolt.

b. On 9-30-71 a thorouch visual inspection was made of piping

. and equipment inside the dr.vwc11. No abnormalitics were noted except for an 8' section (3 pieces) of Pirror insulation which had become loosened from the pipe. The impressions en the insulation plus scoring ~of the pipa at the cupport caddle showed that abnormal movement of this section had occurred in the amount, of 5/8". No permanent set was observable in the pipin:;.

c. On 9-30-71 the 1A valve was oper sted to determine by valve observation the limit'cwitch actuation and valyc movement. The valvo closed fully electrically coven times. The red position

< indicating lir,ht cleared only 3 out of 7 times. The valve uns fully scated in all cases as shown by attempts to manually " pull up" on the valve operator,

d. On October 1, 1971 the two ucida at the elbou in line 2 1001 1%"-B were magnetic particle inspected and no defects found,

e. On October 1, 1971 the "A" recirculating uator pump was operated at 285 speed and vibration data taken as performed during the pre op tests. The highcot vibration noted was only 0.6 mils which

.. compared favorably with the pre-op data. (The motor max. vibration

. was only 0.7 mils). -

f. On 101-71 the station maintenance crew checked the 1A valve

, operation and Limitorque operator. It was concluded that,the valve

, operator tripped on torque on valve seatin;; prior to engaging the closed limit switch. The 2B valve, which could not be opened when attemptingd te place the shutdown cvstem in operation on 9-30-71 was repaired after inspection showed mechanical problems in the ,

limitorque operator.

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g. On 101-71 Sargent & Lundy Engincors calculated the stresses in the shutdoun loop piping due to the movement shown during inspection of s' the piping. The highest stress calculated was 16,715 psi; well

. within the yeild strength of the material. The calculational results

. were discussed by S & L with G.E. Co. engineers w:to concluded that no

stresses of concern could be developed within the recirculation system

! piping or connections based on input from S & L. G.E. made a detailed calculation by a computer run for the data supplied by S & L to determine the magnitude of stress at areas of interest at the connection to the recirculating water piping. It was concluded that no significant stresses occurred and that further

. examination of the recirculating vater piping was not justified.

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HYPOT!ESIS FOR h%TER HAIGR The last use of th'c shutdown coaling system was on July 22, 1971 It was the normal practico to leave the reactor coolant side of the heat exchangers full of water. They had never been inerted.

Reviewing the valve operatinq sequence it can be hypothesized that between 7 2.2-71 and 9 00-71 the "B heat cxchanger partially drained through valve Icakage. Since the 1 and 2 valves retcained closed during this period it is assur.ed that the header was initially full, and becama pressurized when the 1A & B valves were opened. The opening of 5A & B valves had no effcet since the LPCI check valves were closed. The opening of the 2A, B & C valves allowed the pressure in the header to be

. impressed on the A & C heat exchangers (pump discharges pressures noted at 175 and 50 psi respectively after the incident whereas B. was 0);

and A & C had previously been noted at a pressuro lowr than 175 and

< 50 respectively. Since (by assunption and the o pressure reading) the "B" heat exchanger was partially drained, the precsure did not incroaco, but some flou passed throu:;h the pump (warr!.ng of the lines

- were noted following the incident) and into the partially drained heat exchanger. s The 2B valve is in a vertical section of lino and when fully opened night have left an air bubble into the cuction header in the drywell if tho header had been sufficiently depressurized. However it is probably more likely that the header was still partially pressurized (since "C"

.- shutdown pump increased to 50 psi and suction valve uas opened after "B'). It is likely that partial venting of the header to the void in the "B" heat exchanger allowed some hot water in the header to converb to steam as the pressure was dropped to 50 psi. This left a steam bubble in the header which was collapsed when the 1A valve was opened and water rushed in the header toward the 1B valve (close to the "A" recirculating

. water pump) causing a mild thrust at that end of the pipe (verified .

by the dislocated insulation). This would account for the "A" recire.

pump high vibration.

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< DRESDEN UNIT 3 No Abnormal Occurrences in Piping Systems a

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ABNORM 3L OCCURRENCES IN PIPI N .i SYSTEMS AT QUAD-CITIES STATIO '

I 1/16/73 t Recirculation /RHRS Vibration, Unit 1 I NCE: A and F CAUSE AND OPERATIONAL SEQUE I i culation flow, a noised in the Uni 0 While increasing power with rec r high frequency vibrationpoint was wherehearvibration thewasB LPCI waspipewastron 3

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The The vibration i ry penetrates the' 7 percent.lpump drywell.recirc tion loop piping inside speeds of 84 pr to maA.

8 Gia also present in the B recircu aB. Stephenson letter to Mr.

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dated 2/16/73; boo-73-23) . '

CORRECTIVE ACTION: hot-standby condition, and aNo damagl The reactor was brought to thewas conducted. RHRS piping LPCI supports. j thorough dyrwell inspectionwere observed in any recirc ort r w J normalitiesA vibration recorder and detec wero oi g unit startup.

duplicated, no i i nsReactor pressurt was varied pipe to monitorwere vibration evident. dur nlevel andt recirc pum vibrations or noises ump h

speed range with no effec s through the 84 to 87 percent pSincehas A modification .this beenoccurren i ing.

on the recirculation or RHRS p pibration detector with a contro proposed, however, to install a v ,

room alarm. ,

Torus Suction Header

' Unit'2 Failure of Hancer Bolts for CAUSE AND OPERATION SEQUENCE lief valves 1 t p testing, at which time resuppression chamber,~

.During Phase IV star uwere being discharged to the were found to have failed. segme an'd ECCS systemsfour torus suction h header boltsd approxima

, The hangers supporteInvestigation revealed had been that tcut torch e rather the than header.

the torus and header brackets ified size, and it' appeared ther thatd cleanly sharpdrilled edge.

to the spechanger re used, strap holes had b leaving a t than partially threaded bolts we ,

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CORRECTIVE ACTION

• The failed specimens and the areas subjected to maximum s~ tresses were inspected by an Edison metalurgist, representatives of Chicago Bridge and Iron Company, and Sargent & Lundy Engineers.

The bolts were found to have sheared and no apparent yielding of the suppression chamber shell or the suction header were found to have occurred. Larger hanger straps, larger unthreaded bolts and drilled bolt heads were installed to prevent,any further occurrences. (

Reference:

F.A. Palmer letter to Mr. E. J. Block dated 6/7/72; FAP-72-107) .

Unit 1 Damaged RHRS Seismic Restraints 4/4/72 CAUSE AND OPER.ATIONAL SEQUENCE While the reactor was in the shutdown mode, a damaged RHRS system pipe restraint was discovered and reported to the Unit

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1 Operating Engineer. Subsequent visual inspection of the RHR system revealed:

three seismic restraints damaged; two spring hangers bottomed; grout chipped on a seismic restraint; a valve '

would not open. electrically; and four hangers damaged. The cause of the incident is believed to be improper venting of the RER system with the resultant water hammer. The filling

-and venting procedure required the use of the jockey pump and

, ,the venting of system high points. The venting at high points '

left several possible points for air accumulation.

CORRECTIVE ACTION -

Seismic restraints and pipe hangers were evaluated for damage by Sargent and Lundy and repaired under the direction of the -

General Electric Company. The filling and venting procedure was altered so that the larger flow and higher pressure con-densate transfer system was used instead of the jockey pump.

The motor operated valve was found to have a mechanical failure of the motor housing causing the brake to engage; it was re-paired and tested satisfactorily. (Reference F. A. Palmer letter to Dr. Peter A. Morris dated April 11, 1972; FAP-72-84).

An intensive study is to be undertaken by Commonwealth Edison, General Electric and Southwest Research Institute concerning all i

vibration problems at Quad-Cities. Vibration data will be obtained throughout the feedwater system, as well as other systems and

..of corrective action recommendations will be given following completion these special tests.

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MEMO ROUTE SUP _

Su me amt this. Fw concunence. For adlon.

Forma AEC.95 ( Rev. May 14.4947) AECM 0240 Note and retura. For sitaature. For tsformation.

70 (Name and unit) AM DALS REMARK $

RO Chief, FS&EB Commonwealth Edison Company RO:HO (4) Dresden Units 1, 2 & 3 50-10, 50-237 and 50-249 Licensing (4) oAn Quad-Cities 1 & 2 50-254 & 50-265 DR Central Files Region I TO (Name and unst) IMITIALS REMAAKS Region II PDR-Local PDR mn NSIC ,

DTIE TO (Hame and unst) penALs aEMAAKs un FROM (Name and unst) REMAans G. Fiore111 Attached is a copy of licensee's reply dt.1 2-14-74 to RO -

RO:III intormation Request /4-1.

mm oAn3-6-74 USE OTHEA 540E FOR ADDtTIONAL REMAAKS CPO r 1971 O . 445 489

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