ML20084L767

AO 50-237/1974-24,25 & 26:on 740722,during Reactor Load Changes,Three Motor Operated Valves Failed to Operate When Given Open Signal from Control Room.Caused by Mounting Bolts That Vibrated Loose.Bolting Replaced

ML20084L767
Person / Time
Site:	Dresden
Issue date:	07/31/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084L770	List: ML20084L767 ML20084L771
References
549-74, NUDOCS 8305230707
Download: ML20084L767 (3)

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.fg Comn toalth Edison t 3)f Om Fnct ..aton2 Ftsza. Ctrcno. tifuncts O

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. Q, / Address Rep:y CNcago, to:60S90 lihnois Post Office Box 767 -

BBS Ltr.d549-74' Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 July 31, 1974 j' D

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.Mr. J. F. O' Leary, Director 50-237 g.,_.; -

Directorate of Licensing U. S. Atomic Energy Commission g,y . . .

Q( .i,'; ,/s Washington, D. C. 20545 \ Av X1T/^

SUBJECT:

REPORT OF ADNORMAL OCCURRENCE FER SECTION 6.6.A 0F THE TECHNICAL EPECTFICATIO!IS.

FAILURE OF LPCI SYSTEH VALVES TO OPERATE.

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

2) Notification of Region III of AEC Regulatory Operations l' Telephone: Mr. F. Haura,1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br /> on July 22, 1974.

Tclogram: Mr. J.-Keppler, 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on July 22, 1974

3) Drawing Number M-29 b ft .lJ7 Report Hu=bers: 50-N &/1974-24,25,26 opner s m r.. ....yu. swm-Occurrence Date: July 22, 1974

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l Facility: Dresden Nuc1 car Power Station, Morris, Illinois IDENTIFICATION OF OCCURPINCE This lotter is to report an occurrence relating to the operation of the unit on July 22, 1974. While performing routine valve. operability checks on 'the LPCI system prior to removing Unit 2/3 'diccel generator frcm service for rulintenance, three motor operated valves failed to operate when given on open signal from the control room.

- CONDITIONS PRIOR TO OCCURRENCS Prior to the abnormal occurrenca, reactor load changes were-in prcgress at 50 INc/ hour from an initial 465 INe with a' thermal power of 1

1530 PMt.

i In addition, the torus water was being cooled due to a high temp- l eratura condition. During. this operation,' two LPCI pumps were running with l

torus water being pumped thrcush the contairmont cooling , heat exchangers j

nud back to the t. crus throur,h MO 3EA cod 363 (/" spray r,i'ng header) . 1

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.Y k 0305230707 740731 1 EC B 4

. PDR ADOCK 05000237  ?'g'* i 51 B PDR j 1

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Mr. J. F. O' Leary O

July 31, 1974 With the routine valve cperability checks in progress, one LPCI pump was secured but torus water cooling continued.

DESCRIPTION OF OCCURREMCE Subsequent to the failure of three motor operated valves; 1501-22A, 22B, and 19B, an operator was dispatched to the valve and valve breaker locations for inspection. Upon inspection of 1501-22A and 22B breakers, the operator reset the breakers and requested that the control room give the valve an open signal. At that time, the valves cycled satisfactorily. As a result, however, a work request was issued to inspect these two valves for malfunctions.

On inspection of valve 1501-198, the operator manually moved the valve off its seating surface. Then he requested an open signal be provided.

The valve operated satisfactorily, however, on the second attempt at operation, the valve would not open. As a result, a work request was issued to inspect the valve. At 1110, this valve was taken out of service for inspection.

DESIGMTTON OF_ APPARBNT _ CAUSE OF OCCURRENC3 Through further investigation, it was determined that a probica did not exist with valve 1501-22A snd 22B. For while the valve operability checks r::: b:ing c:ndu:::d, the ::: : waa Ecir.g ccelod b., wi. oloilos iho watui through the contain=cnt cooling heat exchangers and MO valve 38A and B and back to the torus. In thin valve lineup, an interlock is created between MO valve 38A and 383 and 1501-22A and B. Above 350 psi reactor pressure inboard injection valve IS01-22A or B can be opened if both the outboard injection valve, 1501-21A or B, and the test line throttle valve, 1501-38A or B are closed, i

During the period between the failure of these valves to open and l the operator requesting the operation of these valves after resetting the l

thermal overloads, torus water cooling was terminated with the LPCI pu=p '

j being shutdown and both 1501-3SA and B being clor.cd. Thus, thia action i' removed the interlock condition and permitted succer.sful operations of valvas 1501-22A and B.

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On investigating the 1501-19B failure, a visual inspection of the  !

valve revealed that the mounting bolts connecting the valve yoke to the }

limitorque operator had vibrated loose. The operator was found to have spun

• off of the sten and resting on the guard rail adjacent to the valve.

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It appears that the valve was cycled one time with the operator f being held on by four bolts with a ccaple of thrcads. On the second attecpt '

at operation, the bolts finally broke loose. Inspection of bolts revealed

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tha t they were not the right icngth. The bolts were 1 inch x 5/16" diameter, i whereas 1-3/8 inch x 5/16" diameter bolts cheuld be the original bolts. #

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• r Mr. J. F. O' Leary July 31, 1974 AHALYSIS OF OCCURRENCE 4

The failures of 1501-22A and B to open due to an interlock condition did not endanger the public health or safety because valve 1501-3gA and B were operable and would have closed automatically in the accident condition. Below 350 psi reactor pressure, when tho' LPCI system is needed, valve 1501-21 (inboard) and 1501-22 (outboard) injection valves automatically open and valve 1501-38 automatically closes. .

The failure of 1501-19B to open did not endanger the public health or safety because the redundant system was operable. The Technical Specifica-tion 3.5.A 6 does allow operation of the reactor with a maximum of one dryucli ,

spray loop inoperable for thirty days. The one spray loop was inoperable for approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

_ CORRECTIVE ACTICN I With regard to.the failures of MO valve 1501-22A and B, the corrective action was to remove the interlock condition by closing E0 valve 1501-38A and B. In addition, the surveillance procedure has been changed to ensure that prior to operating 1501-22A and B,1501-38A or B will be verified closed, thus climinating the possibility of recurrence of this type of interlock condition. i In addition, the valves were cicctrically checked to ensure uuut.'uility.

The corrective action taken to correct no valve 1501-19B failure

-vas to replaco the bolting found in the valve which were 1 inch length x  !

5/16 inch diamator with 1-3/8 inch length x. 5/16 inch diameter. ~The replace- )

ment bolts will ensure that the operator is securely fastened by over b inch j of threaded bolt rather than the previous few threads. 3 The above actions should prevent or minimize the recurrence of similar failures.

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FAILURE _ DATA k To date, no previous failures or malfunctions of this nature have

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.f occurred on 10 valves 1501-22A and B, which are 16 inch 900 lb ' pressure seal bonnet gate valves made by Cranc Company.- t, With regard to MO valve 1501-19B, one previous failure on August 21, 1973 occurrence in which the valves failed to operate due to faulty torque switches. These switches were replaced and the valves operated satisfactorily.

This valve is a 6 inch gate valve made also by Crane Company.

Sincerely, h( %M M B. B. Stephenson Superintendent.

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-BBS:RLW:do t