ML20086L515

AO 74-12:on 740318,relief Valve Failed to Close Resulting in Reactor Blowdown to Torus Until Reactor Was at About Atmospheric Pressure.Caused by Actuator Plunger Stuck in Extended Valve Open Position.Air Operator Adapter Replaced

ML20086L515
Person / Time
Site:	Peach Bottom
Issue date:	03/29/1974
From:	Meyer R PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
AO-74-12, NUDOCS 8402080277
Download: ML20086L515 (3)

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March 29, 1974 %//%jnp%gy

' Al c-50-277 Mr. 'A. Giambusso .

Deputy Di rector of Reactor Projects United States Atomic Energy Comission Di rectorate *of Licensing Washington, D.C. 20545 Sub_iect: Abnormal Occurrence

Dear Mr. Giambusso:

The following occurrence was reported to Mr. D. Caphton, A.E.C. Region I Regulatory Operations Office on March 19, 1974.

Written notification was made to Mr. James P. O'Reilly, Region I Regulatory Operations Office on March 19, 1974. In accordance wi'th Section 6.7.2.A of the Technical Specifications, Appendix A of DPR-44 for Unit 2 Peach Bottom Atomic Power Station, the following reports is being submitted to the Directorate of Licensing as an Abnormal Occurrence.

Reference:

License Number DPR-44, Amendment Number 1 Technical Speci fication 3.6.0 Report No.:

• 50-277-74-12 Report Date: March 29,1974 Occurrence Date: March 18, 1974 Facility: Peach Bottom Atomic Power Station - Uni t 2 R. D. 1, Delta, Pennsylvania 17314 Identi fication of Occurrence:

l Following a Group I isolation and scram from abo 0t 48%

power, a relief valve which was manually operated failed to close resulting in reactor blowdown to the torus until the reactor was at about atmospheric pressure.

Conditions Prior to Occurrence:

Plant stable at about 48% power.

Description of Occurrence:

During instrument surveillance testing a Group I isolation, j 2800 was initiated due to valving an instrument into service. Followingj L, .

8402080277 PDR ADOCK 0 00 7 <

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COPY SENT REGION #. * ' h. 3' i 1

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O Description of Occurrences (continuzd)

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.the Group I isolati.on and tesultant ' scram', the 71D reif ef valve was - '

, .qqnua l ly , opera te,d :to. r. educe pre,ssu,re. When" clos,ure was ini tiated 'at ,', , ~ . , ,'

900 'psig, the' relief-Valve ' failed to close.- -Rupeated at' tempts to *"

close this valve failed, resulting in a reactor blowdown to the torus '

'to about atmosphbric ' pressure. -

Designation of Apparent Cause:

- Inspection of' the 7ID relief valve air operato,r Yevealed that -

the actuator plunger was stuck in the extended (valve open) position.

Tear down of the air operato.r indicated severe galling between the actuator plunger and the adapt.or sector bore. ,Further ex6mination ,

. revealed that the adapter was out. of straightness tolerance.

Analysis of Occurrence:

Temperature transient data following this occurrence was collected and transmitted to the nuclear steam supplier for his re-view. A review by the nuclear steam supplier of the referenced data yielded no conditions in the vessel more severe than the specified events for which the design adequacy was demonstrated in the RPV vendor stress report. Specifically, the temperature changes in the bottom head were less severe than specified for the loss of feedwater pumps event. The temperature changes in the feedwater nozzle are smaller than during normal shutdown wi th 25% flow, compared to the low 3 in.

bypass line flow actually used. In addition, it was found that the short period of head spray operation after the blowdown event caused a less severe temperature distribution in the closure flange region than during the shutdown with flooding event specified.

Since the temperature and pressure transient experienced by the reactor vessel was less severe than conditions used in the reactor pressure design and since no radiation releases occurred as a result of the transient, no safety significance is associated with this occurrence.

Corrective Action:

The 710 relief valve was disassembled to identify the cause of the occurrence as described above. The air operator adapter and plunger of the 71D relief valve were replaced. As a result of this failure, the other ten air operators were disassembled and inspected.

Two other air operator plungers were found .to be out of straightness tolerance and were replaced, although they exhibi ted no signs of galling or binding. All eleven air operators were functionally tested prior to and following installation on _ their respective valves.

Failure Data:

The pilot valve stem of this air actuator had stuck previously on January 12, 1974. Refer to letter dated 1/14/74, W. T. Ullrich to .

James P. O'Reilly.

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. R. D. Meyer s

• General Superintenddht '

Generation Division cc: Mr. J. P. O'Reilly Di rector, Region i United States Atomic Energy Commission 631 Park Avenue King of Prussia, PA 19406 4

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