ML19262A255

Abnormal Occurrence 50-289/75-06:on 750312,during Reactor Bldg Isolation & Cooling Surveillance Test,Valve RR-V3C Failed in Nonengineered Safeguards Position.Caused by Improper Mfg or Installation.Valve Repaired

ML19262A255
Person / Time
Site:	Three Mile Island
Issue date:	03/21/1975
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-0866, GQL-866, NUDOCS 7910260590
Download: ML19262A255 (4)

Text

ILEFORT OF ABNORMAL CCCURRENCE AND/02 INCIDE!TI tv..; DISTRIBUTION FOR PART 50 DOLnET MATERI At.

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(TEMPORARY FORM)

., , . CONTROL NO: '1 M FILE: INCIDE!Tr REPCRT FILF FROM: Metropolitan Edison Co. DATE OF DOC DATE REC'D- LTR TWX RPT OTHER Reading, Pa.

R.C. Arne.ld 3-21-75 3-24-75 XX ORIG CC OTHER SENT AEC POR vvy TO:

NRC 1 Signed SENT LOCAL PDR _ XXX CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:

XXX 1 50-289 DESCRIPTION: ENCLOSURES:

Ltr. trans the following. .. Abn. Occurr. # 75-06, on 3-12-75, concerning

- Failure of the Reactor Bldg. E:::ergency Cooler Inlet Valve (RR-V3C) in the~ Non-Engineered Safeguards (Closed) position...

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PLANT NAME: Metropolitan Edison Co.

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POST CFFICE BCX 542 READING, PENNSYLVANI A 19603 TELEPHONE 215 - 92%C01 March 21, 1975 cqL 0866 g.

Directo r .. - ,

Division of Reactor Licensing ' -

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U. S . Nuclear Regulatory Commission v ,; 4' / 75 ,,, -

Washington, D.C. 20555 s- --~4-., 4,

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Dear Sir:

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Operating License DPR-50 Docket #50-289 In accordance with Technical Specifications for the Three Mile Island Nuclear Station Lbit 1, we are reporting the following abnormal occurrence:

(1) Report Number: A0 50-289/75-06 (2a) Report Date:

(2b) Occurrence Date: March 12, 1975 (3) Facility: Three Mile Island Nuclear Station Unit 1 (4) Identification of Occurrence:

Title:

Failure of the Reactor Building Emergency Cooler Inlet Valve (RR-V3C) in the Non-Engineered Safeguards (Closed)

Position Type: An abnormal occurrence as defined by the Technical Specifications, paragraph 1.8d, in that the failure of the Reactor Building Emergency Cooler Inlet Valve in the non-engineered safeguards (closed) position threatened to cause an Engiueered Safeguards feature or system to be incapable of performing its intended function.

(5) Conditions Prior to Occurrence:

The unit was at steady state power with major parameters as follows:

Power: Core: 98.9%

Elec: 861 MW (Gross)

RC Flow: 136 x 10 6 lb/hr S id 1484 250

RC Pressure: 2155 psig RC Temp: 579 F PRZR Level: 235 in.

PRZR Temp : 650 F (6) Description of Occurrence:

At 1150 hours0.0133 days <br />0.319 hours <br />0.0019 weeks <br />4.37575e-4 months <br /> on March 12, 1975, while conducting Reactor Building Isolation and Cooling Surveillance Test 1303 -6.1, Reactor Building Emergency Cooler Inlet Valve RR-V3C failed in the non-Engineered Safe-guards (closed) position. The valve had operated properly on three previous automatic Engineered Safeguards test signals but failed when attempting to open it from the controlroom prior to the manual Engineered Safeguards test.

The other Reactor Building Emergency Cooler Inlet Valves, RR-V3A and RR-V3B, were tested and found to be operable.

An investigation was made into the cause of the failure. It was found that a lock nut within the valve operator had been improperly staked, had worked loose, and had permitted the disengagement of the stem nut from the valve steam. As a result, the transuission of force was not made from the valve motor to valve stem and the valve did not open.

RR-V3C was then repaired, returned to service, and tested satisfactorily.

(7) Designation of Apparent Cause of Occurrence :

The apparent cause of the occurrence appears to have been improper manufacture or installation. The lock nut is normally secured by staking the thread area of the lock nut. In this case, the punch mark was on the Jock nut body, not in the thread area, and the lock nut could thus become unthreaded. The lock nut could have been installed in the factory or during construction.

(8) Analysis of Occurrence:

It is believed that the f ailure of RR-V3C in the closed position did not represent a threat to the health and safety of the public in that post-accident reactor building emergency cooling may be accomplished by using either both paths of the reactor building spray system or one reactor building emergency cooler and one path of the reactor building spray system. Both paths of the spray system and two reactor building coolers were operable and available for emergency use.

(9) Corrective Action:

Immediate corrective action was taken as described above. The stem and

' lock nut for the motor operator were placed back on the valve stem and staked in place. Limit switches were checked for proper adjustment and the valve operator checked for proper operation. The valve was then tested and verified to be operating properly.

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The Plant Operaticns Reviev Conmiteee (PORC) met after the cecurrence, reviewed and approved the above action, and reconmended to the Station Superintendent that the Reactor Building inlet and outlet valve opera-ters be checked for loose lock nuts and improper staking. If this is found in any of these six valves, additional valve operators vill be checked. In addition, station electrical persennel vill be verbally instructed in the importance of properly securing the lock nut and to check the lock nut for tightness during routine inspection or main-tenance of the operators.

The Station Superintendent ccncurred with PCRC's reccmmendations and has taken steps to insure that these acticns are carried cut.

(10) Failure Data:

a. Previous Failures: Ncce

b. Equipment Identification: Limitorque Valve Operator Size SM30 Sincerely, f

7%

WL R. C. JYeold Vice President-Generation RCA:RSB:tas cc: Office of Inspection and Enforcement, Region 1 U.S. Nuclear Regulatory Ccc=issicn 631 Park Avenue King of Prussia, PA 19h06 File: 20.1.1/7 7.3.5.1 1484 252