ML19210A131

Event Rept 76-21/3L:on 760521,reactor Bldg Isolation Valve on Engeneered Safeguards Actuation Sys Failed to Close. Caused by Binding of MU-V2B Packing/Stem.Valve Cycled Successfully Following Occurrence,Assuring Proper Operation

ML19210A131
Person / Time
Site:	Three Mile Island
Issue date:	06/18/1976
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-0892, GQL-892, NUDOCS 7910240849
Download: ML19210A131 (4)

Text

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R.C. Arnold DATE RECClVEO

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• Reportable Occurrence # 76-21/3L on 5-21-76 Concerning. Failure of a Reactor Buildi.ig isolat-

. ion valve to clese on an Engineered Safeguards l -Actuation System (ESAS) test signal.......

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Docket No. 50-289 Operating License No. DPR ';0 In accordance with the Technical Specifications of our Three Mile Island Nuclear Station Unit 1 (:C-1), we are reporting the following reportable occurrence:

(1) Report Number: ER Tf-21/3L (2a) Required Report date: June 20, 1976 (2b) Date of Occurrence: May 21, 1976 (3) Facility: Three Mile Island Nuclear Station - Unit 1 (h) Identification of Occurrence:

Title:

Failure of a Reactor Euilding isolation valve to close on an Engineered Safeguards Actuation System (ESAS) test signal.

Type: A reportable occurrence as defined by Technical Specification 6.9 2.3(2) in that failure of containment isolation valve MU-V2B to close on an ESAS test signal lead to operation in a degraded mode permitted by a limiting conditicn for operaticn as defined b, Technical Specification 3.6.6.

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Mr. J. P. O'Reilly, Director June 18, 1976 GQL 0692 (5) Conditions Prior to Occurrence:

Pover: Core: 0%

Elec: 0 MWe 6

RC Flow: 141 x 10 lbs/hr RC Pressure: 2155 psig RC Temp: 532 ?

PRZR: Level. 100 inenes PRZR Temp. 655 F (6) Description of Occurrence:

At 1245 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.737225e-4 months <br /> on May 21, 1976, while performing Surveillance Procedure 1303-5 1, Reactor Building Cooling and Isolation System Logic Channel & Component Test, containment isolation valve MU-V2B failed to close on an auto logic ESAS test signal. MU-V2B isolates the "B" Letdown Cooler outlet line inside the Reactor Building. The valve closed (ES position) satisfactorily on auto Test 1 (Logic Channels 1 & 2) and auto Test 2 (Logic Channels 2 & 3) but failed to close on auto Test 3 (Logic Channels 1 & 3). MU-V2B than closed properly when the manual ESAS signal was used. Each time the valve closed electrically, it had to be opened manually.

Immediately, MU-V3, the redundant isolation valve for the "B" Letdown Cooler outlet line, was verified operable and MU-V2B inspected to determine the cause of the failure.

(7) Designation of Apparent Cause of Occurrence:

The cause of this occurrence has been determined to be material in that mechanical binding of MU-V2B's packing and/or stem appeared to be the cause of the valve failure. MU-V2B was tested in an effort to reproduce and locate the cause of its failure. The valve cycled properly each time, although in the first few cycles it was observed to be drawing excessive current as evidencei by heating of the thermal overload. Subsequently, measurements of running current came well within motor naceplate rating. After cycling the valve several times, the valve operated freely as evidenced by current measurements.

1490 015

s Mr. J.-P. O'Reilly, Director ,

fe0 2 1976 (8) Analysis of Occurrence:

It has been determined that this occurrence did not constitute a threat to the health and safety of the public in that:

a. One (1) containment isolation valve is sufficient to isolate the "3" Letdown Cooler outlet line in the event of a loss oC coolant accident and,

b. MU-V3, the redundant containment isolation valve for the "B" Letdown Ceoler outlet line, was operable.

(9) Corrective Action:

In addition to the immediate action described above, MU-V2B vas cycled and its ESAS auto logic tested to verify it was fully operable.

The valve vill be cycled once per week for four (h) veeks to assure the problem does not recur.

(10) Failure Data:

Valve Operator Manufactarer: Limitorque Type / Size: SMB-00 Motor: Reli ace Valve: 2 "-1500# Globe Stop Valve 460". 3d Rockwell Mfg. Co. Fig. 3628(F316)JM 60 h: Butt Weld end.

2.8 A=ps 316 stainless steel body Type B Operating Press. 2500 psig 1700 RPM Operating Temp. 300 0 F F-56 Frame No.

Similar Occurrences: A0 Th-28; A0 75-30; ER 76-20/3L Sincerely, l

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i R. C. Arnold Vice President RCA:rk 1490 016