ML19210A172

Abnormal Occurrence 50-289/75-17:on 750615,reactor Bldg Purge Isolation Valve Failed Local Leak Rate Test.Caused by Improper Valve Adjustment Procedures & Matl Defects Not Allowing Long Term Retention of Adjustment

ML19210A172
Person / Time
Site:	Three Mile Island
Issue date:	06/25/1975
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-1195, NUDOCS 7910240895
Download: ML19210A172 (4)

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Dear Sir:

Docket No. 50-289 Operating License No. DPR-50 In accordance with Technical Specifications for the Three Mile Island Nuclear S tation Unit I, we are herewith submitting abnormal occurrence report number A0 50-289 /75-17.

(1) Report Number: A0 50-289/75-17 (2a) Report Date: June 25,1975 (2b) Occurrence Date: June 15, 1975 (3) Facility: 'Ihree Mile Island Nuclear Station Unit I (4) Identification of Occurrence:

Title:

Failure of Reactor Building Purge Isolation Valve to Pass Local Leak Rate Test Type: An abnormal occurrence as defined by Technical Specifications paragraph 1.8e, in that the failure of the Reactor Building purge isolation valve (AH-VlA) to pass the local leak rate test conatituted an abnormal degradation of one of the several boundaries designed to contain the radioactive materials resulting from the fission process.

(5) Conditions Prior to Occurrence:

Power: Core: 89.5% (2270 !Mt)

Elect.: 740 MWe \k]h }k9 6

RC Flow: 133 x 10 lb/hr.

6053

RC Pressure: 2155 psi RC Temp.: 5790F PRZR Level: 240 in.

PRZR Temp.: 6500F (6) Description of Occurrence:

During the yearly leak rate test of the Reactor Building Purge Isolation Valves, valve AH-VlA leakage prevented test pressure from increasing to 55 psi. Inspection of the valve seating surfaces showed that there was approximately a 1/16 inch gap between seating surfaces in the closed position. This gap was caused by misadj ustment of the operator for this valve.

Valve AH-VlB was determined to be seating properly when checked with soap solution.

The operating mechanism for AH-VlA was adjusted and subsequent leak rate testing indicated that the leak rate was considerably within the requirements of Technical Specification 4.4.1.2.3.

(7) Designation of Apparent Cause of Occurrence:

The apparent cause of this occurrence is not known. However, it is believed that the possible cause is either:

(a) procedure in that the valve operator adjustment procedure may not be adequate to assure proper long term valve adjustment, or (b) material in that the valve and/or valve operator design may not permit proper adjustment and/or long term retention of adjustment.

(8) Analysis of Occurrence:

Although valve AH-VlA did not meet acceptance criteria, the in series valve (AH-VlB) was shown to have acceptable leakage such that the combined leakage did not exceed acceptance criteria and, therefore, containment integrity was maintained. Since containment integrity was maintained, there was no potential threat to the health and safety of the public as a result of this occurrence.

(')) Corrective Actions:

Immediate:

The seating surfaces of AH-VlA and B were visually inspected.

The hydraulic operator of AH-VlA was re-adjusted to assure tight closure of this valve using normal operating methods .

Valves AH-VlA and B were successfully retested and met acceptance criteria.

1476 150

Long Term:

The seating surfaces of valve AH-VlA will be inspected approximately once every two weeks until confidence is gained that the valve is and will remain properly adjusted. In the event that any procedural or material inadequacies are discovered, appropriate corrective actions will be taken.

The Plant Operations Review Committee and Station Superintendent reviewed and approved the above lis ted actions , and steps have been taken to ensure impicmentation of the yet to be completed long term corrective actions.

(luj Failure Data:

P/evious Failures : None E t uipment Identification: Valve: Pratt 48 in.

Butterfly Valve Actuator: Be ttis Co rp .

Robotarn Actuator 80889B K DC 1074 - 15R75 Since rely ,

t R. C. Arnold Vice President RCA/CWS/cas File : 20.1.1/7.7.3.5.1 1476 151