ML19261F252

Abnormal Occurrence 50-289/74-21:on 741031,high Pressure Injection Valve MU-V16A Failed to Open on Control Room Signal.Caused by Insufficient Guidance Re Switch Adjustment. Switch Adjusted & Maint Procedures Under Review

ML19261F252
Person / Time
Site:	Three Mile Island
Issue date:	11/08/1974
From:	Arnold R MEDINA ELECTRIC COOPERATIVE, INC.
To:
References
GQL-0461, GQL-461, NUDOCS 7910250684
Download: ML19261F252 (4)

Text

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TO: ORIG CC OTHER SENT AEC PDR unx3xn Directorate of Licensing 1-signed SENT LOCAL POR mnn CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:

mnxn 1 50-289 DESCRIPTION: ENCLOSURES:

Ler Reporting Abnormal Occurrence #74-21 .,

on 10-31-74 concerning Failure of High _ 1)

Pressure Injection Valve MU-V16A to .

open on a signal from the control room... T-  :- ., -

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Dear Sir:

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\ r Docket No. 50-289 Operating License DPR-50 In accordance with the Technical Specifications for our Three Mile Island Nuclear Generating Station, Unit 1, we are reporting the following abnormal occurrence:

(1) Report Number: A0 50-289/74-21 (2a) Report Date: November 8, 1974 (2b) Occurrence Date: October 31, 1974 (3) Facility: Three Mile Island Nuclear Station, Unit 1 (4) Identification of Occurrence:

Title:

Failure of High Pressure Injection Valve MU-V16A to Open on a Signal from the Control Room Type: An abnormal occurrence as defined by the Technical Specifications, paragraph 1.8d, in that the failure of High Pressure Injection Valve MU-V16A to open threatened to cause an Engineered Safeguard feature or system to be incapable o~ performing its intended function.

(5) Conditions Prior to Occurrence: The reactor was at steady state power with maj or plant parameters as follows :

Power : Core: 81% ,.

Elec.: 675 W (Gross)

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RC Flow: 138 x 106 lbs/hr \

R ~2 1.1. w 3 %

2155 psig RC Pressure:

RC Temp.: 579 F PKZR Level: 242 in PRZR Temp. : 650 F (6) Description of Occurrence:

At 1525 hours0.0177 days <br />0.424 hours <br />0.00252 weeks <br />5.802625e-4 months <br /> on October 31, 1974, High Pressure Injection Valve MU-V16A of the Makeup and Purification System failed to open on a signal initiated manually from the Control Room. This occurred as preparations were being made to troubleshoot a problem involving the Engineered Safeguards indicator light for this valve. After partially opening the valve with the local handwheel, the valve was fully opened electrically. The valve was then closed electrically, but again failed to open on a signal from the Centrol Room.

It was then determined that a limit switch was out of adjustment and should have been closed when the valve was completely closed.

Instead, te switch was open and this condition prevented the valve operator motor from operating.

(7) Designation of Apparent Cause of Occurrence:

It has been determined that the misadjusted limit switch may have resulted from there not being sufficient procedural guidance regarding the adjustment of this type of switch.

(8) Analysis of Occurrence:

It is believed that the f ailure of High Pressure Injection Valve MU-V16A did not constitute a threat to either the health or safety of the public in that only one of two flow paths is required for high prescure injection during a Loss of Coolant Accident and only one operational valve is required to complete each flow path. In the present instance, both High Pressure Injection Valves in the "B" flow path and the remaining valve in the "A" flow path were tested and found to be operational; hence, both flow path "A" and "B" were available.

(9) Corrective Action:

Immediate actions were taken to ensure redundant components of the affected safeguard system were operable, and to determine the cause of the valve failure. Once it was determined that the cause of the failure was a misadjusted limit switch, the switch in question was properly adjusted; checks were made on the motor to ensure it was not damaged; and the valve was then tested satisfactorily and returned to service.

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. At a meeting held shortly after the occurrence was reported, the Plant Operations Review Comittee (PORC) reviewed and gave its approval of the above mentioned corrective actions.

Further, PORC recomended to the Station Superintendent that the following long-term actions be taken to prevent any recurrence of the incident:

a. Inspect the limit switches for the remaining valve along the "A" flow path and for the two valves along the "B" flow path to ensure that they are properly adjusted,

b. Prepare a maintenance procedure, giving additional guidance on adjusting limit switches.

The Station Superintenc'ent concurred with these recocnendations and has directed that step; be taken to implement these recomendations.

(10) Failure Data:

Not applicable.

Sincerely,

1. C. .old Vice President RCA/cas File: 20.1.1/7.7.3.5.1 cc: J . P . O 'Reilly g81 259