05000254/LER-1979-024-03, /03L-0:on 790724,pressure Suppression Chamber Reactor Bldg Vacuum Breaker Pressure Switch Was Found to Actuate Below Limiting Condition for Operation Level.Caused by Instrument Setpoint Drift.Switch Recalibr

/03L-0:on 790724,pressure Suppression Chamber Reactor Bldg Vacuum Breaker Pressure Switch Was Found to Actuate Below Limiting Condition for Operation Level.Caused by Instrument Setpoint Drift.Switch Recalibr

ML19208A112
Person / Time
Site:	Quad Cities
Issue date:	08/10/1979
From:	Kooi M COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19208A111	List: 05000254/LER-1979-024, Forwards LER 79-024/03L-0 05000254/LER-1979-024-03, /03L-0:on 790724,pressure Suppression Chamber Reactor Bldg Vacuum Breaker Pressure Switch Was Found to Actuate Below Limiting Condition for Operation Level.Caused by Instrument Setpoint Drift.Switch Recalibr
References
LER-79-024-03L-02, LER-79-24-3L-2, NUDOCS 7909120596
Download: ML19208A112 (2)

LER-1979-024, /03L-0:on 790724,pressure Suppression Chamber Reactor Bldg Vacuum Breaker Pressure Switch Was Found to Actuate Below Limiting Condition for Operation Level.Caused by Instrument Setpoint Drift.Switch Recalibr

Event date:
Report date:
2541979024R03 - NRC Website

text

N RC F CA M 366f U. S. NUCLEAR REGULATORY COMMIS5 ton (7 77)

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8 60 61 00CKET NUMBER 68 63 EVENT DATE 74 75 REPCRT CATE 83 EVENT DESCRIPTION AND PROBA8LE CONSECUENCES h O

2 l While performing the Pressure Suppression Chamber Reactor Building Vacuum Breaker l

g Actuation Calibration and Functional Test, procedure QlS 48-1, pressure switch l

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l PS 1-16228 was found to actuate at 0.61 psid. This was less conservative than the l

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l was found to actuate within limits and would have opened vacuum breaker A01-1601-20A l 0

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o j The cause of this occurrence is attributed to instrument setooint drift. There was no l i ijl evidence of physical damage to the switch. Corrective action taken was to recalibrate I 7

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NAME 4 P A e p t. P n

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LER NUMBER: LER/R0 79-24/03L-0 11.

LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station Ill.

FACILITY NAME: Unit One IV.

DOCKET NUMBER: 050-254 V.

EVENT DESCRIPTION

On July 24, 1979, while performing the Pressure Suppression Chamber Reactor Building Vacuum Breaker Actuation Calibra-tion and Functional Test, procedure QTS 48-1, pressure switch PS 1-16228 was found to actuate at 0.61 psid. This is in excess of Technical Specification 3.7.A.3.a limiting condition for operation of 0.5 psid.

The immediate corrective action was to recalibrate the switch. There have been occurrences of this type on Unit One in the past, with the latest being documented by R0 78-22/03L which occurred on July 26, 1978.

VI.

PROBABLE CONSEQUENCES OF THE OCCURRENCE: The reactor building to sup-pression chamber vacuum breaker system consists of two, 100 percent flow capacity systems.

Pressure switch PS 1-1622A was found to trip within limits and would have actuated within the required differential pressure and opened vacuum breaker A0 1-1601-20A, relieving any negative pressure in the suppression chamber, had the need arose.

Pressure switch PS 1-1622B would have tripped at 0.61 psid, which is well under the 2 psid suppression chamber design external pressure. Therefore, the safety implications of this event were minimal.

In addition to this, the vccuum breakers were at all times remotely-manually operable from the Control Room, and the suppression chamber pressure indicator was fully operable.

Vll.

CAUSE

The cause of this occurrence is attributed to instrument setpoint drift.

There was no evidence of physical damage to the switch. The switch is manufactured by the Static-0-Ring Company and are of a diaphram type, model number 12NN-KK215-VX.

Vill. CORRECTIVE ACTION: The corrective action was to recalibrate and functionally test the pressure switch. This is the second instance of instrument set-point drift since these particular switches were installed on Unit One on December 13, 1977 1

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