ML19276F321

LER 79-014/03L-0 on 790214:automatic Blowdown Timers Exceeded Tech Spec Limits During Tests.Caused by Instrument Setpoint Drift.One Timer Readjusted,Another Replaced

ML19276F321
Person / Time
Site:	Quad Cities
Issue date:	03/09/1979
From:	Tietz G COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19276F316	List: ML19276F315 ML19276F321
References
LER-79-014-03L, LER-79-14-3L, NUDOCS 7903280348
Download: ML19276F321 (2)

Text

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j o l a i L Blowdown time r 287-105A took 125 seconds to time out and timer 287-105B took 135 o ! ..j l seconds to time out. These times were in excess of Technical Specification Table 1 3.2-2 allowable limi t of 120 seconds or less. Even though the times were in excess l 5s i ta s [ of 120 seconds, the timers were operational and would not have prevented the fulfillmeht

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43 lG l0 l8 l0 lg 44 47 CAuSE DESCRIPTION AND COnRECTIVE ACTIONS The cause of this occurrence was instrument set point drift. Timer 287-105A, would l

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of 115 seonds. Timer 287-105B was re-adjusted to a new time of 110 seconds. A simulated

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1. LER NUMBER: LER/R0 79-14/03L-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 February 14, 1979, while performing the Automatic Blowdown Logic Test, procedure QMS 700-1, Automatic Blowdown timer 287-105A took 125 seconds to time out and timer 287-105B took 135 seconds to time out. These times were in excess of the Technical Specification Table 3 2-2 allowable limit of 120 seconds or less. The reactor mode switch was in SHUTDOWN at the time of the occurrence, and the Automatic Blowdown System was in the test condition.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE:

The safety implications of this occurrence were minimal due to the fact the Automatic Blowdown System is a back-up system for the HPCI system. Also, even though the timers were found to time out in excess of 120 seconds, the timers were operational and would have performed properly and would not have prevented the fulfillment of the functional requirements of the Automatic Pressure Relief System.

Vll. CAUSE:

The cause of this occurrence was instrument set point drift.

The 287-105 A and B timers are General Electric CR120ST 02241 AA, 125 VDC time delay relays.

Vill. CORRECTIVE ACTION:

Timer 287-105A, which took 125 seconds to time out, would not respond to adjustment and was replaced. The replacement timer has a new time of 115 seconds. Timer 287-105B, which took 135 seconds to time out, was re-adjusted to a new time of 110 seconds. On February 25, 1979, a Simulated Automatic Initiation Surveillance test was performed on the Auto-Blowdown System (procedure QTS 110-2) . Proper timer operation was verified during this test, and relief valve pilot actuation took place within the 120-second Tech Spec limit.