05000280/LER-1981-023-01, /01T-0:on 810708,delta T Protection Channel T-1-422A Was Found to Indicate Zero.Caused by Incorrect Wiring of Tc & Th RTD Following Design Change.Rtd Wired Correctly

/01T-0:on 810708,delta T Protection Channel T-1-422A Was Found to Indicate Zero.Caused by Incorrect Wiring of Tc & Th RTD Following Design Change.Rtd Wired Correctly

ML20009F751
Person / Time
Site:	Surry
Issue date:	07/21/1981
From:	Joshua Wilson VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009F730	List: 05000280/LER-1981-019-01, /01T-0:on 810707,urgent Failure Alarm for Control Rods Occurred,Indicating Rods Were Inoperrable.Caused by Blown Fuse in Power Cabinet.Fuse Replaced ML20009F729
References
LER-81-023-01T, LER-81-23-1T, NUDOCS 8107310505
Download: ML20009F751 (3)

LER-1981-023, /01T-0:on 810708,delta T Protection Channel T-1-422A Was Found to Indicate Zero.Caused by Incorrect Wiring of Tc & Th RTD Following Design Change.Rtd Wired Correctly

Event date:
Report date:
2801981023R01 - NRC Website

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ATTACHMENT 1 S'URRY POWER STATION, UNIT 1 DOCKET NO:

50-280 REPORT NO:

81-023/OlT-O EVENT DATE:

07-08-81 PROTECTION DELTA T READING ZERO 1.

DESCRIPTION OF EVENT

On July 8, at 1630, Unit One was returned to service following the Steam Generator Replacement.

Delta T protection channel T-1-422A was found to indicate zero.

Technicians placed the bistables in trip at 2130 as they began their investigation using the functional Periodic Test.

At 0045, July 9, the technicians were requested to perform the HiH1 CLS logic Periodic Test (8.5) in order to continue Power Escalation of Unit

One, in accordance witt, their normal procedures, the technicians took tMe bistables out of trip and restored the circuit with T-1-422A still indicating zero.

The protectic'n Delta T was not piaced in trip again until approximately 0800 when the Day Shift began investigating the problem.

The Protection channel was inoperative and not in the tripped mode for approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

This event is contrary to the Redundancy Requi re-ments of Technical Specification 3.7, Table 3 7-1, and is reportable in accordance wien T.S. 6.6.2a(2).

2.

PROBABLE CONSEQUENCES AND STATUS OF REDUNDANT EQUIPMENT:

The Delta T trip circuits provide protection from DNB and power density in excess of-ll8%.

During this event the Redundant Delta T channels remained operable and therefore the health and safety of the public were not affected.

3

CAUSE

The Tc and TH RTD's were wired incorrectly when they were returned to service following completion of a design change during the steam generator replace-ment.

The failure to place and maintain the channel in trip was personnel l

error.

i l

k.

IMMEDIATE CORRECTIVE ACTION

The Delta T bistables were placed in trip.

5 SUBSEQUENT CORRECTIVE ACTION:

RTD's were reconnected to the correct Delto T inputs and the functional Periodic Test was performed to verify operability.

5 ACTION TAKEN TO PREVENT RECURRENCE:

i Persennel will be reinstructed on the Technical Soecification requirements for redundant enannels.

1

iTTACHMENT 1 SURRY POWER STATION, UHli i DOCKET NO:

50-280 REPORT NO:

81-023/01T-0 EVENT DATE:

07-08-81 Page 2 7.

GENERIC IMPLICATIONS:

None.