05000339/LER-1980-024-01, /01T-0:on 800619,during Low Power Physics Testing in Mode 2,discovered That Main Feedwater Flow Transmitters FT-476,477,487,496 & 497 Were Isolated.Cause Could Not Be Determined.Transmitters Valved in & Returned to Svc

/01T-0:on 800619,during Low Power Physics Testing in Mode 2,discovered That Main Feedwater Flow Transmitters FT-476,477,487,496 & 497 Were Isolated.Cause Could Not Be Determined.Transmitters Valved in & Returned to Svc

ML19326D748
Person / Time
Site:	North Anna
Issue date:	06/30/1980
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19326D744	List: 05000339/LER-1980-024, Forwards LER 80-024/01T-0 05000339/LER-1980-024-01, /01T-0:on 800619,during Low Power Physics Testing in Mode 2,discovered That Main Feedwater Flow Transmitters FT-476,477,487,496 & 497 Were Isolated.Cause Could Not Be Determined.Transmitters Valved in & Returned to Svc
References
LER-80-024-01T, LER-80-24-1T, NUDOCS 8007030267
Download: ML19326D748 (3)

LER-1980-024, /01T-0:on 800619,during Low Power Physics Testing in Mode 2,discovered That Main Feedwater Flow Transmitters FT-476,477,487,496 & 497 Were Isolated.Cause Could Not Be Determined.Transmitters Valved in & Returned to Svc

Event date:
Report date:
3391980024R01 - NRC Website

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8 60 61 DOCKET NUMBER 68 69 EVENT D ATE 74 75 REPORT 04TE 60 EVENT GEScRIPTION AND PROBABLE CONSEQUENCES h Lo_L_] I Durino low power physics testing in Mode 2 at </= 0% power, main feedwater flow trans-1 1o13i I mitters FT-476, FT-477, FT-487, FT-496 and FT-497 were found to be isolated. Addi-l Il o 141 I tionally, transmitters were not returned to service within one hour. Since the l

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L Virginia Electric and Power Company North Anna Power Station, Unit No. 2

Attachment:

Page 1 of 2 Docket No. 50-339 Report No. LER 80-024/01T-0

Description of Event

During the performance of 2-SU-31, the Nuclear and Temperature Instruments Calibration and Thermal Power Measurements, it was discovered that feedwater flow transmitters FT-476, FT-477, FT-487, FT-496, and FT-497 were isolated at the transmitter stop valves. The reactor was in Mode 2 and these transmitters are required to be operable by technical specification 3.3.1.1 (Table 3.3.-1, item 15).

In addition, personnel involved did not recognize a need for prompt corrective action required by technical specification 3.3.1.1 (Table 3.3.-1 Action Statement No.

7).

Probable Consequences of Occurrence The consequences of this event were limited since the isolated transmitter produced a minimum feedwater flow output, thereby providing a conservative signal to the feedwater flow less than steam flow mismatch reactor protection logic. The health and safety of the general public were not affected by this occurrence.

Cause of Event

The exact time and date of isolation could not be determined.

Normally transmitter stop valves are controlled by Instrument and Control procedures, since the primary use of the valves is to enable calibration of the transmitter. The latest procedure performance indicates valves were left in the correct position.

Immediate Corrective Action

Incorrett valving was identified at 1745 on 6-19-80 and all trans-mitters were returned to service by 0730 on 6-20-80.

Scheduled Corrective Action As followup corrective action to the occurrence, all other Unit 2 safety related transmitter stop valves were verified for correct position.

Of the transmitters checked (4) additional transmitters were found to have valves incorrectly positicned. These were the transmitter for instrument channels number P-446 and P-447 (first stage pressure),

F-FW-201 (aux feed pump recirculation flow to the condenser storage tank), F-482A (reactor coolant system relief line flow switch). All i

incorrectly positioned valves were returned to the correct position.

A fifth transmitter channel F-CC-200B (Component cooling water heat exchanger l

IB outlet flow) was initially identified to be incorrectly isolated.

Further review revealed a maintenance report existed and the channel was awaiting a new primary sensor and should remain isolated.

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Page 2 of 2 Of the isolated' transmitters discovered during the followup action, a review was made for any adverse consequences and the review revealed the health and safety of the general public were not affected. Channels P-446 and P-447 are required for Mode 2 operation in accordance with TS 3.3.2.1, Table 3.3.-3 item 1.f.

Since these transmitters were isolated, a minimum high steam flow setpoint was generated thereby providing a conservative signal to the safety injection actuation logic. Addition-ally, first stage pressure provides an input to the P-7 interlock, which blocks the at power reactor trips below 10% power. This interlock remained in effect during the occurrence. Future operation of the turbine would have revealed lack of necessary first stage pressure indication. The transmitter would have been unisolated at that time with no adverse consequences.

Flow channel F-FW-201 is used during periodic testing to locally indicate the auxiliary feedwater pump recirculation flow.

No on line protective function is generated and the indicator could have been utilized at the next periodic test.

Flow channel F-482A provides a signal to the protective interlock to permit opening of the reactor coolant loop "C" cold leg isolation valves in accordance with T.S. 3.4.1.3.

Since the channel transmitter was isolated, a conservative low flow signal was delivered to the logic.

All reactor coolant loop isolation valves were open at the time of the occurrence. Future closure and operation of the loop isolation valves interlock would have revealed the lack of necessary relief line flow.

The transmitter would have been unisolated at that time with no adverse consequences.

Action Taken to Prevent Recurrence The subject event indicated the need to reinstruct operations and instrument department personnel in the importance of communications and the strict adherence to existing procedures and controls.

Instrument department personnel received this training on June 20, 1980.

Operating personnel will also receive similar training.

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