05000339/LER-1980-105-03, /03L-0:on 801226,w/Unit 2 at 99.5% Power Turbine First Stage Pressure Channel Failed.Caused by Frozen Transmitter.Ventilation & Heating Problems Corrected & Channel Returned to Svc

/03L-0:on 801226,w/Unit 2 at 99.5% Power Turbine First Stage Pressure Channel Failed.Caused by Frozen Transmitter.Ventilation & Heating Problems Corrected & Channel Returned to Svc

ML20009C317
Person / Time
Site:	North Anna
Issue date:	01/21/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009C307	List: 05000339/LER-1980-105, Forwards LER 80-105/03L-0 05000339/LER-1980-105-03, /03L-0:on 801226,w/Unit 2 at 99.5% Power Turbine First Stage Pressure Channel Failed.Caused by Frozen Transmitter.Ventilation & Heating Problems Corrected & Channel Returned to Svc
References
LER-80-105-03L, LER-80-105-3L, NUDOCS 8107200457
Download: ML20009C317 (3)

LER-1980-105, /03L-0:on 801226,w/Unit 2 at 99.5% Power Turbine First Stage Pressure Channel Failed.Caused by Frozen Transmitter.Ventilation & Heating Problems Corrected & Channel Returned to Svc

Event date:
Report date:
3391980105R03 - NRC Website

text

z U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

/0/1/

/V/A/N/A/S/2/ (2)

/0/0/-/0/0/0/0/0/-/0/0/ (3)

/4/1/1/1/1/ (4)

/ / / (5)

LICENSEE CODE LICENSE NUMBER LICENSE TYPE CAT

]

/0/1/

/L/ (6)

/0/5/0/0/0/3/3/9/

(7)

/1/2/2/6/8/0/

(8) / Of 1/ ?/1/ 8/1/ (9)

DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

/0/2/

/

On December 26, 1980, with Unit 2 at 99.5 percent power, a turbine first stage /

/0/3/

/

pressure channel failed. This channel is used to generate a high steam line

/

/0/4/

/

flow protection setpoint for 1 of 2 high steam line flow protection channels. /

/0/5/

/

This event is reportable pursuant to T.S. 6.9.1.9.b.

One high st.eam line flow /

/0/6/

/

protection channel remained operable. The public health and safety were not

/

/0/7/

/

affected.

/

/0/8/

/

/

SYSTEM

CAUSE

CAUSE COMP.

VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

/0/9/

/I/B/ 0 1) /C/ (12) /_Z/ (13) /I/N/S/T/R/U/ (14) /T/ (15)

/Z/ (16)

SEQUENTIAL OCCURRENCE REPORT REVISION LER/R0 EVENT YEAR REPORT NO.

CODE TYPE NO.

(17) REPORT NUMBER

/8/0/

[-/ /1/0/5/

[1/

/0/3/

/L/

/-/

/0/

ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD MOURS StsMITTED F0P11 SUB. SUPPLIER MANUFACTURER g/ (18) /G/ (19) /Z/ (20) [Z/ (21) /0/0/0/0/ (22) /Y/ (23) /N/ (24) /N/ (25) /F/1/8/0/ (26)

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

/1/0/

/

Due to failures in the turbine building ventilation and heating systems, a

/

/1/1/

/

turbine first stage transmitter froze. Due to inadequate procedures, channels /

/1/2/

/

required bv T.S. to be placed in trip within one hour were not placed in the

/

/1/3/

/

trip condition for 63 minutes.

Procedures will be revised. Ventilation

/

/1/4/

/

problems were corrected and the channel returned to service.

_/

FACILITY METHOD OF STATUS

• /. POWER OTHER STATUS DISCOVERY DESCRIPTION (32)

/ ( 0) DISCOVERY

/1/5/

g/ (28)

/1/0/0/ (29)

/

NA LA/ (31)

/ ODERATOR OBSERVATION /

ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY (35)

LOCATION OF RELEASE (36)

/1/6/

/Z/ (33)

/Z/ (34)

/

NA

/

/

NA

/

PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION (39)

/1/7/ /0/0/0/ (37) LZ/ (38)

/

NA

/

PERSONNEL INJURIES NUMBER DESCRIPTION (41)

/1/8/ /0/0/0/ (40) /

NA

/

LOSS OF OR DAMAGE TO FACILITY (43)

TYPE

DESCRIPTION

/1/9/

LZ[ (42)

/

NA

/

PUBLICITY ISSUED DESCRIPTION (45)

NRC USE ONLY

/_2/0/

/N/ (44) /

I!A

/////////////

8107200457 elo15s ~ ~ -"*RER

%. R. CARTWRIGHT PHONE (703) 894-5151 PDR ADOCK 05000339

~

S PDR

P e

Virginia Electric and Power Company North Anna Power Station, Unit #2

Attachment:

Page 1 of 2 Docket No. 50-339 Report No. LER 80-105/03L-0

Description of Event

On December 26, 1980, with Unit 2 at 99.5 percent power, the sensing line of a turbine first stage pressure transmitter (PT-2446) froze causing the transmitter to fail high. Turbine first stage pressure is used to generate a high steam line flow protcetion setpoint. Due to the failure or the transmitter, one of two high steam line flow protection channels became inoperable. This event is reportable pursuant to T.S.

6.9.1.9.b.

Probable Consequences of Occurrence The redundancy for high steam line flow protection was reduced.

Since high steam line flow protection is designed to detect a steam line break accident and initiate appropriate corrective actions (SI, feeduster isolation, and trip of the main steam isolation valves), protection against a steam line break accident was reduced.

In addition to the operable high steam line flow channel the following signals were available for protection against a ; team line break accident.

1)

Pressurizer low pressure 2)

High differential pressure between steam lines 3)

Hi h containment pressure b

4)

Overpower reactor trips The refundancy provided by the P-7 interlock (blocks at power reactor trips during low power operation) was reduced. The redundancy of signals used for P-7 and the operability of all other signals used for P-7 except the one turbine impulse chamber pressure channel, made the effect of the failure on the P-7 signal negligible from a safety standpoint.

P-7 could have failed in the conservative direction only.

In addition to the protection functions described above the failed turbine first stage pressure transmitter provides control inputs for steam generator level, control rod, and condenser steam dump control.

Because the Unit was at 99.5% reactor power when the failure occurred and the transmitter failed high control functions were not affected.

Controls which could have been affected if power had been reduced were either placed under manual control or their first stage pressure input was switched to the operable turbine first stage pressure channel.

Coatrol functions were not affected.

The public health and safety were not sffected.

Cause of Event

The transmitter failed because its associated sensing line froze.

The t;ansmitter sensing line froze because a set of turbine building louvers were mechuaically bound in the open position allowing cold outside air emission to the lower level of the turbine building and two local area steam heaters were inoperable.

)

/'--

Attachment:

Page 2 of 2 Immediate Corrective Acti,on Automatic controls receiving input from the failed turbine first stage pressure transmitter were either placed under manual control or input was switched to the operable turbine first stage pressure transmitter.

Operations personnel immtdiately addressed a " Loss of Vital Instrumentation" procedure.

Unfertunately the procedure was inadequate and did not describe the actions to be taken when a turbine first stage pressure channel failed. Due to the inadequacy of the procedure, the high steam flow protection channel which receives an input frem the failed turbine first stage pressure channel was not tripped until 63 minutes after the event began. This is contrary to the action statement of the LCO (Actica Statement #14 T.S. 3.3.2.1) which requires trip of the inoperable channels within one hour.

The open turbine building louvers were covered, an asbestos blanket was wrapped around the instrument rack containing the failed transmitter and a heat lamp was placed in the instrument rack.

The transmitter sensing line was blown down and the turbine first stage pressure channel was declared operable after a channel functional test and channel check.

Scheduled Corrective Action The " Loss of Vital Instrumentation" procedure will be revised to include appropriate actions to be taken when a first stage pressure channel fails. This change should prevent recurrence of time delays in excess of those specified in the T.S. before appropriate actions are taken in response to a failed turbine first stage pressure channel.

Ares heaters in the turbine building will be repaired.

A formal winterization program will be developed to insure that freeze grotection equipment remains operable. The program will be implemented during the fall of 1981.

Actions Taken to Prevent Recurrence The initial actions and scheduled corrective action described above should prevent recurrence.

Generic Implications This event Lad no generic implications.

i 1

l

- nn