ML19354E103

LER 89-042-00:on 891219,false RCIC Div I Steam Line Differential Pressure High Signal Caused RCIC Turbine Steam Supply Isolation Valve to Shut & RCIC Sys to Trip.Caused by Sensor Design Error.Field Alteration begun.W/900118 Ltr

ML19354E103
Person / Time
Site:	Clinton
Issue date:	01/18/1990
From:	Freeman R, Holtzscher D ILLINOIS POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-042, U-601590, NUDOCS 9001250378
Download: ML19354E103 (4)

Text

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ILLINDIS POWER COMPANY .

l CLINTON POntR STATION. P.O. BOX 678. CLINTON. ILLINOIS 01727 ,

, i January 18, 1990  !

l i- 10CFR50.73  !

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Docket No. 50 461' ,

U.S. Nuclear Regulatory Commission Document Control Desk

-Washington, D.C.- 20555

Subject:

Clinton Power Station - Unit 1 Licensee Event Recort No. 89 042 00

Dear Sir:

Please find enclosed Licensee Event Report No. 89 042-00:

Sensor System Desien Causes False Reactor Core Isolation Cooline (RCIC)

Steam Line Differential Pressure Hich Sirnal and RCIC Isolation. This report is being submitted'in accordance with the requirements of 10CFR50.73.

Sincerely yours,

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D. L. Iloltzscher Acting Manager -

Licensing and Safety TSA/krm l> Enclosure L cc: .NRC Resident Office.

NRC Region III, Regional Administrator INPO Records Center Illinois Department. of Nuclear Safety NRC Clinton Licensing Project Manager -/

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The cause of this event is attributed to the sensor system design. The system's sensitivity to minor changes in sensing line pressure resulted in the falso RCIC Division I steam line differential pressure high ,

( signal. The sensitivity of transmitter IE31 N084A was reduced by l implementing Field Alteration C F031 for that transmitter. At 2235 hours0.0259 days <br />0.621 hours <br />0.0037 weeks <br />8.504175e-4 months <br />, on December 24, 1989, implementation of Field C F031 Alteration was completed for lE31 N084A, and RCIC was declared operable. This Field Alteration will be installed as necessary on other transmitters which exhibit similar sensitivity to minor changes in sensing line pressure.

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voci n--. . = anc , an w nri DESCRIPTION OF EVENT on December 19, 1989, at approximately 1555 hours0.018 days <br />0.432 hours <br />0.00257 weeks <br />5.916775e-4 months <br />, with the plant in Mode 1 (POWER OPERATION), at eighty four percent reactor [RCT) power, a false Reactor Core Isolation Cooling (RCIC) [BN) Division I steam line  !

differential pressure high signal caused valve 1E51 F064, the RCIC l turbine [TRB] steam supply containment isolation valve (ISV), to shut *

(isolating RCIC) and the RCIC turbine to trip.  ;

control room operators immediately verified that valve 1E51*F031, the RCIC pump [P) suppression pool suction 1.olation valve, was closed and that the RCIC Division I steam line differential pressure' high

• annunciator was illuminated. RCIC was declared inoperable in accordance with Technical Specification 3.7.3.

At 1615 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.145075e-4 months <br />, operators attempted to restore steam to RCIC by opening valve 1E51 F064 and then opening valves 1E51-F025 and 1E51 F026, the RCIC steam supply condensate return control valves, locally. Operators checked the RCIC steam line flow ATMs and noted erratic readings, between

-30 and 20 inches of water, for 1E31 N684A and a zero reading for 1E31 N683A. Valve 1E51 F064 shut again on a false RCIC Division I steam line differential pressure high signal. ,

No additional attempts were made to open valve 1E51 F064 and restore steam to RCIC. A maintenance work request (MWR), D19199, was initiated to investigate and repair the cause of the RCIC isolation.

On December 21, 1989, Control and Instrumentation (C&I) technicians began investigating the isolation in accordance with MWR D19199, The investigation determined that the isolation was caused by the sensitivity of steam line flow transmitter [FT) 1E31 N084A to minor changes in sensing line pressure.

i on December 22, 1989, C&I to:hnicians replaced the amplifier [ AMP) and calibration cards in transmitter 1E31 N084A in accordance with Field Alteration C-F031 and Field Engineering Change Notice (FECN) 24557. The new cards have an adjustable inherent time delay which reduces the sensitivity of the transmitter. At 2235 hours0.0259 days <br />0.621 hours <br />0.0037 weeks <br />8.504175e-4 months <br />, on December 24, 1989, implementation of Field Alteration C F031 was completed for 1E31-N084A,  !

and RCIC was declared operable.

l No automatic or manually initiated safety system responses were necessary to place the plant in a safe and stable condition. No equipment or -

components were inoperable at the start of this event such that their inoperable condition contributed to this event.

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- - 0F 0l3 CAUSE OF EVENT The cause of this event is attributed to the sensor system design. The system's sensitivity to minor changes in sensing line pressure resulted in the false RCIC Livision I steam line differential pressure high signal.

CORRECTIVE ACTION The sensitivity of transmitter 1E31 N084A was reduced by implementing Field Alterction C F031 for that transmitter.

This Field Alteration allows for the installation of the adjustable time delay feature on other transmitters which exhibit sensitivity to minor changes in sensing line pressure. This Field Alteration will be installed as the affected systems become available for work.

ANALYSIS OF EVENT Assessment of the safety consequences and implications of this event indicates that this event was not nuclear safety significant. The RCIC system isolated as designed, in response to the RCIC Division I steam line differential pressure high signal. The liigh Pressure Core Spray (llPCS) system [BG), the alternate means of providing reactor core cooling under high reactor pressure vessel pressure conditions, was available at the time of this event.

This event is reportable under the provisions of 10CFR50.73(a)(2)(iv) because of an automatic isolation of the RCIC system. RCIC was isolated and inoperable from 1555 hours0.018 days <br />0.432 hours <br />0.00257 weeks <br />5.916775e-4 months <br /> on December 19, 1989 until 2235 hours0.0259 days <br />0.621 hours <br />0.0037 weeks <br />8.504175e-4 months <br /> on December 24, 1989.

ADDITIONAL INFORMATION The flow transmitter discussed in this LER is a model number 1153DBSPC manufactured by Rosemount, Incorporated.

LER 88 022 01 discusses an HPCS initiation caused by an oversensitive reactor pressure vessel water level transmitter resulting from the sensor system design.

LER 87 052-00 discusses an RCIC isolation caused by personnel error while investigating erratic readings on the Division II RCIC steam flow indication, j

for further information regarding this event, contact R. D. Freeman, Manager - Nuclear Station Engineering Department at (217) 935 8881, extension 3538.

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