ML20042F411

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LER 90-007-00:on 900331,inadequate Determination of Equipment Status Resulted in de-energization of Nuclear Sys Protection Sys.Caused by Personnel Error.Fact Sheet on Operation Issued & Personnel retrained.W/900430 Ltr
ML20042F411
Person / Time
Site: Clinton Constellation icon.png
Issue date: 04/30/1990
From: Morris D, Spangenberg F
ILLINOIS POWER CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-007, LER-90-7, U-601657, NUDOCS 9005080293
Download: ML20042F411 (6)
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L45 90(04 30)-LP 20.220 llLINDIS POWER COMPANY CLINTON POWER $TATION, P.O. BOX 678. CLINTON. ILLIN0l$ 61727 April 30, 1990 i 4 10CFR50.73

. Docket No. 50 461 U.S. Nuclear _ Regulatory Commission Document Control Desk Washington,-D.C. 20555

Subject:

Clinton Power Station : Unit 1 jfeensee-Event Reoortjlq;90-007 00

]

DeariSir:

Please find enclosed Licensee Event Report No.90-007 00:

Inadeounte Determination of Eautement Status Durine Restoration Results ittpe-energization of Nuclear Systgg Protection System Loads and-Asj;uation of Engineered Saferv Features. -This report is being submitted i in accordance with the requirements of 10CFR50.73. 3 Sincerely yours, j 0 A.,Qo F. A. SpangbrJ,u.t 1

, III Manager Licensing and S, ety TSA/csm t

Enclosure i

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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Inadequate Determination of Equipment Status During Restoration Results in De-energization of Nuclear System Protection System Logds and Actuation of Engineered Safety Features ,  ;

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On March 31, 1990, the plant was in Mode 4 (COLD SHUTDOWN). Operators were in the process of restoring Nuclear System Protection System (N5PS)

Division II to its nornal configuration following the completion of maintenance. A control room operator (CRO) requested that the 'C' area operator determine the status of the Division II NSPS Inverter. The 'C' area operator incorrectly determined that the Inverter was de energir.ed.

In accordance with section 8.1.1, "NSPS Bus Energization," of nroceduro 3509.01, " Instrument Power System", the operator opened the cir.uit breakers associated with the Division II loads. Opening the breakers de-energized the Division II NSPS loads resulting in the automatic initiation of a number of Engineered Safety Features. The cause of this -

event is attributed to personnel error. The CR0 did not consult Main Control Room indications to determine the status of the Division II NSPS Inverter. The 'C' area operator incorrectly evaluated the indications at the Inverter. Inadequacy of procedure 3509.01 contributed to the event.

The format of the proc 9 dure makes it difficult for operators to identify applicable steps. Corrective actions includa distribution of a " fact sheet" on NSPS operation, retrainin5 on the importance of monitoring equipment configuration, and revising procedure 3509.01.

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  • LICENSEE EVENT REPORT (LER) TEXT CONTINUATION mnovso ove ne saa-cio.

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, o l6 l0 l0 l0 l4 l 6l1 9l0 O j 0l 7 0l0 y2 op 0 g 5 DESCRIPTION OF EVENT M

On March 31, 1990, the plant was in Mode 4 (COLD SHUTDOWN) and the reactor.[RCT) was at atmospheric pressure and approximately 132 degrees Fahrenheit. The Division II emergency diesel generator (EDG) [DG) was E out of service for maintenance. The Reactor Protection System (RPS) (JC) s was in a tripped condition and the Control Rod Drive (CRD) [AA) Charging Water lleader. Isolation Valve [ISV), IC11F034, was in the closed position c to allow the performance of maintenance on the Instrument Air (IA) system

[LD).

s At 0054 hours6.25e-4 days <br />0.015 hours <br />8.928571e-5 weeks <br />2.0547e-5 months <br />, a non licensed utility operator, in attempting to restore the Nuclear System Protection System (NSPS) [JE] to its.normab configuration, following the completion of maintonance, de energized the Division II NSPS loads causing the actuation of a number of Engineered y Safety foatures (ESFe),

g Each division of NSPS is normally supplied power via an internal solid state inverter which converts 125 voir direct current (VDC) '[EJ) to 125 volt alternating current (VAC) [ED). Alternate power to the-inverter is provided by a 120 VAC bus [BU). A static transfer switch [HS) automatically switches the Invertor povar supply from its normal to its ,

alternate source upon inverter failure. The static transfer switch can be used to manually transfer the Inverter power supply. Indicating *l lights on the Inverter are enar;ized when the Inverter is receiving power from its normal source.  ;

On March 30, 1990, Electrical Maintenance personnel begu. performing maintenance in accordance with Maintenance Work Roquest (MWR) D15009. '

This MWR provided directions for the replacement of the variable resistor s in the Division II NSPS Inverter (IvVT). S To allow installation of the variable resistor in the Division II Inverter, at 2245 hours0.026 days <br />0.624 hours <br />0.00371 weeks <br />8.542225e-4 months <br />, Operations potsonnel transferred the Inverter power supply from its normal to its alternate source using the internal -

static transfer switch. Use of the static transfer switch is an electronic method of alternating power supplies. The manual transfer L switch on the Inverter theref,cre remained in the Normal / Inverter position.

At 2330 hours0.027 days <br />0.647 hours <br />0.00385 weeks <br />8.86565e-4 months <br />, following completion of shift briefings and turnover, the

, "mid shift" Oparations crew assumed control of plant operations. ,

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l On March 31, 1990, at 0030 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />, Electrical Maintent.nce notified Operations personnti that they had completed replacement of the variable resistor. A licensed control room operator (CRO) dispatched a non-licensed utility 'C' area operator to the Division II NSPS Inverter to detatnine its status and to restore NSPS to its normal configuration.

s The G'O was unsure of the status of the Inverter and did not review the indications in the Main Control Room or discuss the status with the Shift Superviso rs .

The 'C' area operator reviewed the status of the meters [MTR), switches, and indicating lights [IL) at the NSPS Inverter and incorrectly determined that the Division II NSPS bus was de energized. This .

determination was based upon the de energized indicating light 1*or the *

, static transfor switch end the incorrect belief that the output frequency

!. and voltage meters had ofailed as is". The indicating light was  !

de energized because the Inverter was receiving power from its alvornite source. Since the indicating light was de energized the operator .

l believed the meters had " failed as is". although they indicated normal- '

l frequency and voltage. The operator did not inspect the position of the

internal static transfer switch.

The 'C' crea operator informed the CR0 that the Division II USPS Inverter 6 was c'a energized. Tho operators determined that the appropriate portion E

et Clinton Power Station (CPS) procedure 3509.01, " Instrument Power System", to be utilized to restore NSPS to its normal configuration was-i section 8.1.1, "NSPS Bua Energirstion" rather than section 8.1,14, l " Energizing Inverter With the Bus Energized."

At 0051 hours5.902778e-4 days <br />0.0142 hours <br />8.43254e-5 weeks <br />1.94055e-5 months <br />, in acc.ordance with section 8.1.1, the 'C' area operator

.de energized the Division II NSPS loads by opening the following circuit breakers [BKR): Leak Detection [IJ) 1H13 P642; NSPS Division II Logic Test and Transmitter Power Supply 1H13 P662 and Scram Discharge Volume '

Controls and indication H13-P662; Power and Startup Range Neutron Monitoring and Process Radiation Monitoring [IL) 1H13-P670; Loss of Coolant Accident Bypass Relays [RLY) Division II 1H13-P851; and tNuclear Steam Supply Shutoff System Valves [V). Loss of these loads resulted in the actuation of the following signals: a Reactor Water Low Level signal; High Drywell Pressure , signal;'a Main Steam [MB) Line High Radiation signal: and a Leak Detection, safety signal. These' signals' resulted in the automatic initiation of a number of Engineered Safety Features. Di/ision II of the Neatron Monitoring System tripped. A Reactor Core Isolation Cooling (RCIC) [BN) system initiation signal initiated causing the RCIC gland seal compreosor [ CMP) to start, i However, since the-plant was shutdown the low pressure RCIC isolation s signal prevented system injection. The 'A' Reactor Water Cleanup System

[CE) pump [P) tripped. Valves 1E12 F034B and 1E12-F0340, the Low Pressure Coolant Injection (LPCI) [BO) isolation valves opened, however, since the plant was in Node 4 no water was injected. The Drywell Cooling N!C FORM $364 *

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,y I Clinton Power Station 0 [t, l0 l 0 l o l4 l 6]1 9l0 0l0l7 0]O 0l4 or 0l5 stxi ca ne, sou, a o e.m. e., ema.nne re,,, anu n un System (VB) chilled water pump tripped. High level trip signals were .

received on Source Range Monitor 'B', Intermediate Range Monitors 'B' and

'F', Av w .ge Power Range Monitor 'B', and the Main Steam Line Radiation Monitors. The Division II EDG received a start signal but since the'EDG was removed from service it did not start.

At 0152 hours0.00176 days <br />0.0422 hours <br />2.513228e-4 weeks <br />5.7836e-5 months <br />, after verifying that all valves affected by the ESF actuations were in the expected positions, in accordance with CPS  ;

l procedure 4001.020001, " Automatic Isolation Checklist," operators re- '

energized and restored NSPS to its normal configuration.

By 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br />, the systems and components affected by the de energization of the Division II NSPS loads were restored to their previous configuration.

l No automatic or manually initiated safety system responses wer. necessary to place the plant in a safe and stable condition. No other equipment or components were inoperable at the start of this event such that their inoperable condition contributed to this event.

CAUSE OF EVENT I

p The cause of this event is attributed to personnel error by utility operators. The CR0 failed to utilize available Main Control Room indications.to determine the status of the Division II NSPS Inverter. ,

Additionally, although the status of the Inverter was discussed at shift turnover, the CR0 failed to consult with other members of the t.hift crew when unsure of its status. The 'C' area operator incorrectly determined that the Division II NSPS Inverter was de energized. The operator believed that the voltage and frequency meters at the NSPS Inverter had

" failed as is" although they indicated normal voltage and frequency. The indicating light for the static transfer switch was not energized since

,the Inverter was receiving power from its alternate source. The 'C' area operator did not verify the position of the static transfer switch.

Contributing to this event was the inadequacy of procedure 3509,01. This procedure is a generic procedure for NSPS. Uninterruptible Power Supplies

[EF), and Reactor Protection !iystem Scram Solenoid (SOL) power distribution systems. Currently this procedure is divided into two sections, 8.1, Normal Operation and 8.2, Abnormal Operation. The subsections for energization, deenergization and transfer of loads for j each of the types of power supplies are distributed among each of these i

two sections. This format makes it difficuir for operators to identify the applicable subsections.

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UCENSEE EVENT REPORT (LER) TEXT CONTINUATION w aovtoowowo.v u.eios (XP AES: SWm iAcetsty naut us u n gg nyuggn m vtAh Clinton Power Station sw wm. .,m e=w =.,nomenw nc m wnn CORRECTIVE ACTIONS Operations shif t personnel were provic'ed with a " fact sheetr that described this event and pertinent details on NSPS power supply operation.

Each shift crew has been retrained on the importance of closely monitoring equipment configuration and performing thorough equipment status checks during shift turnovers.

During the in progress requalification training cycle, active licensed operators will perform a job performance meacure to demonstrate their understanding of NSPS indications and operation. This action is expected to be completed by July 15, 1990.

Procedure 3509.01 will be revised to separate the steps for each type of power supply into sections. Then distinct sections will enable the operators to more easily determine which steps are applicable. This action is expected to be completed by July 30, 1990.

ANALYSIS OF EVENT This event is reportable in accordance with the provisions of 10CrR50.73(a)(2)(iv) due to the actuation of various Engineered Safety Features.

Analysis of the nucicar safety significance and consequences of this event indicates that this event was not significant under these or any other operating conditions. All equipment and components responded as designed, placing the plant in a safe and stable condition, upon the de energizstion of the Division II NSPF loads. If this event had

,securred at power it is possible injection into the reactor would have

, occurred. This possibility is analyzed in Chapter 15 of the Updated Safety Analysis Report, ADDITIONAL INFORMATION No Engineered Safety Feature actuations have previously occurred as a result of inadequate determination of equipment status by utility operators.

No components failed to perform as designed during this event.

For further information regarding this event contact D. R. Morris, Director Plant Operations at (217)935-8881, extension 3205.

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