ML19327B049

LER 89-015-00:on 890916,during Transfer,Loss of Power to Off Gas Monitor a Caused Contacts to Open Giving Upscale Radiation Signal,Thus Starting Off Gas Timer.Caused by Inadequate Procedures.Off Gas Sys reset.W/891016 Ltr

ML19327B049
Person / Time
Site:	Quad Cities
Issue date:	10/16/1989
From:	Bax R, Dolecheck D COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-015-02, LER-89-15-2, RLB-89-232, NUDOCS 8910250016
Download: ML19327B049 (4)

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1 RLB-89-232 October 16, 1989 U. S. Nuclear Regulatory Commission Document Control Desk  ;

Washington, DC 20555 i, i

Reference:

Quad Clties Nuclear Power Station Docket Number 50-254. DPR-29. Unit One l

i s  ;

i Enclosed 1s Licensee Event Report (LER)89-015. Revision 00, for Quad Cities

Nuclear Power Station.  ;

This r oort is submitted in accordance with the requirements of the Code of Federal Regulations, Title 10, Part 50.73(a)(2)(iv): The licensee.shall report  :

any event or condition that resulted in manual or automatic actuation of any '

Engineered Safety Feature (ESF), including the Reactor Protection System (RPS). [

Respectfully,

'f CO MONWEALTH EDISON COMPANY l QyADCITIESNUCLEARPOWERSTATION j R. L. ai pl q Station Manager RLB/MJB/ad Enclosure L

cc: R. Stols R. Higgins INPO Records Center NRC Region III 8910250016 891016 PDR #

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AB$ TRACT (Limit to 1400 spaces, t.e. approximately fif teen single-space typewritten lines) (16) f On September 16, 1989, Unit One was in the REFUEL mode at 0 percent power. Both  !

Off Gas [WF) Radiation Monitors (MON) were downsc&Ie, which is the normal condition then the reactor (RCT) is in the REFUEL mode. The Operations Department completed i a power supply changeover (JX) of the Reactor Protection Bus from the Motor  !

Generator Sets (MG) to bus (BU) 15-2. During the transfer, the loss of power to i the "A" off gas monitor caused its contacts to open giving an upscale radiation signal, thus starting the off gas timer (THR). The timer completed its 15-minute [

cycle and as designed isolated the Off Gas System. The proper procedures were used  ;

to complete this changeover; however, they do not alert the operators to the '

potential Engineered Safety Feature (ESF) actuation. The procedures will be changed to reflect the potential ESF actuation.

The Off Gas System was reset and no other unexpected actions occurred.

This report is submitted to comply with the requirements of 10CFR50.73(a)(2)(iv).

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of 2 or el 3 l PLANT AND SYSTEM IDENTIFICATION:

Gentral Electric - Boiling Water Reactor - 2511 MWt rated core thermal power. I EVENT IDENTIFICATION: Off Gas Isolation After Reactor Protection System Bus Power Supply Change Due to Inadequate Procedures  ;

1 A, CONDITIONS PRIOR TO EVENT:

e Unit: One Event Date: September 16, 1989 Event Time: 1620 l Reactor Mode: 2 Mode Name: REFUEL Power Level: 00%

This report was initiated by Deviation Report 0-4-1-89-078.

REFUEL Moie (2) - In this position interlocks are established so that one control ,

rod only may be with(frawn when flux amp 1tfiers are set at the proper sensitivity l 1evel and the refueling crane is not over the reactor. Also, the trip from the  ;

turbine control valves, turbine stop valves, main steam isolation valves, and '

condenser vacuum are bypassed. If the refueling crane is over the reactor, all rods must be fully inserted and none can be withdrawn.

8, DESCRIPTION OF EVENT:  !

At 1605 hours0.0186 days <br />0.446 hours <br />0.00265 weeks <br />6.107025e-4 months <br />, on September 16, 1989, Unit One was in the REFUEL mode at 0 percent of rated core thermal power. The Off Gas (WF) Radiation Monitors (MON) (1-1705-13 i and 1-1705-14) were both in the downscale position, which is the normal condition i when the reactor (RCT) is shut down. The Operating Department had just completed a ,

power supply changeover (JX) of the Reactor Protection System (RPS) (JC) bus EBU)  ;

, from the Motor Generator Sets (MG) to bus 15 2 in order to perform preventive ,

maintenance on bus 13. The MG Sets power RPS Bus A, which powars the "A" off-gas .

radiation monitor. The "B" off gas radiation monitor is powered from the 120-volt  !

Essential Service System (ESS) bus. Since the normal power supply, bus 13, was to be deenergized for maintenance, the power supply changeover of RPS bus A to the l alternate power supply, bus 15-2, was needed. The operators used QOP 7000-1, t Reactor Protection System MG Sets, and 00A 7000-1, 120 VAC Reactor Protection

• System Bus failure. This changeover is a dead bus transfer in which the RPS bus is [

deenergized before it is reenergized. When power was removed from the RPS bus, the i "A" monitor contacts opened, causing the Off Gas Tirer (TMR) to start. At 1620  !

hours, the timer timed out and the Off Gas System isolated as designed. Ite Center l Desk Nuclear Station Operator (NS0) observed the Off Gas isolation and subsequently t checked the radiation monitors; noting normal indications for the plant conditions, he reset the system.

C. APPARENT CAUSE OF EVENT: j This report is being submitted to comply with 10CFR50.73(a)(2)(iv), which states "

that the licensee shall report sny event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature, including the Reactor Protection System. ,

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The cause of this event is attributed to inadequate procedures. Neither the operating procedure nor the abnormal operating procedure alertad the operator that the Off Gas System timer under certain plant conditions would start, snd if not reset, time out and initiate the system isolation. In order to start the Off Gas Timer, both channels on the monitor must be upscale or one channel upscale and on!

channel downscale. At the time of the changeover, both channels were downscale.

The loss of power to the "A" off gas monitor caused it to fall safe, which opened its contacts and gave an upscale signal.

D. SAFETY ANALYSIS OF EVENT:

The safety of plant and personnel was not affected by this event. The Off Gas System is provided as a means for removal and processing of noncondensable gases from the main condenser and to prevent radiation releases in accordance with 10CFR20. The 15-minute timer is provided to allow sufficient time for the operator to evaluate the situation in the case of a spurious high radiation signal and, if necessary, isolate the system before any high radiation gases reach the chimney.

The radiation monitor sen: ors which provide the signal to annunciate the high radiation signal and start the 15-minute timer are located at the inlet of the holdup pipe. The holdup pipe is designed to provide a time delay of approximately four hours for the decay of radioactive gases / elements. This ensures more than sufficient time for a system isolation either by the operator or an auto isolation signal to prevent any excessive releases from escaping through the chimney. An isole.tlon valve downstream of the holdup pipe and upstream of the chimney is also provided to isolate any unwanted releases from reaching the chimney and being exhausted.

In this event, the NSO realized that system conditions did not warrant the (

isolation of the Off Gas System and reset the system. The safety consequences of -

this event are further minimized by the fact that the Off Gas System was not in  !

operation during this event. i I

E. CORRECTIVE ACTIONS:

The immediate corrective action was to reset the Off Gas System. A procedure change has been submitted to QOP 7000-1 to alert the operators that the Off Gas radiation monitor may spike high during a power supply changeover and may start the i timer. The timer should be checked and reset if necessary when the power supply l changeover is complete. 00A 7000-1 will also be updated to reflect the timer actuation (NTS 2542008907801). This event will be discussed during the operators'  !

safety and tailgate meetings (NTS 2542008907801),

l .F. PREVIOUS EVENTS: '

i No reportable events of this nature were identified during a review of previous l l Licensee Event Reports / Deviation Reports, t

! G. COMPONENT FAILURE DATA:

There was no component failure associated with this event.

l 2283H/06822 -

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