ML19351A672

LER 89-009-00:on 891115,unexpected Steam Generator a lo-lo Level & Steam Generator B lo-lo Level Reactor Trip Signals Experienced.Caused by Installation of Analog Signal Generator.Procedures revised.W/891215 Ltr

ML19351A672
Person / Time
Site:	Point Beach
Issue date:	12/15/1989
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-89-159 LER-89-009-01, LER-89-9-1, VPNPD-89-660, NUDOCS 8912200402
Download: ML19351A672 (5)

Text

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%;f POWER COMPANY 231 W IAcNam Po. Box 2046. Mdwodoe. VA 53201 (414j 224 234$

i VPNPD-89-660 10 CFR 50.73 l- NRC-89-159 I December 15, 1989 U. S. NUCLEAR REGULATORY COMMISSION L

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Document Control Desk Mail Station P1-137

' Washington, D. C. 20555 Gentlemen:

DOCKET 50-301 LICENSEE EVENT REPORT 89-009-00 L UNEXPECTED " LEVEL LOW" REACTOR TRIP SIGNAL L

DURING EMERGENCY DC LIGHTING TEST POINT BEACH NUCLEAR PLANT. UNIT 2 Enclosed is Licensee Event Report 89-009-00 for Point Beach Nuclear Plant, Unit 2. This report is provided in accordance with 10 CFR 50.73 (a) (2) (iv) and (vi), "Any event or condition that resulted in manual or automatic actuation of any engineered safety feature (EST), including the reactor protection system (RPS).

This report describes the unexpected actuation of the reactor protection system as a result of receiving steam generator low level signals during the performance of operations refueling tests. Unit 2 was in a refueling shutdown.

If any further information is required, please contact us.

Very truly yours, 9 .

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C. W. ay Vice President Nuclear Power Enclosure Copies to NRC Regional Administrator, Region III j .' NRC Resident Inspector 8912200402 891215

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.,o n l l l On November 15, 1989, at 0445, Unit 2 experienced unexpected "SG A Lo-Lo Level," and "SG B Lo-Lo Level" reactor trip signals. The unit ,i was in a refueling shutdown and the steam generators were empty at the time of the event. The signals occurred during performance of -

an operations refueling test (ORT) of the control room and Unit 2 turbine hall emergency DC lighting system. This test involved opening lighting panel breaker 2B52-46C. In addition to supplying control room and Unit 2 turbine building lighting, the breaker supplied the receptacle into which an analog simulator had been plugged. This simulator was providing a steam generator level indication so that the reactor trip breakers could be closed for another test. When the lighting panel breaker was opened, the analog simulator was deenergized and the "SG A Lo-Lo Level" and "SG B Lo-Lo Level" reactor trip signals occurred as a result of actual steam generator levels.

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On November 14, 1989, Point Beach Nuclear Plant, Unit 2, was in a refueling shutdown. During that afternoon, and in accordance with ICP 10.22, an analog simulator was installed in place of steam generator level transmitters to simulate steam generator A and B level signals of about 50%. This was done in preparation for

" Safety Injection Actuation With Loss of Engineered Safeguards AC" -

test (ORT 3) which was scheduled for the morning of November 15, 1989. ,

ORT 3 is a refueling test involving actuation of safety injection with a loss of engineered safeguards AC. To accomplish the test, it is necessary to close the reactor trip breakers. Because the steam generators are empty at this point of the outage, normal instrument sensing and logic prevents closure of the trip breakers.

In order to accomplish ORT 3, it is necessary to simulate steam generator levels greater than the reactor trip setpoint. In preparation for the test, a temporary analog simulator (signal generator) was installed in the reactor protection racks to simulate steam generator levels of approximately 50%. This action allowed the "SG A LoaLo Level" and "SG B Lo-Lo Level" trip signals to clear and closure of the trip breakers as required for conduct ,

of ORT 3. The analog simulator was plugged into a receptacle '

supplied by the AC lighting panel 2B01 breaker 2B52-46C.

On November 15, 1989, in preparation for the " Safety Injection Actuation With Loss of Engineered Safeguards AC" test, the Operations crew was completing CLORT 3 (a checklist for Operations Refueling Test 3). One section of CLORT 3 involves a "Backshift Test of Emergency DC Lighting." The test requires opening breaker 2B52-46C on lighting panel 2B01. This was the same breaker that was supplying the analog simulator.

At 0445 hours0.00515 days <br />0.124 hours <br />7.357804e-4 weeks <br />1.693225e-4 months <br /> on November 15, 1989, in accordance with CLORT 3, plant operators opened breaker 2B52-46C to conduct the emergency DC lighting test. When the breaker was opened, power supply to the analog simulator was deenergized. This resulted in the steam generator level transmitters, rather than the analog simulator, supplying the signals to the reactor protection system. Because the steam generators were empty at this point in the outage, the "SG A Lo-Lo level" and the "SG B Lo-Lo Level" reactor trip (first out) signals were received. Receipt of these signals resulted in an

-unexpected automatic actuation of the reactor protection system.

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The reason for the "SG A Lo-Lo Level," and "SG B Lo-Lo Level" signals was readily determined by plant operators and was noted in the shift log book and on the CLORT 3 in use at the time of the occurrence. i SYSTEM AND EQUIPMENT RESPONSE 3 All systems and equipment responded as designed. Because the reactor was in cold shutdown, and because the reactor trip breakers were open at the time of the occurrence, there were no additional i responses resulting from the reactor trip signal.

I CAUSE ,

l Use of an analog signal simulator to clear reactor trip signals in ,

conjunction with conduct of the " Safety Injection Actuation with l Loss of Engineered Safeguards AC" test has been common practice and is directed by ICP 10.22. What was different in this case was the l sequencing of two events: 1) Installation of the analog signal generator and, 2) Conduct of the " Emergency DC Lighting Test."

Typically, the " Emergency DC Lighting Test" is conducted between 0300 and 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br />, as directed by CLORT 3 and prior to instal-l lation of the analog simulator. On November 14-15, 1989, the sequence was reversed. Conduct of the " Safety Injection Actuation '

l with Loss of Engineered Safeguards AC" had been scheduled to occur L on November 15, 1989, at a time somewhat earlier than usual to l facilitate timely completion of this complex test by one operating shift. To allow this earlier start, Instrument & Control personnel

• ' performed some steps of ICP 10.22 during the afternoon of November 14, 1989. One of those steps involved the installation of the l analog simulator which defeated the reactor trip signal as required I for the " Safety Injection Actuation with Loss of Engineered Safeguards l .AC" test. As stated earlier, AC current for the analog simulator was supplied via lighting panel breaker 2B52-46C. Power to the analog simulator was lost during the " Emergency DC Lighting Test" and resulted in the steam generator level transmitters causing "SG A Lo-Lo Level" and "SG B Lo-Lo Level" reactor trip signals.

CORRECTIVE ACTION (S)

Because the reactor was in a refueling shutdown condition, receipt of "SG A Lo-Lo Level" and "SG B Lo-Lo Level" reactor trip signals and alarms did not require immediate operator response. Operators did 73,0.,, . . . ..o s ...+.u . n.

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Point Beach Nuclear Plant ,g , , 3 , 0,1 8, 9 _ q C' 5 ,_ g 0 ;4 o, l4 von . . .ac = maw nn identify loss of power to the analog simulator as the cause for the unexpected reactor trip alarms. This was noted in the shift 109 and on the checklist (CLORT 3) being used in conjunction with the emergency DC lighting test. '

Procedures will be revised prior to conduct of the " Safety Injection Actuation with Loss of Engineered Safeguards AC" test during the Unit 1, 1990, refueling outage. Revision will be made to assure that analog simulators for steam generator level signals are put in place at some time following completion of the emergency DC lighting test, but prior to conduct of the " Safety Injection Actuation with Loss of Engineered Safeguards AC" test.

GENERIC CONCERNS AND SIMILAR OCCURRENCES There are no industry generic concerns and there have been no similar occurrences at Point Beach Nuclear Plant.

REPORTABILITY The licensee event report is provided pursuant to:

10 CFR 50.73(a)(2)(vi) - Any event or condition that resulted in manual or automatic actuation of any engineered safety feature (ESF), including the reactor protection system (RPS).

This occurrence is reportable in view of the fact that reactor trip signals and alarms were not expected in conjunction with the emergency DC lighting test.

The emergency notification system call was made at 0655, 1

November 15, 1989, in accordance with 10CFRS,0.72(b)(2)(ii).

l SAFETY ASSESSMENT Because the unit was in a refueling shutdown and all safety equipment operated as designed, the health and safety of the i

general public and plant employees were not affected during this event.

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