05000266/LER-1985-009, :on 851009,turbine Runback Occurred Due to Rod Drop Signal on Power Range Nuclear Instrumentation Sys. Caused by Technician Introducing Signal During Calibr of Negative Rate Runback Setpoint
| ML20138P746 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 10/30/1985 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| CON-NRC-85-117 LER-85-009, LER-85-9, VPNPD-85-499, NUDOCS 8511070481 | |
| Download: ML20138P746 (3) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation |
| 2661985009R00 - NRC Website | |
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NRC Form See U S. NUCLEAR LEGULATORY COsasiesiON W3 APrfiOVED oms NO. 3190-610e LICENSEE EVENT REPORT (LER)
F ACILITY NAast (1)
DOCRET NuesgER (33 PAGE (E Point Beach Nuclear Plant
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At 1007 hours0.0117 days <br />0.28 hours <br />0.00167 weeks <br />3.831635e-4 months <br /> on October 9, 1985, Unit 1 experienced a turbine run-back from 100% to 97.5% power.
This was due to a momentary sensing of an artificially induced negative rate on the rod drop circuitry of the power range nuclear instrumentation Channel 42.
This artificial signal was introduced by an Instrumentation & Control technician during a calibration of the negative rate runback setpoint.
The plant was returned to 100% power a short time after the runback.
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.,im Description of the Occurrence:
On October 9, 1985, at 1007 hours0.0117 days <br />0.28 hours <br />0.00167 weeks <br />3.831635e-4 months <br />, Unit 1 at the Point Beach Nuclear Plant experiencec a turbine runback from 100% power to approximately 97.5% power.
The runback was due to a nuclear instrumentation system (NIS) channel sensing a negative 5% power spike in less than 5 seconds i
I thereby activating the rod drop turbine runback circuitry.
This negative power spike was introduced to the circuitry by the Channel 42 control switch being mistakenly turned from bypass to normal while the artificially high 105.5% power signal was being supplied to the NIS drawer as part of the surveillance test.
This resulted in an essentially instantaneous 5.5% drop in the power signal resulting in the initiation of a runback signal to the turbine.
The total runback was 13 megawatt.s electric or 2.5% of full power.
Since the runback signal provides for a runback of 200% per minute to 80%, the total time the switch was in the normal instead of bypass position was 0.75 seconds.
It, therefore, appears the technician realized the error and returned the switch to the bypass position terminating the runback prior to hearing the audible alarm announcing the runback.
Apparent Cause of the occurrence:
4 The runback was caused by a personnel error.
The adequacy of the i
procedure and the human engineering of the NIS drawer were investi-gated.
The procedure is clear as to which switch is to be turned and when it is to be turned.
The procedure is therefore considered adequate to complete this calibration without the type of occurrence discussed in this report occurring again.
The human engineering of the NIS drawer was also considered.
The switch (normal / bypass) which was turned in error during this incident is above and to the right of the switch (operation selector) which should have been turned.
One of the switches could be changed in shape or texture to enhance the awareness of the technician as to which switch is in hand.
The location of the switches on the drawer are different enough to provide adequate indication of which switch is to be turned during each portion of the procedure.
Corrective Action
All Instrumentation & Control technicia$s will be routed a copy of this LER as required reading so that each is aware of the necessity to pay close attention to actions being taken when performing test procedures.
Additionally, an investigation will be performed into the appropriateness of making improvements in the human engineering design of the NIS i
drawers.
This investigation will be completed by March 1, 1986.
Improvements found to be necessary will be implemented using the plant modification procedure.
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1 Wisconsin Electnc eaara coupasr 231 W. MICHIGAN, P.O. BOX 2046. MILWAUKEE, WI S3201 VPNPD-85-499 NRC-85-ll7 October 30, 1985 Mr. J. G.
Keppler, Regional Administrator Office of Inspection and Enforcement, Region III U.
S.
NUCLEAR REGULATORY COMMISSION 799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Mr. Keppler:
DOCKET NO. 50-266 LICENSEE EVENT REPORT NO. 85-009-00 NUCLEAR INSTRUMENTATION TURBINE RUNBACK POINT BEACH NUCLEAR PLANT, UNIT 1 Enclosed is Licensee Event Report No. 85-009-00 for Point Beach Nuclear Plant, Unit 1.
This report provides a description of an incident involving a runback of the turbine due to a rod drop signal on the power range nuclear instrumentation system.
This event is reportable in accordance with 10 CFR 50.73 (a) (2) (iv),
"Any event or condition that resulted in manual or automatic actuation of any engineered safety feature, including the reactor protection system."
Very truly yo,urs, l
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C. W.
Fay Vice President Nuclear Power Enclosure l
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Copies to A C Document Control Desk, Washington, D.
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NRC Resident Inspector [h
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