05000315/LER-1985-015, :on 850408,09 & 11,several Spurious High Alarms Received on Lower Containment Radiation Monitor Particulate Channels Ers 1301 & Ers 1401.Caused by Jump in Rate Count. New Program Chips Purchased

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:on 850408,09 & 11,several Spurious High Alarms Received on Lower Containment Radiation Monitor Particulate Channels Ers 1301 & Ers 1401.Caused by Jump in Rate Count. New Program Chips Purchased
ML20127L254
Person / Time
Site: Cook American Electric Power icon.png
Issue date: 05/07/1985
From: Kriesel T
INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:
Shared Package
ML20127L110 List:
References
LER-85-015, LER-85-15, NUDOCS 8505220303
Download: ML20127L254 (3)
v • d • e


LER-1985-015, on 850408,09 & 11,several Spurious High Alarms Received on Lower Containment Radiation Monitor Particulate Channels Ers 1301 & Ers 1401.Caused by Jump in Rate Count. New Program Chips Purchased
Event date:
Report date:
3151985015R00 - NRC Website
v • d • e

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.,... -,., o e, ON APRIL 8, 9, AND II,1985 WITH THE REACTOR COOLANT SYSTEM IN MODE 3 (HOT STANDBY),

SEVERAL SPURIOUS HIGH ALARMS WERE RECElVED ON THE LOWER CONTAINMENT RADIATION MONITOR PARTICULATE CHANNELS, ERS 1301 AND ERS 1401, THAT RESULTED IN A CONTAINMENT ISOLATION, AN AUTOMATIC ACTUATION OF AN ENGINEERED SAFETY FEATURE.

REVIEW OF THE DATA FROM THE RADIATION MONITORS REVEALED THAT AT CERTAIN INPUT COUNT RATES A JUMP IN COUNT RATE WOULD OCCUR WITH NO INCREASE IN CONTAINMENT AIRBORNE RADIOACTIVITY. THE JUMP IN COUNT RATE RESULTED IN A SPURIOUS ALARM CAUSING THE AUTOMATIC CLOSURE OF THE CONTAINMENT PURGE ISOLATION VALVES.

TO PREVENT RECURRENCE EBERLINE CORPORATION HAS SUPPLIED THE PLANT WITH NEW PROGRAM CHlPS WITH THE CORRECTION TO THE SOFTWARE.

THESE HAVE BEEN INSTALLED IN THE LOWER CONTAINMENT MONITORS AND HAVE BEEN TESTED SATISFACTORILY.

THE HEALTH AND SAFETY OF THE PUBLIC WERE NOT AFFECTED.

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- - ma n,m ON APRIL 8, 9. AND 11, 1985 WITH THE REACTOR COOLANT SYSTEM IN MODE 3.(HOT STANDBY),

SEVERAL SPURIOUS HIGH ALARMS WERE RECEIVED ON THE LOWER CONTAINMENT RADIATION MONITOR PARTICULATE CHANNELS, ERS 1301 AND ERS 1401, THAT RESULTED IN A CONTAINMENT ISOLATION, AN AUTOMATIC ACTUATION OF AN ENGINEERED SAFETY FEATURE.

THE ATTACHED TABLE SHOWS THE DATE TIME, CHANNEL NUMBER AND BEFORE AND AFTER ALARM READINGS OF THE CHANNEL AT THE TIME OF THE ALARM.

INVESTIGATION SHOWED THAT AT GENERATED INPUT SIGNALS OF APPROXIMATELY 2400, 5800 AND 8700 COUNTS PER MINUTE A JUMP IN COUNT RATE WOULD OCCUR WITH NO INCREASE IN CONTAltlMENT AIRBORNE RADIOACTIVITY.

THIS JUMP IN COUNT RATE RESULTED IN A SPURIOUS HIGH ALARM CAUSING THE AUTOMATIC CLOSURE OF THE CONTAINMENT ISOLATION VALVES.

THIS CONDITION WAS VERIFIED BY INJECTING A VARIABLE COUNT RA?E SIGNAL INTO A SIMILAR CHANNEL ON A TEST MONITOR. AT INPUT SIGNALS OF 5970 AND 8970 COUNTS PER MINUTE, THE MONITOR COUNT RATE WOULD JUMP APPROXIMATELY 3000 COUNTS PER HINUTE.

EBERLINE INSTRUMENT CORPORATION WAS CONTACTED ABOUT THIS. PROBLEM. THEY WERE ABLE TO DUPLICATE THIS PROBLEM AND DISCOVERED THE CAUSE TO BE A SOFTWARE ERROR. A CHANGE TO THE SOFTWARE WAS MADE AND TESTED SATISFACTORlLY.

TO PREVENT RECURRENCE, EBERLINE CORP 0r.ATION HAS SUPPLIED THE PLANT WITH NEW PROGRAM CHIPS WITH THE CORRECTION TO Tile SOFTWARE.

THESE HAVE BEEN INSTALLED IN THE LOWER CONTAINMENT MONITORS AND HAVE BEEN TESTED SATISFACTORILY.

THE HEALTH AND SAFETY OF THE PUBLIC WERE NOT AFFECTED.

THE SAME CHANGE TO UNIT TWO LOWER CONTAINMENT MONITORS WILL BE MADE BY JUNE 30, 1985 l

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4-8/2049 1401 1.84E-1 1.35E-1 11948 8766 3

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