05000416/LER-1990-020-01, :on 901016,containment Cooling Sys Found on High Radiation Level

:on 901016,containment Cooling Sys Found on High Radiation Level

ML20197H520
Person / Time
Site:	Grand Gulf
Issue date:	11/13/1990
From:	Cottle W, Summers J ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
AECM-90-0193, AECM-90-193, LER-90-020-01, LER-90-20-1, NUDOCS 9011160157
Download: ML20197H520 (4)

LER-1990-020, on 901016,containment Cooling Sys Found on High Radiation Level

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
4161990020R01 - NRC Website

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. November 13, 1990 W. T. cotue i

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'U.S. Nuclear Regulatory Commission Mail. Station P1-137 Washington, D.C.

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SUBJECT: Grand Gulf Nuclear Station l

Unit 1 Docket No. 50-416 l

License No. NPF-29

' Containment Cooling System Isolation On High Radiation Level LER 90-020 I

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Attached is. Licensee Event Report (LER)90-020 which is a final report.

Yours truly, w f~~~C*w WTC/JS:cg Attachment

cc: Mr. D'.-C. Hintz (w/a)

Mr. R. B. McGehee (w/a))

Mr. N. S. Reynolds. (w/a

. Mr. H.. L. Thomas (w/o)

' Mr. H. 0. Christensen (w/a)

Mr. Stewart D. Ebneter (w/a)

Regional Administrator U.S. Nuclear Regulatory Commission Region 11 101.Marietta St., N.W., Suite 2900 Atlanta, Georgia 30323 Mr. L. L. Kintner, Project Manager (w/a)

Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 11D21 Washington, D.C.

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REPORT DATE 17)

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On October 16, 1990, two containment vent isolation dampers isolated on a high radiation level signal received when the steam separator was being lifted from the reactor vessel.

Radiation Monitor (EIIS Code: IL) D17-K609 tria circuits actuated, causing the containment vent exhaust inboard and outaoard isolation dampers to close.

Integrated Operating Instruction 03-1-01-5, Refueling, has been changed to anticipate isolation of the containment vent exhaust dampers as a preplanned evolution.

The Containment Cooling System and Subsystems functioned as designed when radiation levels reached the trip level setpoints, i

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Reportable Occurrence On.0ctober.16, 1990, two containment vent isolation dampers isolated on a high radiation level signal received when the steam saparator was being lifted from the reactor vessel. This event is considered an Engineered Safety Feature (ESF) automatic actuation and is

reportedpursuantto50.73(a)(2)(iv).

B.

Initial Condition The plant was in Mode 5, Refueling, at the time of the event.

C.

Description of Occurrc-3 On_ October 16,'1990, during the steam separator lift from the reactor vessel to the storage area, Radiation Monitor (EIIS Code: IL)

D17-K609. trip circuits actuated, causing the Containment Cooling System (EIIS Code: VG) vent exhaust inboard-and outboard isolation dampers.M41-F034 and M41-F035 to close on a high radiation level signal. 'The radiation emitted during the lift of the separator was a

" controlled source" being monitored by Health Physicists on the refueling floor, and not an effluent release.

Operators in the Control Room verified that dampers M41-F034 and M41-F035 had, in fact, isolated and recorded the actuation in the Control Room Log Book. They immediately notid ed the refueling floor of the isolation and confirmed that Health physics personnel were present during this evolution to take the' required radiological readings.

The separator was placed into the storage pric alarms cleared, and the system restored to normal.

.D.

Apparent Cause The Containment Cooling System is equipped with redundant isolation dampers (M41-F034 and M41-F035) that prevent airborne contaminants from escaping to the environment following a Loss of Coolant Accident (LOCA).

The radiation monitoring portion of the system is designed to detect, measure, indicate, and record levels of radiation to ensure that the release of radioactivity to unrestricted areas is within permissible limits.

Four radiation detector units for the containment and drywell vent exhaust plenum are located in the duct upstream of the isolation dampers to detect and measure radiation level outputs.

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,nn, During previous outages, the separator was successfully lifted and set into the storage area, without causing an isolation. The plant directive controlling the removal of the separator alerted operators of

. the possibility of receiving radiation' alarms; however, it did not warn operators that an isolation could occur if radiation levels reached the trip circuit setpoints. Operators did not antici) ate that the Containment Cooling System would isolate.during tie separator lift, since it had not isolated during other previous outages.

E.

Supplemental Corrective Actions Integrated Operating Instruction 03-1-01-5, Refueling, has been changed to anticipate. isolation of the containment vent exhaust dampers as.part of a preplanned evolution during future separator lifts.

F.

Safety Assessment

The Containment Cooling System's instrumentation and control logics functioned as required when radiation levels approached the design trip setpoints, Q,"" '" '

LER9020/SCMPFLR - 5