05000245/LER-1997-015-01, :on 970321,inadvertent Actuation of Group Six Containment Isolation Identified Due to Noise Spike Generated from Maint Activities.Bypass Containment Hrrm to Preclude Inadvertent High Radiation Alarms & Actuations

:on 970321,inadvertent Actuation of Group Six Containment Isolation Identified Due to Noise Spike Generated from Maint Activities.Bypass Containment Hrrm to Preclude Inadvertent High Radiation Alarms & Actuations

ML20138B764
Person / Time
Site:	Millstone
Issue date:	04/21/1997
From:	Robert Walpole NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20138B658	List: 05000245/LER-1997-015, Forwards LER 97-015-00,documenting Event at Plant on 970321 & Licensee Commitments 05000245/LER-1997-015-01, :on 970321,inadvertent Actuation of Group Six Containment Isolation Identified Due to Noise Spike Generated from Maint Activities.Bypass Containment Hrrm to Preclude Inadvertent High Radiation Alarms & Actuations
References
LER-97-015-01, LER-97-15-1, NUDOCS 9704290268
Download: ML20138B764 (3)

LER-1997-015, on 970321,inadvertent Actuation of Group Six Containment Isolation Identified Due to Noise Spike Generated from Maint Activities.Bypass Containment Hrrm to Preclude Inadvertent High Radiation Alarms & Actuations

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(iv), System Actuation
2451997015R01 - NRC Website

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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (4 95)

EXPIRES 04/30/98 L5/ot'J?#iis"/c'1"J$le"Js? A r%s*'%Mrro^"?N80 s

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LICENSEE EVENT REPORT (LER) lSm^u'? 'Off""^lo*,"tr&a18" As"s'n TE,WM"@

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FActuTY NAME (1)

DOCKET NUMBER (2)

PAGE 13)

Millstone Nuclear Power Station Unit 1 05000245 1cf3 TITLE 14)

Inadvertent Actuation of Group Six Containment Isolation EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEQUENTIAL REVISION MONTH DAY YEAR FACIUTY NAME DOCKET NUMBER NUMBER 03 21 97 97 015 00 04 97 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check one or more) (11)

ODE (9)

N 20.2201(b) 20.2203(aH2)(v) 50.73(aH2Hi) 50.73(aH2)(viii)

POWER LEVEL (10) 000 20.2203(a)(1) 20.2203(aH3)(i) 50.73(a)(2Hii) 50.73(aH2Hx) 20.2203(aH2Hi) 20.2203(aH3)(ii) 50.73(a)(2Hiii) 73.71

. 03(aH2M 20.22MaHo X 50.73(aH2m OTHER 20.2203(aH2)(iii) 50.36(cH1) 50J3(a)(2Hv) specif y m Abstract tielow or in NRC Form 366A 20.2203(a)(2)(iv) 50.36(cH2) 50.73(a)(2)(vii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (include Area Codel Robert W. Walpole, MP1 Nuclear Licensing Manager (860)440-2191 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

]

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE

]

TO NPRDs TO NPRDs l

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SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONTH DAY YEAR SUBM.SSION f

YES NO l

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(if yes, complete EXPECTED SUBMISSION DATE).

l ABSTRACT (Limit to 1400 spaces, i.e., approxirnately 15 single-spaced typewritten hnes) (16)

On March 21,1997, at 1053 hours0.0122 days <br />0.293 hours <br />0.00174 weeks <br />4.006665e-4 months <br />, with the plant in COLD SHUTDOWN and no fuel in the reactor, an inadvertent group six (containment ventilation) isolation occurred while maintenance cleaning and welding activities were being performed in areas local to the Containment High Range Radiation Monitor detector RIT-1825 and its cables. This condition was reported on March 21,1997, pursuant to 10 CFR 50.72(b)(2)(ii), "any event or condition that results in manual or automatic actuation of any engineered safety feature." There were no safety consequences as a result of this event. Primary containment was not required and there was no high radiation condition. There are no safety l

implications since this event does not impact any accident analysis.

The cause of the event has been attributed to a noise spike generated from maintenance activities resulting in an inadvertent actuation via the Containment High-Range Radiation Monitor RIT-1825.

Corrective actions include procedure revisions to bypass the group six isolation signal from both Containment High-Range Radiation Monitors, at tha discretion of the Shift Manager, to preclude inadvertent high radiation alarms and actuations when work is being p:rformed and primary containment is not required. Also, prior to startup for operating Cycle 16, testing will be performed to determine operability of the Containment High-Range Radiation Monitor, t

i 9704290268 970421 PDR ADOCK 05000245_

s PM

.U.s. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

~.

TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVISION Millstone Nuclear Power Station Unit 1 05000245 NUMBER NUMBER 2 of 3 97 015 00 TEXT (11more space is required, use additional copies of NRC Form 366A) (17) 1.

Descriotion of Event On March 21,1997, at 1053 hours0.0122 days <br />0.293 hours <br />0.00174 weeks <br />4.006665e-4 months <br />, with the plant in cold shutdown, an inadvertent group six (containment ventilation) isolation occurred while maintenance cleaning and welding activities were being performed in areas local to the drywell high radiation monitoring equipment and its cabling runs. An inadvertent high noise signal caused the trip of the Containment High-Radiation Monitor RIT-1825 (channel 1), closing its associated containment ventilation isolation valves and H202 sample isolation valves. Operations stopped all containment work and notified Health Physics to perform a radiation survey of the area. After several hours of investigation and verification of conditions, the alarm and isolation signals were reset and personnel were allowed to resume work. Although the specific work activity that caused this inadvertent alarm and isolation is not known, it is I

l conciuded that a noise spike, resulting from welding or handling of cables, caused the event. Both Containment-High-Range Radiation Monitor group six isolation signals have been bypassed since primary containment is not required in the present plant mode of operation and work local to these radiation monitors is ongoing.

Testing has been performed to demonstrate that the Containment High-Range Radiation Monitor RIT-1825 and its cables meet equipment acceptance criteria and are not suspect. A review of recorder traces and testing also demonstrated that the handling of the sensitive radiation monitor cables can cause a noise spike large enough to actuate the high alarm.

I This event was reported on March 21,1997, pursuant to 10 CFR 50.72(b)(2)(ii), any event or condition that l

results in manual or automatic actuation of any Engineered Safety Feature."

ll.

Cause of Event

The cause of this event has been attributed to a spike generate <1 from maintenance activities resulting in an inadvertent actuation via the Containment High-Range Radiation Monitor. The specific work activity that caused this event is not known, however it is concluded that welding or handling cables caused the noise spike.

til. Analysis of Event l

Per the Millstone Unit No.1 Updated Final Safety Analysis Report, Section 7.3.1.2, Primary Containment Isolation System, upon the detection of a high radiation signal, via the Containment High-Range Radiation Monitors, the group six valves are isolated. The high radiation isolation signal setting is high enough to avoid i

spurious isolation, yet low enough to detect the presence of a small break Loss of Coolant Accident. For the event on March 21, 1997, the Containment High-Range Radiation Monitor RIT-1825 was subjected to a noise spike with a magnitude large enough to reach the high alarm setting.

A survey was performed that verified that this event was not due to a high radiation condition. A review of the recorder traces for both Containment High-Range Radiation Monitors has determined that there is no erratic behavior of the monitors and that noise spikes have been measured concurrent with the work activities local to these monitors (i.e., radiography, welding, Electro-Magnetic Force, and cable handling at penetrations).

Furthermore, electronic cable checks, from the monitoring trip units to the detector, and a detector calibration check successfully demonstrated no equipment problems. Testing proved that handling the sensitive radiation j

monitoring cables can cause a noise spike with a magnitude large enough to reach the high alarm setpoint.

1 While a spike was not duplicated on RIT-1825 sufficient to cause an isolation actuation signal, one of sufficient i

magnitude was duplicated for RIT-1826.

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NRC FORM,366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVISION Millstone Nuclear Power Station Unit 1 05000245 NUMBER NUMBER 3 of 3 97 015 00 TEXT Uf more space is required use additional copies of NRC Form 366A) (17}

This event is reportable pursuant to 10 CFR 50.73(a)(2)(iv), "any event or condition that resulted in a manual or automatic actuation of any Engineered Safety Feature." There were no actual safety consequences as a result of this event. This event did not impact any system's or component's capability to perform its safety related function. As such, this event did not impact any accident analysis.

IV. Corrective Action

1.

The immediate corrective action was to bypass both Containment High-Range Radiation Monitor group six isolation signals at the Shift Manager's discretion, when primary containment is not required, to preclude inadvertent actuations.

2.

To prevent recurrerice of this event, procedures will be revised, prior to startup for operating Cycle 16, to bypass the group six isolation signal from both Containment High-Range Radiation Monitors, at the discretion of the Shift Manager, to preclude inadvertent high radiation alarms and actuations when work is being performed and primary containment is not required.

3.

The following corrective actions have been completed to verify that equipment malfunctions were not the cause of this event:

Electronic cable checks for integrity from the monitoring trip units to the detector have been performed and yielded acceptable results. This was a comparison to previous checks to ensure cabling had not been degraded, Handling of signal cables at the penetrations and cable trays to observe sensitivity was performed and e

demonstrated that the resulting noise spikes can reach the high alarm setpoint.

Detector calibration and response to a radiation source per IC407H was performed and yielded acceptable results.

4.

Additional testing will be performed on the Containment High-Range Monitors to verify operability prior to reactor restart.

V.

Additional Information

Similar Events There were no similar ESF actuations in the past two years.

Manufacturer Data Not Applicable l

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