ML18100A363

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LER 91-035-01:on 911127,RMS 1R12A Containment Noble Gas Radiation Monitor Channel Alarmed,Resulting in Containment Purge Isolation Signal.Caused by Failure of Detector Connector.Connector Replaced & Housing Cleaned
ML18100A363
Person / Time
Site: Salem PSEG icon.png
Issue date: 05/04/1993
From: Pollack M
Public Service Enterprise Group
To:
Shared Package
ML18100A362 List:
References
LER-91-035, LER-91-35, NUDOCS 9305120061
Download: ML18100A363 (5)
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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (6-891 APPROVED OMB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LERI COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P*530I, U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-01041. OFFICE I

OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1 I Salem Generating Station - Unit i DOCKET NUMBER (21 o I 5 I o I o l o I 2 I 7 12 , PAGE 131 OF 015 TITLE (41 F.no-ineered Safetv Feature signal initiated from the Radiation Monitoring System.

EVENT DATE (51 LER NUMBER (61 REPORT DATE (71 OTHER FACILITIES INVOLVED (81 MONTH DAY YEAR YEAR [:} SEQUENTIAL NUMBER E> REVISION NUMBER MONTH DAY YEAR FACILITY NAMES DOCKET NUMBERISI o1s1010101 I I i Ii 21 7 9 i 91 i o 13 Is 0 Ii 0 b 0 14 9 IJ o 1s 1010 1 o 1 I I THIS REPORT IS SUBMITTED PURSUANT TO THE Rl<;lUIREMENTS OF 10 CFR §: (Chock one or more of th* following) (111 OPERATING MODE (Bl 1 20.402(b)

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  • 60, 73(1)(21 (viiillBI 60.73(111211*1 366A)

NAME LICENSEE CONTACT FOR THIS LER (12)

TELEPHONE NUMBER AREA CODE M. J. Pollack - LER Coordinator 61 01 9 3 13 I 9 1- 12 I 0 12 I 2 COMPLETE ONE .LINE FOR EACH COMPONENT FAILURE DESCRIBED JN THIS REPORT 1131 MANUFAC* REPORTABLE :::::::: ::::: :::::*>:*:*:- ::::::::: MANUFAC* REPORTABLE .;.;.;.:  :::: :*:*:*:* *:'

CAUSE SYSTEM COMPONENT TO NPRDS CAUSE SYSTEM COMPONENT TUR ER TUR ER TO NPRDS I: :*:-:-:.; *:*::::: .;.;::::. *:*:::::

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SUPPLEMENTAL REPORT EXPECTED 1141 MONTH DAY YEAR EXPECTED n YES (If y6S, comp/et* EXPECTED SUBMISSION DATE)

ABSTRACT (Limit to 1400 spaces. i.~ .. approximately fifteen single-space typewrirten lines) 116) k-i NO SUBMISSION DATE 1151 I I I This LER is a supplement to LER 272/91-035-00. The Apparent Cause of occurrence section has been revised to address the results of subsequent investigation. On November 27, 1991, at 0042 hours4.861111e-4 days <br />0.0117 hours <br />6.944444e-5 weeks <br />1.5981e-5 months <br />, the Radiation Monitoring System (RMS) 1R12A Containment Noble Gas Radiation Monitor channel alarmed resulting in a Containment Purge/Pressure-Vacuum Relief (CP/P-VR) system isolation signal. Investigation of the event was initiated which included taking a portable Containment air sample. The sample did not indicate any increased activity. The 1R12A RMS channel was declared inoperable and Technical Specification 3.3.3.l Table 3.3-6 Action 20 was entered on November 27, 1991, at 0334 hours0.00387 days <br />0.0928 hours <br />5.522487e-4 weeks <br />1.27087e-4 months <br />. The root cause of the ESF signal actuation is equipment failure. Investigation identified that the detector connector had failed. The signal ground wire, in the connector, had broken. Also, the cable shield wire was found unconnected and pushed back into the connector. The connector was subsequently replaced. The channel was then tested successfully and returned to service. A program to replace older RMS channel connectors has been initiated.

93051200~~

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER . LER NUMBER PAGE Unit 1 5000272 91-035-01 2 of 5 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification system (EIIS) codes are identified in the text as {xx}

IDENTIFICATION OF OCCURRENCE:

Engineered Safety Feature signal initiated from the Rad'iation Monitoring System

  • Event-.Date: 11/27/91 Report Date:. 5/4/93 I This report is a supplement to LER 272/91-035-00 which was initiated by Incident Report No. 91~864. The Apparent Cause of Occurrence section has been revised -to address the results of subsequent investigation (committed to in the original LER). *
  • CONDITIONS PRIOR TO OCCURRENCE:

Mode 1 Reactor Power 100% - Unit Load 1.160 MWe DESCRIPTION OF OCCURRENCE:

On November 27, 1991, at 0042 hours4.861111e-4 days <br />0.0117 hours <br />6.944444e-5 weeks <br />1.5981e-5 months <br />, the Radiation Monitoring System

{RMS) {IL} 1Rl2A Containment Noble Gas Radiation Monitor channel alarmed resulting in a Containment Purge/Pressure-Vacuum Relief (CP/P-VR) System {BF} isolation signal. Investigation of the event was initiated which included taking a Containment air sample. The sample did not indicate any iricreased activity. The 1R12A RMS channel was declared inoperable and Technical Specification 3.3.3.1 Table 3.3-6 Action 20 was entered on November 27, 1991, at 0334 hours0.00387 days <br />0.0928 hours <br />5.522487e-4 weeks <br />1.27087e-4 months <br />.

The CP/P-VR System isolation signal is an Engineered Safety Feature

{ESF) {JC}. Therefore, the Nuclear Regulatory Commission was notified of the automatic actuation signal in accordance with Cod~ of Federal Regulations 10CFR 50.72(b) (2) (ii) on November 27, 1991, at 0119 hours0.00138 days <br />0.0331 hours <br />1.967593e-4 weeks <br />4.52795e-5 months <br />.

  • Technical Specification Table 3.3-6 Action 2o states:

"With the number of channels OPERABLE less than required by the Minimum Channels.OPERABLE requirement, comply with the ACTION requirements of Specification 3.4.6.1 11

"The following Reactor Coolant System leakage detection systems

~ICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-035-01 3 of 5 DESCRIPTION OF OCCURRENCE: (cont'd) shall be OPERABLE:

a. -The containment atmosphere particulate radioactivity monitoring system,
b. The containment sump level monitoring system, and
c. Either the containment fan cooler condensate flow rate or the containment atmosphere gaseous radioactivity monitoring system."

Technical Specification 3.4.6.1 Action Statement states:

"With only two of the above required leakage detection systems OPERABLE, operation may continue for up to 30 days provided grab samples of the containment atmosphere are obtained and analyzed at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when the required gaseous and/or particulate radioactivity monitoring system is inoperable; otherwise, be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />."

APPARENT CAUSE OF OCCURRENCE:

The root cause of the ESF signal actuation is equipment 'failure.

Investigation identified that the de.tector connector had_ failed. The signal ground wire, in the connector, had broken. Also, the cable shield wire was found unconnected and pushed back into the -

connector. The connector was subsequently replaced. The channel was then tested successfully and returned to service.

Detector connector failures have been experienced with other RMS channels in both Salem Units (e.g., LER 311/90-021-00, 2Rl2A ESF signal actuation). A program to replace older RMS channel connectors has been initiated.

  • ANALYSIS OF OCCURRENCE:

This event did not affect the health-or safety of the public.

However, due to the automatic actuation signal of an ~SF system, it

  • is reportable in accordance with Code of Federal Regulations 10CFR l

50.73 (a) (2) (iv).

Isolation of the *CP/P-VR System is an ESF. It mitigates the release of radioactive material to the environment after a design basis accident.

Air samples are pulled from the Containment atmosphere through filter paper which continuously moves past the lRllA (Containment

  • Particulate Radiation Monitor) detector. The air sample then passes

- ::=1

- I LICENSEE EVENT REPORT_ (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 . 5000272 91-035-()1 4 of 5 ANALYSIS OF OCCURRENCE: (cont'd) through a charcoal cartridge (monitored by the 1R12B detector) and is then mixed into a fixed shielded volume where it is viewed by the 1R12A (Containment Noble Gas Radiation Monitor) detector. The air sample is then returned to the Containment.

The 1R12A, Containment Noble Gas Monitor, (a geiger-mueller detector) monitors the radioactive noble gas activity in the Containment atmosphere. It is used to identify RCS leakage in conjunction with the containment sump level monitoring system, and either the. .

containment fan cooler condensate flow rate monitoring system, or the containment radioactive particulate (lRllA) radioactivity monitoring system. ~

Both the lRllA and 1R12A RMS channels provide an alarm signal which will cause automatic isolation of the CP/P-VR System.

At the time of the 1R12A ESF signal actuation, Containment Purge and Pressure-Vacuum Relief activities were not in progress. The. I Containment Ventilation valves were closed. They did not change position as a result of the isolation signal.

During the 1R12A event, RCS leakage within the containment did not increase nor were there any significant indications of increasing Containment activity based on subsequent air samples.

The* initial investigation (as discussed in the original issue of this LER) identified that the 1R12A monitor may have responded to actual radioactivity, the source of which was not presently known. Prior to the event, on November 26, 1991, the 1R12A count rate was observed to be trending up. During this increase, the 1R11A Containment Particulate Monitor RMS channel spiked high resulting in a CP/P-vR System isolation signal (see LER 272/91-034-00) . Investigation of the lRllA event identified 1800 cpm above background on the lRllA _

filter paper. The lRllA and 1Rl2A monitor the same sample of Containment air. The lRllA RMS channel activity was determined to be Pb-214 and Bi-214 (naturally occurring Radon daughter products) .

This activity was thought to_ also be the reason for the observed increase in 1Rl2A background counts. The 1R12A detector housing and detector were subsequently cleaned, on November 26, 1991, resulting in the lowering of the 1R12A background count rate to a nominally expected value.

The investigation of the November 27, 1991 1R12A event included*

cleaning the detector housing and detector, again resulting in the lowering of the 1R12A background count rate to a nominally expected value. Also, a channel calibration check was successfully performed..

A search for leaks, within the Containment, was conducted. An extremely small leak was identified on the Pressurizer Relief Tank (PRT) rupture disc. This leak was determined to be inconsequential

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-035-01 5 of 5 ANALYSIS OF OCCURRENCE: (cont'd}

to an increase in Containment airborne activity. An air sample by the PRT did not show an increase in airborne activity.

The 1R12A RMS channel was subsequently returned to service on November 29, 1991, at .1125 hours0.013 days <br />0.313 hours <br />0.00186 weeks <br />4.280625e-4 months <br />, 'at which time Technical Specific::ation Table 3.3-6 Action 20 was exited.

On December 5,* 1991, at 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br />, 1R12A RMS channel was taken out of service due to observed readings approaching the channel's warning setpoint. The appL:icable Action Statement was entered. Containment air samples, as before, did not show any increase in background activity. Analys,is of detector and detector housing smears showed Pb-214, Bi-214 and Rb-88. The channel was returned.to service and the Action Statement exited on December 6,. 1991, at 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />.

Subsequent analysis has shown that Pb-214/BI-214 acitivty was not sufficient to drive the 1Rl2A RMS channel into warning or alarm.

CORRECTIVE ACTION:

The 1Rl2A failed connector was replaced. The channel was then tested successfully and returned to service.

A program to replace older RMS channel connectors has been initiated.

The 1Rl2A channel detector and detector housing were cleaned and a channel calibration check was performed satisfactorily. The channel was returned to service on November 29, 1991, at 1125 hours0.013 days <br />0.313 hours <br />0.00186 weeks <br />4.280625e-4 months <br />, at which time Technical Specification Table ~.3-6 Action 20 was exited.

The PRT rupture disc leak was repaired.

MJP:pc SORC Mtg.93-040 t

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