ML20029D776

LER 94-002-00:on 940303,noble Gas Monitor in R-35 Did Not Respond When source-checked During Surveillance.Caused by Component Failure.Corrective Actions:Monitor Repaired & Returned to svc.W/940504 Ltr

ML20029D776
Person / Time
Site:	Prairie Island
Issue date:	05/04/1994
From:	Richard Anderson, Hunstad A NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-94-002-01, LER-94-2-1, NUDOCS 9405100075
Download: ML20029D776 (4)

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Northem States Power Company

. 414 Nicollet Mall Minneapolis, Minnesota 55401 1927 Telephone (612) 330-5500 May 4, 1994 10 CFR Part 50 Section 50.73 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISIAND NUCLEAR GENERATING PIANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Inoperability of RadWaste Building Ventilation System Radiation Monitor R-35 Went Undetected Because of Component Failure The Licensee Event Report for this occurrence is attached. In the report, we made the following new NRC commitment:

Functional testing of the downscale failure feature for this type of i monitor will be added to the annual calibration procedure.

Please contact us if you require additional information related to this event.

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4 a C) A " & -

Roger 0 Anderson Director Licensing and Management Issues c: Regional Administrator - Region III, NRC NRR Proj ect Manager, NRC Senior Resident Inspector, NRC Kris Sanda, State of 111nnesota Attachment 9405100075 940504 PDR ADOCK 05000282 '

O b" g S PDR

NRC FORQ 366 U.S. NUCLEAR REGULAIC Y COPMISSI C APPROVED BY CMB CD. 3150-0104 l (52 92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH I I"' ** L ' '"

LICENSEE EVENT REPORT (LER) $ARD [osgEN7S REGARDlN BURDEN ES TE O THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, (See reverse for required ruber of digits / characters for each block) WASHINGTON, DC 20555 0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150 0104), OFFICE OF MANACEMENT AND BUDGET. WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NLMBER (2) PAGE (3)

Prairie Island Nuclear Generating Plant U1 05000 282 1 OF 3 TITLE (4) Inoperability of Radwaste Building Ventitation System Radiation Monitor R 35 Went Undetected Because of Ccunporwnt Failure EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

SEQUENTIAL REVISION FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR " H ^ ^

NUMBER NUMBER Prairie Island U2 05000 306 FACILITY NAME DOCKET NUMBER 03 03 94 94 --

02 --

00 05 04 94 05000 CPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR h (Check one or more) (11)

MODE (9)

N 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b)

POWER 20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73. 71(c)

OM LEVEL (10) 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER 20.405(a)(1)(iii) X 50.73(a)(2)(1) 50.73(a)(2)(vi l l )( A) (Specify in Abst act ow 20.405(a)(1)(iv) 50.73(a)(2)(li) 50.73(a)(2)(viii)(8) 20.405(a)(1)(v) 50.73(a)(2)( l i t ) 50.73(a)(2)(x) NRC Form 366A)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Arne A Hunstad 612-388-1121 COMPLETE ONE TINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) 0 E CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR YES SUBMISSION (if yes, complete EXPECTED SUBMISSION DATE). X NO DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On February 7, 1994, radiation monitor R-35, RadWaste Building Ventilation System Monitor, was removed from service for modification of its sampling system. The modification was completed and the monitor was returned to service on February 11. On March 3, the noble gas monitor in R-35 did not respond when source-checked during the routine radiation monitor surveillance. The RadWaste Building Ventilation System was secured OFF until the monitor could again be made operable. During investigation of the failure on March 4, a broken detector signal lead was discovered.

Further investigation led to the conclusion that the lead had probably been broken during the modification done in February, and that the monitor had been inoperable since that time. The monitor was repaired, source-checked and returned to service on March 9. Based on weekly grab samples and historical monitoring data, it was shown that no releases via the RadWaste Building Ventilation System took place during the event.

i i

NRC FORM 366 (5-92)

i o

NR'C FORM 366A U.S. NUCLEAR REGULATORY CupMISSION APPROVED BY OMB NO. 3150-0104 (5 92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO LICENSEE EVENT REPORT (LER) THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNes 7714), u.S. wuCLEAR REGULATORY COMMIS$10N, TEXT CONTINUATION WASHINGTON, DC 20555 0001 AND TO THE PAPERWORK REDUCTION PROJECT (31$0-0104), OFFICE OF i MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKFT NUMBER (2) LER NUMBER (61 PAGE (3)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Prairie Island Unit 1 05000 282 94 __ og __ 00 l

TEXT (if more soace is recuired, use additional copies of NRC Form 366A) (17)

EVENT DESCRIPTION On February 7, 1994, radiation monitor R-35, RadWaste Building Ventilation System Monitor (EIIS Component Identifier MON), was removed from service for modification of its sampling system. The modification was completed and the monitor was returned to service on February 11. On March 3, the '

noble gas monitor in R-35 did not respond when source-checked during the  !

routine radiation monitor surveillance. The RadWaste Building Ventilation i System was secured OFF until the monitor could again be made operable. I During investigation of the failure on March 4, a broken detector signal  !

lead was discovered. Further investigation led to the conclusion that the lead had probably been broken during the modification done in February, and that the monitor had been inoperable since that time. The monitor was i repaired, source-checked and returned to service on March 9. Based on I weekly grab samples and historical monitoring data, it was shown that no  ;

releases via the RadWaste Building Ventilation System took place during the  !

period R-35 was inoperable. j CAUSE OF THE EVENT Cause of the monitor inoperability discovered on March 4 was component failure. Post-modification testing of the monitor in February did not detect its inoperability. The Mesting did not include source checking.

, Inoperability of the monitor's detector circuitry should have been seen as l a downscale failure of the monitor's indicating meter. Degradation of a capacitor in the monitor electronics had defeated the downscale failure feature.

ANALYSIS OF THE EVENT Technical Specification 3.9.F requires the RadWaste Building Ventilation Radiation Monitor to be operable with its alarm setpoint set to insure that release limits are not exceeded. The monitor provides no other automatic actions. If it is not operable, effluents may continue to be released if grab samples are taken every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. Since ventilation flow was occurring during the time the monitor was inoperable, a discharge above allowable limits would not have been alarmed, and grab samples would not have been taken. This event is being reported pursuant to 10CFR50.73 (a) (2) (1) (B) .

No release occurred via the RadWaste Building Ventilation System during the event; therefore, public health and safety were not affected.

The event date (the day the inoperability was discovered) was March 3, 1994. Discussions within the plant staff and, later, discussions with the resident inspectors resulted in the conclusion that the monitor inoperability may not be reportable because no releases took place.

NR'C FORM 366A U.S. IRJCLEAR REGJLATORY C0pellSSION APPROVED BY OMB No. 3150-0104 (5 92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH

. THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE 10 LICENSEE EVENT REPORT (LER) THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, TEXT CONTINUATION WASHINGTON, DC 20555-0001 AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGE' MENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAfE (1) DOCKET IRDWER (2) LER 3RDWER (6? PAGF (3)

YEAR SEQUENTIAL REVISION NuMsER NuMsER Prairie Island Unit 1 3W3 05000 282 94 --

02 -- 00 TEXT (If more space is reauired. use additional copies of NRC Form 366A) (17)

Further discussion with the resident inspectors and a Region III-based NRC inspector, on April 4, 1994, led to the conclusion that the event is reportable. Therefore, the 30-day clock for reporting started on April 4.

CORRECTIVE AC-l' ION When the monitor failed to respond during its routine surveillance on March 3, the RadWaste Building Ventilation System was shut down, and investigation of the failure was begun.

The broken detector signal lead was repaired, the monitor source-checked and returned to service on March 9.

The degraded capacitor was replaced. The downscale failure feature of similar monitors was tested; one other monitor had to be adjusted to attain the desired response. Functional testing of the downscale failure feature for this type of monitor will be added to the annual calibration procedure.

The installed check souren in this type of monitor is not useful for operability testing because of its low strength. Therefore, source-checking is done with an external source. For this reason, from an ALARA ,

standpoint it is not prudent to source check the monitor after each l maintenance activity. The monitor would be source-checked only after i detector replacement or other work involving the detector or its cabling. '

Source-checking is done monthly and at the annual calibration.

FAILED COMPONENT IDENTIFICATION Nuclear Measurements Corporation Gas Monitor Model APM-G25.

PREVIOUS SIMILAR EVENTS A previous event regarding inoperability of R-35 was reported as Unit 1 LER 91-006.

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