ML20085G708

AO BFAO-50-259/7458W:on 741126,main Stack Gas Radiation Monitoring Sys Found Inoperable.Caused by Excess Water in Sys Due to Isolation Valve Leakage from Demineralized Water Back Flushing Connection

ML20085G708
Person / Time
Site:	Browns Ferry
Issue date:	12/06/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Case E US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085G714	List: ML20085G708 ML20085G719
References
NUDOCS 8308290293
Download: ML20085G708 (3)

Text

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ABNORMAL OCCURRENCE RER)RT Report No.

BFAO-50-259/745BI Report Date: Dece ber 6, 1974 ,

Occurrence Date: November 26, 1974 Facility: Browns Ferry Nuclear Plant - stack radiation monitor (common)

Identification of Occurrence The main stack gas radiation monitoring system was inoperable for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 33 minutes.

Conditions Prior to Occurrence Unit 2 was in the cold shutdown condition. Unit 1 was operating at about 64-percentpower,andthestackreleaseratewas40uCi/sec.

Description of Occurrence At 1342 hours0.0155 days <br />0.373 hours <br />0.00222 weeks <br />5.10631e-4 months <br />, the stack gas sample flow abnor=al alarm was received in the I

main control room. An operator and a laboratory analyst were dispatched to replace the stack =cnitor particulate and/or iodine charcoal filters which,

, in the past, usually resolved this problem. In this case, water was found in the stack sampling syster; and the system was isolated at 1425 hcurs to drain the water and replace the filters. At 1442 hours0.0167 days <br />0.401 hours <br />0.00238 weeks <br />5.48681e-4 months <br /> after the stack gas radiation monitoring system had been inoperable for one hour, an orderly 3

unit 1 shutdown was initiated.

After the stack gas sampling system was drained and new particulate and iodine i filters were installed, a stack gas grab sample was taken at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> with a portable millipore vacuum pump while' the stack gas sample pumps were being i restored to service. The stack gas monitoring system was restored to normal operation at 1615 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.145075e-4 months <br />, and the unit 1 controlled shutdown was ceased.

Designation of Apparent Cause of Occurrence The source of excess water in the stack gas sampling system was not. precisely deter.ined. Ccndensation was improbable since the system had becn inspected and found free of visible water at about 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />, and the sa=pling line heat trace system was confirmed operable and in service. The only other '

possible source of the approxi=ately 2000 ml of water found in the system was a domineralized water back-flushing connection piped sclid through an isolation valve into the stack gas sampling line up::tream of the particulate / iodine filter unit. The demineralized water isolation valve was found closed and failed to show any sign of leakage. However, this valve is located in close proximity to, and could be mistaken for, the stack gas sample influent isolation valve.

Analysis of Occurrence During the time the stack gas monitoring cyci;em was out of service, there was no indicated increase in the unit'l offgas radiation monitor. Additionally, stack 8308290293 741206 PDR ADOCK 05000259 g PDR 4

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Mr. Edson G. Case N /+I, Acting Director of Licensing 'g [,i Office of Regulation U.S. Atomic Energy Cornission Q[~'

Washington, DC 20545

Dear Mr. Case:

TECTESSEE VALL7 A'JTHORITI - BRO'TJS FERRY I!UCLEAR PLAIIT UITIT 1 -

DOCEET 170. 50-259 - FACILITI OPERATIIIG LICEIISE DPR ABITORMAL OCCURREiCEREFORTBFAO-50-259/7458W The enclosed report is to provide details concerning the main stack gas radiation tonitoring systen which was inoperable for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 33 minutes and is submitted in accordance with Appendix A to Regulatoiy Guide 1.16, Revision 1, October 1973. This event occurred on the Browns Ferr/ IIuclear Plant stack radiation monitor.

Very truly yours, TEmiESSEE VALLEY AUTr'ORITY

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E. F. Tnomas Director of Power Production Enclosure-CC (Enclosure):

Mr. Iiornan C. 2/oseley, Director  ;

Region II Regulatory Operations Office, USAEC i

, 230 Peachtree Street,174., Suite 818.

Atlanta, Georgia 30303 f .

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_2 Analysis of Occurrence (Continued) gcs grab samples also reflectt:d no significant change in the stack effluent.

Thus, this occurrence did not endanger the health and safety of the public.

Corrective Action A caution tag has been placed on the demineralized water back-flushing valve to administratively protect it from being opened by mistake until the following changes e.re implemented.

A modification change request has been initiated to eliminate the solid piped back-fluching demineralized water connection from the stack sampling system.

This change requests quick disconnect couplings to allow a flexible hose to be connected under controlled and intentional conditionc. The flexible hose will ncrmally be disconnected and removed to prevent a possible flow path of demineralized water into the stack gas sampling system.

Another modification change request has been initiated requesting the installation of stack gas sampling line " tees" to enable rapid substitution of a vacuum pump to temporarily restere the stack gas sampling system to service in the event of failure of sampling pumps.

Failure Data Not applicable.

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