ML20085G860

AO BFAO-50-260/7421W:on 741017,two Offgas HEPA Filters Not Installed Before Startup,Contrary to Section 9.4 of Fsar. Caused by Personnel Error.Filter Sample Lines Blown Out W/Station Air.New Filters Installed

ML20085G860
Person / Time
Site:	Browns Ferry
Issue date:	10/25/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Case E US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8308290467
Download: ML20085G860 (3)

Text

O* ABNORMAL OCCURREUCS REPORf3 G

l' Report No.: 3FAO-50-260/7421h' Report Date: October 25, 1974 Occurrence Date: October 17, 1974

. Facility: Brcuns Ferry nuclear Plant unit 2 Identification of Occurrence Contrary to the Brcwns Ferry nuclear Plant Final Safety Analysis Report, Secticn 9 4, the unit 2 offgas HEFA filters were not installed before startup.

Conditiens Pricr to Occurrence Unit 2 was in the cold shutdcun cendition during forced maintenance cutage when the absence of both offgas HEFA filters was discovered. The unit was in the startup test program and had operated the equivalent of 300 full-power hours between July 7 and October 12, 1974, achieving a maximum pcwer level of c4 percent.

Description of Occurrence On October 4,1974, during a rcutine analysis of the stack monitor particulate filter, with unit 1 shut dcwn and unit 2 at about 60 percent power, a slight increase in activity was noted for the sample period of October 1-2. The particulate decentaminaticn factor (DF) for the in-service unit 2 offgas EEEA filter 2A (assumed to be installed) was measured on Octcber 5,1974. DF results of abcut 1.2 indicated that the perforrance of filter 2A was questicnable; and the standby filter 23 (also accured to be installed) was inmediately valved into service. A DOP test was scheduled for tne next unit 2 outage. Because of cenbustibJ e gases, a DOP test is not ccnducted with the effgas system in service. On Cetcber 7, the particulate DF cf HEFA filter 23 was measured to be about 2.0, also indicating questionable perfcrmance. That came day at 1456 hours0.0169 days <br />0.404 hours <br />0.00241 weeks <br />5.54008e-4 months <br />, unit 2 tripped by main transformer protective relay operatien and an cutage was started. On October 16, during the outage, both unit 2 HEEA filters failed to pass DOP tests. Filter assembly 23 was opened, and the absence of the HEEA filter was discovered. On October 17, it was disecvered that HEEA filter 2A was also not installed.

Analysis of Occurrence Failure to install the filters passed unnoticed because there was no discernible increase in stack release rates as a result of unit 2 operation. The manaccuent control to verify filter performance was a DOP test conducted en July 27, 1974, following open vessel testing and before nuclear heatup. These D0P tests apparently satisfied test requirements but are ncw recognized invalid because the cample line was blocked by forei n6 matter and the sample probe was nct sealed into the sample line, thus permitting air to be drawn into the sample probe.

No airborne release rates were exceeded during unit 2 operation. The plant average I-131 ana particulate relep+se rates from July 7 through October 12, 1974, indicate that they were 4.44 x 10- uCi/sec and 1.64 x 10-3 uCi/sec, respectively, compared to the technical specification quarterly limit of 0.8 uCi/sec. Atmos-pheric monitors surrounding the plant did not detect any increase in particulute activity attributable to the operation of Browns Ferry Nuclear Plant since the startup of unit 2.

8308290467 741025 PDR ADOCK 05000260 S PDR f

1 Corrective Action l l

l Following the discovery of this incident, all unit 2 offcas HEEA filter cample lino., were blown cut with statien air. Proper clearing of the blocked offcac EPA filter effluent ca..plinc line wac dencnctrated by free air flow diccharge

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from the cample line opening.when station air was forced into the offgas cysten at another point.

Hew HEEA filterc were inctalled in 2A and 2B offcac filter houcingc. The adequacy of DOP testing was confirr^d by conducting DCP testa with and without an EP.1 filter installed. Final valid DOP test results shcu 100 percent removal efficiency for particles 3 0.3 niercnc.

A sign-cff will bc added to the offgas preoperational tect TVA-15 for unit 3 te verif; the inctallaticn of bcth 3; and 3B HZDa filterc. The DOP tect requircr. cat will be recoved frc.7 STI-l and placed in precperational test TVA-15 to ensure that the inctallcticn was satisfactory and teets the criteria specified in the FSAE tefere unit 3 ctartup. Additicnally, the DOP test precedure will be reviccd to require that all cample lines be blenn cut before testing and that all sample ccnnecticna are properly sealed during testing.

Although unit 1 cffgas EEFA filters have separate and unique DOP carpling 31nes, DOP test results fcr bcth 1A and 13 filter will be validated at the next acheduled outace. DF values for both unit 1 cffgas EIFA filters confirm the precence of HEFA filterc in each filter housing.

Failure Data Hot applicable, l

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October 25, 197h r, -

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Mr. Edson G. Cace Acting Director of Licensing Office of Regulaticn U.S. Atcmic Energy Cericcicn -

Washingtcn, DC 20545

Dear Mr. Case:

TEI!IIE03EE VALIEY AUTHCRITY - BROWS FERRY IrJCIEAR FUd.'T UIIIT 2 -

DOCE7f I;0. 50-260 - I!.CILITY OPERATII G LICEESE DPR ABHOR'G.L OCCUMREILE REPOIC 3FAO-50-260/7421W The enclosed repcrt is to provide details ccncerning the finding that both cetc cf cffgas HEFA filters were not inctalled and is submitted in acccrdance with Appendix A to Regulatcry Guide 1.16, Re"i-sicn 1, October 1973 Thic event occurred on Brcuns Ferry I!uclear Plant unit 2 on Octcber 17, 1974.

Very truly yours, TEIH;ESSEE VALLEY /tUTECRITY .

C* /f-G. l '0 i,r^.Le,

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7' E. F. Thomas Director of Pcuer Production Enclosure CC(Enclocure):

Mr. Hor:.an C. Moseley, Director Region II Regulatory Operaticnc Office, USAEC;___.

l 'fpK 230 Peachtree Street, EW. , Suite 818 Atlanta, Georgia 30303 .

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