ML20085M151

AO BFAO-746W:on 731113,during Startup Test Program, Radioactive Matl Discovered Released to Unit 2 Reactor Bldg Floor Drain Sumps.Cause Undetermined.Lines Connecting Unit 1 & 2 Backwash Sys Modified

ML20085M151
Person / Time
Site:	Browns Ferry
Issue date:	01/30/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085M142	List: ML20085M143 ML20085M151
References
AO-BFAO-746W, NUDOCS 8311080061
Download: ML20085M151 (3)

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TENNESSEE VALLEY AUTHORITY E7 [7, CHATTANOOGA, TENNESSEE

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January 30, 1974 S M'E85feis PAAT N E AS HIP

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Mr. John F. O' Leary, Director ,kg { N 4, Directorate of Licensing  ;

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Office of Regulation U. S. Atcmic Energy Comission Washington, DC 20545

Dear Mr. O' Leary:

TENNESSEE VALIEY AUTHORITY - BROWHS FERRY NUCLEAR PIANT UNIT 1 -

DOCKET NO. 50-259 - FACILITY OPEPATING LICENSE DPR ABNOE%L OCCURRENCE REP 0FC' BFAO-746W The enclosed report; is to provide details concerning the release of radioactive material to the unit 2 reactor building floor drain sumps, which occurred on 3rewns Ferry Nuclear Plant unit 1 on November 13, 1973, and is submitted in accordance with Appendix A to Regulatory Guide 1.16, Revision 1,' October 1973 Very truly yours, TENNESSEE VALIEY'AUfEORITY s

b w_ [eC i 7 tsm E. F. Thomas Director of Power Production Enclosure CC (Enclosure):

Mr. Norman C. Moseley, Director Region II ReEulatory Operations Office,.USAEC 230 Peachtree Street, IM., Suite 818 Atlanta, Georgia 30303.

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Report No. BFAO-746W Report Date: January 30, 1974 Occurrence Date: November 13, 1973 Facility: Browns Ferry Nuclear Plsnt, Unit 1 Identification of Occurrence On November 13, 1973, it was deter =ined that radioactive material had been released to the unit 2 reactor buildin6 floor drain sumps. At that time, it was felt that this was not a reportable abncrral occurrence as defined in the technical specifications. During the AEC regulatory inspection of

, January 8-11, 1974, the Azr: inspectors requested we submit a report of the radioactive release as an abnor=al occurrence.

Conditions Prior to Occurrence The unit 1 reactor was operaticnal during the startup test program. The unit 2 reacter cleanup backwash transfer pump and backwash receiver tank rooms had been previcusly barricaded and zoned as a restricted area for control of exposure to radiation and radicactive caterials because of the

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presence of radiation dose rates of approximately 1-2 rRem/hr at contact on some of the units 1 and 2 backwash transfer m tie lines on the unit 2 side. This dose rate apparently came from resins that had breached the closed, tagged, and Iceked interface valves between units 1 and 2. At the time the barricades were established, the line frc= the unit 2 bachash transfer A suction to the unit 2 backwash receiver tank (which was disconnected from the tank) was checked and no radioactive material was present. In addition, a smear survey of the floor was rade and no contamination was present.

Description of Occurrence On November 13, the unit 2 cleanup backwash receiver tank rocm was surveyed '

as a prerequisite to entry by ecnstruction employees. A recheck of the system tie lines showed radiation dose rates up to 10 rRem/hr at contact.

A survey of the line frc= the backwash transfer pump suction to the backwash receiver tank indicated the presence of radiccctive material on the open -

flange of this line and en the floor under the tank. Contamination was-found leading from a point under the open flange to a floor drain nearby.

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Samples of the two unit 2 reactor building floor drain sumps were.immediately

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. collected, and no activity above Maximm Permissible Concentrations (MPC) was found.

At this time, both units 2 and 3 east reactor building floor' drain sumps were barricaded and zoned into the restricted area.

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t Description of Occurrence (continued) ,

Samples were obtained and counted frca all units 2 and 3 su=ps and indicated no presence of radioactivity above IGC execpt the sludge in the unit 2 reactor building west ficor drain su=p. On Hove =ber 15, this sump was pumped down to sa=ple the botten sludse. This sa=ple was analyzed on the gasca spectro-meter, which detected the following isotopes and concentrations:

51cr - 8.48 x 10-3 uci/ml 58co - 6.58 x 10-3 uci/ml ,

6qco - 4.83 x 10-4 uci/ml Analyses of Occurrence It has not been absolutely determined how the radioactive material was discharged out the pu=p suction to the receiver tank line. Although hold orders had been issued and placed on each applicable valve in the bachash system, apparently leaking valves during cperation of the unit 1 backwash transfer purp allcwed contaminated unit 1 backwash resins to escape the open line and enter the floor drain. .

The only sample that exceeded 12C during the period was the sample of sludge from the unit 2 west reactor building floor ' drain su=p. This su=p was full of water, it had no pu=p installed, and it has an opening only 18 x 18 inches with no ladder. An individual eculd net have been exposed to the sludge without deliberately installing a pump, pu= ping the water out, placing a ladder into the sump, and climbing down into the sludge.

Corrective Acticn All units 2 and 3 areas were freed of significant radioactive conta=ination and returned to unrestricted zone status.

The line' from the unit 2 bachash receiver tank to the transfer pu=p was reconnected, the tank was filled with clean water, and the unit 2 backwash system was flushed to the radwaste system until no radioactive caterial could be detected. All lines connecting the units 1 and 2 backwash system were modified so that there were at least two closed valves between the units. A telltale valve was installed between the two valves on the unit 1 side of the dividing. wall. The telltale valve will remain open so that any leak from the units 1 and 2 reactor cleanup system tie lines will drain to the radwaste system.

The unit 2 reactor building floor drain sumps are on a periodic saepling.

schedule so that each su=p is sampled at least twice weekly.

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