ML20085M143

AO BFAO-746W:on 731113,during Startup Test Program, Radioactive Matl Discovered Released to Unit 2 Reactor Bldg Floor Drain Sumps.Cause Undetermined.Rept Mistakenly Submitted to Directorate of Licensing on 740130

ML20085M143
Person / Time
Site:	Browns Ferry
Issue date:	02/22/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Knuth D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085M142	List: ML20085M143 ML20085M151
References
AO-BFAO-746W, NUDOCS 8311080056
Download: ML20085M143 (3)

Text

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PARTNEHSHIP February 22, 1974 Mr. Don Knuth Directorate of Regulatory Operations U.S. Atomic Energy Commission Washington, DC 20545

Dear Mr. Knuth:

TENNESSEE VALLEY AUTHORITY - BRGiNS FERRY NUCLEAR PIANT UNIT 1 -

DOCKET NO. 50-259 - FACILITY OPERATING LICENSE DPR ABNORMAL OCCURRENCE REPORT 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 Browns Ferry Nuclear Plant unit 1 on November 13, 1973, and is submitted in accordance with 10 CFR 20 Paragraph 405(a).

This report was mistakenly submitted to the Directorate of Licensing on January 30, 1974.

Very truly yours, TENNESSEE VALLEY AUTHORITY

- . . _a. j irector of Power Production )

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, . 1 x.. . O -O Report No. BFAO-746W l Report Date: January 30, 1974 l Occurrence Date: November 13, 1973 Facility: Browns Ferry Nuclear Plant, Unit 1 Identification of Occurrence On November 13, 1973, it was determined that radioactive material had been released to the unit 2 reactor building floor drain sumps. At that time,-

it was felt that this was not a reportable abnormal occurrence as defined in the technical specifications. During the AEC regulatory inspection of January 8-11, 1974, the AEC inspectors requested we submit a report of the radioactive release as an abnormal occurrence.

Conditions Prior to Occurrence The unit 1 reactor was operational during the startup test program. The unit 2 reactor cleanup backwash transfer pump and backwash receiver ' tank

-/ rooms had been previously barricaded and zoned as a restricted area for control of exposure to radiation and radioactive materials because of the '

presence of radiation dose rates of approximately 1-2 mrem /hr at ~ contact -

on some of the units 1 and 2. backwash transfer pump tie lines on the unit 2 side. This dose rate apparently came from resins that had breached the closed, tagged, and locked. interface valves between units-1 and 2. At the time the barricades were established, the line from the. unit 2 backwash transfer pump 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 'made and no contamination was preseut.

Description of Occurrence i

! On November 13, the unit- 2 cleanup backwash receiver tank room was surveyed .

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

A survey of the line frcm the backwash transfer l pump suction' to the backwash receiver tank indicated the presence of radioactive material on the open.

flange of this line. and' on the floor under .the tank. Contamination was-

. found leading from a point under the' open f3ange .to a floor drain nearby. .

! SamplesDof the:two unit 2_ reactor building floor drain sumps 'were immediately 4

colle'eted, and no activity above l Maximum' Permissible Concentrations _ (MPC) _was - .

-found.

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- At this time, _both units l2 and 3- east reactor building floor. drain sumps

• were barricaded and zoned into the restricted area.-

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Description of occurrence (continued)

! Samples were obtained and counted from all units 2 and 3 sumps and indicated no presence of radioactivity above MPC except the cludge in the unit 2 reactor building west f1cor drain sump. On November 15, this sump was pumped.down to sample the bottom sludge. This cample was analyzed on the gamma spectro-i meter, which detected the following isotopes and concentrations:

4 skr - 8.48 x 10-3 uci/ml 58co - 6.58 x 10-3 uci/ml 60cc - 4.83 x 10-4 uci/ml i

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] Analyses of Occurrence i

! It has not been absolutely determined how the radioactive material was discharged out the pump suction to the receiver tank line. Although hold orders had been issued and placed on each applicable valve in the backwash system, apparently leaking valves during operation of the unit 1 backwash transfer pu=p allowed contaminated unit 1 backwash resins to escape the open line and enter the floor drain.

. The only sample that exceeded MPc during the period was the sample of sludge

! from the unit 2 west reactor building floor drain sump. _ This sump was. full

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of water, it had no pump installed, and it hes an opening only 18 x 18 inches j with no ladder. An individual could not 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.

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i Corrective Action All units 2 and 3 areas were freed of significant radioactive contamination -

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and returned to unrestricted zone status.

The line from the unit 2. backwash receiver tank to the transfer pump was reconnected, the tank was filled with clean water, and the unit 2 back. ash system was flushed to the radwaste system until no radioactive material 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 i units. A telltale valve was -installed between the two valves 'on the unit 'l 3 side of the dividing wall. The telltale valve will remain open so that any leak 1 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 sampling schedule so that each sump.is sampled at least twice weekly.

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