ML20084U255

Ro:On 721218,waste Gas Decay Tank C Inadvertently Discharged Through Auxiliary Bldg Vent.Caused by Foreign Matl Lodged in Root Valve & Sample Line Leakage.Potential Sources of Leakage Isolated.Final Action Will Be Reported

ML20084U255
Person / Time
Site:	Palisades
Issue date:	12/27/1972
From:	Walke G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
AO-721227, NUDOCS 8306280307
Download: ML20084U255 (2)

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December 27, 1972 Mr. John F. O' Leary, Director Re: Docket No 50-255 Directorate of Licensing License No DPR-20 US Atomic Energy Commission Washington, DC 20545

Dear Mr. O' Leary:

This is written to apprise you of a recent occurrence at the Palisades Plant involving the unplanned release from "C" waste gas tank.

The occurrence was discussed by telephone with your Mr. Cook on December 18, 1972.

Because of a combination of a root valve malfunction and sample line leakage, the contents of "C" waste gas decay tank were inadvertently discharged to the plant vent through the auxiliary building. An opera-tor, intending to align "A" gas decay tank for sampling, opened the root valve on "C" tank. The error was discovered and corrected when no sample was available from the "A" tank sample line at the sample panel. Shortly thereafter, however, it v&s noted that the pressure on "C" tank was de-creasing and that the continuous air monitor (CAM) located near the rad-vaste exhaust plenum was alarming.

At the time the "C" tank pressure decrease and CAM alarm were noted, operators were dispatched to recheck valve alignment. Although no misvalving was found, the tank pressure continued to decrease and the CAM indicated high airborne radioactivity for approximately four hours.

The area of high airborne radioactivity was evacuated during the period.

3' Our investigation leads to the conclusion that foreign material became lodged in the root valve on "C" tank, allowing the line from the root valve to the sample panel to become pressurized. The sample line, normally isolated from the decay tank by the root valve, apparently

' leaked into the auxiliary building. The gas from the decay tank was diluted with auxiliary building ventilation air and discharged through the filter system to the plant stack.

The estimated unplanned release, based on samples from other tanks, previous experience and CAM calibrations, con 91sted of the following:

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Mr. John F. O' Leary,, 2 Docket No 50-255 License No DPR-20 December 27, 1972 Xe-133 16.4 Ci Xe-133m 0.14 Ci Xe-135 0.007 Ci The maximum in-plant airborne concentration was 1.4 x 10-pCi/cm3, whereas the most restrictive MPC for the nuclide mixture in-volved is 1 x 10-6 pCi/cm3 As a result of the low concentration of radioactivity and being limited to noble gas, the radiological consequences of the above occurrence were negligible, both in-plant and off-site. We are, however, taking corrective action to isolate and eliminate all potential sources of leakage from the vaste gas decay system. We vill keep both Directorate of Licensing and Directorate of Regulatory Operations representatives inforned as to the final action taken to insure system integrity.

Yours very truly, Gerald J. Walke (Signed)

WGF/ map Gerald J. Walke Nuclear Fuels Administrator CC: BHGrier, USAEC s

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