ML20209G715

Discusses Evaluation of Newberry Township beta-gamma Survey Meter.Failure of Instrument to Stabilize in Constant Radiation Field Indicates Problem W/Survey Meter

ML20209G715
Person / Time
Site:	Three Mile Island
Issue date:	09/28/1984
From:	Dan Collins NRC
To:	Travers W Office of Nuclear Reactor Regulation
Shared Package
ML20209G708	List: ML20209G703 ML20209G710 ML20209G715 ML20209G740 ML20209G746
References
FOIA-85-428 NUDOCS 8509190669
Download: ML20209G715 (2)

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g "*  % UNITED STATES NUCLEAR REGULATORY COMMisslON I Df4, .E WA$mNGTON. D. C. 20555

[ September 28, 1984 .

s . .v MEMORAi;DUM FOR: William D. Travers, Deputy Program Director Till Program Office FROM: David J. Collins, Radiation Specialist TMI-2 Project Section

SUBJECT:

EVALUATION OF NEWBERRY TOWNSHIP SURVEY METER A flewberry Township beta-gama survey meter, equipped with an external detector, has reportedly been used as e reference to ascertain the operability of several privately owned survey instruments. Because of this, TMIPO obtained oral permission from the Newberry Township Emergency Management Director to evaluate the present condition of this meter. In its condition as of September 4,1984, the survey meter does not demonstrate reliable detection of a calibrated radiation field. The instrument should be serviced and calibrated prior to further use. This information was contained in a note I

accompanying the instrument which was returned to Newberry Township on September 4, 1984 Further details are presented below.

Instrument Type: CDV-700 Beta-Gama Survey Meter

.- Model: 6B Serial Number 126861 Manufacturer: Victoreen Instrument Company Owner: Newberry Township, York County, Pennsylvania Scale Ranges: XI O- 0.5 mR/hr, 0 - 300 counts / minute X10 0- 5 mR/hr, 0 - 3,000 counts / minute X100 0- 50 mR/hr, 0 - 30,000 counts / minute The instrument was evaluated at the GPU Nuclear radiological instrument facility on September 4,1984. At no time were any adjustments made to the instrument. The instrument remained in the control of TMIPO personnel at all times while at TMI.

The instrument was evaluated on a calibration range equipped with National Bureau of Standards (NBS) traceable sources. Source radiation levels were verified with .NBS traceable instruments. Gamma radiation response was determined with respect to a 100 millicurie 137-cesium source. Beta radiation response was determined with a uranium slab source. Since statements had been !

made that this instrument was alpha radiation sensitive, it was checked against a 239-plutonium alpha source emitting 50,800 disintegrations per minutc. As expected, no alpha radiation could be detected with this instrument. i 8509190669 8M829 "

PDR FOIA KUCHENB85-428 PDR

• William D. Travers September 28, 1984 l When the instrument was hand-held in a constant radiation field, meter deflection ranged from 1/3 to 2/3 full scale, and would not stabilize. I Because of this characteristic, this meter could only render information of i limited usefulness to a surveyor. The instrument did respond to a beta j radiation field from a uranium slab. No attempt was made to quantify the beta i response.

When the instrument was placed on a frame to eliminate any inadvertent movement, meter deflections on the X1 scale were 1/2 to 2/3 full scale.

Meter fluctuations on the X10 and X100 scales were substantially lower, but l did not stabilize. Failure of the instrument to stabilize in a constant - i radiation field indicates, a problem with the survey meter. Instrument technicians and their supervisors with experience with this type meter stated the problem most likely was related to the cable connecting the meter and ,

detector.  !

4 GAN . /

David J. Colli n ,

Radiation Specialist j TMI-2 Project Section cc: B. Snyder  ;

M. Reilly f W. Kirk /

R. Cook P. Grant l