U.S. Nuclear Regulatory Commission

Technical Assistance Request Regarding Electronic Calibration of Survey Instruments

HPPOS-279 PDR-9306140215

Title: Technical Assistance Request Regarding Electronic

Calibration of Survey Instruments

See the memorandum from J. E. Glenn to R. R. Bellamy dated

October 30, 1991. This memo responds to a technical

assistance request by Region I, dated September 16, 1991,

regarding a determination of the acceptability of the

survey meter calibration protocol proposed by St. Barnabas

Medical Center. The proposed protocol would allow the

licensee, St. Barnabas Medical Center, to do calibrations

of lower ranges on GM instruments with an electronic pulse

generator.

The substitution of an electronic pulse generator for

radiation from a calibrated radioactive source to calibrate

a radiation detection instrument is not acceptable. Use of

the electronic pulse generator will properly calibrate the

electronics, but will not determine whether the detector is

operating properly. The licensee indicated in the TAR that

Ludlum Measurements, Inc., used only electronic means for

calibrations on the lower scales. Ludlum Measurements,

Inc., was contacted to verify this assertion. A Ludlum

representative clarified that they first calibrate the

electronics with the electronic pulse generator, then

reattach the probe and make measurements in a radiation

field to find the conversion factor from counts per minute

to millirem per hour.

If the licensee determines that due to the fluctuations of

background radiation, precise calibration of the lowest

scale of the instrument is not possible, the licensee may

choose to label the lowest scale with the most conservative

three methods. The first possibility is to label the

lowest scale by the average correction factor obtained from

the radiation measurements. The second possibility is to

make a graph from which the correction factor may be

deduced. The third possibility is to show that the scale

was checked for function but not calibrated, or indicate

that the scale is not operative. [NOTE: If this scale is

necessary to show compliance with NRC's regulations or the

licensee's license, then the instrument will be considered

out of calibration and in noncompliance.]

Regulatory references: 10 CFR 20.1501, 10 CFR 35.51

Subject codes: 6.4

Applicability: All