HPPOS-279 PDR-9306140215

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