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Appendix F: Atomlab Dose Calibrator
Calibration and Traceability
This appendix describes the calibration procedures performed on the Atomlab Dose Calibrator
and the traceability to the National Institute of Standards & Technology.
Calibration & Traceability
The calibration of the Atomlab Dose Calibrators is directly traceable to the National Institute of
Standards & Technology, formerly the National Bureau of Standards (NBS). This is achieved
through the establishment of a set of working laboratory standards, the maintenance of these
working standards, and the use of these working standards to calibrate each Atomlab Dose
Calibrator.
The working standards consist of two ionization detectors identical to the detectors used in
each Atomlab dose Calibrator for radiation measurement and several long-lived radiation
sources.
The two standard ionization detectors have been calibrated using radionuclides that were
calibrated by the National Institute of Standards generating response numbers. These response
numbers were used to determine the photon response function of the ionization detectors. The
shielding configuration is identical to that of the Atomlab Dose Calibrator design.
The National Institute of Standards & Technology sources are in glass ampule form, and
because of the potential for breakage, they are not suitable for routine calibration. Instead the
working standards are in epoxy resin form in a plastic vial package. These standards have been
calibrated against the National Institute of Standards & Technology sources in the two standard
ionization detectors. Together, the detectors and the sources provide a high degree of accuracy
and redundancy. Periodically, the source activity is measured in the two standard detectors and
the results are compared to the expected decayed activity.
The Atomlab Dose Calibrator must first pass all electronic testing and operate for three days
prior to dose calibrator factory calibration. Calibration takes place with the Co-60 working
standard. The calibration value is stored in a special memory chip on the detector circuit board.
Calibration is verified by measuring the activity of all the working standards, including Co-60,
Cs-137, Ba-133, and Co-57.