Developing a method and deriving an uncertainty budget for the internal calibration of dosemeters for radiographic equipment

Any institution wishing to perform an internal cross calibration of its diagnostic dosemeters should first quantify the uncertainty associated with this to demonstrate that it remains appropriate for the measurements being undertaken. An uncertainty budget for internal cross calibration that covers a range of locally used dosemeters has been derived using the methodology of the International Atomic Energy Agency. The specific internal cross calibration protocol requirements necessary for this uncertainty budget to be valid are discussed. The final quantified uncertainty is 5.31%; this is dominated by the 5% uncertainty associated with the calibration of the reference instrument. The next largest contributions are from differences in temperature and pressure and dosemeter energy dependence. It has been demonstrated that with careful adherence to a well designed internal cross calibration protocol, dosemeters can be calibrated in-house against a calibrated reference dosemeter with very little increase in the associated calibration uncertainty.