The dosimeters used in irradiation processing commonly experience significant temperature rises whilst being irradiated. This needs to be accounted for when measuring absorbed dose following irradiation, as the alanine dosimeter signal has a small but known temperature dependence. Not taking this into account is a common pitfall when first starting out with alanine dosimetry systems.

It’s recommended that as part of the IQ & OQ, the temperature of the bunker is tracked and logged over a 12 month period to calculate the average annual temperature. This ensures when the calibration takes place, it’s requested at the average bunker temperature so  the calibration curve generated accounts for this. 

Given each irradiation facility is of a different design, and geography, the calibration curves from one facility to another cannot be shared, as these differences cannot be accounted for within the calibration.  

The two most common factors affecting the temperature within the bunker are a facilities geography and the quantity of cobalt-60 within the bunker. 

Facilities operating in warmer climates may see that the ambient air drawn into the bunker may be warmer than the temperature within the bunker itself. Further, the quantity of cobalt-60 also needs to be considered, as if there is a significant change in cobalt activity, the ambient temperature within the bunker will likely increase, which again could result in dose variations.

Should there be a wide range between the high and low temperatures seen within the bunker each year, then to mitigate the impact of on the calibration curve, it’s recommended that two calibrations are completed, at the temperature mid points of the high and low temperatures that are observed, to allow for seasonal temperature variances.