Supplementary comparison CCRI(I)-S3 of standards for absorbed dose to water in ⁶⁰Co gamma radiation at radiation processing dose levels

A supplementary comparison of standards for absorbed dose to water in ⁶⁰Co fields used for calibrations at radiation processing dose levels has been completed. Alanine dosimeters from the NIST and the NPL were used as transfer dosimeters and all participant irradiations were carried out in self-shielded irradiators. Irradiations were also carried out at the BIPM to allow direct comparison of dose ratios with the Key Comparison BIPM.RI(I)-K4. No significant difference was seen between the dose ratios obtained using the NPL and NIST alanine systems, no significant impact of mailing on dosimeter response was noted, and the adopted protocol limited any dose rate effects to the level of Type A uncertainties. The national standards of the participants are in agreement within the standard uncertainties, which are in the range from 1 to 2 parts in 10².