We have presented to the CCRI the new BIPM graphite cavity primary standard for the determination of air kerma in gamma ray beams, based on the differential volume measurements and Monte Carlo calculations. The new value of the BIPM's air kerma rate, which is indeed higher than the previous value, is chiefly a result of the increased value to the correction factor for axial non-uniformity of the beam, which has been determined with an improved precision by using Monte Carlo calculations. The new value was accepted by the CCRI in May subject to a scientific publication describing the results, after which time it will be announced and introduced from a fixed date. The prototype graphite calorimeter for absorbed dose to water is being constructed ready for the first trials. The concept is based on the pre-determined value of the specific heat capacity of the graphite core which is under measurement at the moment. The primary standard free air chamber for mammography dosimetry has been designed and constructed and is presently being compared with the low-energy free air standard.
Seven new dosimetry comparisons and some further measurements for an earlier comparison have been made. No progress has been made regarding the planned brachytherapy comparison due to lack of resources. Three comparison reports have been published and the others are at different draft stages. Twenty-one national secondary standards have been calibrated and the Quality System for calibrations successfully underwent its second peer-review. Continuing effort was expended to comply with French environmental regulations concerning high activity 60Co sources, including a series of in-house seminars on radiation protection.
We have completed the analysis of the 55Fe comparison that was held in 2006 and the results have the potential to support the measurement of 23 other radionuclides through the grouping system set up by the CCRI(II). Of the nineteen laboratories that participated in this comparison, two had results that differed significantly from the key comparison reference value and this is being investigated. Following the significant delays in receiving the samples experienced by some NMIs, caused by the difficulties in cross-border movement of radioactive material, a seminar was presented to the IAEA on the margins of their General Conference, and they offered their support for any international effort in this respect.
Thirteen laboratories submitted ampoules to seventeen of the BIPM ongoing activity comparisons using the International Reference System (SIR). Studies of 237Np, 241Am and 85Kr measurements have been made to support international comparisons and 99Tcm was measured successfully in both the SIR and the SIR transfer instrument to provide the link needed to extend such comparisons specifically to NMI on-site measurements for short-lived radionuclides. The new SIR measurement system continues to produce consistent results and should be adopted at the end of 2007. Impurity activity levels were measured using the BIPM Ge(Li) gamma spectrometer for seven radionuclides submitted for comparisons. Due to lack of resources, no progress has been made in calibrating the HPGe spectrometer. The BIPM Quality System has been extended to include the SIR, which was successfully peer-reviewed at the end of 2006.
The Section has given strong support to both the Consultative Committee for Acoustics, Ultrasound and Vibration and the Consultative Committee for Ionizing Radiation, and their associated meetings held over 23 days in the last 12 months.
Summary
