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Efficiency extrapolation is a common technique in the standardization of radionuclides by the technique of 4pibeta-gamma coincidences. It can be achieved in two ways: adding thin films onto the radioactive source or by electronic discrimination in a pressurized 4pibeta-gamma system. The last case is the most extensively used actually in metrology laboratories. There is a need to know the electron energy loss inside the proportional counter as a function of the electron energies and working pressures. Calculations of electron energy loss have been performed for electron energies in a range from a few keV to 2 MeV in a mixture of Ar(90%) CH4(10%) and for pressures ranging from 100 to 2000 kPa in a 5 cm radius proportional counter. Wall effects, such as electron backscattering, are included in the calculations. Results are provided in the form of graphs and some recommendations are given about the optimal values of the energies that can be used to perform the extrapolation in the standardization of some radionuclides.

Conference of 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013 ; Conference Code:102802; International audience; The radioactivity measurement techniques developed within the EURAMET EMRP 'MetroFission' Joint Research Project, were aimed at performing on-site activity measurements at the primary standard level (4πβ-γ coincidence counting) for a wide range of radionuclides utilizing recent advances in high-speed digital sampling and digital signal processing. The state-of-the-art technology employed within this project provides up to 14-bit digitizer systems operating with sampling rates in the order of 108 to 109 samples-per-second, incorporating on-board FPGA devices, which greatly enhances the application of digital signal processing for the implementation of digital coincidence counting. These devices when coupled to suitable analysis software, demonstrate a significant improvement in the provision of primary standards of radioactivity. This manuscript provides a description of the systems employed, along with recommendations regarding optimization of the digital sampling of signals from photo-multiplier tubes and pre-amplifiers and compare the benefits of 'off-line' versus 'on-line' 4πβ-γ digital coincidence counting systems.

The half-life of the positron-emitter (68)Ga has been measured by following the decay rate with two systems based on ionization chamber and Ge detectors. The decay rate was measured for periods of time up to 10 half-lives. The combination of the 6 results obtained with both systems gives a value of T1/2=67.845(18) min, in good agreement with recommended data and with an uncertainty lower than any other previously reported value.

Since 1975, seven national metrology institutes (NMI) have submitted eleven samples of known activity of 113Sn to the International Reference System (SIR) for activity comparison at the Bureau International des Poids et Mesures (BIPM), with comparison identifier BIPM.RI(II)-K1.Sn-113. The values of the activity submitted were between about 0.7 MBq and 22 MBq. The present primary standardization results for the PTB, Germany and the LNE-LNHB, France, replace their earlier results of 1989 and 1992, respectively. A key comparison reference value (KCRV) has been evaluated for the first time for 113Sn. There are only three results remaining in the BIPM.RI(II)-K1.Sn-113 comparison, all the previously published ones being outdated. The degrees of equivalence between each of these three equivalent activities measured in the SIR and the KCRV have been calculated and the results are given in the form of a table. A graphical presentation is also given. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The half-life of the positron-emitter (18)F has been measured by following the decay rate with three systems: ionization chambers, Ge detectors and coincidence with fast scintillators. The decay rate was measured for periods of time up to 9 half-lives. The combination of the results obtained with the three measuring systems gives a value of T(1/2)=1.82871 (18)h, in good agreement with recommended data and with an estimated uncertainty lower than any other previously reported value.

The nuclide 67Ga is widely used in nuclear medicine for diagnostic purposes. It decays with a half-life of 3.259 days to 67Zn, a stable nuclide. The decay mode is electron capture with several branches followed by gamma-de-excitation. One of the excited levels of 67Zn with energy 93 keV has a half-life of 9.1 micros, which makes its absolute standardization by coincidence methods difficult. Two methods were used to standardize a solution of this nuclide: (a) 4pi-EC(PPC)-gamma(NaI) coincidence counting with efficiency extrapolation to infinite dead time and (b) high-efficiency 4pigamma counting with a well-type NaI detector.

Detailed uncertainty reporting is imperative for proficiency tests and comparison exercises because uncertainties need to be comparable and trusted by all the participants. Even though participants do their best to follow the Guide to the Expression of Uncertainty in Measurement, ambiguities and divergences about uncertainty evaluation remain. Consequently, to analyze the situation, the CCRI (II) Uncertainties Working Group proposed a comparison exercise (CCRI(II)-S7) about the uncertainty evaluation of a relatively simple primary activity measurement: the standardization of a 60Co source by coincidence counting. To be able to understand how various NMIs calculate coincidence counting uncertainties, our study focused on two of the dominant uncertainty components commonly quoted for 4πβ-γ coincidence counting in the International Reference System (SIR) submissions and Key Comparison exercises: efficiency-extrapolation and weighing. Participants from twelve different laboratories were sent the same set of measurement data from the analysis of a 60Co solution standardized at the National Physical Laboratory (NPL). Our study demonstrated the extent of the different interpretations of the uncertainty components. Some factors causing large discrepancies were isolated and are discussed. Further studies of other techniques using a similar approach would be beneficial for the metrology community. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).