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Accurate measurements were performed of the photon emission probabilities following the α decay of 235U to 231Th. Sources of highly enriched 235U were characterised in terms of isotopic composition by mass spectrometry and their activities were standardised by means of alpha-particle counting at a low defined solid angle. The standardised sources were subsequently measured by high-resolution γ-ray spectrometry with calibrated high-purity germanium detectors to determine the photon emission probabilities. Four laboratories participated in this work and reported emission probabilities for 33 γ-ray lines. Most of them agree with previously published evaluated data. In addition, new values are proposed for γ-lines which have been measured only once in the past. © 2017 The Authors

The GERDA experiment at the Laboratori Nazionali del Gran Sasso (LNGS) searches for the neutrinoless double beta decay of 76-Ge. In view of the GERDA Phase II data collection, four new 228-Th radioactive sources for the calibration of the germanium detectors enriched in 76-Ge have been produced with a new technique, leading to a reduced neutron flux from ( alpha; n ) reactions. The gamma activities of the sources were determined with a total uncertainty of 4 percent using an ultra-low background HPGe detector operated underground at LNGS. The emitted neutron flux was determined using a low background LiI(Eu) detector and a 3-He counter at LNGS. In both cases, a reduction of about one order of magnitude with respect to commercially available 228-Th sources was obtained. Additionally, a specific leak test with a sensitivity to leaks down to 10 mBq was developed to investigate the tightness of the stainless steel capsules housing the sources after their use in cryogenic environment., 14 pages, 5 figures, 3 tables

In 2014, comparisons of activity measurements of 99mTc using the Transfer Instrument of the International Reference System (SIRTI) took place at the VNIIM (Russian Federation) and at the ENEA-INMRI (Italy), with comparison identifier BIPM.RI(II)-K4.Tc-99m. Ampoules containing about 32 kBq of 99mTc solutions were measured in the SIRTI for three half-lives. There are now nine results in the BIPM.RI(II)-K4.Tc-99m comparison. This comparison is linked to the BIPM.RI(II)-K1.Tc-99m comparison and the key comparison reference value (KCRV) of the BIPM.RI(II)-K1.Tc-99m has been updated to include eligible results from BIPM.RI(II)-K4.Tc-99m. The degrees of equivalence between each equivalent activity measured in the SIR or the SIRTI 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).