Results of an international comparison of activity measurements of $^{68}$Ge

J. T. Cessna (1) , R. Fitzgerald (1) , E. Zimmerman (1) , L. Laureano-Pérez (1) , E. Bergeron (1) , F. van Wyngaardt (2) , M. Smith (2) , T. Jackson (2) , B. Howe (2) , J. da Silva (3) , A. Iwahara (3) , P.A.L. da Cruz (3, 4) , M. Zhang (5) , H. Liu (5) , J. Liang (5) , Carole Fréchou (6) , Christophe Bobin (6) , Philippe Cassette (6) , K. Kossert (7) , O. Nähle (7) , J. Marganiec-Gałązka (7) , L. Joseph (8) , A. Ravindra (8) , D.N. Kulkarni (8) , A. Yunoki (9) , Y. Sato (9) , K.B. Lee (10) , J. R. Lee (10) , . Agung (10) , T. Dziel (11) , A. Listkowska (11) , Z. Tymiński (11) , M. Sahagia (12) , A. Antohe (12) , M. Ioan (12) , A. Luca (12) , M. Krivosek (13) , J. Ometakova (13) , A. Javornik (13) , M. Zalesakova (13) , E. García-Toraño Martinez (14) , M. Roteta (14) , M. Mejuto (14) , Y. Nedjadi (15) , F. Juget (15) , M.-C. Yuan (16) , C.Y. Yeh (16) , E. Yeltepe (17) , A. Dirican (17) , J. Keightley (17) , A. Pearce (18)

1 NIST - National Institute of Standards and Technology [Gaithersburg]
2 ANSTO - Australian Nuclear Science and Technology Organisation [Australie]
3 Laboratório Nacional de Metrologia das Radiações Ionizantes
4 Instituto de Radioproteção e Dosimetria
5 National Institute of Metrology [Beijing]
6 LNHB - Laboratoire National Henri Becquerel
7 PTB - Physikalisch-Technische Bundesanstalt [Braunschweig]
8 BARC - Bhabha Atomic Research Centre
9 AIST - National Institute of Advanced Industrial Science and Technology
10 KRISS - Korea Research Institute of Standards and Science [Daejon]
11 National Centre for Nuclear Research Radioisotope, Centre POLATOM
12 Horia Hulubei National Institute for Physics and Nuclear Engineering
13 Slovenský Metrologický Ústav
14 CIEMAT - Centro de Investigaciones Energéticas Medioambientales y Tecnológicas [Madrid]
15 Institut Universitaire de Radiophysique Appliquée
16 Institute of Nuclear Energy Research
17 Turkish Atomic Energy Authority
18 NPL - National Physical Laboratory [Teddington]

An international key comparison, identifier CCRI(II)-K2.Ge-68, has been performed. The National Institute of Standards and Technology (NIST) served as the pilot laboratory, distributing aliquots of a $^{68}$Ge/$^{68}$Ga solution. Results for the activity concentration, CA, of $^{68}$Ge at a reference date of 12h00 UTC 14 November 2014 were submitted by 17 laboratories, encompassing many variants of coincidence methods and liquid-scintillation counting methods. The first use of 4π(Cherenkov)β-γ coincidence and anticoincidence methods in an international comparison is reported. One participant reported results by secondary methods only. Two results, both utilizing pure liquid-scintillation methods, were identified as outliers. Evaluation using the Power-Moderated Mean method results in a proposed Comparison Reference Value (CRV) of 621.7(11) kBq g$^{−1}$, based on 14 results. The degrees of equivalence and their associated uncertainties are evaluated for each participant. Several participants submitted 3.6 mL ampoules to the BIPM to link the comparison to the International Reference System (SIR) which may lead to the evaluation of a Key Comparison Reference Value and associated degrees of equivalence.

Keywords: Germanium-68; Equivalence; International comparison; Gallium-68; CALIBRATION METHODOLOGY; STANDARDIZATION; Metrology; ionizing radiation; radioactivity; calibration; Primary activity measurement; Reference material; Nuclear instrumentation; instrumentation

Domains: Nuclear Experiment [nucl-ex]

J. T. Cessna, R. Fitzgerald, E. Zimmerman, L. Laureano-Pérez, E. Bergeron, et al.. Results of an international comparison of activity measurements of $^{68}$Ge. Applied Radiation and Isotopes, 2018, 134 (SI), pp.385 - 390. ⟨10.1016/j.apradiso.2017.10.052⟩. ⟨cea-01773729⟩