Results of an international comparison of activity measurements of 68Ge.

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 68Ge/68Ga solution. Results for the activity concentration, CA, of 68Ge 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)ß-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)kBqg-1, based on 14 results. The degrees of equivalence and their associated uncertainties are evaluated for each participant. Several participants submitted 3.6mL 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.

Standardization of 67Cu and calibration of the ionization chamber. Impurities and decay scheme problems.

This paper describes the standardization of 67Cu by the 4πß(PC)-γ coincidence method, and the calibration of ionization chamber. The difficulties were. (i) One of the excited levels of 67Zn has a half life of 9.10µs. (ii) A recent publication reconsiders the decay scheme parameters. (iii) The solution had a significant content of impurities. The conclusions were that the result of absolute standardization is less influenced by the decay scheme parameters and impurities than the measurements by ionization chamber.

Measurement of liquid scintillation sources of (210)Pb obtained from (222)Rn decay.

Liquid scintillation samples were filled with (222)Rn and the activity was measured with good precision after reaching the secular equilibrium with the progeny (218)Po, (214)Pb, (214)Bi and (214)Po. After decay of most of (222)Rn activity, the samples contain (210)Pb and progeny. The activities of (210)Pb and progeny can be calculated as a function of time using the initial (222)Rn activity. The samples were measured in a TDCR counter and the experimentally determined counting efficiencies are in accordance with previously published results.

Measurement of (124)I.

The paper describes the measurements performed at IFIN-HH regarding the creation of a Romanian (124)I standard, consisting of: absolute standardization of the solution by the application of the 4πß(PC)-γ coincidence method; Calibration of the CENTRONIC IG12/20A ionization chamber with a standardised solution and comparison with a calculated efficiency; γ-ray spectrometry activity measurement and determination of the impurity levels; Comparison of the results of the three methods.

Standardization of Tc-99 by two methods and participation at the CCRI(II)-K2. Tc-99 comparison.

The work accomplished within the participation at the 2012 key comparison of Tc-99 is presented. The solution was standardized for the first time in IFIN-HH by two methods: LSC-TDCR and 4π(PC)ß-γ efficiency tracer. The methods are described and the results are compared. For the LSC-TDCR method, the program TDCR07c, written and provided by P. Cassette, was used for processing the measurement data. The results are 2.1% higher than when applying the TDCR06b program; the higher value, calculated with the software TDCR07c, was used for reporting the final result in the comparison. The tracer used for the 4π(PC)ß-γ efficiency tracer method was a standard (60)Co solution. The sources were prepared from the mixture (60)Co+(99)Tc solution and a general extrapolation curve, type: N(ßTc-99)/(M)(Tc-99)=f [1-ε(Co-60)], was drawn. This value was not used for the final result of the comparison. The difference between the values of activity concentration obtained by the two methods was within the limit of the combined standard uncertainty of the difference of these two results.

Standardization of ¹8F and its use for the Romanian PET metrological traceability chain assurance.

This paper presents the work performed at IFIN-HH and at the users' sites, aimed to establish the (18)FDG Romanian PET traceability chain. It summarizes the operations: (i) Absolute standardization of a (18)F solution, by the 4πß(PC)-γ coincidence method; (ii) Control of gamma-ray impurity content and measurement of the activity by gamma ray spectrometry; (iii) Measurement of the half life, for detection of some short/long life positron emitter impurities; (iv) Calibration of the CENTRONIC IG12/20A ionization chamber; (v) Calibration of commercial radionuclide calibrators.

Results of an international comparison for the activity measurement of 177Lu.

An international Key Comparison of (177)Lu has recently been carried out. Twelve laboratories performed assays for radioactivity content on aliquots of a common master solution of (177)Lu, leading to eleven results submitted for entry into the Key Comparison Database of the Mutual Recognition Arrangement. A proposed Comparison Reference Value (CRV) was calculated to be 3.288(4)MBq/g using all eleven results. Degrees of equivalence and their uncertainties were calculated for each laboratory based on the CRV. Most of the values reported by the participating laboratories were within 0.6% of the CRV.

Standardization of 64Cu and 68Ga by the 4π(PC)ß-γ coincidence method and calibration of the ionization chamber.

The paper treats the application of the 4π(PC)ß-γ coincidence method for the standardization of the radionuclides (64)Cu and (68)Ga. The general coincidence equations are written. Two types of extrapolation were described and used in measurement: the positron-annihilation coincidence, and the counting of all emitted radiations; both methods are compared with respect to results, advantages and drawbacks. The impurities' content correction was applied. The standardized solutions were used to calibrate the ionization chamber CENTRONIC IG12/20A and to determine the gamma-rays emission intensities.

Standardization, decay data measurements and evaluation of 64Cu.

The purposes of this study were to create national activity standards of (64)Cu, to make possible the definition of an international key comparison reference value and to determine the decay data in order to improve the decay scheme. Four laboratories measured the activity of a (64)Cu solution; these results were compared through the International Reference System. Moreover, the laboratories carried out new measurements of the photon emission intensities and of the half-life. A new decay scheme was derived from these new values and the previously published ones.

The 222Rn standard system established at IFIN-HH, Romania.

The paper presents the (222)Rn Standard System realized at the Radionuclide Metrology Laboratory from IFIN-HH, Romania. It contains a Pylon solid (226)Ra source, and a glass circuit for circulation and recovery of (222)Rn in glass ampoules, at the 77K temperature. The radon can be recovered both in ampoules with liquid scintillator (LS), for absolute standardization of (222)Rn by liquid scintillation counting (LSC) (Cassette et al., 2006), and in evacuated ampoules as gas, simultaneously or by the transfer of radon from gas into LS ampoules, in order to establish the traceability chain. The absolute standardization consists in the registration of the double coincidence counting rate in LS, due to the whole sequence of short life components of the (222)Rn chain, in equilibrium conditions. The main correction applied to the measurement results is due to the decay of (214)Po during the extendable dead time of the system. The following procedure was applied to take it into account. The value of the base duration of the dead time was precisely measured and used for the data corrections. The measurements of each source were repeated during a period of several days, and the decay curve parameters were calculated. If the dead time value and the correction formulae, presented throughout the paper, were adequate, then the re-determination of the (222)Rn half life, T(1/2)=(3.8232+/-0.0008) d, using the decay curve of the corrected counting rates should be correct. On the other hand, the effective dead time values obtained by parallel calculations were compared. The paper presents the results obtained in the standardization of several sources, by LSC, and the evaluation of the uncertainties associated to the method.