Standardization of 226Ra solutions with descendants by 4παß LSC counting.

In this work, a method to standardize 226Ra solutions with descendants by 4παß liquid scintillation counting (LSC) has been used. The standardization can be carried out provided that the equilibrium state of 226Ra solutions, the counting efficiency of short-lived 214Po and/or the counter dead time are known. Procedures to obtain these requirements have been set up.

Standardization of non-equilibrium 210Pb solutions by LSC and 2πα counting.

A procedure for the standardization of 210Pb solutions in radioactive disequilibrium, or incompletely purified from its descendants, has been set up and successfully validated. The method, based on joint measurements of 210Po by alpha-particle spectrometry (2πα counting) with grid ionization chamber and liquid scintillation counting for overall activity estimation, is presented as an alternative to 210Pb measurement by LSC with α/ß discrimination.

Design and optimization of a proportional counter for the absolute determination of low-energy x-ray emission rates.

We recently presented the construction of a proportional counter for the absolute measurement of low-energy x-ray emission rates. Its main features were presented in a previous study, along with the testing of its performance as an absolute technique. Full details on its design, construction, and characterization processes are given in this paper. First, the analytical calculations and Monte Carlo simulations that led to the choice of optimal dimensions will be presented, followed by the study of the charge creation and the modeling of the electric field that confirmed that the criteria for a reproducible charge multiplication are met. Afterward, details on the electronics and gas control system will be provided. The dimensional measurements for the accurate determination of the solid angle will be described in detail. Special emphasis will be placed on the production of the detector window, which was made of reduced graphene oxide instead of beryllium. Some tests on the operation of the counter will be presented, namely, the measurement of spectra of several radionuclides that emit x-rays between 3 keV and 9 keV, as well as the fluorescence spectrum of chlorine, at 2.6 keV. A brief explanation of the determination of emission rates will be given, including the approach adopted for the treatment of the escape-peak area. The emission rate measured with the proportional counter was converted into activity concentration using the emission probabilities from the bibliography, in order to compare the results with those obtained by liquid scintillation counting, and both results were found to be in good agreement.

Absolute determination of low-energy X-ray emission rates with a proportional counter.

A defined-solid-angle proportional counter has been designed for the absolute determination of X-ray emission rates between 2 keV and 10 keV. The main features of the counter are described in this work, and spectra of two radionuclides with low-energy X-ray emissions are presented. The activity concentration of an 55Fe solution was determined by measuring the emission rate of three samples and using tabulated emission probabilities. This activity concentration is compared with the value obtained by liquid scintillation counting, and an excellent agreement has been found.

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.

Standardisation and half-life of 89Zr.

The nuclide 89Zr is being tested for the labelling of compounds with long blood circulation times. It decays by beta plus emission (22.8%) and by electron capture (77.2%) to 89Y. Its half-life has been determined by following the decay rate with two measurement systems; an Ionisation Chamber and an HPGe detector. The combination of six results gives a value of T1/2 = 78.333 (38) h, slightly lower than the DDEP recommended value of 78.42 (13) h. This radionuclide has also been standardised by liquid scintillation counting, 4πγ counting and coincidence techniques.

Study of the 243Am decay.

Gamma-ray emission probabilities for 243Am were published in 1996. Three new gamma transitions were then found: 46.84, 98.36 and 102.02keV. In the last evaluation by the Decay Data Evaluation Project, the emission probabilities of 46.84 and 102.02keV transitions were not included. Alpha-gamma coincidence measurements have been now used to check and revise the values for these two transitions and their emission probabilities. The emissions of the 31.13, 43.53, 74.66, 86.71 and 141.89keV transitions were also studied.

Standardisation and precise determination of the half-life of (44)Sc.

The half-life of the positron-emitter (44)Sc has been determined by following the decay rate with two measurement systems; an Ionisation Chamber and a HPGe detector. The combination of seven results gives a value of T1/2=4.042 (25)h, about 2% higher than the recommended value of T1/2=3.97 (4)h (Browne, 2011) and with a lower uncertainty. This radionuclide has also been standardised by coincidence counting, and liquid scintillation counting techniques. A (44)Ti/(44)Sc generator developed at CIEMAT was used to obtain the (44)Sc solutions used in all measurements.

Preparation and characterisation of a (226)Ra spiked slag as reference material for radioactive control of steelworks.

One of the issues of the European Research Project MetroMetal is to develop reference materials in order to provide SI-traceable radioactivity monitoring in foundries. For this purpose, a protocol for preparing a set of identical standard slag samples, containing known activity concentrations of (226)Ra, has been developed. This paper describes the preparation of the raw material, the characterisation in terms of its mineralogical, chemical and radiological features, the spiking procedure and the homogeneity testing of the spiked samples.

Standardization of 134Cs by three methods.

The nuclide 34Cs decays by beta-emission followed by gamma-deexcitation to 134Ba with a half-life T(1/2) = 2.065 a. It has been standardized by three methods: liquid scintillation counting (LSC), 4pi beta-gamma coincidence counting and 4pi gamma counting. In the LSC measurements, the CIEMAT/NIST method was used to calculate the efficiency. For the coincidence measurements, a conventional 4pi beta (proportional counter)-gamma(NaI) system was used. For the 4pi gamma standardization, a well-type Nal(Tl) detector was modeled with the Monte Carlo package PENELOPE, and the counting efficiency obtained by calculation. Results of the three methods agree within 0.65%.

Standardization of 110mAg by liquid scintillation and 4pibeta-gamma coincidence counting

The nuclide 110Ag is a beta-gamma emitter with a very complex decay scheme, including more than 50 gamma-rays. It has been standardized by two methods: liquid scintillation counting (LSC) and 4pibeta(pc)-gamma coincidence measurements. In the LSC measurements the CIEMAT/NIST method was used, with 3H being used as a tracer for efficiency calculations. In the 4pibeta(pc)-gamma standardization, Monte Carlo calculations have been made to determine the optimal measurement conditions. Results obtained with both methods for the activity concentration of the solution are in good agreement.