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In this paper we describe experiments on two enriched 40 K solutions to accurately determine decay data. The first solution was measured in 2004/2005 by means of a gamma-ray spectrometer with low background and a liquid scintillation (LS) counter to apply the CIEMAT/NIST efficiency tracing method. A combination of results yields an emission probability of the 1461 keV gamma-rays of P γ  = 0.1030(11) which is lower than current results of data evaluations. The activity concentration of the second solution was also determined by means of LS counting, but here, the CIEMAT/NIST efficiency tracing method as well as the TDCR method were applied. Again, the result was combined with that of independent gamma-ray spectrometry and the gamma-ray emission probability was found to be P γ  = 0.1029(9) in good agreement with the result obtained from the first solution. A combination of both experiments yields P γ  = 0.1029(9). The spectra of a TriCarb LS counter were carefully analyzed and a beta minus emission probability [Formula: see text]  = 0.8954(14) was determined. The new results for P γ and [Formula: see text] indicate that the overall probability of the decay via EC in recent data evaluations is overestimated. The LS counting efficiencies were computed with a stochastic model and up-to-date calculations of the beta spectrum and fractional EC probabilities were used. The final activity result of the second solution is combined with the outcome of a comprehensive isotopic analysis to determine the half-life of 40 K which is found to be 1.2536(27) ·10 9 years. All above-stated uncertainties are standard uncertainties (k = 1)., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

166Ho (T 1/2 ≈ 26.8 h) is an emerging theragnostic radionuclide of interest in nuclear medicine due to its peculiar decay scheme, featuring high-energy β− emission (≈ 1.8 MeV) coupled with the main gamma-ray emission (≈ 80.6 keV). Using the new 166Ho activity standard and the well-calibrated, high-energy resolution HPGe detector, both available at ENEA-INMRI, a new determination of several 166Ho gamma-ray emission intensities, I γ , was performed with low uncertainty. The new I γ values contributed to the Decay Data Evaluation Project. • 166Ho and its use in nuclear medicine as theragnostic radionuclide. • Absolute activity measurements by Triple-to-Double Coincidence Ratio (TDCR) technique. • Hidex and portable ENEA-INMRI TDCR counters. • Gamma-ray spectrometry technique. • 166Ho gamma-ray emission intensities. [ABSTRACT FROM AUTHOR]

The Bureau International des Poids et Mesures (BIPM) is developing, with the support of national metrology institutes, an extension to the existing international reference system for international comparisons in radionuclide metrology. The extended system is addressing pure α-, pure β-emitting and some electron capture-decaying radionuclides. The new system is based on a custom-built liquid scintillation counter and the triple-to-double coincidence ratio (TDCR) technique. Particular emphasis was placed on long-term stability and excellent reproducibility in sample preparation. The analytical method is based on a special approach that uses the TDCR value as a parameter to compensate for fluctuations caused by changes in detection efficiency or photomultiplier asymmetries that cannot be excluded when considering very long periods. Measures for quality assurance were established. They are based on periodic controls of unquenched toluene-based liquid scintillation sources with 3H and 14C. In this way, the reproducibility of the system results is demonstrated for a test period of about twenty months. [ABSTRACT FROM AUTHOR]

The accuracy of activity determination for activated nuclide 56Mn is the key to the manganese bath method applying to the characterization of radionuclide neutron source. As an alternative to the 4π(Č)-γ method, TDCR-Čerenkov method could also be applied to the measurement of 56Mn in the manganese bath device, if the existing calculation model is extended. There are two difficulties when the existing TDCR-Čerenkov method is applied to the activity determination of 56Mn. One is that the efficiency computation of gamma transitions, and the other is the interference contributed by Čerenkov photons emitted in the photomultiplier windows induced by Compton scattering. In this study, the above two difficulties are solved by extending the calculation model. For efficiency computation, the decay scheme of 56Mn is taken into account in the calculation of efficiency. Among them, the efficiency of gamma transition is calculated from the simulated secondary electronic spectra. In addition, Čerenkov photons emitted in photomultiplier windows are corrected by additional light proof experiment and improved calculation model. The results derived from this extended method are in good agreement with other standardization technique. • 56Mn is measured by means of TDCR counter. • The TDCR-Čerenkov method is extended for complex decay schemes. • The interference contributed by Čerenkov photons emitted in the PMT induced by Compton scattering is corrected. [ABSTRACT FROM AUTHOR]

An activity standard for 212Pb in equilibrium with its progeny was realized, based on triple-to-double coincidence ratio (TDCR) liquid scintillation (LS) counting. A Monte Carlo-based approach to estimating uncertainties due to nuclear decay data (branching ratios, beta endpoint energies, γ-ray energies, and conversion coefficients for 212Pb and 208Tl) led to combined standard uncertainties ≤ 0.20 %. Confirmatory primary measurements were made by LS efficiency tracing with tritium and 4παβ(LS)-γ(NaI(Tl)) anticoincidence counting. The standard is discussed in relation to current approaches to 212Pb activity calibration. In particular, potential biases encountered when using inappropriate radionuclide calibrator settings are discussed. • A solution of 212Pb in equilibrium with its progeny was standardized for activity • Triple-to-double coincidence ratio (TDCR) liquid scintillation counting was used • Efficiency tracing and anticoincidence provided confirmatory measurements • Settings for radionuclide calibrators are discussed • Earlier recommended radionuclide calibrator settings did not account for all progeny [ABSTRACT FROM AUTHOR]

A new 18 F primary standardization carried out at ENEA-INMRI by three different absolute techniques, i.e. 4πγNaI(Tl)γ high-efficiency counting, TDCR and 4πβ(LS)-γ[NaI(Tl)] coincidence counting method, allowed the calibration of a fixed well-reentrant IG11 ionization chamber (IC), with an uncertainty lower than 1%, and to check the calibration factor of a portable well-type IC NPL-CRC model, previously calibrated. By the new standard the ENEA-INMRI was linked to the BIPM International Reference System (SIR) through the BIPM SIR Transfer Instrument (SIRTI). [ABSTRACT FROM AUTHOR]

Technetium-Tc is the most widely used radionuclide for obtaining diagnostic imaging in nuclear medicine and its demand is growing every year. In order to provide metrological traceability to producers and end users in Brazil to fulfil nuclear regulatory requirements for radiopharmaceuticals, National Laboratory of Ionizing Radiation Metrology/Institute of Radioprotection and Dosimetry attended, in 2013, an activity comparison measurement of Tc through BIPM Transfer Instrument SIRTI. The measurement results and the degree of equivalence between the key comparison reference value and LNMRI value are presented. The LNMRI result agreed with the measured value by SIRTI within one standard uncertainty. [ABSTRACT FROM AUTHOR]

The triple to double coincidence ratio (TDCR) liquid scintillation measurement technique is commonly used in national metrology institutes (NMIs) to perform standardization of pure beta emitters. The LNE-LNHB historical device, RCTD1, is a quite large device, which has been developed and commonly used over the past 30 years with its associated electronics for measurements of various radionuclides. During the last 4 years LNE-LNHB has developed two new portable TDCR devices. Such portable instrumentation gives end-users access to a reference measurement method that can be used for a large number of radionuclides. It addresses a wide range of industrial and medical applications for radionuclide metrology, including calibrations of solutions containing short-lived radionuclides, avoidance of radioactive source transportation, and performing on-site comparison to promote radionuclide metrology harmonization. In this paper, we will present the newly developed portable TDCR liquid scintillation measurement systems. Two kinds of devices have been developed and designed at LNE-LNHB and built using fused deposition modelling (FDM) 3D printing: a mini-TDCR (25 cm diameter, 10 cm height) and a micro-TDCR (16 cm diameter, 10 cm height). After a detailed discussion of the design and the possibilities offered by 3D printing for their conception, this paper will present the performance of the devices obtained for several radionuclides. The results will be compared with the RCTD1 in order to validate the performance of the new devices. They exhibit improved performance, such as higher detection efficiency, and include various useful tools for proper on-site metrology. The first tests, which were performed in Orsay Hospital (CEA/SHFJ) and in another laboratory (IRSN), allowed us to show the very good overall performance of the systems including their outstanding linearity, which was tested in the range from 430 000 s−1 down to 160 s−1 in the double coincidences channel. Applications of the developed systems for high and low activity measurements are also discussed. Finally, the portable device has been used for half-life measurements in order to check for impurities in a radio-pharmaceutical solution. [ABSTRACT FROM AUTHOR]

Abstract: The triple-to-double coincidence ratio (TDCR) method is frequently used to measure the activity of radionuclides decaying by pure β emission or electron capture (EC). Some radionuclides with more complex decays have also been studied, but accurate calculations of decay branches which are accompanied by many coincident γ transitions have not yet been investigated. This paper describes recent extensions of the model to make efficiency computations for more complex decay schemes possible. In particular, the MICELLE2 program that applies a stochastic approach of the free parameter model was extended. With an improved code, efficiencies for β−, β+ and EC branches with up to seven coincident γ transitions can be calculated. Moreover, a new parametrization for the computation of electron stopping powers has been implemented to compute the ionization quenching function of 10 commercial scintillation cocktails. In order to demonstrate the capabilities of the TDCR method, the following radionuclides are discussed: 166mHo (complex β−/γ), 59Fe (complex β−/γ), 64Cu (β−, β+, EC and EC/γ) and 229Th in equilibrium with its progenies (decay chain with many α, β and complex β−/γ transitions). [Copyright &y& Elsevier]

Abstract: The activity concentration of a solution of 99Tc was absolutely determined by liquid scintillation measurements based on the triple-to double-coincidence ratio method (TDCR) and compared with the results given by 4πβ(LS)-γ(NaI) live-timed anticoincidence (with extending dead-time) and classical 4πβ(PC)-γ(NaI) coincidence counting systems based on using 60Co as the efficiency-tracing radionuclide. The results of anticoincidence and coincidence counting are, respectively, 0.18% and 0.66% higher than the result from TDCR measurements, but they are consistent within uncertainties. [Copyright &y& Elsevier]

Abstract: A new primary standardization of 18F by NIST is reported. The standard is based on live-timed beta-gamma anticoincidence counting with confirmatory measurements by three other methods: (i) liquid scintillation (LS) counting using CIEMAT/NIST 3H efficiency tracing; (ii) triple-to-double coincidence ratio (TDCR) counting; and (iii) NaI integral counting and HPGe γ-ray spectrometry. The results are reported as calibration factors for NIST-maintained ionization chambers (including some “dose calibrators”). The LS-based methods reveal evidence for cocktail instability for one LS cocktail. Using an ionization chamber to link this work with previous NIST results, the new value differs from the previous reports by about 4%, but appears to be in good agreement with the key comparison reference value (KCRV) of 2005. [Copyright &y& Elsevier]

Abstract: In the triple-to-double coincidence ratio (TDCR) method of liquid scintillation counting, unaccounted or improperly accounted impurities can result in lower-than-expected or higher-than-expected recovered activities, depending on the counting efficiency of the nuclide of interest, the counting efficiency of the radionuclidic impurity, and the amount of impurity present. We describe these general dependences using a simple model. The trends predicted by the model are tested experimentally using a series of mixed 241Am/3H and 63Ni/3H sources. An “impurity surface” is derived to facilitate an intuitive grasp of impurity phenomena in TDCR. [Copyright &y& Elsevier]

Abstract: Beta-emitters 36Cl and 63Ni, and the electron capture radionuclide 55Fe were used to calibrate a secondary standardization instrument Quantulus-1220TM. An external standard technique was applied to assess the quenching level of samples. Nitromethane as an artificial quencher was used for sample preparation at different quenching levels. The dependence of the counting efficiency on the quenching level was determined. Samples of beta-emitters were re-measured with the triple-to-double coincidence ratio (TDCR) primary standardization instrument. The specific activities of beta-emitters were determined with the help of the software TDCRB-02 and compared with known values. It was found that for 36Cl and 63Ni the discrepancy was 0.9% and 2.7%, respectively, within the specified uncertainty limits. A new sample with 90Sr was prepared and measured with the TDCR device. In this case, the divergence from the expected value was 1.7%. Results suggest the suitability of the TDCR techniques for low-level counting. [Copyright &y& Elsevier]

Abstract: In liquid scintillation (LS) counting, the CIEMAT/NIST efficiency tracing method and the triple-to-double coincidence ratio (TDCR) method have proved their worth for reliable activity measurements of a number of radionuclides. In this paper, an extended approach to apply a free-parameter model to samples containing a mixture of solid plastic scintillation microspheres and radioactive aqueous solutions is presented. Several beta-emitting radionuclides were measured in a TDCR system at PTB. For the application of the free parameter model, the energy loss in the aqueous phase must be taken into account, since this portion of the particle energy does not contribute to the creation of scintillation light. The energy deposit in the aqueous phase is determined by means of Monte Carlo calculations applying the PENELOPE software package. To this end, great efforts were made to model the geometry of the samples. Finally, a new geometry parameter was defined, which was determined by means of a tracer radionuclide with known activity. This makes the analysis of experimental TDCR data of other radionuclides possible. The deviations between the determined activity concentrations and reference values were found to be lower than 3%. The outcome of this research work is also important for a better understanding of liquid scintillation counting. In particular the influence of (inverse) micelles, i.e. the aqueous spaces embedded in the organic scintillation cocktail, can be investigated. The new approach makes clear that it is important to take the energy loss in the aqueous phase into account. In particular for radionuclides emitting low-energy electrons (e.g. M-Auger electrons from 125I), this effect can be very important. [Copyright &y& Elsevier]

nalysis of alpha and beta emitters in aerosol filters and swabs of different materials by liquid scintillation counter is discussed. This method appears suitable for fast determination of activity of radionuclides due to direct alpha and beta separation, measurement in 4π geometry and without sample treatment. The selected group of radionuclides was chosen with respect to military significance, radiotoxicity, and possibility of potential misuse. Sr and Pu were selected as model radionuclides. Three types of filters were examined, and the attention was also focused on optimizing the type and volume of LSC cocktail. The efficiencies for Pu and Sr were 90% and 79%, respectively. This method was the most effective for the glass fiber filters measured with the MaxiLight cocktail. [ABSTRACT FROM AUTHOR]

Abstract: The methods to compute the counting efficiency of electron-capture nuclides in liquid scintillation counting have been improved in several previous studies. The main improvements comprise a more realistic treatment of the ejection of photoelectrons and subsequent rearrangement processes in the atomic shell as well as a more detailed atomic rearrangement model. The latter was realized in the MICELLE code by means of a new stochastic approach. This new model was also developed to account for energy deposits within micelles. The recent improvements have now been combined in an updated version of the MICELLE code, which also makes the computation of the counting efficiency of complex decay schemes possible. In this paper, we describe and discuss recent extensions and improvements of the models and further corrections. The calculated counting efficiencies of selected radionuclides are compared with the experimental data obtained by liquid scintillation counting. For the measurements, we use standard solutions, which were calibrated by other methods. [Copyright &y& Elsevier]

Abstract: The nuclide 241Am decays by alpha emission to 237Np. Most of the decays (84.6%) populate the excited level of 237Np with energy of 59.54keV. Digital coincidence counting was applied to standardize a solution of 241Am by alpha–gamma coincidence counting with efficiency extrapolation. Electronic discrimination was implemented with a pressurized proportional counter and the results were compared with two other independent techniques: Liquid scintillation counting using the logical sum of double coincidences in a TDCR array and defined solid angle counting taking into account activity inhomogeneity in the active deposit. The results show consistency between the three methods within a limit of a 0.3%. An ampoule of this solution will be sent to the International Reference System (SIR) during 2009. Uncertainties were analysed and compared in detail for the three applied methods. [Copyright &y& Elsevier]

The responses of the three photomultiplier tubes (PMTs) in a triple-to-double coincidence ratio (TDCR) liquid scintillation (LS) system are often not identical. Such asymmetries can have a significant influence on activity determinations. The problem is often solved by means of a minimization algorithm which can easily be applied when analytical methods are used for the efficiency calculation, as is usually done for pure beta emitters. However, for radionuclides with more complex decay schemes, the counting efficiencies are often calculated with stochastic methods and the computation of the required corrections becomes very challenging. This paper presents a new numerical method to overcome the asymmetry problem for such complex decays and a comprehensive study on 55Fe is described in detail. For the measurements, the asymmetry was varied by means of grey filter films which were placed in front of one of the photomultiplier tubes. In the case of the pure electron-capture (EC) radionuclide 55Fe, the asymmetry can also be taken into account with a very simple correction which is derived assuming monoenergetic emissions. This work is also of great importance for the planned extension of the International Reference System (SIR) at the BIPM which will be used for international comparisons in radionuclide metrology. • PMT asymmetries in TDCR systems and related corrections are discussed. • A new method based on a stochastic model is presented and applied to 55Fe. • A simple correction based on a monoenergetic assumption is presented. • Experimental studies indicate that both corrections work well for 55Fe. • The monoenergetic approach is very useful as a comparison indicator for ESIR. [ABSTRACT FROM AUTHOR]

This work presents the design and the basic features of a newly developed front-end digital pulse processing device for the application of the triple-to-double coincidence ratio (TDCR) method in liquid scintillation (LS) counting. The device (hereafter called nanoTDCR) allows coincidence counting of the signals from LS counters equipped with three photomultiplier tubes (PMT) and is designed for the primary standardization of radionuclides by the TDCR method. In contrast with other front-end TDCR acquisition systems developed by metrology institutes, it uses extendable dead-time systems in each PMT channel. The system allows simultaneous counting within two different base dead-time durations and two different coincidence windows. The important characteristics and the operation of the device are presented. The specific metrological features of the system are discussed, including the observed linearity of the system, tested up to 90 ks−1 with more than 95% dead-time. Several applications of TDCR measurements with the nanoTDCR device are demonstrated: absolute standardization of pure beta radionuclides (3H, 90Sr/90Y), standardization of radionuclides decaying through electron-capture followed by gamma de-excitation (103Pd, 103mRh) and absolute activity measurements of 222Rn. The use of this system for the measurement of the decay of radionuclides is illustrated by the determination of the half-lives of 103mRh, 223Ra and the assessment of the concentration of a pure-beta impurity, 33P in 32P. [ABSTRACT FROM AUTHOR]