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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]

A liquid scintillation background sample was measured daily in a custom-built TDCR counter for more than 17 months. The double and triple coincidence counting rates exhibit an annual sinusoidal fluctuation with a maximum in winter and a minimum in summer. Possible correlations with air temperature, air humidity, radon concentration and secondary cosmic radiation were investigated. The observation of a correlation with the ambient dose equivalent rate H ˙ * (10) SCR originating from the charged component of secondary cosmic radiation and an anti-correlation with the effective atmospheric temperature T eff suggest that the seasonal fluctuations in the background counting rate may be primarily driven by temporal variations in the muon flux at ground level. Additionally, a correlation was found with the indoor 222Rn concentration in air. • A long-term TDCR measurement of a dummy sample was analyzed. • A seasonal variation of counting rates was found with a maximum in winter. • Possible correlations were investigated. • The fluctuations may be primarily driven by secondary cosmic radiation. • Additionally, a correlation was found with the indoor 222Rn concentration. [ABSTRACT FROM AUTHOR]

Measurements were made using the TDCR method. POLATOM prepared and distributed for the key comparison participants the 55Fe solution and 55Fe ready-to-measure sources in the Ultima Gold™ scintillator in polyethylene vials. The stability of the sources was confirmed. Source counting efficiency decreased proportionally with time by about 0.7% per month, possibly due to colour quenching. The POLATOM measurement result was consistent with the key comparison reference value. The nuclear data for 55Fe were adopted in accordance with the KCWG(II) recommendation. Measurement results obtained in non-diffusive (glass) vials were lower than in diffusive vials. [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]

When employing the TDCR method for standardization of low-activity liquid scintillation samples, fluctuations in system background can significantly impact both measurement uncertainties and minimum detectable activity (MDA). To mitigate this impact, a TDCR counting system with anti-coincidence detectors was developed. By analyzing the time difference distribution spectrum between the anti-coincidence channel and β channel, optimal parameters for the anti-coincidence module are determined. The objective of the study is to enhance the effectiveness of the anti-coincidence technique while minimizing the removal of real events. Finally, two sets of 3 H and 14 C samples with known activities of around 1 Bq are prepared via dilution to validate the performance of the system. Compared to without anti-coincidence, the background has been reduced by nearly 84%, leading to decreased fluctuations in the activity results., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

BackgroundThe triple-to-double coincidence ratio-Čerenkov (TDCR-Čerenkov) method can be applied to the activity measurement of radionuclides by detecting the Čerenkov photons produced in a non-scintillation solution. The computation of the detection efficiency of this method is based on the premise that the energy of emitted β is completely deposited in the solution. However, this precondition is ideal and does not apply to the actual measurement because of the counting loss caused by the restrictions of a finite solution and the wall of the counting vial (i.e., wall effect).PurposeThis study aims to analyze the influence of the wall effect on the computation of detection efficiency.MethodsThe transport process of emitted β from the solution to the vial wall was analyzed in sections. Thereby the relationship between the number of Čerenkov photons and the deposition energy spectra of emitted β with different energies in different matrices was obtained. This relationship was used to further improve the calculation model of the TDCR-Čerenkov method. Subsequently, the calculation model was simplified to reduce the required time. Geant4 calculated the deposition spectra of emitted β in different matrices, subsequently, the efficiency of different nuclides was calculated using curves of the number of Čerenkov photons vs. the energy of the emitted β. To verify the accuracy of the improved calculation model, measurements were carried out on a variety of pure β-emitters.ResultsThe results derived from the improved TDCR-Čerenkov method are in good agreement with those of the TDCR-LS method. Especially for high energy β-emitters, the relative deviation of the results between the TDCR-Čerenkov and TDCR-LS methods is reduced from 0.47% for the original method to 0.02% (90Y), and 0.64% to -0.16% (32P).ConclusionsThe TDCR-Čerenkov method is more accurate when considering the wall effect in the activity measurement of high-energy β-emitters.

The development of a multi-systems triple-to-double coincidence ratio (TDCR) and coincidence 4pb-g methods, based on liquid scintillation to radionuclide standardization is presented in this work. The adjustments of multi-systems were made using standards of 3H and 14C and 60Co. The initial stage was performing measurements of pure beta-emitters 3H, 63Ni, and 90Sr90Y standard solutions by TDCR. The results were consistent within the standard uncertainty. Measurements will be performed with a beta-gamma 60Co in a comparison to the SIR / BIPM to assess the multi-system's performance.

Gadolinium-153 was standardized for activity by live-timed anticoincidence counting and an ampoule was submitted to the international reference system (SIR). Absolute emission intensities for the main γ rays were determined with calibrated high-purity germanium (HPGe) and lithium-drifted silicon (Si(Li)) detectors. A revised decay scheme is indicated, with no probability of direct electron capture to the 153Eu ground state. Triple-to-double coincidence ratio (TDCR) efficiency curves indicate that the revised decay scheme is consistent with experiment. Half-life measurements agree with a previous NIST determination and show no sensitivity to chemical environment. • Standardization of 153Gd activity by live timed anticoincidence (LTAC) counting • Absolute photon emission intensities measured by gamma ray spectrometry • Efficiencies for triple-to-double coincidence ratio (TDCR) liquid scintillation counting • Data support a decay scheme with no direct electron capture to 153Sm ground state • No sensitivity of measured 153Gd half-life to chemical environment detected [ABSTRACT FROM AUTHOR]

This work explores the primary activity standardisation of 32Si as part of the SINCHRON project that aims at filling the geochronological dating gap by making a new precise measurement of the half-life of this nuclide. The stability of some of the radioactive test solutions, providing 32Si as hexafluorosilicic acid (H 2 32SiF 6), was monitored over long periods, pointing to the adequate sample composition and vial type to ensure stability. These solutions were standardised using liquid scintillation counting with the triple to double coincidence ratio (TDCR) technique and the CIEMAT-NIST efficiency tracing (CNET) method. Complementary backup measurements, using 4πβ-γ coincidence counting with 60Co as a tracer, were performed with both liquid and plastic scintillation for beta detection. While 60Co coincidence tracing with a liquid scintillator predicted activities in agreement with the TDCR and CNET determinations, using plastic scintillation turned out to be unfeasible as the addition of lanthanum nitrate and ammonia to fix the silicon during the drying process generated large crystals that compromised the linearity of the efficiency function. • Several 32Si solutions were standardised using the TDCR and CNET methods. • Issues with a tritium impurity and long-term stability were dealt with effectively. • β(LS)-γ coincidence tracing with 60Co supports TDCR and CNET determinations. • 60Co tracing with plastic scintillation is unfeasible because of severe self-absorption. • 32Si activity can be determined with about 0.4% relative standard uncertainty. [ABSTRACT FROM AUTHOR]

Despite widespread radon-in-water measurements, no primary radon-in-water standards currently exist. This work aims to bridge this gap by developing a system to produce radon-in-water reference materials. The system relies on cryogenic, loss-free transfer of radon, which is standardized through defined solid angle measurements, to a radon standard in water. It allows for preparation of liquid scintillation and gamma-ray spectrometry samples with traceable radon-in-water concentrations. The system's design, functionality, and the results of pilot performance tests are described. • A new system for preparation of radon-in-water reference materials is developed. • The system allows to prepare LSC sources traceable to a radon primary standard. • The system allows to prepare gamma-spectrometry sources traceable to a radon primary standard. • The system allows direct comparison of the radon-in-water measurement methods. [ABSTRACT FROM AUTHOR]

Atomic and nuclear data represent an important input for the accuracy of primary activity measurements based on liquid scintillation. In particular, the reliability of β-spectrum computation has been investigated for several years through experimental and theoretical studies providing solid evidence for the need to consider the atomic effects. In the present study, the activity standardization of two β-emitting radionuclides (60Co, 106Ru/106Rh) was carried out by means of the 4πβ−γ coincidence and Triple-to-Double Coincidence Ratio (TDCR) methods. The comparison between the activity concentrations given by both primary techniques presents new evidence that a better agreement is obtained when the exchange and screening effects are included in the β-spectra implemented in the model of light emission for TDCR measurements. A new development of a stochastic model based on Geant4 simulations for TDCR calculations is also presented. • Primary activity measurements of 60Co and 106Ru/106Rh are presented. • Activity assessment with the TDCR method depends on β-spectra computation. • For both radionuclides, the TDCR and 4πβ−γ coincidence results are compared. • Good agreement is obtained when the atomic effects are considered in the β-spectra calculation. [ABSTRACT FROM AUTHOR]

A method for absolute measurements of the 225Ac activity in equilibrium with its progeny was developed. Measurements were performed using the triple-to-double coincidence ratio (TDCR) method in two different TDCR counters. The activity concentration of an 225Ac solution was determined and the solution was sent to the SIR system for a comparison. The half-life of 225Ac was determined by one of the TDCR counters and found to be 9.9150(63) days. • Detailed determination of the counting efficiency of the 225Ac in radioactive equilibrium with its progeny. • Description of the measurements of the activity of 225Ac sources using the TDCR method. • Result of activity comparison in the International Reference System (SIR) at BIPM. • Results of half-life determination of 225Ac at POLATOM compared to other published values. [ABSTRACT FROM AUTHOR]

In the Triple to Double Coincidence Ratio method in Liquid Scintillation Counting, the detection efficiency is calculated from the value of a free parameter describing the intrinsic light yield of the counting system. This model is generally based on a Poisson distribution of the number of photoelectrons detected and the detection efficiency is obtained from the complement of the non-detection efficiency. In the classical free parameter model, the mean of the Poisson distribution, m , is a constant but some variability of this mean could be expected from optical effects due to internal reflections inside the LS source or from non-homogeneity of the detection efficiency of the photomultiplier tubes. Then, m becomes a random variable and the distribution of the photoelectrons becomes a compound Poisson distribution, with a random variable as mean value. This paper explores the implications of the variance of m , which were, to our knowledge, never considered previously in the uncertainty budget of TDCR measurements. • Internal light reflection and photomultiplier tubes inhomogeneity introduces variability of the free parameter model in LSC. • This variability causes additional variance on the counting rates. • The importance of this effect is studied for TDCR counting of 3H and 55Fe. • The effect mostly concerns triple coincidences and low efficiency detection. • Reporting experimental standard deviation of repeated measurement instead of standard deviation of the mean is recommended. [ABSTRACT FROM AUTHOR]

177Lu decays through low-energy β-- and γ-emissions in addition to conversion and Auger electrons. To support the use of this radiopharmaceutical in Switzerland, a 177Lu solution was standardised using the β-γ coincidence technique, as well as the TDCR method. The solution had no 177mLu impurity. Primary coincidence measurements, with plastic scintillators for beta detection, were carried out using both analogue and digital electronics. TDCR measurements using only defocusing were also made. Monte Carlo calculations were used to compute the detection efficiency. The coincidence measurements with both analogue and digital electronics are compatible within one standard uncertainty, but they are lower than (and discrepant with) the TDCR measurements. An ampoule of this solution was submitted to the BIPM as a contribution to the Système International de Référence. • 177Lu was standardised with the β-γ coincidence and TDCR techniques. • Analogue and digital coincidence measurements are self-consistent and compatible within one standard uncertainty. • β-γ coincidence measurements are 1.8% lower than the TDCR determination. [ABSTRACT FROM AUTHOR]

A bilateral comparison to determine the activity concentration of the same 125I solution was organized. As electron-capture radionuclide with a rather high atomic number, 125I must be regarded as difficult to measure. The situation is partly exacerbated by the fact that some established standardization methods, like photon-photon coincidence counting, can no longer be applied due to the unavailability of appropriate equipment and expertise. One aim of this work is to compare modern liquid scintillation counting methods for the standardization of 125I. Both participating metrology institutes have used their custom-built triple-to-double-coincidence ratio (TDCR) counters and the determined activity concentrations are in excellent agreement even though the ways to analyze the data and to compute counting efficiencies were widely independent. The results also agree with the outcome of 4π-γ counting that was carried out at LNHB. In both laboratories, the measurements were complemented by measurements with several secondary standardization methods which even allow to establish a link to the CCRI(II)–K2.I-125(2) comparison started in 2004. A good agreement between the TDCR results and the key comparison reference value of the 2004/2005 comparison was obtained. • The activity concentration of a125I solution was measured in two laboratories. • The TDCR liquid scintillation counting technique was used. • 4πγ counting was used as an independent method. • Secondary activity standardization was used to establish a link to a previous international comparison. • The results from all primary methods are in good agreement. [ABSTRACT FROM AUTHOR]

The complex decay scheme that makes 64 Cu promising as both an imaging and therapeutic agent in medicine also makes the absolute measurement of its activity challenging. The National Institute of Standards and Technology (NIST) has completed a primary activity standardization of a 64 CuCl 2 solution using the 4πβ(LS)-γ(NaI) live-timed anticoincidence (LTAC) counting method with a combined standard uncertainty of 0.51 %. Two liquid scintillation (LS) counting methods were employed for confirmatory measurements. Secondary measurements were made by high-purity germanium detectors, pressurized ionization chambers (IC), and a well-type NaI(Tl) counter. Agreement between the LTAC-based standard and standards from other laboratories was established via IC calibration factors. Poor agreement between methods and with theoretical IC responses may indicate a need for improved β +/- branching probabilities and a better treatment of β +/- spectra. [ABSTRACT FROM AUTHOR]

A comparison of calculations of the activity of a 3 H 2 O liquid scintillation source using the same experimental data set collected at the LNE-LNHB with a triple-to-double coincidence ratio (TDCR) counter was completed. A total of 17 laboratories calculated the activity and standard uncertainty of the LS source using the files with experimental data provided by the LNE-LNHB. The results as well as relevant information on the computation techniques are presented and analysed in this paper. All results are compatible, even if there is a significant dispersion between the reported uncertainties. An output of this comparison is the estimation of the dispersion of TDCR measurement results when measurement conditions are well defined. [ABSTRACT FROM AUTHOR]

The activity concentration of a 60 Co solution was measured by means of two 4πβ-γ coincidence counting systems using a liquid scintillation counter and a proportional counter (PC) in the beta channel, respectively. Additional liquid scintillation measurements were carried out and CIEMAT/NIST efficiency tracing as well as the triple-to-double coincidence ratio (TDCR) methods were applied to analyse the data. The last two methods require computed beta spectra to determine the counting efficiencies. The results of both 4πβ-γ coincidence counting techniques are in very good agreement and yield a robust reference value. The initial activity concentration determined with liquid scintillation counting was found to be significantly lower than the results from 4πβ-γ coincidence counting. In addition, the results from TDCR and CIEMAT/NIST show some inconsistency. The discrepancies were resolved by applying new beta spectrum calculations for the dominant allowed beta transition of 60 Co. The use of calculations which take screening effects as well as the atomic exchange effect into account leads to good agreement between all four methods; the combination of these techniques delivers an important validation of beta spectra. [ABSTRACT FROM AUTHOR]

In this work, a 68 (Ge+Ga) solution has been standardized at the National Institute of Ionizing Radiation Metrology (LNMRI), in Brazil, in the frame of an international key comparison CCRI(II)-K2.Ge-68 piloted by National Institute of Standards and Technology (NIST/USA). The 4πβ(LS)-γ(NaI(Tl)) anticoincidence method with live-time and extended dead-time was used and its result was validated by 4πβ(LS)-γ(NaI(Tl)) coincidence counting and liquid scintillation counting using the Triple to Double Coincidence Ratio (TDCR) method. The deviations of the activity concentration values of coincidence and TDCR measurements from the anticoincidence result were 1.7% and 0.63%, respectively, which were within experimental evaluated uncertainties at ~95% level of confidence (coverage factor k = 2). The combined relative standard uncertainties were 0.65%, 0.70% and 0.53% for anticoincidence, coincidence and TDCR methods, respectively. These values are consistent with the results reported by Cessna at the ICRM2017 conference. [ABSTRACT FROM AUTHOR]

In response to the increasing application of 68 Ge/ 68 Ga and 68 Ga in nuclear medicine, an international comparison of activity measurement of 68 Ge in equilibrium with 68 Ga was organised. ANSTO standardised the comparison solution by the 4π(LS)β + -γ coincidence extrapolation and TDCR efficiency calculation methods, with excellent agreement between the two results. The primary standard was transferred to the ANSTO Secondary Standard Ionisation Chamber. Internationally traceable Australian Certified Reference Materials (ACRMs) of 68 Ge/ 68 Ga can now be prepared in various measurement geometries applied in nuclear medicine. [ABSTRACT FROM AUTHOR]

A bilateral comparison of C activity measurements between ENEA-INMRI (Italy) and NCBJ RC POLATOM (Poland) was organized in the year 2015 and piloted by POLATOM, which provided the sources for the comparison. A set of six sources in Ultima Gold scintillator was measured at POLATOM using four different counters by two liquid scintillation counting methods: TDCR and CIEMAT/NIST. Three of sources were measured also at ENEA-INMRI by using two different TDCR counters. The results achieved in the comparison show an excellent agreement. [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]

This work looks into the tracks of electrons in nanoemulsive scintillating media using the Monte Carlo Geant4-DNA code which simulates event-by-event interactions of electrons in liquid water down to the eV, without resorting to the condensed history method. It demonstrates that the average number of micelles in which electrons deposit energy is quite large, increasing with their emission energy, decreasing with micelle size, and rising with micelle concentration. The probability of an electron ending its track in a micelle is found to be rather large and micelle size-dependent below 1 keV, and approximating the aqueous fraction at higher energies. Analyses of the Monte Carlo estimated energy depositions in the aqueous phase and in the scintillant tell of a micelle quenching effect, with the micelle size shaping the quenching at low energy and the micelle concentration governing it at higher energies. The micelle effect on the 3 H and 63 Ni beta spectra is discussed for a range of micelle sizes and concentrations. This paper also computes the ionisation quenching function using Birk's law whilst considering the full energy losses in the micelles bisecting the electron pathway, and not just that incurred in the primary micelle enclosing the decaying nuclide. The ionisation quenching function is then used to calculate the detection efficiencies for 3 H, 63 Ni, 54 Mn and 55 Fe. The effect of the micelle size is found to be small for beta emitters but significant for the electron capture nuclides. TDCR measurements of 63 Ni samples covering 8 aqueous fractions are analysed with and without explicit treatment of the micelle effect. Activities in the two representations agree within 0.02%. The ratios of the corresponding figures of merit are found to coincide with the scintillant fractions. [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]

This work demonstrates that a Liquid Scintillation Counting (LSC) technique using a Triple to Double Coincidence Ratio counter with extending dead-time is very appropriate for the accurate measurement of 222 Rn activity absorbed in thin polycarbonate foils. It is demonstrated that using a toluene-based LS cocktail, which dissolves polycarbonates, the 222 Rn activity absorbed in thin Makrofol N foil can be determined with a relative standard uncertainty of about 0.7%. A LSC-based application of the methodology for determination of the diffusion length of 222 Rn in thin polycarbonate foils is proposed and the diffusion length of 222 Rn in Makrofol N (38.9±1.3 µm) and the partition coefficient of 222 Rn in Makrofol N from air (112±12, at 20 °C) and from water (272±17, at 21 °C) are determined. Calibration of commercial LS spectrometers for 222 Rn measurements by LSC of thin polycarbonate foils is performed and the minimum detectable activities by this technique are estimated. [ABSTRACT FROM AUTHOR]

An informal bilateral comparison of 14 C liquid scintillation (LS) counting at the National Research Council of Canada (NRC) and the National Institute of Standards and Technology (NIST) has been completed. Two solutions, one containing 14 C-labeled sodium benzoate and one containing 14 C-labeled n-hexadecane, were measured at both laboratories. Despite observed LS cocktail instabilities, the two laboratories achieved accord in their standardizations of both solutions. At the conclusion of the comparison, the beta spectrum used for efficiency calculations was identified as inadequate and the data were reanalyzed with different inputs, improving accord. [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]

A new 4πβ(LS)-γ digital coincidence counting (DCC) system has been developed at NIM. The system equipped with a triple-to-double coincidence ratio (TDCR) counter in the β-channel and a NaI(Tl) scintillation detector in the γ-channel. A dedicated DCC software was designed for off-line implementation of 4πβ(LS)-γ coincidence counting method. The software consists of three modules: software-based circuits module, dead-time and resolving-time correction module and efficiency extrapolation module, respectively. The performance of the newly developed 4πβ(LS)-γ DCC system was demonstrated by a comparison measurement of Co-60 solution with the conventional 4πβ(PC)-γ DCC system. • A new 4πβ(LS)-γ digital coincidence counting (DCC) system has been developed at NIM. • A dedicated DCC software was designed for off-line implementation of 4πβ(LS)-γ coincidence counting method. • The system was satisfactorily validated by a comparison measurement of Co-60 solution with the conventional 4πβ(PC)-γ DCC system. [ABSTRACT FROM AUTHOR]

A custom-built liquid scintillation counter was used for long-term measurements of 90 Sr / 90 Y sources. The detector system is equipped with an automated sample changer and three photomultiplier tubes, which makes the application of the triple-to-double coincidence ratio (TDCR) method possible. After decay correction, the measured decay rates were found to be stable and no annual oscillation could be observed. Thus, the findings of this work are in strong contradiction to those of Parkhomov (2011) who reported on annual oscillations when measuring 90 Sr / 90 Y with a Geiger–Müller counter. Sturrock et al. (2012) carried out a more detailed analysis of the experimental data from Parkhomov and claimed to have found correlations between the decay rates and processes inside the Sun. These findings are questionable, since they are based on inappropriate experimental data as is demonstrated in this work. A frequency analysis of our activity data does not show any significant periodicity. [ABSTRACT FROM AUTHOR]

The activity concentration of a 63 Ni solution was determined by means of two liquid scintillation counting techniques: the TDCR method and the CIEMAT/NIST efficiency tracing technique. The results of both methods are in excellent agreement, provided that the 63 Ni beta spectrum calculation accounts for the atomic exchange effect. Thus, new beta spectrum calculations resolve a discrepancy that has been found in previous analyses. The influence of the computed beta spectrum on the final uncertainty of the activity concentration is discussed. [ABSTRACT FROM AUTHOR]

A Petri dish was filled with liquid scintillator and then used to trap 219 Rn from a 223 Ra source. The liquid scintillator was then transferred to a vial which was measured in a custom-built triple-to-double coincidence ratio (TDCR) counter. Two Cherenkov samples were prepared in a similar manner. The measurements were used to determine the 211 Pb half-life which was found to be 36.165(37) min. [ABSTRACT FROM AUTHOR]

A triple-to-double coincidence ratio (TDCR) counter was recently constructed at IRA-METAS for liquid scintillation based primary activity standardisations. A description of its optical chamber, efficiency change tools, photomultiplier tubes (PMTs) and electronics is given. This TDCR system was validated by measuring several standard solutions of beta emitters including 45 Ca, 14 C, 63 Ni and 3 H. The activity concentrations, obtained from these measurements and efficiencies computed with a FORTRAN code we developed for symmetric and asymmetric PMTs, agree with the certified values within uncertainties. [ABSTRACT FROM AUTHOR]

The activity concentrations of solutions containing 227 Ac and 223 Ra in equilibrium with their progenies, respectively, were measured by means of liquid scintillation counting. The counting efficiencies were determined with the aid of a free parameter model. The corresponding calculations comprise the computation of several alpha, beta and beta/gamma branches. For short-lived progenies like 215 Po the counting efficiency depends on the counter dead time. Measurements were made in custom-built triple-to-double coincidence ratio (TDCR) systems and various dead-time adjustments were used. In addition, two commercial counters were used to apply the CIEMAT/NIST efficiency tracing technique using 3 H as a tracer. For the 227 Ac solution, the overall relative standard uncertainty of the activity concentration was found to be 0.93%. The dominant uncertainty components are assigned to the efficiency computation of the low-energy beta transitions of 227 Ac. We have identified a need for improved 227 Ac decay data to achieve a significant reduction in the overall uncertainty. In the case of 223 Ra, the activity concentrations were determined with relative standard uncertainties below 0.3%. Hence, PTB is prepared to provide calibration services for 223 Ra, which is an isotope of increasing interest in nuclear medicine. The TDCR measurements were also used to determine the half-life of 223 Ra. The decay was followed for about 58 days and a half-life T 1/2 =11.4362(50) d was obtained. [ABSTRACT FROM AUTHOR]

Iron-59 was measured in three commercial and two custom-built liquid scintillation counters. The counting efficiencies were determined using CIEMAT/NIST efficiency tracing and the triple-to-double coincidence ratio (TDCR) method, respectively. The efficiency computation for the TDCR method was realized by means of the MICELLE2 program, applying a stochastic model for the computation of electron emission spectra. The program was extended to make calculations of spectra originating from complex decay schemes possible. In addition, a new parameterization of electron stopping powers for 10 commercial liquid scintillation cocktails was included in the software. The activities determined with the two methods were in very good agreement; the relative standard uncertainty of the combined result was found to be 0.16%. It was used to calibrate a 4π ionization chamber at PTB for future calibrations of this isotope which is used for investigations of iron metabolism. A standardized solution was submitted to the Bureau International des Poids et Mesures (BIPM) to be measured in the ionization chambers of the International Reference System (SIR) for comparison purposes. The liquid scintillation samples were also measured in a new portable TDCR system with three channel photomultipliers. Although this system has a much lower counting efficiency, the activity was in satisfactory agreement with the conventional TDCR system. The usage of the portable TDCR system, thus, provides an important test of the free parameter model. [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]

A beaker was filled with a liquid mineral oil scintillator to catch 220 Rn from a 228 Th source. The liquid scintillator was then transferred to a polyethylene vial which was measured in a custom-built triple-to-double coincidence ratio (TDCR) counter. The measurements were used to determine the 212 Pb half-life which was found to be 10.622(7) hours. [ABSTRACT FROM AUTHOR]

The commercial Hidex LSC system has been used to measure triple to double coincidence ratio (TDCR), experimental counting efficiency (CE) and the absolute activity for radioactive standards of pure beta emitters viz. H, Ni and Fe, an electron capture nuclide. Colour and chemical quench measurements of Ni and Fe have been done. An excellent match between TDCR and CE has been obtained for beta emitters, while very large deviations have been observed for Fe. The deviation between TDCR and experimental efficiency has been found to be nearly uniform. Based on this, an empirical correction factor for TDCR which gives the correct efficiency has been evaluated, to enable efficient application of this commercial instrument for Fe estimation. These TDCR correction factors were further validated by applying for Fe activity measurements in ASTM standard steel samples irradiated to a fixed neutron flux in research reactor CIRUS. Finally, Fe activity in steel sample from APSARA reactor decommissioning waste was successfully estimated using this modified TDCR. [ABSTRACT FROM AUTHOR]

Abstract: Liquid scintillation measurements of 229Th in radioactive equilibrium with its progenies were carried out. The counting efficiency was determined by means of a free parameter model. The measurements were made in a custom-built triple-to-double coincidence ratio (TDCR) system. In addition, a new portable mini-TDCR system with three channel photomultipliers and two commercial counters were tested. The decay of the short-lived 213Po requires great care, since it often occurs during the dead time of the counter systems. Also the rather short-lived 217At may decay during the dead time caused by 221Fr decay events. The overall counting efficiency of the TDCR system of PTB was found to be about 700% (depending on the degree of chemical quenching) and the relative standard uncertainty of the activity concentration was found to be about 0.23%. The determined activity concentration was compared with the outcome of alpha spectrometry under defined solid angle and excellent agreement was found. The TDCR efficiency calculations can be easily adapted to activity determinations of 225Ra or 225Ac in equilibrium with their progenies. [Copyright &y& Elsevier]

In the framework of the European Metrology Research Programme (EMRP), the Joint Research Project MetroFission has a dedicated work package for the development of a portable Triple-to-Double-Coincidence-Ratio (TDCR) system dedicated to in-situ activity measurements of low-energy beta emitters arising from the operation of the next generation of nuclear power plants. In the design phase of the NPL version of the mini-TDCR, a wide range of metrological aspects and detector types was considered. This paper summarizes these aspects of design, in the light of previous experience with the primary TDCR system at NPL. For example, in this miniature version of the TDCR, the optical chamber was simplified and cylindrical geometry was deemed sufficient. The reflectivity of the surface was increased by painted layers of Spectraflect®, a specially formulated barium sulphate coating with high reflectivity across a wide range of wave lengths including UV. This option was chosen rather than the high performing and more expensive Spectralon® material used for the primary NPL TDCR. The miniature TDCR system is intended for on-site monitoring and will not require as high a performance as the primary system. Other factors that were considered included sample changing, light tightness, type of photo detector, method for varying the detection efficiency, shielding and the possible addition of an internal gamma-ray source for determination of the quench parameter of the source. In this version, the sample changing is performed using a piston and an automatic shutter. Significant design effort has been applied to ensure minimal ingress of light from the piston. Efficiency variation is accomplished by increasing the vertical displacement of the vial. Provision has been made to automate this at a later stage. Maximum light transmission to the photo-multiplier tubes is obtained at the “zero” reference height. Validation measurements were successfully performed using four different radionuclides: 3H, 241Pu, 63Ni, and 99Tc. [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 NMISA participated in the international key comparison of the pure beta-emitter Technetium-99, CCRI(II)-K2.Tc-99. The comparison solution was standardized using three methods, namely the TDCR efficiency calculation method, the CIEMAT/NIST efficiency tracing method and the 4π(LS)β–γ coincidence tracing method with Co-60 as tracer. Excellent agreement between results obtained with the three methods confirmed the applicability of the beta spectral shape given by the latest (2011) DDEP evaluation of Tc-99 decay data, rather than the earlier (2004) evaluation. [Copyright &y& Elsevier]

Abstract: The triple-to-double-coincidence ratio method (TDCR) is an important method for activity standardization in metrology institutes worldwide. There is an increasing interest in portable systems that allow activity determination outside of specialized laboratories with high accuracy. Within the framework of the EMRP “MetroFission” project, several portable systems using different designs were developed. The PTB system described here is based on channel photomultipliers incorporated in a portable detection module, a separate electronics bin and a computer for data acquisition and storage. This miniature TDCR system was extensively tested and compared to the PTB reference TDCR system that is very well characterized and has been used in several intercomparisons. [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]