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The half-lives of 44Sc and 44mSc were measured by following their decay rate using several measurement systems: two ionization chambers and three γ-spectrometry detectors with digital and/or analogue electronics. For 44Sc, the result was the combination of seven half-life values giving a result of 4.042(7) h, which agrees with the last reported value of 4.042(3) h and confirms the near to 2% deviation from the recommended half-life of 3.97(4) h. Scandium-44 is present as an impurity in the production of 44Sc by cyclotron proton irradiation. Its half-life was determined by measurements performed a few days after End of Bomardment (EoB), so that the 44Sc decayed down to a negligible level. Seven measurements were combined to obtain an average of 58.7(3) h, which is in agreement with the recommended value of 58.6(1) h.

Internal Bremsstrahlung (IB) is a continuous electromagnetic radiation accompanying beta decay; however, this process is not considered in radiation protection studies, particularly when estimating exposure from beta-decaying radionuclides. The aims of the present work are: i) to show that neglecting the IB process in Monte Carlo (MC) simulation leads to an underestimation of the energy deposited in a ionization chamber, in the case of a high-energy pure beta emitter such as Yttrium-90 (90Y), and ii) to determine the most reliable choice of source term for 90Y IB to be used in MC simulations. For this radionuclide, commonly employed in nuclear medicine and radiochemistry applications, experimental data acquired with a well ionization chamber have been compared with Monte Carlo (MC) calculations carried out in the GAMOS framework. Simulations that do not include the effect of the IB process, are found to give results underestimating the experimental values by 12–14%. Consequently, two models for the IB energy spectra, previously described by Italiano et al. [1] , have been implemented using MC simulation and a good agreement has been achieved with one of them. We therefore conclude that inclusion of IB process in Monte Carlo simulation packages is advisable for a more accurate and complete treatment of electromagnetic interactions.

The half-lives of

$^{175}$Yb is a radionuclide that can be generated by neutron capture on $^{174}$Yb and whose decay properties make it useful for developing therapeutic radiopharmaceuticals. As it happens with many of the emerging radionuclides for medical uses in recent years, its nuclear data were determined decades ago and are not thoroughly documented nor accurate enough for metrological purposes. The last documented reference for the $^{175}$Yb half-life value is 4.185(1) days and dates back to 1989, so a redetermination of the value was considered appropriate before standardization at the Institute of Radiation Physics (IRA, Lausanne, Switzerland) primary measurements laboratory. Three independent measurement methods were used to this purpose: reference ionization chamber (CIR, $chambre$ $d'ionization$ $de$ $référence$), CeBr$_{3}$ γ-ray detector with digital electronics and a second CeBr$_{3}$ detector with analog electronics and single-channel analyzer (SCA) counting. The value obtained for the $^{175}$Yb half-life is 4.1615(30) days which shows a 0.56% relative deviation to the last nuclear reference value (ENSDF 2004) and is supported with a detailed calculation of the associated uncertainty.

Internal Bremsstrahlung (IB) is a continuous electromagnetic radiation accompanying beta decay; however, this process is not considered in radiation protection studies, particularly when estimating exposure from beta-decaying radionuclides. The aims of the present work are: i) to show that neglecting the IB process in Monte Carlo (MC) simulation leads to an underestimation of the energy deposited in a ionization chamber, in the case of a high-energy pure beta emitter such as Yttrium-90 (

We report here on the primary activity standardisation of a

In this study, the gamma and X-ray emission intensities of

A comparison of the activity concentration measurement of a 3H2O solution was organized by the LNE-LNHB under the auspices of the CCRI(II). The solution was sent to thirteen laboratories and eleven measurement reports were received. The results, as well as relevant information on the measurement techniques, are presented and analysed in this paper. All results are consistent within uncertainties. As the solution was traceable to the solution used in the CCRI(II)-K2.H-3 comparison in 2009, the results of both comparisons are also presented. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

IRA recently launched a project to digitize all the data acquisition systems it uses for primary radionuclide standardizations. It is well-known that the digital approach presents numerous advantages over the traditional analog electronics such as information losslessness, scalability, online and/or offline data processing, and it is also a solution to the growing difficulties to repair or renew ageing modules. As a first step in this wider program, our institute set-up a 4πβ-4πγ digital coincidence counting system, with FPGA (Field Programmable Gate Array)-based commercial boards from National Instruments (NI), to perform data acquisition and offline data analysis. Choosing all components and software from the same supplier provides a full compact and consistent electronic system. To demonstrate and validate the capacity of this system to standardize the activity of radioisotopes, we compare its predictions for the activity concentration of 133Ba, 166mHo and 18F solutions with the results from a coincidence counting system with analog electronics, as well as with the results from other primary methods and a secondary measurement performed with an IG11 ionization chamber (CIR, chambre d'ionization de reference) with an equivalent activity traceable to the Systeme International de Reference.

The gamma and X-ray emission intensities of 169Er were determined using radionuclidically pure 169Er. The activity of the 169Er source was standardized by the triple-to-double-coincidence ratio technique. Three independent measurements were performed to measure the emission intensities using calibrated high-purity germanium spectrometers. The efficiencies were computed with the Monte Carlo method and validated using several experimental measurements. Final results present a large uncertainty reduction compared to previous evaluations. The emission intensities per decay of 169Er are reported as 1.401(40).10−5 for the 109.8 keV line and 1.513(19).10−6 for the 118.2 keV line. The values obtained for the X-ray lines show large discrepancies with the reference values.

We report here on the primary activity standardisation of a223Ra dichloride solution in equilibrium with its decay daughters. Both the triple-to-double-coincidence-ratio (TDCR) method with an in-house TDCR detector and the CIEMAT-NIST efficiency tracing (CNET) technique with a commercial counter were used. The liquid scintillation efficiencies for both methods are about 6 while the activities they predict with about 0.4% relative standard uncertainty agree within 0.15%. For backup, the solution was also standardised with 4πγ NaI(Tl) integral counting with a well-type NaI(Tl) detector, and efficiencies computed by Monte Carlo simulations using the GEANT code. This simple technique, unused previously for this nuclide, yielded an activity concentration compatible with, but 1% lower than, the one determined by liquid scintillation counting.

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.

The half-life of 137Cs was measured with an ionization chamber by following the decay of 5 sources over a 30 years period between 1983 and 2013. The ratio between the ionization chamber current for the cesium sources and 226Ra source was used for the half-life calculation. The value found for the 137Cs half-life is 10,955.2±10.7 days, where the uncertainty evaluation combines type A and B for one standard deviation.

The stability of 3H and 63Ni samples, made with Ultima Gold and Ultima Gold AB using eight aqueous fractions ranging between 0.1% and 10%, was monitored over a period of 32 weeks. Counting rate losses were measured in all cases, but were found to be particularly severe for samples with low aqueous fractions. Hydrodynamic diameter measurements of the reverse micelles of 3H and 63Ni in Ultima Gold and Ultima Gold AB samples were performed with dynamic light scattering. For Ultima Gold, the micelle diameters were measured to be about 2nm and slightly dependent of the aqueous fraction, while for Ultima Gold AB they were found to vary strongly with the aqueous fraction and range between 1 and 4nm. The hypothesis that the counting rate instabilities derive from changes in the sizes of micelles was tested by measuring them four times over the monitoring period. The measurement results do not support this claim.

International audience; The hypothesis that seasonal changes in proximity to the Sun cause variation of decay constants at permille level has been tested for radionuclides disintegrating through electron capture and beta plus decay. Activity measurements of Na-22, Mn-54, Fe-55, Co-57, Zn-65, Sr82+85, Sr-90, Cd-109, Sb-124, Ba-133, Eu-152, and Bi-207 sources were repeated over periods from 200 d up to more than four decades at 14 laboratories across the globe. Residuals from the exponential nuclear decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ from one data set to another and appear attributable to instabilities in the instrumentation and measurement conditions. Oscillations in phase with Earth's orbital distance to the sun could not be observed within 10(-4)-10(-5) range precision. The most stable activity measurements of beta(+) and EC decaying sources set an upper limit of 0.006% or less to the amplitude of annual oscillations in the decay rate. There are no apparent indications for systematic oscillations at a level of weeks or months.

The radiolanthanide

Signal processing is a core part of any electronic chain for radioactivity measurement systems and can influence measurement results drastically. A thorough study of the different alternatives for this treatment is especially worthwhile when developing a new digital system. This article describes an evaluation performed to optimize the digital pulse processing stage of the β-γ coincidence counting system at the Institute of Radiation Physics (IRA) designated laboratory for the activity unit. This study is a part of IRA's digitalization project to modernize the aging analog electronic hardware of its primary measurement systems. The β-γ coincidence counting system consists of a plastic scintillation detector in the beta channel and a well-type NaI detector in the gamma channel. Six pulse shaping digital filters along with amplitude calculation algorithms were implemented to obtain beta and gamma pulse amplitude values. In addition, four timing digital filters and time pick-off methods were set up to calculate arrival times (timestamps) for the pulses generated by both detectors. Filter parameters and algorithm settings were adjusted to obtain the best performance. Combination of filters into traditional two channel (fast for timing and slow for shaping) or one channel configuration using dCFD (digital constant fraction discrimination) and LE (leading edge) time pick-off methods were also tested and compared to study the whole digital pulse processing system, using both real measurement signals (241Am, 137Cs, 60Co and 166mHo) and simulated reference pulses. The results of these tests were quantified by evaluating the following metrics: processing speed, signal-to-noise ratio (SNR) at different energies, gamma energy resolution, time measurement accuracy, time resolution and detection efficiency. The results of this evaluation provide a rational ground to assess the system and help decide which digital pulse processing (DPP) method should be the most appropriate.

A comparison of calculations of the activity of a 3H2O 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. 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. KEY WORDS FOR SEARCH Radionuclide metrology, supplementary comparison, tritium, liquid scintillation Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

161Tb, which emits low-energy β−- and γ-particles in addition to conversion and Auger electrons, has aroused increased interest for medical imaging and therapy. To support the use of this radionuclide, a161Tb solution was standardised using the β-γ coincidence technique, as well as the TDCR method. The solution had 4.5·10−3% of 160Tb impurities. Primary coincidence measurements, with plastic or liquid scintillators for beta detection, were carried out using both analogue and digital electronics. TDCR measurements using defocusing, grey filtering and quenching for varying the efficiency were also made. Monte Carlo calculations were used to compute the detection efficiency. The coincidence measurements with analogue electronics and the TDCR show a good consistency, and are compatible with the digital coincidence results within uncertainties. An ampoule of this solution was submitted to the BIPM as a contribution to the international reference system.

The radiolanthanide 161Tb is being studied as an alternative to 177Lu for targeted radionuclide tumor therapy. Both β--particle emitters show similar chemical behavior and decay characteristics, but 161Tb delivers additional conversion and Auger electron emissions that may enhance the therapeutic efficacy. In this study, the half-life of 161Tb was determined by a combination of three independent measurement systems: reference ionization chamber (CIR, chambre d'ionization de reference), portable ionization chamber (TCIR) and a CeBr3 γ-emission detector with digital electronics. The half-life determined for 161Tb is 6.953(2) days, showing a significant improvement in the uncertainty, which is one order of magnitude lower, with a deviation of 0.91% from the last nuclear data reference value. The previous large uncertainty of the half-life had a direct impact on activity measurements. Now it is no more an obstacle to a primary standardization.

This report summarises the results for the new BIPM.RI(II)-K1.Ge-68 comparison. Six metrology institutes have participated, enabling the first value of the key comparison reference value(KCRV) to be determined. The KCRV was calculated using the power-moderated weighted mean and the results. A link has been made to the CCRI(II)-K2.Ge-68 comparison held in 2015 through the NIST, NIM,IRA-METAS and the LNE-LNHB who participated in both comparisons. One NMI used the K2 comparison to update their degree of equivalence. The degrees of equivalence between each equivalent activity measured in the International Reference System (SIR) and the KCRV have been calculated and the results are given in the form of a table for the remaining five NMIs in the BIPM.RI(II)-K1.Ge-68 comparison and the 12 other participants in the CCRI(II)-K2.Ge-68 comparison. A graphical presentation is also given. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Liquid scintillation counting (LSC) is one of the most widely used methods for determining the activity of 241Pu. One of the main challenges of this counting method is the efficiency calibration of the system for the low beta energies of 241Pu (E max = 20.8 keV). In this paper we compare the two most frequently used methods, the CIEMAT/NIST efficiency tracing (CNET) method and the experimental quench correction curve method. Both methods proved to be reliable, and agree within their uncertainties, for the expected quenching conditions of the sources.

International audience; 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.

A portable instrument was developed at the Institute of Radiation Physics (IRA) for on-site radionuclides measurements. It will enable the measurement of short-lived radionuclides in nuclear medicine departments or isotope production centres. The system involves an ionization chamber read directly by an electrometer and it was optimized to ensure a good reproducibility through the selection of an appropriate vial, filling volume and source position in the well chamber, as well as monitoring the external background and performing a detailed uncertainty estimation. The calibration factors were determined using solutions whose activity concentration is traceable to the international reference system using the IRA reference chamber. Currently the transfer ionization chamber is calibrated for F-18, C-11, O-15, N-13, I-131 and Tc-99m. The final instrument is able to measure isotope activities with a relative standard uncertainty not larger than 1%.

International audience; Claims that proximity to the Sun causes variation of decay constants at permille level have been investigated for alpha decaying nuclides. Repeated decay rate measurements of Po-209, Ra-226, Th-228, U-230, and Am-241 sources were performed over periods of 200 d up to two decades at various nuclear metrology institutes around the globe. Residuals from the exponential decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ in amplitude and phase from one data set to another and appear attributable to instabilities in the instrumentation and measurement conditions. The most stable activity measurements of alpha decaying sources set an upper limit between 0.0006% and 0.006% to the amplitude of annual oscillations in the decay rate. There are no apparent indications for systematic oscillations at a level of weeks or months. Oscillations in phase with Earth's orbital distance to the sun could not be observed within 10(-5)-10(-6) range precision.

International audience; Claims that proximity to the Sun causes variations of decay constants at the permille level have been investigated for beta-minus decaying nuclides. Repeated activity measurements of H-3, C-14, Co-60, Kr-85, Sr-90, Sb-124, Cs-134, Cs-137, and Eu-154 sources were performed over periods of 259 d up to 5 decades at various nuclear metrology institutes. Residuals from the exponential decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ in amplitude and phase from one data set to another and appear attributable to instabilities in the instrumentation and measurement conditions. Oscillations in phase with Earth's orbital distance to the Sun could not be observed within 10(-4)-10(-5) range precision. The most stable activity measurements of beta-decaying sources set an upper limit of 0.003%-0.007% to the amplitude of annual oscillations in the decay rate. There are no apparent indications for systematic oscillations at a level of weeks or months.

The stability of

The half-life of

International audience; The hypothesis that proximity to the Sun causes variation of decay constants at permille level has been tested and disproved. Repeated activity measurements of mono-radionuclide sources were performed over periods from 200 days up to four decades at 14 laboratories across the globe. Residuals from the exponential nuclear decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ from one data set to another and are attributable to instabilities in the instrumentation and measurement conditions. The most stable activity measurements of alpha, beta-minus, electron capture, and beta-plus decaying sources set an upper limit of 0.0006% to 0.008% to the amplitude of annual oscillations in the decay rate. Oscillations in phase with Earth's orbital distance to the Sun could not be observed within a 10−6 to 10−5 range of precision. There are also no apparent modulations over periods of weeks or months. Consequently, there is no indication of a natural impediment against sub-permille accuracy in half-life determinations, renormalisation of activity to a distant reference date, application of nuclear dating for archaeology, geo- and cosmochronology, nor in establishing the SI unit becquerel and seeking international equivalence of activity standards.

The radioactive concentrations of (166m)Ho, (134)Cs and (133)Ba solutions have been standardised using a 4πβ-4πγ coincidence counting system we have recently set up. The detection in the beta channel is performed using various geometries of a UPS-89 plastic scintillator optically coupled to a selected low-noise 1in. diameter photomultiplier tube. The light-tight thin capsule that encloses this beta detector is housed within the well of a 5in.×5in. NaI(Tl) monocrystal detector. The beta detection efficiency can be varied either by optical filtering or electronic discrimination when the electrons loose all their energy in the plastic scintillator. This 4πβ-4πγ coincidence system improves on our 4πβ(PC)-γ system in that its sample preparation is less labour intensive, it yields larger beta- and gamma-counting efficiencies thus enabling the standardisation of low activity sources with good statistics in reasonable time, and it makes standardising short-lived radionuclides easier. The resulting radioactive concentrations of (166m)Ho, (134)Cs and (133)Ba are found to agree with those measured with other primary measurement methods thus validating our 4πβ-4πγ coincidence counting system.

An international exercise, registered as EUROMET project no. 907, was launched to measure both the activity of a solution of (124)Sb and the photon emission intensities of its decay. The same solution was sent by LNE-LNHB to eight participating laboratories. In order to identify possible biases, the participants were asked to use all possible activity measurement methods available in their laboratory and then to determine their reference value for comparison. Thus, measurement results from 4pibeta-gamma coincidence/anti-coincidence counting, CIEMAT/NIST liquid-scintillation counting, 4pigamma counting with well-type ionization chambers and well-type crystal detectors were given. The results are compared and show a maximum discrepancy of about 1.6%: possible explanations are proposed.

The activity of radiopharmaceuticals in nuclear medicine is measured before patient injection with radionuclide calibrators. In Switzerland, the general requirements for quality controls are defined in a federal ordinance and a directive of the Federal Office of Metrology (METAS) which require each instrument to be verified. A set of three gamma sources (Co-57, Cs-137 and Co-60) is used to verify the response of radionuclide calibrators in the gamma energy range of their use. A beta source, a mixture of 90 Sr and 90 Y in secular equilibrium, is used as well. Manufacturers are responsible for the calibration factors. The main goal of the study was to monitor the validity of the calibration factors by using two sources: a 90 Sr/ 90 Y source and a 18 F source. The three types of commercial radionuclide calibrators tested do not have a calibration factor for the mixture but only for 90 Y. Activity measurements of a 90 Sr/ 90 Y source with the 90 Y calibration factor are performed in order to correct for the extra-contribution of 90 Sr. The value of the correction factor was found to be 1.113 whereas Monte Carlo simulations of the radionuclide calibrators estimate the correction factor to be 1.117. Measurements with 18 F sources in a specific geometry are also performed. Since this radionuclide is widely used in Swiss hospitals equipped with PET and PET-CT, the metrology of the 18 F is very important. The 18 F response normalized to the 137 Cs response shows that the difference with a reference value does not exceed 3% for the three types of radionuclide calibrators.

As part of a project to use the long-lived (T(1/2)=1200a) (166m)Ho as reference source in its reference ionisation chamber, IRA standardised a commercially acquired solution of this nuclide using the 4pibeta-gamma coincidence and 4pigamma (NaI) methods. The (166m)Ho solution supplied by Isotope Product Laboratories was measured to have about 5% Europium impurities (3% (154)Eu, 0.94% (152)Eu and 0.9% (155)Eu). Holmium had therefore to be separated from europium, and this was carried out by means of ion-exchange chromatography. The holmium fractions were collected without europium contamination: 162h long HPGe gamma measurements indicated no europium impurity (detection limits of 0.01% for (152)Eu and (154)Eu, and 0.03% for (155)Eu). The primary measurement of the purified (166m)Ho solution with the 4pi (PC) beta-gamma coincidence technique was carried out at three gamma energy settings: a window around the 184.4keV peak and gamma thresholds at 121.8 and 637.3keV. The results show very good self-consistency, and the activity concentration of the solution was evaluated to be 45.640+/-0.098kBq/g (0.21% with k=1). The activity concentration of this solution was also measured by integral counting with a well-type 5''x5'' NaI(Tl) detector and efficiencies computed by Monte Carlo simulations using the GEANT code. These measurements were mutually consistent, while the resulting weighted average of the 4pi NaI(Tl) method was found to agree within 0.15% with the result of the 4pibeta-gamma coincidence technique. An ampoule of this solution and the measured value of the concentration were submitted to the BIPM as a contribution to the Système International de Référence.

International audience; 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 Ca-45, C-14, Ni-63 and H-3. 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.

This paper describes the system of the Swiss national metrological institute (IRA-METAS) for the absolute standardisation of radon gas. This method relies on condensing radon under vacuum conditions within a specified cold area using a cryogenerator, and detecting its alpha particles with an ion-implanted silicon detector, through a very accurately defined solid angle. The accuracy of this defined solid angle standardisation technique was corroborated by another primary measurement method involving 4πγ NaI(Tl) integral counting and Monte Carlo efficiency calculations. The 222Rn standard submitted by IRA-METAS to the Systeme International de Reference (SIR) at the Bureau International des Poids et Mesures (BIPM) has also been found to be consistent with an analogous standard submitted by the German national metrological institute (PTB). IRA-METAS is able to deliver radon standards, with activities ranging from a few kBq to 350 kBq, in NIST-Type ampoules, and glass or steel containers usable for calibrating radon-measuring instruments.

It is the purpose of this paper to present the first relativistic description of alpha-nucleus elastic scattering using an optical model with the Duffin-Kemmer-Petiau (DKP) equation as the applicable wave equation. The DKP optical model potentials that are used are obtained by a folding procedure involving phenomenological Lorentz scalar and vector Dirac nucleon-nucleus potentials. In order to probe the DKP description of the alpha-nucleus interaction, we consider the elastic α-scattering on a range of nuclei over the 100 E

In view of the current interest in relativistic spin-1 systems and the recent work on the Dirac oscillator, we introduce the Duffin-Kemmer-Petiau (DKP) equation obtained by using an external potential linear in r. Since the spin-0 representation leads to a harmonic oscillator in the non-relativistic limit and becomes an harmonic oscillator with a spin-orbit coupling of the Thomas form for vector bosons, we call the equation the DKP oscillator. This oscillator is a relativistic generalization of the quantum harmonic oscillator for scalar and vector bosons. We show that it conserves total angular momentum and that it is exactly solvable for both scalar and vector DKP bosons. We calculate and discuss the eigenvalues and eigenstates of the DKP oscillator in the spin-0 and spin-1 representations.

The work presented here is a new and precise measurement of the half-life of (166m)Ho by determining the activity concentration, using an ionisation chamber calibrated for this nuclide, and measuring the number of (166m)Ho atoms using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Since the isotope (166)Er interferes with the mass spectrometric measurement, Er has to be eliminated from the (166m)Ho radioactive solution. The elimination was achieved using ion-exchange chromatography with the cation exchange resin Dowex AG 50W-X8 and 2-Hydroxybutanoic acid as the mobile phase. After a first transit through the chromatographic column, the purified (166m)Ho eluate was spiked with natural Er to get a resulting Er isotopic composition close to that of natural Er at better than 99.5%, and then it underwent two further separations to eliminate the Er. The activity concentration of this Er-free radioactive (166m)Ho solution was measured in our reference ionisation chamber calibrated for this nuclide by means of the 4πβ(PC)-γ and 4πβ(PS)-4πγ coincidence techniques and integral counting with a well-type NaI(Tl) detector and Monte Carlo efficiencies. An aliquot of this standardized solution was sent to the Paul Scherrer Institute (PSI) for mass concentration determination using an isotope dilution MC-ICP-MS approach. The mass concentration of (166m)Ho in this solution was determined with 0.25% relative standard uncertainty. This value was corroborated by two other independent measurements. The new half-life of (166m)Ho, 1132.6(39) years (k=1), is compatible with the value determined in 1965, but is 5.6% shorter and about 43 times more precise.

Since the 1990s, regular comparisons of gamma-ray spectrometry in Switzerland were organized to improve laboratory abilities to measure the radioactivity in the environment and food stuffs at typical routine levels. The activity concentration of the test samples and the evaluation of the associated uncertainties remained each year the main required test result. Over the years, the comparisons used certified reference solutions as well as environmental samples. The aim of this study is to research the effect of the comparisons on measurement quality. An analysis of the seven last interlaboratory comparisons revealed that the Swiss measurement capability is up to date. In addition, the results showed that the participants now have an improved evaluation of the uncertainties associated with their measurement.

A solution of (18)F was standardised with a 4pibeta-4pigamma coincidence counting system in which the beta detector is a one-inch diameter cylindrical UPS89 plastic scintillator, positioned at the bottom of a well-type 5''x5'' NaI(Tl) gamma-ray detector. Almost full detection efficiency-which was varied downwards electronically-was achieved in the beta-channel. Aliquots of this (18)F solution were also measured using 4pigamma NaI(Tl) integral counting and Monte Carlo calculated efficiencies as well as the CIEMAT-NIST method. Secondary measurements of the same solution were also performed with an IG11 ionisation chamber whose equivalent activity is traceable to the Système International de Référence through the contribution IRA-METAS made to it in 2001; IRA's degree of equivalence was found to be close to the key comparison reference value (KCRV). The (18)F activity predicted by this coincidence system agrees closely with the ionisation chamber measurement and is compatible within one standard deviation of the other primary measurements. This work demonstrates that our new coincidence system can standardise short-lived radionuclides used in nuclear medicine.

We consider 0 + ⇌ 0 − weak-axial transitions in A = 16 nuclei using the Dirac equation with real Lorentz scalar and time-like vector potentials as the relevant nucleon wave equation. We first examine the 16 N (0 − ) → 16 O (0 + ) first-forbidden β-decay using the theory of Schopper and show that the relativistic dynamics strongly enhances the anomalously reduced non-relativistic β- decay rate bringing it closer to the experimental rate. The sensitivity of the β-decay rate to the nuclear model parameters is discussed. We then study the inverse process, the 16 O (0 + ) → 16 N (0 − ) muon-capture, using a new formalism and show that the μ- capture rate may be reproduced simultaneously with the β-decay rate. An analysis of the sensitivity of the μ-capture rate to the induced pionic term and to nuclear model parameters is also made. Overall, although the relativistic effects are appreciable and produce new qualitative features which improve on the standard non-relativistic approach, no conclusive empirical evidence supporting the necessity of adopting the relativistic framework can be inferred.

The radioactive concentrations of (18)F, (88)Y and (152)Eu solutions and the activity of (222)Rn gas ampoules are measured using a primary method involving 4pigamma NaI(Tl) integral counting with a well-type NaI(Tl) detector and efficiencies computed by Monte Carlo simulations. The simulations use the GEANT code coupled with a routine (sch2for), which generates randomly the decay paths and emissions depending on the decay scheme parameters. The resulting radioactive concentrations of (88)Y, (152)Eu and (18)F are found to agree with those measured with other primary measurement methods, such as 4pi (beta, e, X)-gamma coincidence counting or liquid scintillation counting. Results of the determination of the activity of (222)Rn gas ampoules by this method also match the results of an absolute standardisation technique in which radon is condensed onto a cold surface and its alpha-emissions are detected through an accurately specified solid angle.

Detailed uncertainty reporting is imperative for proficiency tests and comparison exercises because uncertainties need to be comparable and trusted by all the participants. Even though participants do their best to follow the Guide to the Expression of Uncertainty in Measurement, ambiguities and divergences about uncertainty evaluation remain. Consequently, to analyze the situation, the CCRI (II) Uncertainties Working Group proposed a comparison exercise (CCRI(II)-S7) about the uncertainty evaluation of a relatively simple primary activity measurement: the standardization of a 60Co source by coincidence counting. To be able to understand how various NMIs calculate coincidence counting uncertainties, our study focused on two of the dominant uncertainty components commonly quoted for 4πβ-γ coincidence counting in the International Reference System (SIR) submissions and Key Comparison exercises: efficiency-extrapolation and weighing. Participants from twelve different laboratories were sent the same set of measurement data from the analysis of a 60Co solution standardized at the National Physical Laboratory (NPL). Our study demonstrated the extent of the different interpretations of the uncertainty components. Some factors causing large discrepancies were isolated and are discussed. Further studies of other techniques using a similar approach would be beneficial for the metrology community. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The IRA and the NPL have submitted ampoules of 166Hom to the International Reference System (SIR) for activity comparison at the Bureau International des Poids et Mesures, thus becoming the third and fourth participants since 1989. The five samples of known activity of 166Hom now recorded in the SIR have activities between about 70 kBq and 500 kBq. The new results have enabled a re-evaluation of the key comparison reference value, and the degrees of equivalence between each equivalent activity measured in the SIR and the key comparison reference value (KCRV) have been calculated. The results are given in the form of a matrix for these four NMIs together with the recalculated degrees of equivalence of an APMP regional comparison held in 2000, comparison identifier APMP.RI(II)-K2.Ho-166m for six other NMIs. A graphical presentation is also given. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section II, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).