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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.

$^{175}$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.

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.

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 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.

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; 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.

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.

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.

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.

In the framework of the EMPIR project MetroBeta, the development and optimization of a double focalizing magnetic spectrometer have been realized in order to measure the beta spectra shape. The acquisition is designed to perform,after focalization by the magnetic field, an energy selection using a window on the deposited energy in the Si detector. The energy calibration is performed using conversion electrons from 109Cd, 137Cs, 133Ba and 207Bi and the measured energy resolution is 1.3% at 1 MeV. The efficiency is measured experimentally using a 204Tl source and is used to reconstruct the spectrum shape for beta emitters with end-point energy up to 750 keV. Two beta emitters with allowed transitions, 134Cs and 60Co, are used to validate the measurement and the reconstruction method. Finally the measurement of the beta shape of 36Cl, a non-unique 2nd forbidden transition is presented.