[en] We report on a feasibility study on precise determination of mass-specific activity of low-energy emitting radioisotopes. Conventional methods of activity measurement suffer from source self-absorption and a strong decrease in detection efficiency for low-energy electrons and photons. We propose a new method based on metallic magnetic microcalorimeters with the source embedded in the detector target in a 4π geometry. First results with a ⁵⁵Fe source show that electrons and photons are detected with a detection efficiency close to unity and with little loss of energy for electrons. The aim of this study is to provide standards of activity with very low uncertainties in the framework of radiation metrology

[en] We have developed a prototype magnetic calorimeter, operated at very low temperature, for absolute activity measurement of low energy emitting radionuclides. A weighed source of ⁵⁵Fe has been enclosed inside the detector absorber assuring a high detection efficiency. The result of a preliminary activity measurement carried out with this prototype is compatible with a measurement by liquid scintillation counting. Apart from the high detection efficiency, this approach is particularly interesting since it introduces a new method into a field where only few measuring techniques are available. (authors)

[en] Cryogenic detectors offer remarkably better energy resolutions than those achievable with conventional semiconductor or scintillation detectors. With the additional asset of a detection efficiency close to unity for low-energy X-ray photons and electrons, these detectors have the potential to perform X-ray, gamma and electron spectroscopy of a hitherto unknown quality, in particular at low energies. Two types of cryogenic detectors are described and the results of prototype detectors are presented

[en] In this paper we present a prototype of a new class of detectors, metallic magnetic calorimeters operating at cryogenic temperatures, which we are developing for absolute activity measurement of low-energy-emitting radionuclides. We explain the detection principle and give a detailed description of the realisation of the prototype, containing an ⁵⁵Fe source inside the detector absorber. The analysis of first data taken with this detector is presented and the result of activity measurement compared with liquid scintillation counting. Some ways for reducing the uncertainty that can be achieved with this new technique are proposed

[en] Experiments were performed to verify the possible influence of the temperature and source matrix on the half-life of ²¹⁰Po. Since the precise measurement of the activity of an α-emitting source at cryogenic temperature is far from trivial, a simpler approach was used: the activity of a ²¹⁰Po source was measured at ambient temperature, but in between the measurements, the source was cooled down during a few weeks in a liquid helium Dewar. A ²¹⁰Po solid source was prepared by electro-deposition on a silver plate. The activity of this source was first measured at room temperature, using the defined solid angle α measurement method. The source was then placed in a specific gastight container inside a liquid helium bath at 4 K during 28 days. Then the source was heated up and measured again using the same instrument in the same geometric conditions. The same experiment was repeated with the source coated with a thin layer of silver, in order to be sure that the radioactive material was fully embedded inside the metallic matrix. Our experiments showed no evidence of ²¹⁰Po half-life change at low temperature. A reduction of the half-life of ²¹⁰Po by 6.3% at low temperature, as claimed by , would have lead to a decay-corrected activity reduction of about 1% after 29 days, which would have been easily detectable. The paper describes the steps of this experiment and gives a detailed uncertainty budget for the measurements. The half-life of ²¹⁰Po obtained in each measurement is compared with the evaluated value of (138.3763±0.0017) d.

[en] Quantitative solid sources are used widely in the field of radionuclide metrology. With the aim to improve the detection efficiency for electrons and x-rays, a comparative study between two source drying techniques has been undertaken at LNE-Laboratoire National Henri Becquerel (LNE-LNHB, France). In this paper, freeze-drying using commercial equipment is compared with a system of drying using hot jets of nitrogen developed at Institute for Reference Materials and Measurements (IRMM, Belgium). In order to characterize the influence of self-absorption, the detection efficiencies for ⁵¹Cr sources have been measured by coincidence counting and photon spectrometry

[en] Gamma imaging is a technique that allows the spatial localization of radioactive sources in decommissioning phases of nuclear facilities, nuclear waste management applications, radiation protection, and Homeland Security. One asset of this technique is the possibility to quickly localize radioactive sources associated with a quantitative information on their intensity. Using gamma camera diminishes the dose received by operators and consequently respects the ALARA principle (“As Low As Reasonably Achievable”). For several years, CEA LIST has been designing a coded aperture gamma camera, called GAMPIX. This imager was industrialized by MIRION Technologies (CANBERRA) under the commercial name of iPIX. An extensive study was initiated to validate the GAMPIX quantitative performances for evaluation of dose rate and associated uncertainties. The validation was performed with single and multiple radioactive sources covering an energy range from 60 keV to 1.3 MeV. This article presents experimental results obtained with the GAMPIX gamma camera in the framework of the EMRP ENV54 METRODECOM project.

[en] The LNE-LNHB is developing metallic magnetic calorimeters, a specific type of cryogenic detectors, for beta spectrometry. The aim is the determination of the shape factors of beta spectra. Our latest detector has been designed to measure the spectrum of ²⁴¹Pu, a pure beta emitter with an endpoint energy of 20.8 keV. In this paper, the detection principle of metallic magnetic calorimeters is explained and a detailed description is given of the realization of the detector enclosing a ²⁴¹Pu source inside the detector absorber. A spectrum resulting from our first measurement is shown and compared with a theoretical spectrum.

[en] A ⁶⁴Cu solution was standardized by means of liquid scintillation counting. The activity of the solution was also determined with an ionization chamber whose response was simulated by using a Monte Carlo code. The photon emission intensities including K X-rays were determined to be I₅₁₁=35.1 (3)%; I₁₃₄₆=0.472 (12)%, IKα=14.41 (15)%, IKβ=2.01 (3)%, respectively. ⁶⁴Cu half-life was also determined as 12.718 (23) h. The new decay scheme used in the present work was established following the EURAMET 1085 exercise where a good agreement between activity measurement techniques was found.

[en] Three new participations in the BIPM.RI(II)-K1.Fe-59 comparison have been added to the previous results and this has produced a revised value for the key comparison reference value (KCRV), calculated using the power-moderated weighted mean. A link has been made to the APMP.RI(II)-K2.Fe-59 comparison held in 2014 through the NMIJ who participated in both comparisons. Five NMIs used the K1 or 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.Fe-59 comparison and the eight other participants in the APMP.RI(II)-K2.Fe-59 comparison. A graphical presentation is also given. (authors)