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The half-life of 55Fe has been measured accurately by following the decay curve of three sources with a large pressurised proportional counter. An argon(90%)-methane(10%) mixture was used as counter gas, at atmospheric pressure (∼1 × 105 Pa) and at enhanced pressures of 5 × 105 Pa and 8 × 105 Pa (for 1 source), respectively. The first measurements were performed in 2001, but the experiment was executed more systematically between 2005 and 2018, covering a period of about 5 half-lives. The residuals from an exponential decay curve were of the order of 0.1% to 0.2% at 1 × 105 Pa, and 0.03% at 5 × 105 Pa and 8 × 105 Pa. The gain of stability with increased gas pressure was due to asymptotically reaching the maximum counting efficiency, resulting in lower sensitivity to pressure variations. The deduced half-life value of T 1/2 (55Fe) = 1006.70 (15) d or 2.7563 (4) a is more accurate than other data in literature, which are mutually discrepant. It is consistent with previous measurements at JRC with an X-ray defined solid angle counter. • Measured 55Fe half-life value of 1006.70 (15) days or 2.7563 (4) a. • Used proportional counter at 0.1 MPa, 0.5 MPa, and 0.8 MPa gas pressure. • Improvement of reference value by order of magnitude. • Literature data highly inconsistent and mostly discrepant with current value. [ABSTRACT FROM AUTHOR]

Some authors have raised doubt about the invariability of decay constants, which would invalidate the exponential-decay law and the foundation on which the common measurement system for radioactivity is based. Claims were made about a new interaction – the fifth force – by which neutrinos could affect decay constants, thus predicting changes in decay rates in correlation with the variations of the solar neutrino flux. Their argument is based on the observation of permille-sized annual modulations in particular decay rate measurements, as well as transient oscillations at frequencies near 11 year −1 and 12.7 year −1 which they speculatively associate with dynamics of the solar interior. In this work, 12 data sets of precise long-term decay rate measurements have been investigated for the presence of systematic modulations at frequencies between 0.08 and 20 year −1 . Besides small annual effects, no common oscillations could be observed among α, β - , β + or EC decaying nuclides. The amplitudes of fitted oscillations to residuals from exponential decay do not exceed 3 times their standard uncertainty, which varies from 0.00023 % to 0.023 %. This contradicts the assertion that 'neutrino-induced' beta decay provides information about the deep solar interior. [ABSTRACT FROM AUTHOR]

First results of a half-life measurement of 209 Po show 20% discrepancy with the formerly recommended value of 102 (5) years, which was based on a single experiment performed in 1956. After one year of measurement, a statistical uncertainty on T 1/2 of 3.5% has been reached and effects of long-term instability are assumed to be less than 5%. The preliminary half-life value obtained in this work, 120 (6) years, supports the newly determined value of 125.2 (33) years by Collé et al. (2014) . The 20% error in the half-life has an impact on numerous measurements in which aged 209 Po solutions were used as a tracer. [ABSTRACT FROM AUTHOR]

At the JRC-Geel's RadioNuclide Metrology sector, a Monte Carlo code based on EGSnrc, and a general purpose calculation sheet implemented in Microsoft Excel ® , have been developed to make the quantitative gamma-ray spectrometry analysis of samples simpler and more robust. The further aim is that the software can be used by non-experts in gamma-ray spectrometry e.g. external researchers using JRC-Geel's facilities through the EUFRAT transnational access scheme. This paper presents the developed Monte Carlo software and the functionality included in the calculation sheet. [ABSTRACT FROM AUTHOR]

A measurement station dedicated for quantitative radiological characterisation of naturally occurring radionuclides in a metallurgical company and based on gamma-ray spectrometry was developed. The station is intended for performing quality control of final non-ferrous metal products and for radiological checks of incoming materials. A low-background point-contact HPGe-detector was used and the signal was split in two branches to enable collecting simultaneously spectra with high amplification (for gamma-ray energies below 250 keV) and low amplification. [ABSTRACT FROM AUTHOR]

Following the accident at the Fukushima Daiichi nuclear power plant, a campaign of sampling and measuring anthropogenic radionuclides in North Pacific seawater was set up. The main aim was to study natural processes using these radionuclides as tracers. Because of dilution, the activities of anthropogenic radionuclides at long range were very low and their measurement required advanced pre-concentration techniques and underground gamma-ray spectrometry. Data and metrological aspects of the measurements using HPGe-detectors are presented and discussed. [ABSTRACT FROM AUTHOR]

Abstract: A new magnet system has been designed and constructed to reduce coincidence effects between alpha particles and conversion electrons in high-resolution alpha-particle spectrometry. By means of a magnetic field, the conversion electrons are deflected away from the PIPS® detector. Compared to existing magnet systems, the new system is not restricted to point sources and can accommodate source diameters up to about 30mm. Two yokes were built, allowing for configurations with 20mm or 36mm distance between the magnets. The effectiveness of both configurations is demonstrated by measuring the conversion electron spectrum of a 237Np source. The magnet system effectively rejects 93 (7)% of electrons up to 85keV (36mm) and 90 (9)% of electrons up to 320keV (20mm). It has been successfully applied in the alpha-particle spectrometry of the long-lived nuclides 236U and 238U, resulting in significant improvement of the accuracy of alpha emission probabilities. [Copyright &y& Elsevier]

Abstract: High-resolution alpha-particle spectrometry was performed with an ion-implanted silicon detector in vacuum on a homogeneously electrodeposited 236U source. The source was measured at different solid angles subtended by the detector, varying between 0.8% and 2.4% of 4π sr, to assess the influence of coincidental detection of alpha-particles and conversion electrons on the measured alpha-particle emission probabilities. Additional measurements were performed using a bending magnet to eliminate conversion electrons, the results of which coincide with normal measurements extrapolated to an infinitely small solid angle. The measured alpha emission probabilities for the three main peaks – 74.20 (5)%, 25.68 (5)% and 0.123 (5)%, respectively – are consistent with literature data, but their precision has been improved by at least one order of magnitude in this work. [Copyright &y& Elsevier]

Abstract: The alpha-particle emission probabilities associated with the three main alpha transitions of 238U were measured by high-resolution alpha-particle spectrometry. Highly enriched 238U material was used and its isotopic composition characterised by mass spectrometry. Source production through electrodeposition was optimised to reconcile conflicting demands for good spectral resolution and statistical precision. Measurements were performed at IRMM and CIEMAT for 1–2 years in three different set-ups. A new magnet system was put into use to largely eliminate true coincidence effects with low-energy conversion electrons. Finally the accuracy and precision of the relative emission probabilities for the three transitions – 77.01 (10)%, 22.92 (10)% and 0.068 (10)%, respectively – have been improved significantly. [Copyright &y& Elsevier]

Abstract: The half-lives of 221Fr, 217At, 213Bi, 213Po, and 209Pb were measured by means of an ion-implanted planar Si detector for alpha and beta particles emitted from weak 225Ac sources or from recoil sources, which were placed in a quasi-2π counting geometry. Recoil sources were prepared by collecting atoms from an open 225Ac source onto a glass substrate. The 221Fr and 213Bi half-lives were determined by following the alpha particle emission rate of recoil sources as a function of time. Similarly, the 209Pb half-life was determined from the beta particle count rate. The shorter half-lives of 217At and 213Po were deduced from delayed coincidence measurements on weak 225Ac sources using digital data acquisition in list mode. The resulting values: T 1/2(221Fr)=4.806 (6) min, T 1/2(217At)=32.8 (3)ms, T 1/2(213Bi)=45.62 (6)min, T 1/2(213Po)=3.708 (8)μs, and T 1/2(209Pb)=3.232 (5)h were in agreement only with the best literature data. [Copyright &y& Elsevier]

Abstract: In this work, 213Bi has been separated from an open 225Ac source by collecting recoil atoms onto a glass plate in vacuum. The activity of such recoil sources has been measured as a function of time, using an ion-implanted planar Si detector in quasi-2π geometry. From these measurements, a new half-life value of T 1/2(213Bi)=45.62 (6)min was derived. Additionally, high-resolution alpha-spectrometry measurements were performed at a solid angle of 0.4% of 4πsr, to verify the energies and emission probabilities of the α-emissions from 213Bi. Using 225Ac, 221Fr, 217At and 213Po peaks as reference peaks, the measured 213Bi α-peak energies at E α,0=5878 (4)keV and E α,1=5560 (4)keV were about 10keV higher than validated data. The relative α-particle emission probabilities of 213Bi, P α,0=0.9155 (11) and P α,1=0.0845 (11), and the 213Bi alpha branching factor, P α=1−P β=2.140 (10)%, are compatible with recommended values, but have a higher accuracy. [Copyright &y& Elsevier]

Abstract: The 225Ac half-life was determined by measuring the activity of 225Ac sources as a function of time, using various detection techniques: α-particle counting with a planar silicon detector at a defined small solid angle and in a nearly-2π geometry, 4πα+β counting with a windowless CsI sandwich spectrometer and with a pressurised proportional counter, gamma-ray spectrometry with a HPGe detector and with a NaI(Tl) well detector. Depending on the technique, the decay was followed for 59–141d, which is about 6–14 times the 225Ac half-life. The six measurement results were in good mutual agreement and their mean value is T 1/2(225Ac)=9.920 (3)d. This half-life value is more precise and better documented than the currently recommended value of 10.0d, based on two old measurements lacking uncertainty evaluations. [Copyright &y& Elsevier]

Abstract: High-resolution alpha-particle spectrometry was performed on the 230U decay series. A 230U source was prepared on a stainless steel disc by electrodeposition in an ammonium nitrate solution. Spectrometry of the alpha-particle energy spectrum was performed with ion-implanted planar silicon detectors in vacuum. A set of alpha emission probabilities is presented for 230U and 226Th. The measured peak intensities were corrected mathematically for coincidental detection of alpha-particles and conversion electrons emitted in the same decay. A good agreement with literature data was observed. The uncertainty budget and the correlation matrix are presented. The validity of the alpha-particle energies was tested and could be confirmed for most peaks within a few keV, but discrepancies were found for the 2nd peak of 226Th and the main peak of 218Rn. [Copyright &y& Elsevier]

Abstract: The half-lives of 226Th and 222Ra were measured by counting alpha-particle emissions from sources as a function of time. The 226Th sources were prepared from an open 230U source, capturing recoil atoms after alpha-particle decay on glass disks or even directly onto a detector. Similarly, the 222Ra sources were obtained by self-transfer of recoil atoms from 226Th sources. The activity measurements were performed in (nearly-)2π geometry with an ion-implanted silicon detector. The decay curves were analysed in different ways, incl. moment analysis, trying to avoid the pitfalls of bias of least-squares fits to Poisson distributed data. The observed half-life values are T 1/2(226Th)=30.70 (3) min and T 1/2(222Ra)=33.6 (4) s. Literature values show some inconsistency. [Copyright &y& Elsevier]

Abstract: The half-lives of 214Po and 218Rn have been measured. The radionuclides were produced in the decay of a 230U source and the emitted alpha-particles were measured in nearly-2π geometry with an ion-implanted planar silicon detector. The data acquisition was performed with a digitiser operated in list mode, saving the energy and time of detection (10ns precision timestamp) of each event. The half-lives were deduced from the time differences between the alpha-decays populating the nuclide of interest and those corresponding to its decay. Different methods were applied, based on delayed coincidence counting and time-interval distribution analysis. The resulting half-lives are 33.75 (15)ms for 218Rn and 164.2 (6)μs for 214Po, both in agreement with some of the literature values, and obtained with higher precision in this work. [Copyright &y& Elsevier]

Abstract: The 230U half-life was determined by measuring the decay curve of 230U sources by various nuclear detection techniques: α-particle counting at a defined small solid angle; 4πα+β counting with a windowless CsI sandwich spectrometer, a liquid scintillation counter and a pressurised proportional counter; gamma-ray spectrometry with a HPGe detector and nearly-2π α-particle counting with an ion-implanted silicon detector. Depending on the technique, the decay was followed for 100–200d, which is 5–10 times the 230U half-life. The measurement results of the various techniques were in good mutual agreement. The mean value, T 1/2(230U)=20.23 (2)d, is lower than the literature value which is based on one measurement in 1948 and resulted in a half-life value of 20.8d without statement of uncertainty. A correction for the ingrowth of the long-lived 210Pb and its daughter products may have been overlooked in the past. [Copyright &y& Elsevier]