The 55Fe half-life measured with a pressurised proportional counter.

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 T1/2(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.

Is decay constant?

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, ß-, ß+ 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.

A gamma-ray spectrometry analysis software environment.

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.

A low-energy set-up for gamma-ray spectrometry of NORM tailored to the needs of a secondary smelting facility.

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 250keV) and low amplification.

Evidence against solar influence on nuclear decay constants.

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.

Tracing radioactivity from Fukushima in the Northern Pacific Ocean.

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.

A new large-volume metal reference standard for radioactive waste management.

A new large-volume metal reference standard has been developed. The intended use is for calibration of free-release radioactivity measurement systems and is made up of cast iron tubes placed inside a box of the size of a Euro-pallet (80 × 120 cm). The tubes contain certified activity concentrations of (60)Co (0.290 ± 0.006 Bq g(-1)) and (110m)Ag (3.05 ± 0.09 Bq g(-1)) (reference date: 30 September 2013). They were produced using centrifugal casting from a smelt into which (60)Co was first added and then one piece of neutron irradiated silver wire was progressively diluted. The iron castings were machined to the desirable dimensions. The final material consists of 12 iron tubes of 20 cm outer diameter, 17.6 cm inner diameter, 40 cm length/height and 245.9 kg total mass. This paper describes the reference standard and the process of determining the reference activity values.

Confirmation of 20% error in the (209)Po half-life.

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 T1/2 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.

A magnet system for the suppression of conversion electrons in alpha spectrometry.

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 30 mm. Two yokes were built, allowing for configurations with 20 mm or 36 mm distance between the magnets. The effectiveness of both configurations is demonstrated by measuring the conversion electron spectrum of a (237)Np source. The magnet system effectively rejects 93 (7)% of electrons up to 85 keV (36 mm) and 90 (9)% of electrons up to 320 keV (20 mm). It has been successfully applied in the alpha-particle spectrometry of the long-lived nuclides (236)U and (238)U, resulting in significant improvement of the accuracy of alpha emission probabilities.

Alpha-particle emission probabilities of ²³6U obtained by alpha spectrometry.

High-resolution alpha-particle spectrometry was performed with an ion-implanted silicon detector in vacuum on a homogeneously electrodeposited (236)U 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.

High-resolution alpha-particle spectrometry of ²³8U.

The alpha-particle emission probabilities associated with the three main alpha transitions of (238)U were measured by high-resolution alpha-particle spectrometry. Highly enriched (238)U 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.

Sildenafil increases serum testosterone levels by a direct action on the testes.

Phosphodiesterase-5-inhibitors, such as sildenafil, increase intracavernosal cyclic guanosine monophosphate levels, which results in corporal smooth muscle relaxation and penile erection. Here, we determined the effects of sildenafil administration on the hypothalamic-pituitary-gonadal axis in men with erectile dysfunction and low testosterone levels. The Testosterone and Erectile Dysfunction trial (ClinicalTrials.gov # NCT00512707) initially administered an optimized dose of sildenafil to 140 men, aged 40-70 years with erectile dysfunction, low serum total testosterone (<11.4 nmol/L; 330 ng/dL) and/or free testosterone (<173 pmol/L; 50 pg/mL) over 3-7 weeks. Sex steroids and gonadotropins were measured at baseline and after sildenafil optimization in a longitudinal study without a separate control group. Serum testosterone, dihydrotestosterone (DHT) and oestrogens were measured using liquid chromatography-tandem mass spectrometry. Administration of an optimized dose of sildenafil was associated with mean increases of 3.6 nmol/L (103 ng/dL; p < 0.001) and 110 pmol/L (31.7 pg/mL; p < 0.001) in total and free testosterone levels respectively. This was accompanied by parallel increases in serum DHT (0.17 nmol/L; 4.9 ng/dL; p < 0.001) and oestradiol (14 pmol/L; 3.7 pg/mL; p < 0.001) and significant suppression of luteinizing hormone (change -1.3 units/L; p = 0.003) levels, suggesting a direct effect at the testicular level. Androstenedione and oestrone increased by 1.3 nmol/L (38 ng/dL; p = 0.011) and 10.7 pmol/L (2.9 pg/mL; p = 0.012), respectively, supporting a possible effect of sildenafil on adrenal steroidogenesis. In conclusion, sildenafil administration was associated with increased testosterone levels likely ascribable to a direct effect on the testis.

Half-lives of 221Fr, 217At, 213Bi, 213Po and 209Pb from the 225Ac decay series.

The half-lives of (221)Fr, (217)At, (213)Bi, (213)Po, and (209)Pb were measured by means of an ion-implanted planar Si detector for alpha and beta particles emitted from weak (225)Ac sources or from recoil sources, which were placed in a quasi-2π counting geometry. Recoil sources were prepared by collecting atoms from an open (225)Ac source onto a glass substrate. The (221)Fr and (213)Bi half-lives were determined by following the alpha particle emission rate of recoil sources as a function of time. Similarly, the (209)Pb half-life was determined from the beta particle count rate. The shorter half-lives of (217)At and (213)Po were deduced from delayed coincidence measurements on weak (225)Ac sources using digital data acquisition in list mode. The resulting values: T1/2((221)Fr)=4.806 (6) min, T1/2((217)At)=32.8 (3)ms, T1/2((213)Bi)=45.62 (6)min, T1/2((213)Po)=3.708 (8) µs, and T1/2((209)Pb)=3.232 (5)h were in agreement only with the best literature data.

Decay data measurements on 213Bi using recoil atoms.

In this work, (213)Bi has been separated from an open (225)Ac 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 T1/2((213)Bi)=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 (213)Bi. Using (225)Ac, (221)Fr, (217)At and (213)Po peaks as reference peaks, the measured (213)Bi α-peak energies at Eα,0=5878 (4)keV and Eα,1=5560 (4)keV were about 10keV higher than validated data. The relative α-particle emission probabilities of (213)Bi, Pα,0=0.9155 (11) and Pα,1=0.0845 (11), and the (213)Bi alpha branching factor, Pα=1-Pß=2.140 (10)%, are compatible with recommended values, but have a higher accuracy.

Measurement of the 225Ac half-life.

The (225)Ac half-life was determined by measuring the activity of (225)Ac 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+ß 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 59-141 d, which is about 6-14 times the (225)Ac half-life. The six measurement results were in good mutual agreement and their mean value is T(1/2)((225)Ac)=9.920 (3)d. This half-life value is more precise and better documented than the currently recommended value of 10.0 d, based on two old measurements lacking uncertainty evaluations.

Measurement of the 230U half-life.

The (230)U half-life was determined by measuring the decay curve of (230)U sources by various nuclear detection techniques: α-particle counting at a defined small solid angle; 4πα+ß 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 100-200 d, which is 5-10 times the (230)U half-life. The measurement results of the various techniques were in good mutual agreement. The mean value, T(1/2)((230)U)=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 (210)Pb and its daughter products may have been overlooked in the past.

Measurement of the 226Th and 222Ra half-lives.

The half-lives of (226)Th and (222)Ra were measured by counting alpha-particle emissions from sources as a function of time. The (226)Th sources were prepared from an open (230)U source, capturing recoil atoms after alpha-particle decay on glass disks or even directly onto a detector. Similarly, the (222)Ra sources were obtained by self-transfer of recoil atoms from (226)Th 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)((226)Th)=30.70 (3) min and T(1/2)((222)Ra)=33.6 (4) s. Literature values show some inconsistency.

High-resolution alpha-particle spectrometry of the 230U decay series.

High-resolution alpha-particle spectrometry was performed on the (230)U decay series. A (230)U 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 (230)U and (226)Th. 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 (226)Th and the main peak of (218)Rn.

Measurements of the half-life of 214Po and 218Rn using digital electronics.

The half-lives of (214)Po and (218)Rn have been measured. The radionuclides were produced in the decay of a (230)U 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 (10 ns 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 (218)Rn and 164.2 (6) µs for (214)Po, both in agreement with some of the literature values, and obtained with higher precision in this work.

Effect of dietary crude protein source on hormone and follicle characteristics in beef heifers.

Ground, raw soybeans (SB), or dried distillers grain plus solubles (DDGS) were utilized in heifer development diets to determine the effect of dietary fat and protein source on hormone and follicle characteristics and ADG. The experiment was conducted over 2 yr with 100 June-born heifers (199 +/- 2 kg initial BW, n = 50 per yr). The experimental periods were 157 and 207 d in yr 1 and 2, respectively. Heifers were provided a dietary supplement (DM basis) of 1.23 kg of SB and 0.40 kg of corn or 1.65 kg of DDGS between weaning and breeding. Estrus was synchronized with 2 injections of PGF(2alpha) 14 d apart. Dominant follicles were measured and aspirated via transvaginal ultrasonography 60 h after the second PGF(2alpha) injection. Heifers were exposed to bulls beginning 14 d after aspiration for 45 d. Heifer ADG was greater (P = 0.02) for DDGS heifers in yr 1, but was similar (P = 0.47) in yr 2. However, there was no difference (P = 0.35) in final BW in either year. There was no difference (P >or= 0.67) in follicle size, follicle hormone concentrations, or pregnancy rate (88%) between yr 1 and 2. Serum estrogen at 48 or 60 h after PGF(2alpha) injection were similar (P >or= 0.91); however, LH at 60 h in yr 2 tended to be greater (P = 0.07) for DDGS heifers. The percentage of heifers experiencing an LH surge 48 and 60 h after PGF(2alpha) injection was not affected (P >/= 0.40) by treatment. Calf production was not affected (P >or= 0.20) by developmental diet. In summary, DDGS and SB have similar effects on hormone and follicle characteristics at the inclusion rates used in these studies.