On the claim of modulations in 36Cl beta decay and their association with solar rotation

Recently, claims were made by Sturrock et al. that beta decay can be induced by interaction of the nucleus with solar neutrinos and that cyclic modulations in decay rates are indicative of the dynamics of the solar interior. Transient modulations in residuals from a purely exponential decay curve were observed at frequencies near 11 year-1 and 12.7 year-1 in repeated activity measurements of a 36Cl source by Alburger et al. at Brookhaven National Laboratory in a period from 1984 to 1985. Sturrock et al. have speculatively associated them with rotational influence on the solar neutrino flux. In this work, more accurate 36Cl decay rate measurements – performed at the PTB in the period 2010-2013 by means of the triple-to-double coincidence ratio measurement technique – have been scrutinised. The residuals from an exponential decay curve were analysed by a weighted Lomb-Scargle periodogram. The existence of modulations in the frequency range between 0.2 a-1 and 20 a-1 could be excluded down to an amplitude of about 0.0016%. The invariability of the 36Cl decay constant contradicts the speculations made about the deep solar interior on the basis of instabilities in former activity measurements.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

A reply to the rebuttal by Sturrock et al.

Sturrock et al. have published a "rebuttal" to a paper by Pommé et al. who refuted their claim that variations in a radon decay experiment at the Geological Survey of Israel (GSI) can be associated with solar rotation. Sturrock et al. misinterpret the variability of the decay rates in the gamma counter to assert influences by solar and cosmic neutrinos on beta decay and draw unsubstantiated conclusions about solar dynamics. Evidence suggests that the radon measurements were susceptible to solar irradiance and rainfall, whereas there is no indication that radioactive decay is influenced by the solar neutrino flux. In this reply to the rebuttal, the arguments raised by Sturrock et al. are scrutinised.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

On the claim of modulations in radon decay and their association with solar rotation

Claims were made by Sturrock et al. that radioactive decay can be induced by interaction of the nucleus with solar neutrinos and that cyclic modulations in decay rates are indicative of the dynamics of the solar interior. They analysed a series of measurements of gamma radiation associated with the emanation and decay of radon in a sealed container at the Geological Survey of Israel (GSI) laboratory. The integral count rates in the NaI detector showed strong variations in time of year and time of day. From time-series analysis, Sturrock et al. claim the presence of small oscillations at frequencies in a range between 7.4 a-1 and 12.5 a-1, which they speculatively associated with rotational influence on the solar neutrino flux. In this work, it is argued that the GSI radon measurements are unsuited for studying the variability of decay constants, because the data are strongly influenced by environmental conditions, such as solar irradiance and rainfall. At the JRC and PTB, decay rate measurements of the radon decay chain were performed with ionisation chambers, gamma-ray spectrometers and an alpha spectrometer. No deviation from the exponential-decay law was observed. The existence of cyclic variations in the decay constants is refuted, as well as the concept of measuring solar rotation through radioactive decay.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Safety, feasibility, and diagnostic value of cardiac magnetic resonance imaging in patients with cardiac pacemakers and implantable cardioverters/defibrillators at 1.5 T

BACKGROUND: Recent studies suggest that magnetic resonance (MR) imaging of the brain and spine may safely be performed in patients with pacemakers (PMs) and implantable cardioverter/defibrillators (ICDs), when taking adequate precautions. The aim of this study was to investigate safety, feasibility, and diagnostic value (DV) of MR imaging in cardiac applications (cardiac MR [CMR]) in patients with PMs and ICDs for the first time. METHODS: Thirty-two PM/ICD patients with a clinical need for CMR were examined. The specific absorption rate was limited to 1.5 W/kg. Devices were reprogrammed pre-CMR to minimize interference with the electromagnetic fields. Devices were interrogated pre-CMR and post-CMR and after 3 months. Troponin I levels were measured pre-CMR and post-CMR; image quality (IQ) and DV of CMR were assessed. RESULTS: All devices could be reprogrammed normally post-CMR. No significant changes of pacing capture threshold, lead impedance, and troponin I were observed. Image quality in patients with right-sided devices (RSD) was better compared with that in patients with left-sided devices (LSD) (P < .05), and less myocardial segments were affected by device-related artefacts (P < .05). Diagnostic value was rated as sufficiently high, allowing for diagnosis, or better in 12 (100%) of 12 patients with RSD, and only in 7 (35%) of 20 patients with LSD. CONCLUSIONS: Cardiac MR may be performed safely when limiting specific absorption rate, appropriately monitoring patients, and following device reprogramming. Cardiac MR delivers good IQ and DV in patients with RSD. Cardiac MR in patients with RSD may therefore be performed with an acceptable risk/benefit ratio, whereas the risk/benefit ratio is rather unfavorable in patients with LSD. Copyright © 2011 Mosby, Inc. All rights reserved

Results of the EURAMET.RI(II)- S7.Sm-151 supplementary comparison (EURAMET Project 1292)

An international comparison of the activity standardisation of the relatively long-lived gamma-ray emitter 151Sm has been recently completed. A total of six laboratories measured a solution prepared by CEA/LNHB and CEA/LANIE. Aliquots of the master solution were standardized in terms of activity per mass unit by participant laboratories using 2 different techniques. The results of the comparison can be used as the basis for establishing equivalence among the laboratories. The activity measurements of this comparison are part of the joint research project “Metrology for Radioactive Waste Management” of the European Metrology Research Programme (EMRP). One aim of this project is a new determination of the 151Sm half-life.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Determination of the 151Sm half-life

New measurements have been undertaken to determine the half-life of 151Sm. A pure 151Sm solution was obtained after chemical separation from a samarium solution resulting from the dissolution of an irradiated samarium sample. The concentration of 151Sm in the solution was measured by mass spectrometry, combined with the isotope dilution technique. The activity of the solution was measured by liquid scintillation counting by six European laboratories as part of an international comparison. These combined results lead to a half-life of T1/2 = 94.6(6) a.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

The half-life of 129I

The radionuclide 129I is a long-lived fission product that decays to 129Xe by beta-particle emission. It is an important tracer in geological and biological processes and is considered one of the most important radionuclides to be assessed in studies of global circulation. It is also one of the major contributors to radiation dose from nuclear waste in a deep geological repository. Its half-life has been obtained by a combination of activity and mass concentration measurements in the frame of a cooperation of 6 European metrology institutes. The value obtained for the half-life of 129I is 16.14 (12) × 106 a, in good agreement with recommended data but with a significant improvement in the uncertainty.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Results of the EURAMET.RI(II)-K2.Ho-166m activity comparison

In 2013, five laboratories took part in the EURAMET.RI(II)-K2.Ho-166m comparison of activity concentration measurements of 166mHo. The activity measurements of this comparison are part of the joint research project “Metrology for Radioactive Waste Management” of the European Metrology Research Programme (EMRP). One aim of this project is a new determination of the 166mHo half-life.The results were found to be in good agreement and no outlier could be identified. A comparison reference value (CRV) has been calculated as the power-moderated mean (PMM) of all final laboratory results and was found to be 119.27(10) kBq g–1. Preliminary degrees of equivalence based on the Comparison Reference Value were also calculated for each reporting laboratory. The Key Comparison Reference Value and final degrees of equivalence will be calculated by the BIPM from the data contained herein and data from measurements made in the International Reference System (SIR).JRC.D.4-Standards for Nuclear Safety, Security and Safeguard