Underground radioactivity measurements of meteorites: Development of methods suitable to determine precise terrestrial age of recent falls.

The L6 chondritic meteorite, HaH-346, fell in Libya. However, neither the exact date of the fall nor the exact size of the original meteoroid or asteroid is known. A specimen of the meteorite, weighing 488 g, was measured using ultra low-background gamma-ray spectrometry in the 225 m deep underground facility HADES. Activation products 22Na, 26Al, 60Co, 57Co, 54Mn and 44Ti were detected. The detection efficiency was determined by 3D scanning the meteorite and introducing this in the computer model of the detector and sample implemented in the MCNP6.2 Monte Carlo code. The activities of 22Na and 26Al support the hypothesis that the fall took place on 26 August 2018. Furthermore, the 60Co and 26Al activities indicate that the original radius of meteoroid was between 50 and 80 cm, which suggests the mass prior to atmospheric entry was between 2400 and 7300 kg.

Performance evaluation of a European wide proficiency test on gross alpha/beta activity determination in drinking water.

JRC-Geel organised a Europe-wide proficiency test on gross alpha/beta activity concentration measurements in water with 154 participants from the field of environmental radioactivity monitoring. The performance of the participants was evaluated by comparing their results to the reference value using percentage deviation, z-score and zeta-score. Many of the participants' results deviated several orders of magnitude from the reference values regardless of the techniques used suggesting that the radioactivity monitoring of drinking water using gross-counting in Europe needs improving. Comparing with a similar proficiency test in 2012 reveals no major improvements and indicate that standards for gross-counting methods need revision. From the accompanied questionnaire, participants' measurement methods, laboratory practices and pitfalls were discussed. From the 14 best performing methods, JRC identified "Best practices".

Search for Dark Matter Induced Deexcitation of

Weak-scale dark matter particles, in collisions with nuclei, can mediate transitions between different nuclear energy levels. In particular, owing to sizeable momentum exchange, dark matter particles can enable de-excitation of nuclear isomers that are extremely long lived with respect to regular radioactive decays. In this Letter, we utilize data from a past experiment with ^{180}Ta^{m} to search for γ lines that would accompany dark matter induced de-excitation of this isomer. Nonobservation of such transitions above background yields the first direct constraint on the lifetime of ^{180}Ta^{m} against dark matter initiated transitions: T_{1/2}>1.3×10^{14} a at 90% credibility. Using this result, we derive novel constraints on dark matter models with strongly interacting relics and on models with inelastic dark matter particles. Existing constraints are strengthened by this independent new method. The obtained limits are also valid for the standard model γ-decay of ^{180}Ta^{m}.

Performance evaluation of a European scale proficiency test on radon-in-water measurements in Europe.

In 2018, a Europe wide proficiency test (PT) on measurements of the massic activity of 222Rn in drinking water was organised with the participation of 101 European environmental radioactivity monitoring laboratories. The performance of the participating laboratories was evaluated by comparing submitted results to the reference value using percentage deviation, z-score and zeta-score. It was found that 84% of the participants' results were within the ±20% reference range. When analysing the zeta-score it was found that 76% of the participants' results were acceptable. The accompanied questionnaire and workshop helped to identify practices that could lead to erroneous results. As it was probably the largest scale PT on radon-in-water ever, the evaluation of results is representative of the quality of radon-in-water monitoring in the EU today.

Underground gamma-ray measurements of radium isotopes from hydrothermal plumes in the deep Pacific Ocean.

The radium isotopes 226Ra and 228Ra can provide important data on the dynamics of deep-sea hydrothermal plumes that travel the oceans for decades and have great impact on the ocean chemistry. This study focuses on parameters important for obtaining low detection limits for 228Ra using gamma-ray spectrometry. It is present at mBq-levels in samples collected during the US GEOTRACES 2013 cruise to the Southeast Pacific Ocean.

Evaluation of a radon-in-water pilot-proficiency test.

A pilot proficiency test (PT) on measurements of the massic activity of 222Rn in drinking water was organised by JRC-Geel. Fourteen environmental radioactivity monitoring laboratories were invited to participate. The key aim of the study was to test, optimise and stream-line the complete process for conducting such a PT in order to perform a large scale Europe-wide PT in a robust manner. The process involved using all state-of-the art knowledge on sampling, transporting and measuring 222Rn in water. It was found that the majority of the participants' results (92%) were within the ±15% reference range. The pilot-PT showed that the applied process was suitable and can be used for the large scale European PT planned for the third quarter of 2018.

Determination of homogeneity of the top surface deadlayer in an old HPGe detector.

A collimated source of 241Am was scanned over the endcap of a 21 year old coaxial HPGe-detector that had spent about 75% of its life at room temperature (and the remaining time at 77 K). The detector response was recorded and used as a measure of the relative thickness of the top deadlayer. This thickness was not homogeneous and was thicker near to the outer surface of the crystal compared to the centre, which could be a result of increased diffusion of Li atoms during times the detector was kept at room temperature. The results were compared with two newer HPGe-detectors that proved to have homogeneous top deadlayers.

Comprehensive study on the technical aspects of sampling, transporting and measuring radon-in-water.

The European Commission's Joint Research Centre organizes proficiency tests (PT) on radon-in-water measurements. In order to optimize sampling, transport and measurement methods many tests and small scale proficiency tests have been performed. The waters from natural springs, wells were sampled on-site in glass bottles then transported cooled to the JRC and collaborating laboratories. For the material characterization standard measurement methods based on gamma-ray spectrometry, emanometry and liquid scintillation counting were used. The influence of sampling, transport and sample handling on radon-loss was tested and quantified. It was observed that parameters like container material, filling height, storage temperature and handling can lead to substantial measurement bias due to radon-loss. This high risk for radon-loss from samples can potentially be a general radioprotection problem as doses to the public may be underestimated. Regular air and road transport can be considered adequate means of transport as they have little influence on radon-loss if a suitable glass sample container with flexible cap is used and that it is completely filled. On the basis of this work, modifications to the related standard as best practices are also proposed.

Evaluation of the 2016 ENV57 MetroERM measurement comparison on 137Cs, 134Cs and 131I in air filters.

In 2016, the European Commission's Joint Research Centre organised an interlaboratory comparison exercise on the measurement of 137Cs, 134Cs and 131I in air filters. The exercise was conducted in the frame of the MetroERM EMRP project with code ENV57. This paper describes the context of the interlaboratory measurement comparison, the technical implementation, the air filter measurements performed by the participating laboratories and finally the evaluation of the comparison results. The intercomparison exercise results are such that 56 out of the 67 laboratories (i.e. 84%) reported values within the ±20% range of the reference value for both the 137Cs and 134Cs. The evaluation of the performance of the laboratories on 131I was complicated and the details are explained. Nevertheless, 20 (30%) laboratories reported results for 131I with a percentage difference from the reference value within the ±20% range.

Characterisation of an ultra low-background point contact HPGe well-detector for an underground laboratory.

Since a few years there are well-type HPGe-detectors with a small, point-like, anode contacts available commercially. This paper describes the characterisation of the first ultra low-background, so-called, SAGe™ well detector with regards to resolution and background performance. Inside a passive lead/copper shield in the underground laboratory HADES a background count rate of 690 ± 6d-1 (268 ± 3d-1 per kg Ge) was recorded 19 months after taking it underground.

Advancements in NORM metrology - Results and impact of the European joint research project MetroNORM.

The results of the three years European Metrology Research Programme's (EMRP) joint research project 'Metrology for processing materials with high natural radioactivity' (MetroNORM) are presented. In this project, metrologically sound novel instruments and procedures for laboratory and in-situ NORM activity measurements have been developed. Additionally, standard reference materials and sources for traceable calibration and improved decay data of natural radionuclides have been established.

Variation of natural radionuclides in non-ferrous fayalite slags during a one-month production period.

The European Basic Safety Standards (EU-BSS) describes a set of NORM (Naturally Occurring Radioactive Material)-processing industries which produce residues known to be possibly enriched in NORs (Naturally Occurring Radionuclides). These residues can be used as a component in building materials aimed for public usage. The industrial processes, in which the residues are produced, are often complex and total monitoring can be challenging especially when the origin of the used raw materials varies. In this study the NORs present in non-ferrous fayalite slags of a secondary smelter facility, a NORM-processing industry according to the EU-BSS, were monitored daily during a one-month production period. In addition flue dust samples and feedstock samples, known to contain elevated levels of NORs, of the same period were measured. The survey involved the gamma-ray spectrometric analysis of the decay products from the 238U and 232Th decay chains, 235U and 40K using HPGe detectors. Secular equilibrium was observed for the slags, flue dust and feedstock samples in the 232Th decay chain, in contrast to the 238U decay chain. During the month in question the ratios of maximum over minimum activity concentration were 3.1 ± 0.5 for 40K, 4 ± 1 for 238U, 6 ± 1 for 226Ra, 13 ± 7 for 210Pb, 4.5 ± 0.6 for 228Ra and 4.7 ± 0.7 for 228Th for the slags. Even with the activity concentration of the feedstock material ranging up to 2.1 ± 0.3 kBq/kg for 238U, 1.6 ± 0.2 kBq for 226Ra, 22 ± 7 kBq/kg for 210Pb, 2.1 ± 0.2 kBq/kg for 228Ra and 2.0 ± 0.4 kBq/kg for 228Th, none of the slag samples exceeded the exemption/clearance levels of the EU-BSS and RP-122 part II, which can respectively provide guidance under equilibrium and in absence of equilibrium. As each NORM-processing industry has its own complexity and variability, the observed variations point out that one should approach one-time measurements or low frequency monitoring methods cautiously. Low frequency measurements should be optimised depending on the discharge of the batches. A follow up of the industrial process and its output can provide important insights to assure a limited public exposure upon application of these industrial residues. Finally a comparison is made with reported data on other metallurgical slags and the use of the slags in building materials is evaluated using the Activity Concentration Index (ACI) proposed by the EU-BSS.

Coordinated underground measurements of gamma-ray emitting radionuclides for plasma physics research.

Forty-eight samples made of CaF2, LiF and YVO4 were placed inside the KSTAR Tokamak and irradiated by neutrons and charged particles from eight plasma pulses. The aim was to provide information for plasma diagnostics. Due to the short pulse durations, the activities induced in the samples were low and therefore measurements were performed in five low-background underground laboratories. Details of the underground measurements, together with data on the quality control amongst the radiometric laboratories, are presented.

Radiological characterization and evaluation of high volume bauxite residue alkali activated concretes.

Bauxite residue, also known as red mud, can be used as an aggregate in concrete products. The study involves the radiological characterization of different types of concretes containing bauxite residue from Ukraine. The activity concentrations of radionuclides from the 238U, 232Th decay series and 40K were determined for concrete mixture samples incorporating 30, 40, 50, 60, 75, 85 and 90% (by mass) of bauxite residue using gamma-ray spectrometry with a HPGe detector. The studied bauxite residue can, from a radiological point of view using activity concentration indexes developed by Markkanen, be used in concrete for building materials and in road construction, even in percentages reaching 90% (by mass). However, when also occupational exposure is considered it is recommended to incorporate less than 75% (by mass) of Ukrainian bauxite residue during the construction of buildings in order to keep the dose to workers below the dose criterion used by Radiation Protection (RP) 122 (0.3 mSv/a). Considering RP122 for evaluation of the total effective dose to workers no restrictions are required for the use of the Ukrainian bauxite residue in road construction.

A brief overview on radon measurements in drinking water.

The aim of this paper is to present information about currently used standard and routine methods for radon analysis in drinking waters. An overview is given about the current situation and the performance of different measurement methods based on literature data. The following parameters are compared and discussed: initial sample volume and sample preparation, detection systems, minimum detectable activity, counting efficiency, interferences, measurement uncertainty, sample capacity and overall turnaround time. Moreover, the parametric levels for radon in drinking water from the different legislations and directives/guidelines on radon are presented.

(60)Co in cast steel matrix: A European interlaboratory comparison for the characterisation of new activity standards for calibration of gamma-ray spectrometers in metallurgy.

Two series of activity standards of (60)Co in cast steel matrix, developed for the calibration of gamma-ray spectrometry systems in the metallurgical sector, were characterised using a European interlaboratory comparison among twelve National Metrology Institutes and one international organisation. The first standard, consisting of 14 disc shaped samples, was cast from steel contaminated during production ("originally"), and the second, consisting of 15 similar discs, from artificially-contaminated ("spiked") steel. The reference activity concentrations of (60)Co in the cast steel standards were (1.077±0.019) Bqg(-1) on 1 January 2013 12h00 UT and (1.483±0.022) Bqg(-1) on 1 June 2013 12h00 UT, respectively.

Distribution of radionuclides in an iron calibration standard for a free release measurement facility.

A Europallet-sized calibration standard composed of 12 grey cast iron tubes contaminated with (60)Co and (110m)Ag with a mass of 246kg was developed. As the tubes were produced through centrifugal casting it was of particular concern to study the distribution of radionuclides in the radial direction of the tubes. This was done by removing 72 small samples (swarf) of ~0.3g each on both the inside and outside of the tubes. All of the samples were measured in the underground laboratory HADES.

Results of a European interlaboratory comparison on gross alpha/beta activity determination in drinking water.

An interlaboratory comparison was organised by JRC-IRMM among environmental radioactivity monitoring laboratories for the determination of gross alpha/beta activity concentration in drinking water. Independent standard methods were used for the reference value determination. The performance of participating laboratories was evaluated with respect to the reference values using relative deviations. Sample preparation and measurement methods used by the participating laboratories are detailed, in particular in the view of method-dependency of the results. Many of the participants' results deviate by more than two orders of magnitude from the reference values regardless of the techniques used. This suggests that gross methods need revision.

Half-life measurements of lutetium-176 using underground HPGe-detectors.

The half-life of (176)Lu was determined by measuring the (176)Lu activity in metallic lutetium foils. Three different HPGe-detectors located 225 m underground were employed for the study. Measurements using the sum-peak method were performed and resulted in an average massic activity of (52.61±0.36) Bq g(-1). The foils were of natural isotopic abundance so using the massic activity and the value of the natural isotopic abundance of (2.59±0.01)%, a half-life of (3.722±0.029)×10(10)a could be calculated.