International Intercomparison Exercise Research Articles

International intercomparison and quality assessment of passive and active 222Rn measuring devices in the Asia-Pacific region

Intercomparison exercise is an integral part of the quality assurance programmes in 222Rn measurements using active and passive devices. Ensuring the accuracy of data generated through measurements necessitates periodic performance checks. To achieve harmonization of methods, quantify biases and errors in measurements, and identify the reasons for discrepancies, there is a pressing need for periodic intercomparison exercises. To address this need of numerous laboratories, particularly in the Asia-Pacific region, a calibration facility for 222Rn measuring devices has been established at the Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, India. An international intercomparison exercise for the 222Rn measuring devices was conducted at this facility in the year 2022 with the participation of 10 laboratories from six countries. A total of 354 devices (comprising of both active and passive detectors) were subjected to intercomparison measurements by exposing them to three concentration levels: (5.97 ± 0.29) × 103 Bq m−3, (0.70 ± 0.09) × 103 Bq m−3 and (2.02 ± 0.20) × 103 Bq m−3 in separate experiments and the exposure durations were 7 days, 15 days, and 10 days respectively. The performance of each laboratory was evaluated following the criterion adopted by the International Atomic Energy Agency (IAEA) in its worldwide proficiency test programmes. This exercise brought out the fact that some of the laboratories need to improve their measurement practices to produce reliable data.

An international intercomparison exercise on passive samplers (DGT) for monitoring metals in marine waters under a regulatory context

In order to move forward in the acceptance of a novel contaminant monitoring technique (Diffusive Gradients in Thin-films: DGT) for assessment of marine water bodies, sensu the WFD, an Inter-Laboratories Comparison (ILC) exercise (nine Europeans laboratories) was organized in the framework of the Interreg Atlantic Area MONITOOL project, which focused on the use of the DGT technique for the measurement of WFD priority metals (Cd, Ni and Pb).Reproducible results were obtained for each metal by several laboratories, supporting the assertion that DGT analysis can be performed satisfactorily by laboratories experienced in measuring metals at trace levels in marine environments, even if they have limited practice in DGT analysis.According to the Z-score analysis, among the 9 participating laboratories, 3 had 100 % of satisfactory results for Cd, Ni, and Pb, 3 had >80 % satisfactory results and 2 had about 60 % satisfactory results.This work highlights the need to clearly describe the DGT method in order to control sources of contamination during analytical steps, in particular the resin gel retrieval and the elution steps.Such international intercomparison exercise is an important step to develop the laboratory network involved in DGT analysis and contributes to the improvement of data quality.

Optimization of the direct LSC method for determination of biogenic component in liquids by applying 14C

Determination of fraction of biogenic component in liquid fuels by a direct radiocarbon measurement in liquid scintillation counter (direct-LSC method) has been validated by participation in the international intercomparison exercise. All the results for samples with the standard quench parameter SQP(E) value above ≈ 650 were accepted. Highly quenched sample of used edible oil was diluted with the 14C-free petroleum ether to optimize the region of applicability. It was established that quantitative results were obtained for SQP(E) values above 700, while in the SQP(E) region between 700 and 600 only the qualitative results of fbio can be taken.

Ensuring robust radiological risk assessment for wildlife: insights from the International Atomic Energy Agency EMRAS and MODARIA programmes

In response to changing international recommendations and national requirements, a number of assessment approaches, and associated tools and models, have been developed over the last circa 20 years to assess radiological risk to wildlife. In this paper, we summarise international intercomparison exercises and scenario applications of available radiological assessment models for wildlife to aid future model users and those such as regulators who interpret assessments. Through our studies, we have assessed the fitness for purpose of various models and tools, identified the major sources of uncertainty and made recommendations on how the models and tools can best be applied to suit the purposes of an assessment. We conclude that the commonly used tiered or graded assessment tools are generally fit for purpose for conducting screening-level assessments of radiological impacts to wildlife. Radiological protection of the environment (or wildlife) is still a relatively new development within the overall system of radiation protection and environmental assessment approaches are continuing to develop. Given that some new/developing approaches differ considerably from the more established models/tools and there is an increasing international interest in developing approaches that support the effective regulation of multiple stressors (including radiation), we recommend the continuation of coordinated international programmes for model development, intercomparison and scenario testing.

Towards the Use of Dgt Technique in a Regulatory Context for Monitoring Metals in Marine Water Bodies: Results of an International Intercomparison Exercise

Towards the Use of Dgt Technique in a Regulatory Context for Monitoring Metals in Marine Water Bodies: Results of an International Intercomparison Exercise

Monte Carlo calculation of organ and effective doses due to photon and neutron point sources and typical X-ray examinations: Results of an international intercomparison exercise

This paper summarizes the results of an intercomparison on the use of the ICRP Reference Computational Phantoms with radiation transport codes, which was organized by EURADOS working group 6. Three exercises are described: exposure to an anterior-posterior (AP) photon point source, exposure to an AP neutron point source, and exposure to two typical medical X-ray examinations. The three exercises received 17, 8 and 8 solutions, respectively. Participants originated from fifteen different countries, and used a wide range of Monte Carlo codes. Due to difficulties in defining the precise source location unambiguously in the exercise description, agreement to within ∼10% of the reference solution was considered satisfactory for a given participant's results. Although some participants provided initial solutions in good agreement with the reference solutions, differences of several tens of percent, or even several orders of magnitude, were exhibited for many of the others. Following feedback and suggestions from the organizers, revised solutions were submitted by some of the participants for the photon exercises; in general, agreement was improved. The overall observations from these three intercomparison exercises are summarized and discussed.

Monte Carlo calculation of organ dose coefficients for internal dosimetry: Results of an international intercomparison exercise

EURADOS Working Group 6 has organized an intercomparison exercise on the use of the ICRP Reference Computational Phantoms with radiation transport codes. This paper summarizes the results of a specific task from the intercomparison exercise modelling internal radiation sources. The quantities to be calculated were absorbed fractions and specific absorbed fractions for monoenergetic photon and electron sources as well as S-values for two radionuclides in four source organs. Twelve participants from eleven countries participated in this specific task using the Monte Carlo radiation transport codes FLUKA, Geant4, the MCNP code family, PenEasy, TRIPOLI-4 and VMC. Although some participants provided initial solutions in good agreement with the master solution evaluated by the organizers, differences of factors or even orders of magnitude were also found. Following feedback from the organizer, most participants submitted revised solutions that were mostly in better agreement with the master solution, although this was not always the case. Some initial and revised results are discussed in detail in this paper, and the reasons of mistakes are described as far as they were revealed by the participants. A full account of all results is presented in specific annexes as supplemental material.

Monte Carlo calculation of organ and effective dose rates from ground contaminated by Am-241: Results of an international intercomparison exercise

An intercomparison exercise is described that examines Monte Carlo modelling of anthropomorphic voxel phantoms in an idealized ground-contamination photon exposure scenario. Thirteen participants calculated and submitted organ and effective dose rates for comparison against a set of verified reference solutions. The effective dose rates are shown to agree with the reference value to within reasonable statistical uncertainties in five of the cases, though in only one of those was similar agreement also demonstrated in the evaluation of all requested organ dose rates. Orders-of-magnitude differences in doses are seen for some of the other participants, both internally within their own dataset and also relative to the reference solutions. Following limited feedback and suggestions from the organizer, up to two sets of revised solutions were resubmitted by some of the participants; these generally exhibited improved agreement, though not always. The overall observations and conclusions from this intercomparison exercise are summarized and discussed.

Radiocarbon Dating of Marine Samples: Methodological Aspects, Applications and Case Studies

Radiocarbon dating by AMS (Accelerator Mass Spectrometry) is a well-established absolute dating technique widely used in different areas of research for the analysis of a wide range of organic materials. Precision levels of the order of 0.2–0.3% in the measured age are nowadays achieved while several international intercomparison exercises have shown the high degree of reproducibility of the results. This paper discusses the applications of 14C dating related to the analysis of samples up-taking carbon from marine carbon pools such as the sea and the oceans. For this kind of samples relevant methodological issues have to be properly addressed in order to correctly interpret 14C data and then obtain reliable chronological frameworks. These issues are mainly related to the so-called “marine reservoirs effects” which make radiocarbon ages obtained on marine organisms apparently older than coeval organisms fixing carbon directly from the atmosphere. We present the strategies used to correct for these effects also referring to the last internationally accepted and recently released calibration curve. Applications will be also reviewed discussing case studies such as the analysis of marine biogenic speleothems and for applications in sea level studies.

A proposal for assessing the uncertainty in the measurement of mean nanoparticle diameter with electron microscopy

Of paramount importance in the field of nanotechnology is the ability to measure reliably the properties of nanomaterials, especially their size. In general, just an estimate of size is not sufficient: a quantitative indication of the estimate’s quality in the form of an assessment of its uncertainty is necessary as well. For example, standard ISO/IEC 17025:2017 (general requirements for the competence of testing and calibration laboratories) stipulates that appropriate methods and procedures shall be used for laboratory activities and for the analysis of data, including the identification and quantification of all contributions to the measurement uncertainties. In order to facilitate compliance with requirements such as these, a procedure is proposed for assessing the uncertainty in the evaluation of the mean area-equivalent diameter of a nanoparticle population by scanning electron microscopy. We take as reference the general approach proposed in the guide to the expression of uncertainty in measurement, which is globally seen as the de facto standard for the evaluation of measurement uncertainty, and as such, it is normally required for accreditation. Thus, the proposed approach, primarily intended for guidance, will hopefully be found practical, understandable and useful. Ideally, it should be validated, and perhaps improved, through international intercomparison exercises.

Results of WEPAL-QUASIMEME/NORMANs first global interlaboratory study on microplastics reveal urgent need for harmonization

To survey the conformity and quality of results among laboratories for microplastics determination worldwide, an international laboratory intercomparison and development exercise was organized. The 34 participants were requested to determine the polymer type and number or mass of polymer particles in 12 samples, i.e. six samples containing of pre-production pellets, five dissolvable soda tablets containing different (smaller) polymer particles and one blank soda tablet. A novel method for providing the test materials in aluminium strips was used. Thirty laboratories (88%) submitted data using their own method of choice, resulting in a variety of identification and quantification methods (n = 7). The majority of the labs (53–100%) correctly identified the type of polymer in all samples but one. The performance of the laboratories in quantifying and weighing the pellets was very good. The analysis of the number of the particles in the soda tablets varied considerably between laboratories (29–91%). The results of this study highlight the complexity of microplastics analysis and the need for harmonization of both reporting format and methods. Continued development and assessment of the comparability among analytical methods and laboratories are urgently needed to support monitoring programmes, research and decision-making.

Experience and performance of In Vivo Monitoring Laboratory of NIRP in 2017 thyroid measurement intercomparison

Determination of the 131I activity in the thyroid of exposed people or workers is one of the major concerns that needs to be addressed following a nuclear or radiological emergency. International intercomparison exercises on bioassay measurements are one of the effective methods to improve the capability and quality of internal dose assessment. In 2017, Working Group 1 (Internal Dosimetry) of the Asian Radiation Dosimetry Group (ARADOS) organized an intercomparison exercise on the thyroid measurement, aiming at enhancing and coordinating the radiation dosimetry capabilities of Asian countries. This paper describes the measurement experience and results of In Vivo Monitoring Laboratory of NIRP in the 2017 intercomparison exercise, which can provide technical reference for laboratories that have not yet participated in such thyroid measurement intercomparsion. It covers technical aspects such as calibration, measurement and data processing. The results presented in this intercomparison are within an acceptable range of performance criteria on the bioassay measurements. In addition, further research work considered in the field of thyroid measurement is described in the discussion section.

DRIFT dispersion model predictions for the Jack Rabbit II model inter-comparison exercise

In 2015 and 2016, the US Army conducted nine large-scale chlorine releases at the Dugway Proving Ground in Utah, known as the Jack Rabbit II trials. The purpose of these experiments was to improve our understanding of pressure-liquefied chlorine releases and atmospheric dispersion, and to provide useful practical knowledge for emergency responders. Data from three of the Jack Rabbit II trials (Trials 1, 6 and 7) were subsequently selected for an international model inter-comparison exercise, which included modelling contributions from the US, UK, Canada, France, Germany, Sweden, Finland and the European Commission. This paper provides details of one of the UK contributions to that exercise, using the DRIFT integral dispersion model. Participants in the exercise were given a set of prescribed model input conditions. The methodology used in DRIFT to model these conditions is described here, which consisted of three runs: a baseline case and two sensitivity tests that examined the effect of variations in the modelled wind-speed profile and the dry deposition rate. A brief review is also provided of the experimental data used for the model inter-comparison exercise. Gas concentrations were measured in the Jack Rabbit II trials using an extensive array of gas sensors arranged on arcs downwind from the release point. Four types of sensors were used, which each had calibration and/or saturation limits. In some of the trials, sensors that recorded the highest concentrations on an arc were saturated with gas and under-recorded the actual concentrations. In other cases, especially near the source, there were only a few sensors on an arc and therefore it is uncertain whether the plume maximum concentrations were recorded. Results from DRIFT are compared to the Jack Rabbit II data in two ways. Firstly, against the full dataset of maximum arc-wise concentrations, and secondly against the subset of measurements that were unaffected by saturation issues or there being a sparse sensor array. In the first case, DRIFT gives higher concentrations than were measured on average, noting that some measurements probably under-recorded the concentration owing to the previously mentioned sensor saturation issues. In the second case, using the more reliable dataset, the statistical performance of DRIFT falls within commonly-used dense-gas model acceptance criteria. Sensitivity tests on the wind speed profile and dry deposition rate had an effect on the DRIFT predictions in Trial 1, but little impact in Trials 6 and 7. This behaviour is likely to be due to the changing meteorology during Trial 1, and the lower wind speed and smaller chlorine mass released in that trial. Remaining knowledge gaps and possible future directions for research are discussed. These include further work on dry deposition, modelling of the other Jack Rabbit II trials (potentially using source models as well as prescribed common source conditions), and comparisons of predicted and measured toxic load, calculated from the time-varying concentrations.

Calibration of a SPECT-CT gamma camera with child and adult thyroid-neck phantoms for in vivo monitoring of radioiodine in the exposed population in case of nuclear emergency

The need to quantify the uptake of 131I in the thyroid of the exposed population or workers is one of the main concerns to take into account in case of nuclear or radiological emergencies. In such scenarios, due to the high volatility and rapid intake by inhalation of 131I, it is very important a rapid identification of the exposed individuals to know their level of internal contamination in order to establish action protocols and countermeasures. In vivo measurements of 131I in the thyroid by gamma spectrometry at Whole Body Counters (WBC) is the recommended technique, but it is difficult to manage in case of a large number of individuals potentially exposed. It is known that gamma cameras located in the nuclear medicine services are available at most hospitals and could be used as an alternative method in order to provide support in the emergency response. Thus, this work describes a methodology to calibrate this kind of equipment with anthropometric phantoms to carry out direct measurement of 131I in thyroid for the quantification of internal contamination of the exposed population. A Gamma Camera (GC) of a public hospital from Madrid, H.U. La Paz, was calibrated for such purpose taking into account that a realistic geometry (10 cm distance from GC to phantom) and a rapid screening (counting time of 300 s with collimators removed) of internally contaminated individuals is necessary at early stage response. The calibration factors obtained for 131I vary with thyroid size being in the range of 0.0459 to 0.0541 cps·Bq-1. The minimum detectable activity (MDA) also varies with the thyroid size of the phantoms being in the range of 67 Bq to 79 Bq. An estimation of minimum detectable effective dose for children (E(70)) and adults (E(50)) has been carried out, taking into account such MDA values. Results show that, assuming a scenario of acute inhalation of 131I by members of the public, this methodology allows estimating doses far below 1 mSv three days after the intake. Moreover, the validation of the methodology has been carried out by participating in an international intercomparison exercise (CATHYMARA project, EC-OPERRA 2016–2017) for the in vivo measurement of 131I in thyroid to the exposed population in emergencies.

Correction to: International inter-comparison exercise on 153Sm

In the original publication of the article, eighteenth author’s name was misspelt. The correct name is given in this correction.

Use of Genie 2000 and Excel VBA to correct for γ-ray interference in the determination of NORM building material activity concentrations

The γ-radiation emitted by building materials is calculated from the activity indices for 232Th, 226Ra and 40K and expressed as the activity concentration index (ACI). Gamma spectroscopy is a non-destructive technique frequently used to simultaneously determine the indices for several radionuclides. Spectral interpretation poses a number of challenges, including identification of γ-lines subject to summing-in effects, interference from other γ-ray emitting radionuclides and the time required to reach secular equilibrium. These challenges are not fully addressed by Canberra Industries’ Genie 2000, the software used by many laboratories to analyse samples. This article describes a Microsoft Excel workbook that exploits Genie 2000 flexibility to program applications with Visual Basic using Canberra's Nuclear Data Access Library and batch procedure tools. The workbook determines 40K activity concentration after correcting for 228Ac interference and 226Ra activity directly from the γ-peak at 186.5 keV. The method proposed was tested by participating in 13 national and international scale inter-comparison exercises. The results were statistically indistinguishable from the reference values at a coverage factor of k = 3 and no statistically significant differences were identified between the respective means by a Student's t pairwise comparison.

New determination of the 3He mixing ratio in the Earth's lower atmosphere from an international tritium intercomparison exercise

The light isotope of helium, 3He, is essentially a primordial substance entrapped within the Earth's interior during the formation of the planet. It is released into the atmosphere by volcanic/magmatic activity, and eventually escapes to outer space. 3He is also produced by the radioactive beta-decay of tritium. Hence, measurements of 3He can be used to derive the concentration of tritium. The so-called “3He ingrowth” method uses a mass spectrometer to detect the amount of 3He that accumulates in a sample during a given period of storage. The 3He measurements are classically calibrated against an air standard. The method thus relies on the accurate knowledge of the atmospheric mixing ratio of 3He. This value is based on mass spectrometric measurements with gravimetrically or volumetrically prepared 3He standard mixtures. Here, we apply the 3He ingrowth method in reverse, using a solution of tritiated water prepared for an international comparison of tritium activity measurements to precisely determine the 3He mixing ratio of our air standard. The measured atmospheric mixing ratio of 3He, based on a series of ten measurements, is [3He] = 7.12 ± 0.06 ppt. This value is between 1% and 2% lower than previous determinations reported in the literature. However, all results remain statistically consistent.

International inter-comparison exercise on $${}^{153}\hbox {Sm}$$

Samarium-153 ( $${}^{153}\hbox {Sm}$$ ) is a short-lived radionuclide that decays to stable europium-153 via beta emission, with subsequent de-excitation via gamma emission and internal conversion. Historical measurements of $${}^{153}\hbox {Sm}$$ by gamma spectrometry and beta liquid scintillation counting have shown a low bias compared to beta proportional counting. In order to investigate this, four national laboratories jointly conducted an experimental inter-comparison exercise on a certified $${}^{153}\hbox {Sm}$$ sample, created from neutron activation of samarium-152. Radiometric measurements were conducted using gamma spectrometry, liquid scintillation counting, gas proportional counting, and passivated implanted planar silicon detectors and compared across the four institutions against the certified value. The results from this experiment are presented together with a number of conclusions which suggest that the current published cumulative fission yield for $${}^{153}\hbox {Sm}$$ , as used by many laboratories, is approximately 15% high and is the likely cause of the previously observed bias.

Dense gas dispersion model development and testing for the Jack Rabbit II phase 1 chlorine release experiments

In 2015 and 2016, the US Army conducted a series of large-scale chlorine releases at the Dugway Proving Ground in Utah, known as the Jack Rabbit II trials. The purpose of these experiments was to improve our understanding of pressure-liquefied chlorine releases and atmospheric dispersion, and provide useful practical knowledge for emergency responders. The tests conducted in 2015 featured a grid of Conex shipping containers around the release point to simulate a mock urban array of buildings, while the tests in 2016 studied different release orientations and culminated in the full discharge of a 20-ton chlorine road tanker.Before, during and after these experiments, a group of dispersion modelling experts from around the world collaborated in simulating the tests to help configure the experiments and evaluate the performance of models. This paper presents the progress made in that modelling activity by two of the groups involved: the UK Health and Safety Executive (HSE) and the US National Center for Atmospheric Research (NCAR). The models tested by HSE and NCAR range in complexity from integral models that can be run quickly for emergency response to Computational Fluid Dynamics (CFD) models that require days of computing time. This paper summarizes these groups' analysis of the 2015 experimental data and initial model findings, and outlines future research directions.The discharge model predictions by HSE show that meta-stable models tended to over-predict the measured release rate from the chlorine tank, whilst flashing models under-predicted the release rate. CFD simulations of the near-field flow behavior show that the chlorine cloud was initially directed laterally, out of the sides of the mock urban array, due to the alignment of Conex containers. The two integral models tested by HSE (DRIFT and PHAST) provide best agreement with the downwind concentration data when they take into account the rainout of liquid from the impinging two-phase jet. The two models tend to over-predict concentrations slightly, but many of the measurements may have under-recorded the peak concentrations, due to sensors saturating and the clouds bypassing sensors. The newly-developed NCAR integral model accounts for the transition from momentum to buoyancy-dominated behavior and shows promising agreement with the CFD results and measured concentrations. In addition, it reproduces the observed −5/3 power law decay in concentration at large distances.Efforts are continuing on analysis of the Jack Rabbit II experiments and a collaborative international model inter-comparison exercise is currently underway. Additional papers by the coordinators of that exercise and other experts should be forthcoming. The Jack Rabbit II dataset will no doubt be used for decades to come as a seminal test case for validating flashing jet and dense gas dispersion models.

Inter-comparison of quantitative imaging of lutetium-177 (177Lu) in European hospitals

BackgroundThis inter-comparison exercise was performed to demonstrate the variability of quantitative SPECT/CT imaging for lutetium-177 (177Lu) in current clinical practice. Our aim was to assess the feasibility of using international inter-comparison exercises as a means to ensure consistency between clinical sites whilst enabling the sites to use their own choice of quantitative imaging protocols, specific to their systems.Dual-compartment concentric spherical sources of accurately known activity concentrations were prepared and sent to seven European clinical sites. The site staff were not aware of the true volumes or activity within the sources—they performed SPECT/CT imaging of the source, positioned within a water-filled phantom, using their own choice of parameters and reported their estimate of the activities within the source.ResultsThe volumes reported by the participants for the inner section of the source were all within 29% of the true value and within 60% of the true value for the outer section. The activities reported by the participants for the inner section of the source were all within 20% of the true value, whilst those reported for the outer section were up to 83% different to the true value.ConclusionsA variety of calibration and segmentation methods were used by the participants for this exercise which demonstrated the variability of quantitative imaging across clinical sites. This paper presents a method to assess consistency between sites using different calibration and segmentation methods.