Spiked air filters for the 2014 EC measurement comparison on simulated airborne particulates

In 2014, the European Commission Directorate-General Joint Research Centre, Institute for Reference Materials and Measurements (JRC-IRMM) organized on request of the Directorate-General Energy an interlaboratory comparison (EC ILC) exercise on 137Cs measurement in air filters; a similar exercise was organized in 2003. This report describes the production and distribution of the reference material to the 76 European laboratories monitoring radioactivity in the environment, which participated at the ILC. The JRC-IRMM provided the comparison samples which were prepared individually for each laboratory using a gravimetrically diluted 137Cs solution standardised by JRC-IRMM. The samples were made by gravimetrically dispensing the necessary activity amounts close to those the laboratories routinely measure.JRC.G.2-Standards for Nuclear Safety, Security and Safeguar

Evaluation of the 2016 ENV57/MetroERM measurement comparison on simulated airborne particulates: 137Cs, 134Cs and 131I in air filters

In 2016, the European Commission (EC) Directorate-General Joint Research Centre (JRC) Geel site (former Institute for Reference Materials and Measurements (IRMM)) organized an interlaboratory comparison (ILC) exercise on the measurement of 137Cs, 134Cs and 131I in air filters. Similar exercises, although EC ILC, were organized in 2014 (Altzitzoglou and Máté, 2016) and in 2003 (Wätjen et al., 2007); in both exercises the measurand was 137Cs only. The 2016 ILC, which is the subject of this report, was conducted in the frame of the EMRP project with code ENV57 and entitled MetroERM "Metrology for radiological early warning networks in Europe" project with the aim to optimise the metrological foundation of measurements for monitoring airborne radioactivity and promote pan-European harmonisation in data reliability. The JRC participates in the ENV57 MetroERM project having the responsibility to carry out a number of tasks. Work Package 3 (WP3) addresses the traceability of dose rate and airborne radioactivity measurements and explicitly supports the process of harmonisation of radiological data from early warning networks in Europe by systematic investigations, comparison exercises and the publication of recommendations. Task 3.2 of WP3 entitled "Traceability management for airborne radioactivity" aims in developing traceable reference materials and standard sources in the form of large-area spiked aerosol filters and conducting a laboratory comparison exercise to quantify the performance of the airborne radioactivity measuring field stations. This report describes the full life cycle of the above mentioned comparison among 67 European laboratories monitoring radioactivity in the environment. JRC provided the comparison samples, which were prepared individually for each laboratory using a gravimetrically diluted solution of 137Cs, 134Cs and 131I. Reference values traceable to the International System of Units (SI) and the International Reference System (SIR) for gamma-ray emitting radionuclides were determined at the JRC. The samples were made by gravimetrically dispensing the appropriate activity amounts, close to those the laboratories routinely measure, on blank air filters provided by the participants. A robust evaluation of the individual performance using three different approaches, percentage difference (D%), En numbers and PomPlots, is presented. Finally, for the laboratories which have participated in the 2003 and 201 exercises, their performance evolution in measuring 137Cs in air filters over the years, is examined. All 67 participating laboratories reported valid results. The majority of the laboratories reported reliable measurement results for 137Cs and 134Cs; 56 (84%) out of the 67 participants reported values with a percentage difference from the reference value within the ±20% range. Furthermore, 42 (63%) of the laboratories fulfilled the criterion of the compatibility test based on En numbers for 137Cs and 36 (54%) for 134Cs. As the calculation of the En numbers takes into account the uncertainties on both the measured activity and the reference value, the lower scores for the En numbers reveals that the uncertainty estimation is not adequate in many laboratories and there is a need to improve their application of uncertainty propagation. An observation for the 134Cs results is a negative bias on the reported results compared to the reference values, which might be partly attributed to a non-adequate summing correction applied by some laboratories. The evaluation of the performance of the laboratories on 131I was complicated by two effects. First, in a number of spiked air filters a fraction of the 131I activity was transferred to the protective plastic bag. Second, the integrity of the 131I activity content of many spiked air filters was compromised to a variable degree. Nevertheless, 20 (30%) laboratories reported results for 131I with a percentage difference from the reference value within the ±20% range and 9 (13%) with compatible En numbers. This performance is not satisfactory, but the difficulties encountered have to be taken into account. A major output of this project is the identification of the need of additional studies on how to perform reliable measurements of radioiodine on air filters. Overall, the majority of laboratories master their gamma-ray spectrometry analytical procedures, including the counting efficiency calibration of the detection systems and the corrections for coincidence summing. More attention has to be paid to the elaboration of the uncertainty to obtain correct and realistic uncertainties on the reported results.JRC.G.2 - Standards for Nuclear Safety, Security and Safeguar

Evaluation of EC interlaboratory comparison on radionuclides in soil

A comparison was organised by the Institute for Reference Materials and Measurements among 73 environmental radioactivity monitoring laboratories for the determination of 15 radionuclides in soil. The reference material IAEA-375 Soil was reprocessed to provide the comparison material and reference values traceable to SI units and SIR were established at IRMM. The analytical procedures used by participating laboratories are described. A robust evaluation of the performance of laboratories is performed using three different approaches: relative deviations, En numbers and PomPlots. The performance of the participating laboratories varied depending on the radionuclide determined and method used. Gamma-ray spectrometry with respect to 137Cs and 40K is well controlled. The determination of 90Sr proved difficult for about two-thirds of the participants, which submitted results outside the acceptable range. Several laboratories need to improve their analytical procedures for the uranium isotopes and 226Ra. Moreover, the results for thorium isotopes are far from satisfactory mainly for the 230Th. The use of the En criterion revealed that the uncertainty estimation of many participants is poor.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Evaluation of spiking methods for the preparation of a proficiency testing material in cereal matrices: Measurements of 131I, 134Cs and 137Cs in cereal matrices

Among many radionuclides released to the environment during a radiological emergency 131I, 134Cs and 137Cs are usually the most abundant ones. They are transferred to air, water and soil and from those media readily relocated to plants, including those intended for human consumption and for animal feed. Ensuring safe feed is an important component of the efforts to reduce and prevent food safety hazards, especially now, as consumers are increasingly aware of food safety issues and their linkage to animal production, including feeding practices. Therefore it is of utmost importance to ensure that the results of measurements of those three radionuclides delivered by the monitoring laboratories across the EU are reliable in order to guarantee a high degree of feed and food safety. It would be also beneficial to establish a standardised method of analysis for those radionuclides, which requires intra- and interlaboratory tests. In order to conduct such tests a reliable reference material is needed. Since one of the radionuclides (131I) is very short-lived (T1/2 = 8.0233 ± 0.0019 days) a spiking method for preparing test samples is necessary. Therefore procedures for spiking of powder were tested. Two methods of material preparation were tested – spiking a bulk sample of powder and individual spiking, where radioactive solution was introduced directly into containers in which samples were being measured. Both methods provided satisfying results. The bulk spiking method was proven to give homogenous samples, which was confirmed by one way analysis of variance (ANOVA) test. In the second method the relative deviation between the amount of the activity added and the calculated activity values was low and lower than the values of uncertainty calculated for the measured activity values. Therefore it can be stated that the closeness of agreement between the activity added to the sample and activity measured was satisfactory. This proves that these samples may be used as a reference material for the method validation and for the next proficiency test planned by the JRC Geel.JRC.G.2-Standards for Nuclear Safety, Security and Safeguar

Evaluation of the 2012 EC interlaboratory comparison on gross alpha/beta activity concentration in drinking water

An interlaboratory comparison was organized among 71 environmental radioactivity monitoring laboratories for the determination of gross alpha/beta activity concentration in drinking water. 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 view of method-dependency of the results. Many of the participants’ results deviate by more than two orders of magnitude from the reference values. This clearly demonstrates gross methods as unreliable and inaccurate in its present form and suggests revising the written standards for gross methods and restricting their application under clearly defined rules. Repeating this interlaboratory comparison is considered.JRC.G.2-Standards for Nuclear Safety, Security and Safeguar

Evaluation of EC Measurement Comparison for 137Cs, 40K and 90Sr in Milk Powder

This report describes the full life cycle of the measurement comparison of 137Cs, 40K and 90Sr in milk powder among 60 European laboratories monitoring radioactivity in food and the environment. An available IAEA reference material was re-processed at IRMM into suitable intercomparison samples and the homogeneity of the distributed samples together with other quality parameters was determined. Reference values of the three radionuclides under study in this intercomparison were determined at IRMM using tracer techniques and standardised radionuclide solutions and are thus traceable to the SI units. The sample preparation and measurement processes applied in the participating laboratories are described and the results of the intercomparison are presented and discussed in detail. Whereas, in general, the measurement results for 137Cs and 40K show good agreement with the reference value, the results of this comparison point at problems of 90Sr determination in about one third of the laboratories. The corresponding participants should investigate and revise their analytical methods, next to many laboratories needing to improve their estimation of measurement uncertainty.JRC.D.4-Isotope measurement

Evaluation of EC Comparison on the Determination of 226Ra, 228Ra, 234U and 238U in Mineral Waters

This report describes all details of the comparison for the determination of 226Ra, 228Ra, 234U and 238U in mineral waters among 45 European laboratories monitoring radioactivity in food and the environment. Three commercially available mineral waters were provided as comparison samples. Reference values of the four radionuclides under study in this comparison were determined in collaborative work of IRMM and the Bundesamt für Strahlenschutz (BfS), using tracer techniques and standardised radionuclide solutions. The reference values are thus traceable to the SI units. The sample preparation and measurement processes applied in the participating laboratories are described and the results of the comparison are presented and discussed in detail. Whereas, in general, the measurement results for the uranium isotopes show a relatively favourable agreement with the reference value, the results of this comparison point at severe problems of 226Ra and 228Ra determination in about one fourth and more than one third of the laboratories, respectively. For radium, 19 results corresponding to 14 % of all are even off by a factor of two or more. By comparison, for uranium, this number amounts to 6 % (9 results out of 150). Nevertheless, also for the determination of uranium, 14 % to 23 % of the laboratories report results not compliant with the En evaluation criterion. The corresponding participants are urgently requested to investigate and revise their analytical methods.JRC.D.4-Nuclear physic

Evaluation of the 2014 EC measurement comparison on simulated airborne particulates: 137Cs in air filters

In 2014, the European Commission Directorate-General Joint Research Centre, Institute for Reference Materials and Measurements (JRC-IRMM) organized on request of the Directorate-General Energy an interlaboratory comparison (EC ILC) exercise on 137Cs measurement in air filters; a similar exercise was organized in 2003. This report describes the full life cycle of the above mentioned comparison among 76 European laboratories monitoring radioactivity in the environment. JRC-IRMM provided the comparison samples which were prepared individually for each laboratory using a gravimetrically diluted 137Cs solution standardised by JRC-IRMM. The samples were made by gravimetrically dispensing the necessary activity amounts close to those the laboratories routinely measure. Reference values were fully documented and available to all participants and nominating national authorities after completion of the comparison. A robust evaluation of the individual performance using three different approaches, percentage difference (D%), En numbers and PomPlots, is presented. Finally, the performance of laboratories which have participated in both the 2003 and the 2014 137Cs measurement in air filters exercises are compared. The majority of the laboratories reported reliable measurement results; only 5 out of 76 participants reported values with a percentage difference larger than ±33% of the reference value. Furthermore, 23 laboratories did not fulfil the criterion of the compatibility test based on En numbers. These results point out eventual problems with radioactivity measurements in the air filters and estimation of uncertainty which need to be addressed by the concerned laboratories.JRC.G.2 - Standards for Nuclear Safety, Security and Safeguar

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

An interlaboratory comparison was organised by the Institute for Reference Materials and Measurements (JRC-IRMM) among environmental radioactivity monitoring laboratories for the determination of gross alpha/beta activity concentration in drinking water. Four independent standard methods were used for the determination of the reference values of three different water samples. 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 described in detail, 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.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Evaluation of EC Measurement Comparison on Simulated Airborne Particulates - 137Cs in Air Filters

This report describes the full life cycle of the measurement comparison of 137Cs in air filters among 43 European laboratories monitoring radioactivity in the environment. Gravimetrically pipetting droplets of a gravimetrically diluted standardised 137Cs solution onto real air filters, SI-traceable reference values were established for intercomparison filters carrying a large range of activity close to the routine measurement conditions of the corresponding laboratory. The sample preparation and measurement processes applied in the participating laboratories are described and the results of the intercomparison are presented and discussed in detail. The results point at some problems of radioactivity measurement in air filters which need to be improved by several laboratories. Overall, with 41 out of 48 reported measurement results lying within +/- 33 % of the IRMM reference value, this comparison renders a rather fair result.JRC.D.4-Isotope measurement