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

Standardisation of the 129I, 151Sm and 166mHo activity concentration using the CIEMAT/NIST efficiency tracing method

The 129I, 151Sm and 166mHo standardisations using the CIEMAT/NIST efficiency tracing method, that have been carried out in the frame of the European Metrology Research Program project "Metrology for Radioactive Waste Management" are described. The radionuclide beta counting efficiencies were calculated using two computer codes CN2005 and MICELLE2. The sensitivity analysis of the code input parameters (ionization quenching factor, beta shape factor) on the calculated efficiencies was performed, and the results are discussed. The combined standard uncertainty of the standardisations of the 129I, 151Sm and 166mHo solutions were 0.3 %, 0.5 % and 0.4 %, respectively. The stated precision obtained using the CIEMAT/NIST method is better than that previously reported in the literature obtained by the TDCR (129I), the 4pi-gamma-NaI (166mHo) counting or the CIEMAT/NIST method (151Sm).JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Optimization of the liquid scintillation counting technique for the European interlaboratory comparison on gross α/β activity concentrations in water

A liquid scintillation counting (LSC) measurement method optimization for the gross α/β activity analysis in drinking waters with different chemical and radionuclide composition was performed. The optimized method was suitable to provide gross radioactivity results in drinking waters with the levels of the accuracy and precision similar to those obtained using other radioactivity screening techniques. Robust LSC results contributed to the calculation of gross α/β activity reference values of EC-JRC interlaboratory comparison water samples in 2012. Some of the most common errors in the determination of the gross radioactivity using the LSC are presented.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Distribution of artificial gamma-ray emitting radionuclide activity concentration in the top soil in the vicinity of the Ignalina Nuclear Power Plant and other regions in Lithuania

The impact of the operating Ignalina Nuclear Power Plant (INPP) on the contamination of top soil layer with artificial radionuclides has been studied. Results of the investigation of artificial gamma-ray emitting radionuclide distribution in soil in the vicinity of the INPP and distant regions in Lithuania in 1996-2008 (INPP operational period) show that nowadays Cs-137 remains the most important artificial gamma-ray emitting radionuclide in the upper soil layer. Mean Cs-137 activity concentrations in the top soil layer in the vicinity of the INPP were found to be significantly lower compared to those in remote regions of Varena and Plunge (similar to 300 km from INPP). In 1996 and 1998 mean Cs-137 activity concentrations were in the range of 28-45 Bq/kg in the nearest vicinity to the INPP, 103 Bq/kg in Varena and 340 Bq/kg in Plunge region. Cs-137 activity concentrations were 5-20 times lower in meadow soil (4-14 Bq/kg) compared to swamp and forest soil. Co-60, the INPP origin radionuclide, was detected in samples only in 1996 and 2000, and the activity concentration of Co-60 was found to be in the range from 0.4 to 7.0 Bq/kg at the sampling ground nearest to the INPP. Average annual activity concentrations of the INPP origin Cs-137 and Co-60 in the air and depositions in the INPP region were modeled using Pasquill-Gifford equations. The modeling results of Cs-137 and Co-60 depositional load in the INPP vicinity agree with the experimentally obtained values. Our results provide the evidence that the operation of INPP did not cause any significant contamination in soil surface. (C) 2012 Elsevier B.V. All rights reserved

Results of the EURAMET.RI(II)-S6.I-129 supplementary comparison

International audienceAn international comparison of the long-lived gamma-ray emitter 129I has been recently completed. A total of 5 laboratories measured a solution prepared by Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT). Aliquots of the master solution were standardized in terms of activity per mass unit by participant laboratories using 4 different techniques. The results of the comparison can be used as the basis for establishing the equivalence among the laboratories

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

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

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