Comparison of two methods for the rapid radiochemical analysis of air dust samples in emergency situations.

The reliable determination of airborne radionuclides in air is a key aspect in decision-making for the protection against public exposure in the event of a nuclear or radiological emergency. Nowadays, this needs to be done in real time and at the international level. These needs require the development of fast response protocols and the harmonisation of results. This work presents two fast radiochemical methods for the simultaneous separation of alpha and beta emitters in aerosols and their performance in a series of samples.

Potential Source Apportionment and Meteorological Conditions Involved in Airborne 131I Detections in January/February 2017 in Europe.

Traces of particulate radioactive iodine (131I) were detected in the European atmosphere in January/February 2017. Concentrations of this nuclear fission product were very low, ranging 0.1 to 10 µBq m-3 except at one location in western Russia where they reached up to several mBq m-3. Detections have been reported continuously over an 8-week period by about 30 monitoring stations. We examine possible emission source apportionments and rank them considering their expected contribution in terms of orders of magnitude from typical routine releases: radiopharmaceutical production units > sewage sludge incinerators > nuclear power plants > spontaneous fission of uranium in soil. Inverse modeling simulations indicate that the widespread detections of 131I resulted from the combination of multiple source releases. Among them, those from radiopharmaceutical production units remain the most likely. One of them is located in Western Russia and its estimated source term complies with authorized limits. Other existing sources related to 131I use (medical purposes or sewage sludge incineration) can explain detections on a rather local scale. As an enhancing factor, the prevailing wintertime meteorological situations marked by strong temperature inversions led to poor dispersion conditions that resulted in higher concentrations exceeding usual detection limits in use within the informal Ring of Five (Ro5) monitoring network.

A review of the TAEA proficiency test on natural and anthropogenic radionuclides activities in black tea.

A proficiency test amongst 15 Turkish laboratories with participation of 5 non-Turkish laboratories was organized to determine the 137Cs, 40K and 90Sr massic activities in black tea powder samples. The bulk material, consisting of tea produced in 2014, was mixed with contaminated tea that was withdrawn from the market after the Chernobyl accident. Nineteen laboratories reported 41 results. The evaluation of the results was based on the accuracy and precision criteria adopted by the IAEA Proficiency Testing Group and resulted in 49% acceptable results, 19% acceptable with warning and 32% were found to be not acceptable.

Development of radiochemical analysis strategies for decommissioning activities.

Radioactive waste generated in decommissioning activities need be classified according to their radioactive content. The radiological information required by national authorities includes diverse alpha and beta emitters, which can only be determined after a radiochemical separation process. This paper presents the work on the development of radiochemical methods for the simultaneous separation of several radionuclides in concrete, steel and graphite samples, on the basis of individual sample treatments which merge in a common radiochemical separation procedure based on extraction chromatography.

Concentrations of iodine isotopes ((129)I and (127)I) and their isotopic ratios in aerosol samples from Northern Germany.

New data about (129)I, (127)I concentrations and their isotopic ratios in aerosol samples from the trace survey station of the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig, Northern Germany, are presented and discussed in this paper. The investigated samples were collected on a weekly basis during the years 2011 to 2013. Iodine was extracted from aerosol filters using a strong basic solution and was separated from the matrix elements with chloroform and was analysed by accelerator mass spectrometry (AMS) for (129)I and by inductively coupled plasma mass spectrometry (ICP-MS) for (127)I. The concentrations of (127)I and (129)I in aerosol filters ranged from 0.31 to 3.71 ng m(-3) and from 0.06 to 0.75 fg m(-3), respectively. The results of (129)I/(127)I isotopic ratios were in the order 10(-8) to 10(-7). The (129)I originated directly from gaseous emissions and indirectly from liquid emissions (via sea spray) from the reprocessing plants in Sellafield and La Hague. In comparison with the results of (131)I after the Fukushima accident, no contribution of (129)I from this accident was detectable in Central Europe due to the high background originating from the (129)I releases of the European reprocessing plants. (129)I atmospheric activity concentrations were compared with those of an anthropogenic radionuclide ((85)Kr). We did not find any correlation between (129)I and (85)Kr, both having nuclear reprocessing plant as the main source.

Determination of the (241)Am activity in real contaminated slag.

One of the main tasks of the EMRP IND04 MetroMetal project "Ionising Radiation Metrology for the Metallurgical Industry" was to develop sets of reference sources in various matrices such as cast steel, slag and fume dust for the calibration of the gamma spectrometric detector prototypes developed in the frame of the project. This work is focused on the characterisation of real contaminated slag material with (241)Am using the transmission measurements in combination with Monte-Carlo simulations. The method and the results are presented and discussed.

New PTB thermal neutron calibration facility: first results.

A new thermal neutron calibration facility based on a moderator assembly has been set up at PTB. It consists of 16 (241)Am-Be radionuclide sources mounted in a graphite block, 1.5 m wide, 1.5 m high and 1.8 m deep. The sources are distributed to eight different positions, at a mean distance of ∼1.25 m from the front face of the moderator. The neutron field at the reference position, 30 cm in front of the moderator device and 75 cm above the floor, has been characterised using calculations, Bonner sphere measurements and gold foil activation. First results are shown. The field is highly thermalised: 99 % in terms of fluence. It is quite homogenous within a 20 cm×20 cm area, but the absolute value of the thermal neutron fluence rate is small and yields an ambient dose equivalent rate of 3 µSv h(-1).

Remarks on representative ground-level air monitoring.

The methods applied and the typical influences affecting representative measurements of radionuclides contained in ground-level aerosols are summarized. The activity concentrations of (7)Be, (22)Na, (40)K, (137)Cs, and (210)Pb were determined in weekly collected samples and the ratio "sample A/sample B" was calculated over a period of 5 years. The results are compared with findings from literature. The estimation of the limits of comparability and reliability were extended to (22)Na, (40)K, (137)Cs, and (210)Pb measurements.

Results of an international comparison for the determination of radionuclide activity in bilberry material.

Radioactivity found in wild food products has assumed greater importance when assessing the total exposure of the population. For this reason, IRMM has been developing a reference material for the activity concentration of three radionuclides in bilberry samples. In order to characterise this new material, a CCRI(II) supplementary comparison was organised. The difficulties encountered in this comparison are discussed, in particular the efficiency calibration for volume sources of gamma-ray emitters, and comparison reference values for (137)Cs and (40)K are calculated.

The new IAEA reference material: IAEA-434 technologically enhanced naturally occurring radioactive materials (TENORM) in phosphogypsum.

A reliable determination of Technologically Enhanced Naturally Occurring Radioactive Materials in phosphogypsum is necessary to comply with radiation protection and environmental regulations. In this respect, a new phosphogypsum reference material was produced and certified to assist in the validation of analytical methods and the quality assurance of produced analytical results. This paper presents the sample preparation methodology, material homogeneity assessment, characterization campaign results and assignment of property values, and associated uncertainties. The reference values and associated uncertainties for Pb-210, Ra-226, Th-230, U-234 and U-238 were established based on consensus values calculated from analytical results reported by three National Metrology Institutes and five expert laboratories.

Activity determination and nuclear decay data of (113m)Cd.

The radionuclide (113m)Cd was extracted from a Cd component, which has been irradiated in a research reactor during its routine operation. A validated separation procedure was then used to obtain a (113m)Cd solution of high radiochemical purity. The solution was measured by means of liquid scintillation counting for activity determination. To this end, the CIEMAT/NIST efficiency tracing method as well as the triple-to-double coincidence (TDCR) counting technique were used. Measurements in a low-background gamma-ray spectrometer were applied to identify any potential photon-emitting impurities and to measure the 263.7 keV photons from the isomer transition. A gamma emission probability of 0.01839(29)% was determined for this line. The liquid scintillation measurements were also used to evaluate the half-life of (113m)Cd. The decay was followed for about 11 months and a half-life T(1/2)=13.97(13) years was obtained.

An inter-laboratory comparison of low-level measurements in ground-level aerosol monitoring.

After the nuclear reactor accident of Chernobyl, the "Integrated Measurement and Information System (IMIS) for Monitoring the Environmental Radioactivity and Detecting Emissions from Nuclear Plants was implemented in Germany. IMIS is a nationwide comprehensive measuring system which permanently monitors the radioactivity in all important environment media in the whole federal territory. At approximately 40 sites, the activity concentration of radioactive substances is measured in air and precipitations. At least 14 of them are responsible for trace monitoring of radionuclides in the air. The legal bases of IMIS prescribe regular inter-laboratory comparison analyses in cooperation with the Physikalisch-Technische Bundesanstalt (PTB), with the use of reference materials prepared by the Federal Coordinating Laboratories. In order to fulfil this requirement in the field of trace survey measurements in ground-level air, the Federal Office for Radiation Protection ("Bundesamt für Strahlenschutz", BfS) and the PTB have conducted a comparison with real, dust-loaded reference filters in 2005. The comparison was organized within the framework of a cooperation of trace survey stations from Austria, Germany and Switzerland. The paper describes the preparation of the real, dust-loaded reference filters, the procedure for spiking the filters with the activity standard solution containing (22)Na, (88)Y, (89)Sr, (90)Sr, (125)Sb, (133)Ba, (134)Cs, and (241)Am. Some results are discussed and conclusions are given.

Characterization of the NIST seaweed Standard Reference Material.

The National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) for seaweed was developed through an interlaboratory comparison with 24 participants from 16 countries. After evaluating different techniques to calculate certified values for the radionuclides, the median method was found to be the most representative technique. The certified values were provided for 13 radionuclides and information values were given for 15 more radionuclides. Results for the natural decay series showed disequilibrium in both the uranium and thorium series.

Development of the NIST bone ash standard reference material for environmental radioactivity measurement.

The bone ash standard reference material (SRM), a blend of 4% contaminated human bone and 96% diluent bovine bone, has been developed for radiochemical method validation and quality control for radio-bone analysis. The massic activities of 90Sr, 226Ra, 230Th, 232Th, 234U, 235U, 238U, 238Pu, (239 + 240)Pu and (243 + 244)Cm were certified using a variety of radiochemical procedures and detection methods. Measurements confirmed undetectable radionuclide heterogeneity down to a sample size of 5 g. thereby implying adequate blending of particulate materials with dilution factors of up to 17,900. The results among most of the intercomparison laboratories and their methods were consistent. Disequilibrium was observed for decay chains: 234U(0.67 mBq/g)-230Th(0.47 mBq/g)-226Ra(15.1 mBq/g)-210Pb(23 mBq/g)-210Po(13 mBq/g) and 232Th(0.99 mBq/g)-228 Ra(6.1 mBq/g)-228Th(7.1 mBq/g). The disequilibria were the results of mixing occupationally contaminated human bone with natural bovine bone and the fractionation during internal biological processes. The massic activity of 210Pb, 228Th and 241Am were not certified because of insufficient 228Ra and 241Pu data and lack of knowledge in how 222Rn and its daughters will be fractionated in the SRM bottle over time.