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The National Institute for Nuclear, Biological, and Chemical Protection, under the European project 16ENV10 MetroRADON (the European metrology program for innovation and research, EMPIR), has developed unique equipment for the testing of measuring devices at low-level radon activity concentrations. The equipment consists particularly of an airtight low-level radon chamber (LLRCH) with an inner volume of 324 liters, a Rn-222 type RF 5 flow-through source with a Ra-226 activity of 4.955 kBq developed by Czech Metrological Institute within the above-mentioned project, and a pressure vessel as a radon-free air source. The mass flow controller of the Bronkhorst EL-Flow type is a part of the apparatus and ensures the requested airflow through the radon source&mdash, partialized if necessary&mdash, through the chamber. The homogeneity of the atmosphere in the chamber is ensured by means of a continuously regulated fan (airflows in the range of 0.1&ndash, 3.5 m&middot, s&minus, 1 can be established). Another important chamber component is the measuring device of climatic conditions, since temperature, air pressure, and relative humidity must be determined. The construction of the equipment allows the time-stable radon activity concentration to be maintained at a precise level for several days. Radon concentration values can be arbitrarily and continuously set in the range from 100 Bq&middot, m&minus, 3 to 300 Bq&middot, 3.

The emission intensities of 186.21keV, 46.54keV, XL(Bi) and XK(Rn) photons were measured with calibrated HPGe detectors. The efficiency was computed with the MCNP Monte Carlo code and validated using experimental points. Sources of Ra-226 were prepared from two different radioactive materials. The X-ray emission intensities in Ra-226 decay were determined without X-rays from the daughter decay products using a radon emanation source. The standard CMI source with Pb-210 was used and compared with a source prepared from the NPL solution delivered under the EMRP project "Metrology for processing materials with high natural radioactivity - MetroNORM".

Accurate measurements were performed of the photon emission probabilities following the α decay of 235U to 231Th. Sources of highly enriched 235U were characterised in terms of isotopic composition by mass spectrometry and their activities were standardised by means of alpha-particle counting at a low defined solid angle. The standardised sources were subsequently measured by high-resolution γ-ray spectrometry with calibrated high-purity germanium detectors to determine the photon emission probabilities. Four laboratories participated in this work and reported emission probabilities for 33 γ-ray lines. Most of them agree with previously published evaluated data. In addition, new values are proposed for γ-lines which have been measured only once in the past. © 2017 The Authors

Proceedings of the 7th International Conference on Radionuclide Metrology - Low Level Radioactivity Measurement Techniques (ICRM-LLRMT), 26 -30 September 2016, Seattle, USA; International audience; 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.

Reliable measurement of Naturally Occurring Radioactive Materials is of significance in order to comply with environmental regulations and for radiological protection purposes. This paper discusses the standardisation of three reference materials, namely sand, tuff and TiO2 to serve as quality control materials for traceability, method validation and instrument calibration. The sample preparation, material characterization via γ, α and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and the assignment of values for both the 4n (Thorium) and 4n+2 (Uranium) decay series are described.

We have tested two digital spectrometer systems, the DSP 9660 and Lynx ® modules, connected to a HPGe detector. Lynx ® is a fully integrated 32 K channel signal analyzer based on digital signal processing techniques, which offers advanced digital stabilization. The model DSP 9660 digitalizes the signal directly at a very high sampling rate. The evaluated properties were integral nonlinearity, differential linearity, channel profiles, resolution and throughput. We found that the DSP system has slightly inferior resolution and throughput in comparison with the Lynx ® system.

A radionuclide solution of 86Rb was standardised by the absolute measurement method 4πβ-γ coincidence counting at the Czech Metrology Institute. The created sources were measured by two calibrated HPGe γ spectrometers in order to estimate the γ-emission intensity, energy of the γ-emission and half-life of the 86Rb. The aim of this work was to improve and spread the currently published values. An intensity value of 8.74 (7) % was achieved for the obtained 1076.772 (75) keV γ-emission. We also determined the half-life 18.684 (9) d of the 86Rb. The obtained energy of the γ-emission and the γ-emission intensity are in a good agreement with the results obtained in recent experiments. The half-life found is in a rather good agreement with previously reported values.