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Decommissioning of nuclear facilities incurs high costs regarding the accurate characterisation and correct disposal of the decommissioned materials. Therefore, there is a need for the implementation of new and traceable measurement technologies to select the appropriate release or disposal route of radioactive wastes. This paper addresses some of the innovative outcomes of the project "Metrology for Decommissioning Nuclear Facilities" related to mapping of contamination inside nuclear facilities, waste clearance measurement, Raman distributed temperature sensing for long term repository integrity monitoring and validation of radiochemical procedures., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This paper addresses the measurement facilities for pre-selection of waste materials prior to measurement for repository acceptance or possible free release (segregation measurement system); and free release (free release measurement system), based on a single standardized concept characterized by unique, patented lead-free shielding. The key objective is to improve the throughput, accuracy, reliability, modularity and mobility of segregation and free-release measurement. This will result in a more reliable decision-making with regard to the safe release and disposal of radioactive wastes into the environment and, resulting in positive economic outcomes. The research was carried out within "Metrology for Decommissioning Nuclear Facilities" (MetroDecom) project., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Monte Carlo (MC) simulations were done for the optimization of shielding configuration of a novel industrial radionuclide-specific pre-selection free release measurement facility. The shielding is made from unique bricks of concrete with very low specific activity of natural radionuclides. The final configuration was selected as a compromise between shielding volume and the simulated 1461keV full-energy peak detector count rates of natural 40 K., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

A Europallet-sized calibration standard composed of 12 grey cast iron tubes contaminated with (60)Co and (110m)Ag with a mass of 246kg was developed. As the tubes were produced through centrifugal casting it was of particular concern to study the distribution of radionuclides in the radial direction of the tubes. This was done by removing 72 small samples (swarf) of ~0.3g each on both the inside and outside of the tubes. All of the samples were measured in the underground laboratory HADES., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

A novel free release measurement facility (FRMF) was developed within the joint research project "Metrology for Radioactive Waste Management" of the European Metrology Research Programme. Before and during FRMF design and construction, Monte Carlo calculations with MCNPX and PENELOPE codes were used to optimize the thickness of the shielding, the dimensions of the container, and the shape of detector collimators. Validation of the numerical models of the FRMF detectors and the results of the optimization are discussed in the paper., (© 2013 Published by Elsevier Ltd.)

We have tested two digital spectrometer systems, the DSP 9660 and Lynx(®) modules, connected to a HPGe detector. Lynx(®) is a fully integrated 32K 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., (© 2013 Elsevier Ltd. All rights reserved.)

The second part of an intercomparison of the coincidence summing correction methods is presented. This exercise concerned three volume sources, filled with liquid radioactive solution. The same experimental spectra, decay scheme and photon emission intensities were used by all the participants. The results were expressed as coincidence summing corrective factors for several energies of (152)Eu and (134)Cs, and different source-to-detector distances. They are presented and discussed., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

In nuclear facilities stack monitors are used for the measurement of the volumetric activity of noble gases. Spectrometric measurement is needed because the content of stack effluents is always a mixture of radionuclides. In some nuclear power plants new types of monitors were installed based on HPGe detectors. For efficiency calibration a standard with the radionuclide Xe-127 was developed and calibration curve constructed in the energy range 81 keV-1293 keV. Experiental efficiencies were checked using an MC model., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

An international exercise, registered as EUROMET project no. 907, was launched to measure both the activity of a solution of (124)Sb and the photon emission intensities of its decay. The same solution was sent by LNE-LNHB to eight participating laboratories, six of which sent results for photon emission intensities both in absolute and in relative terms. From these results and including previous published values, a consistent decay scheme was worked out, proving that problems in activity measurements have not been due to decay scheme data., (Copyright 2010 Elsevier Ltd. All rights reserved.)

An international exercise, registered as EUROMET project no. 907, was launched to measure both the activity of a solution of (124)Sb and the photon emission intensities of its decay. The same solution was sent by LNE-LNHB to eight participating laboratories. In order to identify possible biases, the participants were asked to use all possible activity measurement methods available in their laboratory and then to determine their reference value for comparison. Thus, measurement results from 4pibeta-gamma coincidence/anti-coincidence counting, CIEMAT/NIST liquid-scintillation counting, 4pigamma counting with well-type ionization chambers and well-type crystal detectors were given. The results are compared and show a maximum discrepancy of about 1.6%: possible explanations are proposed., (Copyright 2010 Elsevier Ltd. All rights reserved.)

A comparison of the coincidence summing correction methods is presented. Since there are several ways for computing these corrections, each method has advantages and drawbacks that could be compared. This part of the comparison was restricted to point sources. The same experimental spectra, decay scheme and photon emission intensities were used by all the participants. The results were expressed as coincidence summing correction factors for several energies of (152)Eu and (134)Cs, and three source-to-detector distances. They are presented and discussed., (Copyright 2010 Elsevier Ltd. All rights reserved.)

Two types of detectors (GC 4018 and BE 5030) were compared regarding the signal from the outer dead layer of the detector. Gamma-spectra of Am-241 were acquired with various delays against the starting signal from an alpha LS probe. Coincidence spectra from both detectors were different. The dead-layer signal does not increase the full-energy peak efficiency but it increases the total efficiency, as it was demonstrated by the reconstruction of Am-241 spectra for both detectors., (Copyright 2009 Elsevier Ltd. All rights reserved.)

The Czech Metrology Institute performs calibration and verification of noble gases stack monitors in nuclear power plants and nuclear research facilities. Together with Kr-85 and Xe-133, the radionuclide Ar-41 is measured using HPGe detectors and its activity is determined using a gamma-ray peak at 1293keV. The counting efficiency used in these measurements was calculated by the Monte Carlo method using the MCNP code. Radioactive gas standard is prepared by irradiation of argon in a high-pressure vessel by a Cf-252 neutron generator. The inner shape and thickness of the cylinder walls were determined by radiography. The argon volume under normal conditions is determined from the high-pressure vessel volume and by a precise gas pressure measurement. As a result, the activity concentration of Ar-41 at normal conditions is certified.

The emission probabilities of gamma photons in the decay of (56)Co were determined at Czech Metrology Institute (CMI) by means of an HPGe detector. This detector was calibrated experimentally and by MCNP-computation in the energy range from 40 to 2754keV for a point source geometry and source-to-detector distance of 25cm. Experimental and computed peak and total efficiencies were compared and calibration curves were determined. Full-peak efficiencies were calculated for all (56)Co gamma-ray energies, and were used to calculate the emission probabilities. A set of point sources was prepared from a (56)Co solution. The solution was standardized using the 4pibeta-gamma coincidence method, and an ampoule was sent to international reference system for activity measurement of gamma-ray emitting radionuclides (SIR). Each point source was measured with the HPGe detector at a source-to-detector distance of 25cm. Coincidence emission probabilities of all the gamma photons were calculated and used to determine the summing correction factors.

A precise model of a 40% relative efficiency p-type HPGe detector was created for photon detection efficiency calculation using the MCNP code. All detector parameters were determined by different experiments. No experimental calibration points were used for the modification of detector parameters. The model was validated by comparing calculated and experimental full energy peak efficiencies in the 40-2754 keV energy range, for point-source geometry with the source-to-detector distance of 25 cm.

The properties of digital modules (analog-to-digital converters (ADC), digital signal processor (DSP)) in spectrometric chain are the decisive factors which affect the quality of spectrometric measurements. Several properties, integral and differential linearity, channel profiles and throughput, of various ADC and DSP models by CANBERRA were tested.

This paper describes a method of determination of correction factors for the true summation effect of photons for measurement of activity of radionuclides emitting gamma radiation. The method was tested with Marinelli beakers samples measured with coaxial germanium detectors. The advantage of this method is its simplicity since it is not necessary to determine the curves of total efficiency for each detector. The correction factor for the particular peak is determined by means of a detector index which is calculated from one of the measurements with a calibration standard.

Several systems with large area plastic scintillators were tested, which are used to avoid the undesirable and illegal transport of radioactive materials especially at border crossings, in metallurgical works and in plants processing metal scrap, were tested. Measuring equipment with germanium detectors, which is used for check of material released from the Dukovany Nuclear Power Plant, was also tested. The detection possibilities of a chamber with plastic scintillators, for the use during checking of materials released to the environment, were investigated.