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High-accuracy source standards preparation in radionuclide metrology is based on a properly described and reliable weighing procedure able to achieve relative standard uncertainties below 0.1%. However, the results of uncertainty budget comparison CCRI(II)-S7 put in check the ability of the former pycnometer and substitution weighing methods to attain this goal. As a result, a question arises about the validation of mass measurements performed from the elimination weighing method when appropriate uncertainties are required. In order to address this problem, a comprehensive in situ validation methodology is proposed for the results of the pycnometer, substitution, elimination and modified elimination (MEM) methods. Mass comparisons are applied to evaluate the compatibility between weighing methods’ results. It is possible due to a developed weighing sequence, which allows for the performing of all methods by only one drop deposition in the range of mass from 10 mg to 200 mg. As a result, the high degree of compatibility between the MEM and elimination method for uncertainties below 0.1% has been achieved, as well as for higher uncertainties to pycnometer and substitution methods. Numerical simulations indicate that the validation results remain valid on improved technical implementations for these last two methods.

High-accuracy source standards preparation in radionuclide metrology is based on a properly described and reliable weighing procedure able to achieve relative standard uncertainties below 0.1%. However, the results of uncertainty budget comparison CCRI(II)-S7 put in check the ability of the former pycnometer and substitution weighing methods to attain this goal. As a result, a question arises about the validation of mass measurements performed from the elimination weighing method when appropriate uncertainties are required. In order to address this problem, a comprehensive in situ validation methodology is proposed for the results of the pycnometer, substitution, elimination and modified elimination (MEM) methods. Mass comparisons are applied to evaluate the compatibility between weighing methods' results. It is possible due to a developed weighing sequence, which allows for the performing of all methods by only one drop deposition in the range of mass from 10 mg to 200 mg. As a result, the high degree of compatibility between the MEM and elimination method for uncertainties below 0.1% has been achieved, as well as for higher uncertainties to pycnometer and substitution methods. Numerical simulations indicate that the validation results remain valid on improved technical implementations for these last two methods. [ABSTRACT FROM AUTHOR]

A new method for radionuclide labeling by the use of graphene thin films was previously presented. In this work, a comparison among low energy radioactive sources supported on carbonaceous thin films on polyvinyl chloride-polyvinyl acetate copolymer (VYNS), based on the use of aqueous solutions is investigated as a feasible alternative to the traditional metallized films avoiding the downside of the loss of many broken films. Graphene-based materials were prepared by both oxidation-exfoliation-reduction and direct graphite exfoliation routes. In addition, multiwalled carbon nanotubes (MWCNTs) thin films were also evaluated. The stability of both carbonaceous materials aqueous dispersions were studied by using ionic and non-ionic surfactants. Solid carbon-based materials were characterized by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) whereas the colloidal nature of the aqueous dispersions was verified by the measurement of Tyndall effect and the morphology of thin films was evaluated by Scanning Electron Microscopy (SEM). 55Fe solutions were used to prepare the radioactive sources on the thin films by quantitative drop deposition. The quality of spectra was measured in a pressurized proportional counter. Results showed a resolution higher than 0.9 keV for all the tested sources. However, MWCNT-based along with non-surfactant sources presented non-adequate escape peaks and low energy tails. On the contrary, all the graphene-based sources prepared using surfactants to stabilize aqueous solutions presented an energy resolution comparable to that of the metallized source while offering notable advantages in terms of cost efficiency and reliability of the as-prepared supports. • Carbon-based thin films have been prepared as conductive support for radionuclide labeling. • Thin films were prepared by spin coating from aqueous solutions of rGO, deG and MWCNTs on VYNS films. • Sources prepared with graphene-based materials show spectra comparable to the metallized sources. [ABSTRACT FROM AUTHOR]

Total decay energy spectrometry (Q spectrometry) with cryogenic detectors is a promising technique for analysis of α-emitting actinides. However, this technique is very sensitive to the quality of the source preparation due to the absorption of the nuclear recoil energy in the source material. Drop deposition of the radioactive solution without care produces spectra with unpredictable peak shapes. In order to keep the simplicity of the drop deposition technique, we study the deposition of solution on latex nanoparticles or in nanoporous gold (NPAu) to improve the source quality. 4π absorbers were fabricated and tested using these two techniques. The absorbers contained a mixture of Pu isotopes. From the best Q spectrum, the composition of Pu isotopes and other actinides was measured and it is in very good agreement with the reference values given by alpha and mass spectrometry. [ABSTRACT FROM AUTHOR]

In order to automate sample preparation processes, a precision pattern dispenser was designed to reproducibly dispense radioactive solutions at pre-defined positions. It is composed of an automatic liquid sample handling unit coupled to an XYZ table. Qualification tests were conducted to evaluate the performance of the instrument and to assess the compliance with the requirements, in particular trueness (< 2%) and repeatability (< 1%). The instrument allows preparing sources in different source holders and on air filters, in a fast and accurate way. [ABSTRACT FROM AUTHOR]

A new method for the preparation of conductive thin films is presented. The metallization of VYNS films guarantees the electrical conductivity but it results in the breaking of a high proportion of them. Graphene, a two-dimensional nanostructure of monolayer or few layers graphite has attracted a great deal of attention because of its excellent properties such as a good chemical stability, mechanical resistance and extraordinary electronic transport properties. In this work, the possibilities of graphene have been explored as a way to produce electrical conductive thin films without an extra metallization process. The procedure starts with preparing homogenous suspensions of reduced graphene oxide (rGO) in conventional VYNS solutions. Ultra-sonication is used to ensure a good dispersibility of rGO. Graphene oxide (GO) is prepared via oxidation of graphite and subsequent exfoliation by sonication. Different chemically rGO were obtained by reaction with hydrazine sulfate, sodium borohydride, ascorbic acid and hydroiodic acid as reducing agents. The preparation of the thin graphene films is done in a similar way as the conventional VYNS foil preparation procedure. Drops of the solution are deposited onto water. The graphene films have been used to prepare sources containing some electron capture radionuclides ( 109 Cd, 55 Fe, 139 Ce) with an activity in the order of 3 kBq. The samples have been measured to test the attainable low energy electron efficiency and the energy resolution of Auger and conversion electrons by 4π (electron capture)-γ coincidence measurements. The 4π (electron capture)-γ coincidence setup includes a pressurized proportional counter and a NaI(Tl) detector. Tests with different pressures up to 1000 kPa were carried out. All these tests show similar values in both parameters (efficiency and resolution) as those obtained by using the conventional metallized films without the drawback of the high percentage of broken films. [ABSTRACT FROM AUTHOR]

Determination of content (active concentration) of radio-nuclides has recently become an indispensable part of the study dealing with the protection of the environment. Uranium concentration levels in aquatic environment are of great importance for environmental and safety assessment and for the protection of public health. Achieving this purpose, monitoring program for this radio-nuclide, radium and thorium, as well as gross alpha and beta activities, seems necessary and it is applied in many countries. This study determined the activity concentration of uranium isotopes in 10 samples of drinking water, natural spring and mineral water (bottled, commercially available water). Also, gross alpha and beta activity has been determined for all samples. Activity concentration of uranium isotopes was measured with alpha-spectrometry, while gross alpha-beta activity was measured by low level gas-flow proportional alpha-beta counter. Results of the research show that the concentration of isotopic uranium activities in the tested samples of drinking water varies from 10-8to 10-2 Bq/L, while gross alpha-beta activity is between 10-3 and 10-1 Bq/g.The results show that the analyzed brands of spring, commercially available bottled waters meet the defined criteria of radiological safety. [ABSTRACT FROM AUTHOR]

Nuclear decay data measurements were performed in the frame of a EURAMET project. Two specific goals were addressed: (1) High-precision measurements of ^238U alpha-particle emission probabilities and (2) experimental characterization of the shape of beta spectra using cryogenic detectors. In the paper, specific lessons learned from the metrological work are highlighted. This includes effects of source preparation on the quality of alpha and beta spectrometry, the influence of exchange effects on beta spectra and the use of a magnet system to eliminate coincidence effects by conversion electrons in alpha-particle spectra. [ABSTRACT FROM PUBLISHER]

Electrodeposition is the major method for source preparation of actinides, Pu, Am, Th, U using stainless steel discs and spontaneous deposition for Polonium using discs of silver. Worldwide coins are manufactured of bronze, steel, copper plated steel, cupronickel, brass and alloys of Cu-Ni-Zn. The price of the coins which can be used have a value between 0.1 and 0.4 Euro considerably cheaper than electropolished stainless steel discs, 0.8 Euro. This investigation had the purpose to show the possibility to use coins from different countries for source preparation, the energy resolution and deposition efficiency. We obtained plating recoveries ranging from 50 to 100 % and the energy resolution varied between 21 and 75 keV for the different coins tested. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption of 241Am dissolved in water in different plastic storage vessels was determined. Three different plastics were investigated with natural and distilled waters and the retention of 241Am by these plastics was studied. The same was done by varying vessel agitation time, vessel agitation speed, surface/volume ratio of water in the vessels and water pH. Adsorptions were measured to be between 0% and 70%. The adsorption of 241Am is minimized with no water agitation, with PET or PVC plastics, and by water acidification. [Copyright &y& Elsevier]

Abstract: Differently shaped Pt anodes were used in the electrodeposition procedure and their influence on the quality of the thin layer of deposited radioisotopes was studied. In the micro-coprecipitation procedure the influence of working under vacuum on the homogeneity of the sources was investigated. The homogeneity of the alpha sources was checked by visualization of the activity distribution of the sources using autoradiography. [Copyright &y& Elsevier]

Abstract: The morphology and composition of uranium alpha sources with co-deposited platinum have been investigated by scanning electron microscopy (SEM) with energy dispersive X-ray fluorescence analysis (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) studies. Combined SEM and EDX measurements reveal the effect of porous platinum on the morphology of the sources which in turn affects their alpha-spectral resolution. The XPS analysis suggests that the presence of platinum initially increases the concentration of hydroxyl species in the deposits, which then act as centres for subsequent preferential uranium precipitation. XPS and XAFS analysis also provide for first time an indication of oxidation states of uranium present in the sources prepared by the Hallstadius method. These results are in line with Hansen''s theory of electrodeposition of actinides. [Copyright &y& Elsevier]

Abstract: Optimal thermodynamic stability conditions must prevail when radioactivity standard solutions are prepared. These conditions are studied, they relate to: [•] The nature of the radioactive ion, which makes it possible to establish the pH of the solubilization medium at a given concentration, [•] The carrier concentration, which is determined by considering the radionuclide production method and the prior concentration in the original solution from the supplier, [•] The most stable oxidation state of the radioactive ion and of the carrier ion, which must be considered at the pH established by the solubilization medium. A procedure for all the glassware used in preparation has been implemented. [Copyright &y& Elsevier]

In the framework of R&D studies for the improvement of radioactive source efficiencies prepared on thin films for 4πβ–γ coincidence counting, a comparative study on two drying methods has been undertaken in our laboratory (BNM-Laboratoire National Henri Becquerel, France). The standard method of evaporation at atmospheric pressure and a method based on freeze-drying using commercial equipment are compared. The preliminary results of this study obtained with 65Zn sources are presented and a significant improvement of the detection efficiencies to the electron emission for freeze-dried sources is shown. In the course of validation of this method, other radionuclides were studied and, up to now, the results confirm the better crystallization homogeneity achieved for freeze-dried sources. [Copyright &y& Elsevier]

In the framework of a BIPM 238Pu comparison exercise, a new design for α-radiation counting sources was developed. These sources are constructed with a gold-coated Vyns film stretched over a stainless-steel disk. To improve the crystallization of the radioactive salt, the physical properties of the gold-coated polymer surface which receives the radioactivity deposit is modified. A pad of polystyrene micro-spheres (Estapor® K-007) mixed with a wetting agent (Tween 20®) is directly electrosprayed before the radioactive drop is deposited. After hot air-drying, the source is finally sealed with a thin Vyns film covering the entire radioactive spot. This new design makes it possible to create 238Pu sources that are easy and safe to handle, homogeneous and stable during ageing. [Copyright &y& Elsevier]

Characterization of the homogeneity of thin actinide deposits prior to and after irradiation is important to ensure measurement of high-quality nuclear data in nuclear physics experiments. Autoradiography is frequently used to assess homogeneity, but geometric blur from source thickness, particle range, and source-detector gap can significantly degrade image resolution and introduce bias when estimating source uniformity and activity. We establish a method for minimizing geometric blur using a new autoradiography imaging technique with microcapillary array collimators and a new method to characterize the homogeneity of an imaged deposit. Also, we demonstrate that beta-/gamma-blind imaging is possible for alpha-particle autoradiography with ZnS:Ag scintillators and the ionizing-radiation quantum imaging detector (iQID), a digital autoradiography system with intrinsic spatial resolutions up to 20 μm for alphas. This iQID imaging approach can successfully discriminate alphas in the presence of a beta-gamma source in samples containing >106 dynamic range in activity. We apply this feature to characterize the uniformity of plutonium deposits before and after accelerator irradiation in the presence of a large beta-gamma background. • We have developed a new and novel autoradiographic imaging technique with alpha particle emitters using microcapillary array collimators and the ionizing-radiation quantum imaging detector (iQID). • We present a new method to characterize the homogeneity of an imaged alpha-emitting source deposit. • We demonstrate beta-/gamma-blind autoradiography with alpha emitters using ZnS:Ag scintillators and the single-particle detection capability of the iQID [ABSTRACT FROM AUTHOR]

Abstract: A source preparation procedure was optimised for 235U sources of about 1mg or 100Bq, to be standardised for their activity concentrations by α-particle counting at a defined solid angle. The aim was to obtain quantitative sources having a thin, homogeneous active layer with low self-absorption of the emitted α-particles. The procedure involves spraying the wetting and seeding agent in a circular shape onto a glass or stainless steel substrate, quantitative drop deposition of active solution onto the sprayed area by the pycnometer method and fast drying of the source on a heating plate. The fraction of heavily scattered and self-absorbed α-particles could be reduced to 0.05–0.1% for a majority of the sources. [Copyright &y& Elsevier]

Measuring the radioactive content of environmental samples requires the use of appropriate reference materials with the same composition and density as the matrices to be measured. If they are not available, ad hoc artificially spiked reference materials are an alternative. Spiking in layers requires a detailed study of the drop distribution, as energy and decay scheme of the component radionuclides must be taken into account to produce a reference material that represents, in efficiency terms, a real sample. A method based on Monte Carlo simulation has been developed to find the optimal distribution of drops in layers for the combination of two typical soil samples and four radionuclides. Results have been validated by comparison with samples prepared by two techniques: methanol bath and spiking in layers. • Equivalence of sources prepared by different spiking procedures was studied. • The samples were measured using high-resolution gamma-ray spectrometry. • Monte Carlo numerical model was used to calculate counting efficiencies. • The optimal distribution of the spiked layers was determined. [ABSTRACT FROM AUTHOR]

Abstract: A new set of gamma-ray emitting test sources was designed by the National Institute of Standards and Technology (NIST) for testing of radiation portal monitors for homeland security applications. This paper provides a description of the construction and characterization of these new sources that were designed and built to meet the American National Standard Institute (ANSI) N42.35-2004 and N42.38 standards’ requirements. [Copyright &y& Elsevier]