Novel production method for traceable surface sources by aluminium functionalisation

International audienceAccurate detection of low-level radioactivity is critical in decommissioning. However, commercial sources used for calibration lack representativeness due to their flat surface. The objective of this work is to produce flexible and large area surface sources for alpha and beta emitters by functionalising aluminium foil. Functionalisation strategies were developed to provide these sources. The manganese oxide coated sample shows the highest fixation yield for $^{241}$Am: (70.0 ± 2.6)% and conforms to ISO 8769 for uniformity (92%)

Traceable surface sources by functionalization for initial mapping of nuclear facilities

International audienceDuring decommissioning and dismantling, the initial cartography of all the surfaces is a key step that will enable in the classification of potential future wastes as a function of their radioactivity level. Using relevant surface sources, contamination detectors must be calibrated in terms of emitted flux, or Bq.cm-2. Current standard surface sources are made of thick aluminum with limited surface areas complying with ISO 8769 standard (Reference Sources-Calibration of Surface Contamination Monitors). These sources lack representativeness. This research intends to produce flexible, traceable surface sources with limited radiation self-absorption (for alpha and beta emitters). In this study, we propose a novel approach that will allow us to produce non-contaminating sources, due to the strong chemical bonds between the substrate and radioactive molecule. Using this method, unlike the commercial ones, a protective layer on the surface is not needed. We will then be able to manufacture more representative and non-contaminating sources to be used on-site to check the stability of the measurement devices. Two substrates, aluminium foils and polymeric surfaces, were selected to create sources that are both thin and flexible, curved or rough. Primarily, three molecules were selected to bind to the substrate at one end, and show a high affinity for the radionuclides at the other end. Due to the flexibility of aluminium foils, these sources can also be used to assess the performance of the detector in front of a curved surface. The experimental study includes cleaning, etching, grafting, and radionuclide binding steps. The substrates are cleaned in order to eliminate any organic residues. Afterwards, hydroxide functions were released by etching. Finally, in the grafting step, etched samples are immersed to graft the selected molecule on the substrate. These functionalization methods and their parameters such as concentration, reaction time, temperature, and drying conditions are optimized. In addition to these methods, sulfonation was found to be efficient for radionuclide attachment on polymeric surfaces. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to assess the functionalization success before and after grafting and to identify the functions on the surface. The topography was observed using scanning electron microscopy (SEM). The FTIR spectra results indicated that all of the selected chemicals were grafted onto the aluminum substrate. The SEM images also demonstrate that the surface morphology has changed significantly after grafting. Eventually, radionuclide binding experiments were carried out with 152Eu, used as a chemical surrogate for 241Am. We will present the radionuclide's binding yield obtained as a function of the functionalization as well as the associated surface uniformity of the samples, using respectively liquid scintillation counting and autoradiography

Applying POT methods to the Revised Joint Probability Method for determining extreme sea levels

International audienceNewly exposed concepts of POT declustering (Bernardara et al., 2014) within the GPD-Poisson model are applied to the joint probability of tide and surge for determining extreme sea levels, as a variation of the Revised Joint Probability Method (RJPM, Tawn and Vassie, 1989). A mixture model is proposed for the meteorological residual (surge) component with a non-parametric (empirical) density for the bulk values and parametric models for both the lower and upper tails. In particular, a distinction is made between values observed at regular time steps, called sequential values, and the clusters of extreme values, or events, on which the statistical extrapolations are performed. The sea level distribution is obtained by convolution of the tide and surge density functions. Confidence intervals are also proposed. This model is applied to the case study of Brest, France using both hourly and high water values. Two methods for handling tide–surge interaction are presented and discussed and a comparison with a direct approach is made

Novel production method for traceable surface sources by aluminium functionalisation

International audienceDuring decommissioning, the initial cartography of all surfaces is crucial for identifying potential future waste based on its radiation level. contamination detectors should be calibrated in terms of emission flux or Bq.cm-2 using suitable surface sources. Current standard sources, complying with ISO 8769 (Reference Sources-Calibration of Surface Contamination Monitors ), lack representativeness since they are only made of aluminium and have a limited surface area. This research seeks to produce flexible, traceable surface sources for alpha and beta emitters with low radiation self-absorption. While the existing sources are produced by adsorption on the aluminium surface, we aim to have strong chemical bonds due to the grafting on the surface. A novel functionalisation strategy involving spacer chemicals was developed to provide these sources. We have studied two substrate types: polymeric sources that can be molded into complex shapes and flexible aluminium foils that can be compared to existing ISO 8769 sources. This contribution will focus on aluminium substrate functionalisation . It involved choosing bi-functional compounds that can bind to a radionuclide on one end and be grafted onto aluminium with the free functional group of the compound on the other end. Because the radioactivity is chemically bound to their surfaces, these sources are meant to be non-contaminating and easy to use on-site. Our calibration sources can also be used to assess the detector's performance in front of a curved radioactive surface. Three bi-functional compounds were identified and the three main surface functionalisation steps were optimized. The first step is cleaning, to remove all the residues from the substrates. Then etching proceeded to release hydroxide functions. Next, the etched samples are immersed in the bi-functional compound solution. The influence of the reaction time, temperature, and drying conditions were studied. After the functionalisation, the inactive samples were characterised. The Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy has demonstrated that the ligand molecules are successfully grafted to the aluminium surface. The Scanning Electron Microscopy (SEM) images revealed a change in surface morphology following each functionalisation step. In addition, X-ray Photoelectron Spectroscopy (XPS) was utilised for complementary analysis. Finally, radionuclide binding experiments were conducted with Eu-152 as trivalent Eu is an excellent chemical analog for trivalent actinides such as Am-241. Liquid scintillation counting and autoradiography were used to quantify the radionuclides bound to the grafted surface and check the uniformity of the sources

Surface functionalization to provide flexible surface sources

International audienceDuring the decommissioning and dismantling process, the initial cartography of all the surfaces is vital in classifying potential future waste, depending on their radioactivity level. Contamination monitors, commonly used to measure the surface contamination, need to be calibrated in terms of emitted flux or Bq.cm$^{-2}$ using adequate surface sources. The major drawbacks of existing reference sources is that they are not representative of real sites and their surface areas are limited (<150 cm$^2$) [1]. The objective of this study is to produce uniform, traceable, flexible surface sources with limited radiation self-absorption (for alpha and beta emitters). These sources should be non-contaminating, meaning that the radioactivity is strongly attached to their surfaces. Furthermore, the surface areas targeted are larger than those of the existing sources. To produce sources that are both thin and non-contaminating, a functionalization approach was chosen. The goal is to introduce ligand groups, which are able to bind to a radionuclide (RN), onto the surface by grafting a bi-functional molecule (Fig 1). In this context, we can consider different substrates, such as aluminum foil and polymeric surfaces. In particular, sources prepared using aluminum foil can be flexible, and they can be compared with existing sources, also made of aluminum, which comply with ISO 8769 standard [1].A two-sided literature investigation was carried out, to find the optimal molecule, to allow both the functionalization of the aluminum surface and the RN binding. As a result, three chemicals were selected. Then, four sequential steps were undertaken to produce surface sources by functionalization. The first step was cleaning, to degrease and remove any residues on the surfaces. Then, the samples were etched, to release hydroxide bonds that can be utilized in the grafting step. Next, the etched samples were immersed in different grafting solutions, prepared using the chosen chemicals. The experimental methods were optimized by varying parameters such as the concentration of the chemicals, the reaction time and the drying conditions. Each sample was analyzed by Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and Scanning Electron Micro-scope (SEM) characterization methods. The ATR-FTIR spectra indicated that the grafting reactions were achieved between the spacer molecules and surface. The SEM images of the samples also showed a modification of the surface morphology after grafting. The RN binding experiments were carried out with 152Eu, used as a chemical surrogate for $^{241}$Am. Liquid scintillation counting and autoradiography were performed to evaluate the success of the RN binding on the grafted surface

Custom radioactive standards to assess detector performance

International audienceThe field of CBRNE measurements presents many challenges and requires the development of advanced instrumentation.The Laboratoire National Henri Becquerel (http://www.lnhb.fr/) has the capabilities to manufacture custom radioactive standards, traceable according to ISO 17025. Our calibration certificates are recognized by our homologues [1] (NIST, NPL, etc.) and the laboratory has a comprehensive authorization for radionuclide use. If needed, we can recommend surrogate elements to match the emissions of rare or short-lived radionuclides. In addition to providing custom standards, we can help with their use to evaluate the performance of the RN prototypes being developed in terms of detection limits and linearity of the detector response. In addition, discrimination capabilities can be checked (emission interferences or even cross-talk between channels) via the measurement of radionuclide mixture. The standards manufactured can also be used to test the performance of signal processing algorithms in conditions close to field constraints.Our sources have been successfully used to test an original signal processing strategy based on artificial spiking neural networks to enable fast radionuclide identification at low count rate for radiological threats [2], or to test imaging systems for nuclear medicine needs [3].The LNHB is ready to study what standards can be manufactured to enable a reliable performance assessment of advanced devices developed, or even to test them in our premises

Separation and quantification method for Pd-107 in radioactive waste

International audienceIn spent nuclear fuel, palladium 107 (Pd-107) is one of the longest-lived fissionproducts (FP) resulting from the fission of uranium and plutonium. After use of theUOX fuel in a PWR reactor, 4% of its mass composition is FP, among which 0.66%is Pd-107. This pure beta emitter decays to a stable Ag-107 with a half-life of 6.5 x106 years.In 2022, the French government has announced new nuclear power plants projectsin parallel with the increase in decommissioning and dismantling activities (D&D) ofnuclear sites. In order to ensure a correct disposal of nuclear waste and safe longterm storage in the required facilities, the Pd-107 concentration must be preciselyquantified in a variety of materials