Institute for Radiation Protection and Nuclear Safety (IRSN)
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A neural network encoder-decoder for time series prediction: Application on 137Cs particulate concentrations in nuclearized rivers
No full textInternational audienceMonitoring the impact of human activities on the environment is a major challenge as many pollutants can be found in the different ecosystems. This is the case of the caesium-137 that has been present in the environment for many decades as a result of atmospheric tests, accidents such as Chernobyl and release from nuclear industries. With the recent advance in data-driven models, this study evaluate the relevance of a deep learning tool for reconstructing caesium-137 chronics particulate concentration in rivers. An encoder-decoder neural network, "Hierarchical Attention-Based Recurrent Highway Networks"(HRHN), is proposed notably for its ability to extract the most relevant temporal and spatial information from the databases. Three monitoring stations were studied, one on the Rhône River and two on the Loire River, all of them downstream nuclear industries in these catchments affected by the global fallout and the accident of Chernobyl. The objective is to predict the future concentration from a set of variables providing past information on water discharge, washout flux and industrial radioactive releases. Once optimised, the model generates first results in agreement with the real concentration curves by correctly following the main trends, with a NSE of 0.89, 0.53 and 0.35 respectively for the Rhone station and the two stations on the Loire. The main reason of inaccuracies is due to the quantity of data available. The originality of this model is its capacity to make predictions on different catchment areas. In fact the training was conducted on the Rhône station as the range of the concentration was higher (from 265.4 to 2700.0 Bq/kg) and the testing on the two Loire station. Another encoder-decoder model DA-RNN (Dual-Stage Attention-Based Recurrent Neural Network) was also evaluate in order to compare the performance of an alternative architecture, without convolution layer. The conclusion is that HRHN remains more powerful in the predictions on the 3 systems. With these first interesting results for HRHN, further investigations should be taken into account for other pollutants than caesium-137 to better understand the robustness of the model
Optimal physical experimental designs to calibrate functional Weibull models under cost constraints. Application to a structural reliability problem
No full textInternational audienceWe focus on the specific issue of identifying (static) optimal physical experimental designs when the aim is to calibrate functional Weibull models in an informed context and under cost constraints. In this nonlinear parametric context, a major difficulty is that the exact evaluation of the expected utility function to maximize is intractable. Among the proposed approaches to overcome this difficulty, one can distinguish near optimal Bayesian experimental designs defined by maximizing either an analytical approximation or a numerical estimation of the expected utility. These latest approaches are based on quadratic techniques or simulations produced by stochastic algorithms. They remain computationally intensive, which makes them often limited in practice to very simple designs. In this work, we explore the potential of the Bayesian approach to account for legacy data as a prior informative sample when designing physical experiments. We propose generic design criteria based on a weighted combination of utility functions to balance the statistical gain yielded by a given design and the prospective experimental cost, in an understandable way for the engineer. We consider different utility functions to quantify the statistical gain yielded by a given design when fitting Bayesian functional Weibull models. Finally, we derive analytical asymptotic approximations of the associated expected utility functions that we maximize with a simulated annealing algorithm. Our method is applied to a structural reliability problem informed by a real dataset of U.S. ferric steels. The design problem consists in selecting an optimal number of temperature levels, optimal values of temperature levels and optimal numbers of Charpy destructive impact tests to allocate to each temperature level, in order to produce the most precise estimates of the parameters defining the functional Weibull distribution of steel fracture toughness for a French production park under cost constraints
International Comparison Exercise for Biological Dosimetry after Exposures with Neutrons Performed at Two Irradiation Facilities as Part of the BALANCE Project
No full textInternational audienceIn the case of a radiological or nuclear event, biological dosimetry can be an important tool to support clinical decision-making. During a nuclear event, individuals might be exposed to a mixed field of neutrons and photons. The composition of the field and the neutron energy spectrum influence the degree of damage to the chromosomes. During the transatlantic BALANCE project, an exposure similar to a Hiroshima-like device at a distance of 1.5 km from the epicenter was simulated, and biological dosimetry based on dicentric chromosomes was performed to evaluate the participants ability to discover unknown doses and to test the influence of differences in neutron spectra. In a first step, calibration curves were established by irradiating blood samples with 5 doses in the range of 0–4 Gy at two different facilities in Germany (Physikalisch-Technische Bundesanstalt [PTB]) and the USA (the Columbia IND Neutron Facility [CINF]). The samples were sent to eight participating laboratories from the RENEB network and dicentric chromosomes were scored by each participant. Next, blood samples were irradiated with 4 blind doses in each of the two facilities and sent to the participants to provide dose estimates based on the established calibration curves. Manual and semiautomatic scoring of dicentric chromosomes were evaluated for their applicability to neutron exposures. Moreover, the biological effectiveness of the neutrons from the two irradiation facilities was compared. The calibration curves from samples irradiated at CINF showed a 1.4 times higher biological effectiveness compared to samples irradiated at PTB. For manual scoring of dicentric chromosomes, the doses of the test samples were mostly successfully resolved based on the calibration curves established during the project. For semiautomatic scoring, the dose estimation for the test samples was less successful. Doses >2 Gy in the calibration curves revealed nonlinear associations between dose and dispersion index of the dicentric counts, especially for manual scoring. The differences in the biological effectiveness between the irradiation facilities suggested that the neutron energy spectrum can have a strong impact on the dicentric counts
A multidisciplinary and structured investigation of three suspected clusters of transverse upper limb reduction defects in France
No full textInternational audienceIntroduction: Between 2019–2021, facing public concern, a scientific expert committee (SEC) reanalysed suspected clusters of transverse upper limb reduction defects (TULRD) in three administrative areas in France, where initial investigations had not identified any risk exposure. We share here the national approach we developed for managing suspicious clusters of the same group of congenital anomalies occurring in several areas. Methods: The SEC analysed the medical records of TURLD suspected cases and performed spatiotemporal analyses on confirmed cases. If the cluster was statistically significant and included at least three cases, the SEC reviewed exposures obtained from questionnaires, environmental databases, and a survey among farmers living near to cases’ homes concerning their plant product use. Results: After case re-ascertainment, no statistically significant cluster was observed in the first administrative areas. In the second area, a cluster of four children born in two nearby towns over two years was confirmed, but as with the initial investigations, no exposure to a known risk factor explaining the number of cases in excess was identified. In the third area, a cluster including just two cases born the same year in the same town was confirmed. Discussion: Our experience highlights that in the event of suspicious clusters occurring in different areas of a country, a coordinated and standardised approach should be preferre
Towards a European prospective data registry for particle therapy
No full textInternational audienceThe evidence for the value of particle therapy (PT) is still sparse. While randomized trials remain a cornerstone for robust comparisons with photon-based radiotherapy, data registries collecting real-world data can play a crucial role in building evidence for new developments. This Perspective describes how the European Particle Therapy Network (EPTN) is actively working on establishing a prospective data registry encompassing all patients undergoing PT in European centers. Several obstacles and hurdles are discussed, for instance harmonization of nomenclature and structure of technical and dosimetric data and data protection issues. A preferred approach is the adoption of a federated data registry model with transparent and agile governance to meet European requirements for data protection, transfer, and processing. Funding of the registry, especially for operation after the initial setup process, remains a major challenge
First measurements of electric field variability during fog events in the United Arab Emirates
No full textInternational audienceFor the first time, the changes in the atmospheric electric field (Ez) during foggy conditions is studied in a hyperarid region; the United Arab Emirates (UAE), using comprehensive measurements during the Wind-blown Sand Experiment (WISE)-UAE. The longer the fog persists, the more variable Ez becomes, primarily due to the fog’s ability to absorb and redistribute the charges of the atmospheric small ions. This absorption alters the ion balance, affecting electrical conductivity within the atmosphere, which in turn leads to sustained alterations in Ez. A record high Ez value of 2571 V m− 1 was measured during a long-lasting fog event. Ez values returned to normal during the fog dissipation phase. The results of this work can be applied to develop techniques for fog harvesting and to improve fog forecasting by accounting for the effect of the electric field on fog lifetime and characteristics
Recommendations for harmonized reporting of radiation Dosimetry by adoption of Compatibility in Irradiation Research Protocols Expert Roundtable (CIRPER)
No full textInternational audienceIn radiobiology, radiation physics, and related areas, there is growing interest in transitioning from cesium-based irradiators to X-ray technologies. Therefore, it makes it imperative for reproducibility purposes, for researchers to provide specifications regarding device parameters, machine calibration details, and experimental setup when innovative X-ray technology is being employed
Cross-section measurements of neutron-induced reactions on Ge isotopes in the neutron energy range 14.0–18.9 MeV
No full textInternational audienceThe cross sections of the 70Ge(n,2n)69Ge, 72Ge(n,α)69mZn, 72Ge(n,p)72Ga, 73Ge(n,nα)69mZn, 73Ge(n,np/d)72Ga, 73Ge(n,p)73Ga, 74Ge(n,α)71mZn, 74Ge(n,np/d)73Ga and 76Ge(n,2n)75Ge reactions have been experimentally determined via the activation technique, relative to the 27Al(n,α)24Na reference reaction in the energy range between 14.0 and 18.9 MeV. The quasi-monoenergetic neutron beams were produced via the 3H(d,n)4He reaction at the neutron beam facilities of NCS “Demokritos” (Greece) and AMANDE, IRSN (France). Following the irradiations, the induced radioactivity of the samples was measured via γ-ray spectroscopy using HPGe detectors. For all the cross-section measurements, isotopically enriched Ge targets were employed, producing more accurate cross-section results in comparison with natural ones, that are most commonly used. Finally, theoretical calculations were carried out via the EMPIRE 3.2.3 code, employing a coherent set of input parameters for the simultaneous reproduction of all the aforementioned reaction channels
MR compatible detectors assessment for a 0.35 T MR-linac commissioning
No full textInternational audienceAbstract Purpose To assess a large panel of MR compatible detectors on the full range of measurements required for a 0.35 T MR-linac commissioning by using a specific statistical method represented as a continuum of comparison with the Monte Carlo (MC) TPS calculations. This study also describes the commissioning tests and the secondary MC dose calculation validation. Material and methods Plans were created on the Viewray TPS to generate MC reference data. Absolute dose points, PDD, profiles and output factors were extracted and compared to measurements performed with ten different detectors: PTW 31010, 31021, 31022, Markus 34045 and Exradin A28 MR ionization chambers, SN Edge shielded diode, PTW 60019 microdiamond, PTW 60023 unshielded diode, EBT3 radiochromic films and LiF µcubes. Three commissioning steps consisted in comparison between calculated and measured dose: the beam model validation, the output calibration verification in four different phantoms and the commissioning tests recommended by the IAEA-TECDOC-1583. Main results The symmetry for the high resolution detectors was higher than the TPS data of about 1%. The angular responses of the PTW 60023 and the SN Edge were − 6.6 and − 11.9% compared to the PTW 31010 at 60°. The X/Y-left and the Y-right penumbras measured by the high resolution detectors were in good agreement with the TPS values except for the PTW 60023 for large field sizes. For the 0.84 × 0.83 cm 2 field size, the mean deviation to the TPS of the uncorrected OF was − 1.7 ± 1.6% against − 4.0 ± 0.6% for the corrected OF whereas we found − 4.8 ± 0.8% for passive dosimeters. The mean absolute dose deviations to the TPS in different phantoms were 0 ± 0.4%, − 1.2 ± 0.6% and 0.5 ± 1.1% for the PTW 31010, PTW 31021 and Exradin A28 MR respectively. Conclusions The magnetic field effects on the measurements are considerably reduced at low magnetic field. The PTW 31010 ionization chamber can be used with confidence in different phantoms for commissioning and QA tests requiring absolute dose verifications. For relative measurements, the PTW 60019 presented the best agreement for the full range of field size. For the profile assessment, shielded diodes had a behaviour similar to the PTW 60019 and 60023 while the ionization chambers were the most suitable detectors for the symmetry. The output correction factors published by the IAEA TRS 483 seem to be applicable at low magnetic field pending the publication of new MR specific values
First production of pure Gd targets and Gd(p,x)Tb,Tb cross-section measurements
No full textInternational audience•Production of isotopically pure 155Gd targets.•Proton activation of isotopically pure 155Gd targets.•First measurement of 155Gd(p,x)155Tb and 156Tb cross-sections around 25 MeV.•Comparison of data obtained with pure 155Gd proton-activated targets, with TENDL-2023 library.•Highlight relevance of 155Gd targets use to limit production of the main contaminant 156Tb