Institute for Radiation Protection and Nuclear Safety (IRSN)
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On integrating Monte Carlo calculations in and around near-critical configurations – II. Pressurized water reactors
No full textInternational audienceThis article is the second part of a paper that evaluates a recent approach that has been developed to calculate differential in- and ex-fissile configuration responses employing Monte Carlo with variance reduction. The first part focused more on the methodological aspects and established the circumstances under which a single eigenvalue calculation could be made as efficient as possible, in particular as compared with an empirical approach (involving again a single eigenvalue calculation). Both ex- and in-core test problems were considered. Instead this second part looks at two ex-core PWR sample problems and compares the single eigenvalue approach with an all Monte Carlo decoupled approach with different approximations at the point of decoupling, thus highlighting the sensitivity of the decoupled result to the decoupling approximation
Monitoring of radioactivity along the French Mediterranean coast
No full textInternational audienceSince the beginning of the 90’s, IRSN realised sampling of bioindicators (mullet fishes and mussels) along the French Mediterranean coastline in order to (1) establish reference levels and (2) highlight the possible influence of nuclear installation/activities on the marine environment. Gamma analyses, conducted sincethe beginning, are now completed by measurements of 3H(OBT), 14C, 241Am, 238Pu, 239+240Pu and allow toobtain a new overview of the radiological influence of human activities on this environment. Additionalmeasurements of 210Po in fishes and mussels also used to best estimated the dose by ingestion for seafoodconsumers.Historical and spatial analyses are presented, and the influence of the different nuclear site/activities isinvestigate
Apports de la statistique bayésienne pour l'estimation du risque de cancer radio-induit après exposition aux examens scanner durant l'enfance
No full textInternational audienceBackground: Computed tomography (CT) has been used increasingly over the last decades. However, concerns have been raised about potentially radiation-related cancer risks, particularly after exposure to CT in childhood, due to the greater radiation sensitivity of children. Several CT cohort studies aim at understanding the relationship between CT organ dose and cancer incidence. However, several sources of uncertainty exist but have sparsely been accounted for in risk estimates. This may lead to biased risk estimates and misleading conclusions. In this work, the aim is to study the impact of CT organ dose uncertainties on the risk of central nervous system (CNS) tumors and leukemia in the French CT cohort.Methods: The French CT cohort includes almost 100,000 children who received at least one CT between 2000 and 2011 in one of the 21 participating university hospitals. Patients were followed until the first diagnosis of cancer, the death, the 18th birthday or the 31st December 2016. Examinations and radiological protocols were retrieved to estimate cumulative absorbed doses to the brain and the red bone marrow (RBM) with NCICT 1.2. Sensitivity analysis indices were computed to identify the most influential input parameters in the estimation of organ doses. Bayesian hierarchical models were proposed and compared to simultaneously account for several sources of dose uncertainty, coming from CT acquisition parameters and patient’s morphology, when estimating the risk of childhood cancer following CT scans. Cox and excess hazard ratio survival models were considered as two alternative dose-response models. The submodels were combined into a unique framework and fitted simultaneously using a Bayesian learning algorithm to estimate cancer risks. A transfer learning approach was also implemented to quantify dose uncertainties from an external sample of PACS data (Picture archiving and communication system). Informative prior distributions were assigned to unknown model parameters to provide more accurate risk estimates, in a poorly informed context. The Bayesian inference of each probabilistic model proposed in this work was performed using a Hamiltonian Monte Carlo algorithm implemented in the R package RStan. The LOOIC (Leave-One-Out Cross-Validation Information Criterion) allowed for model comparison. Results and discussion: When not accounting for dosimetric uncertainties, no evidence of association showed statistically significant dose-response relationships for CNS tumors and leukemia. However, accounting for parameters and dose uncertainties change estimates and we observed statistically significant dose-response relationships for leukemia. Results were robust to the errors modeling choices.Ces dernières décennies, une multiplication des examens diagnostiques utilisant les rayonnements ionisants (RIs), comme les examens scanners, a été observée. Cependant, les effets sanitaires à long terme de ces expositions radiologiques sont peu connus. La cohorte Enfant Scanner a ainsi été mise en place en 2009 à l'IRSN afin d'étudier les risques de cancers après l'exposition aux scanners pendant l'enfance. Elle inclut environ 100 000 enfants. Des doses individuelles de RIs attribuables à chaque examen scanner ont été estimées au niveau de la moelle osseuse et du cerveau à partir de protocoles radiologiques et du logiciel NCICT 1.2 développé par le National Cancer Institute/National Institute of Health pour le calcul de dose en scanographie. Dans ce contexte, l'objectif est double : 1) pouvoir mettre en évidence, si elle existe, une association entre l'incidence de cancers (i.e., tumeurs du système nerveux central, leucémie) et la dose à l'organe reçue après la réalisation d'un ou de plusieurs examens scanners pendant l'enfance; 2) estimer le plus finement possible le niveau d'association dose-réponse ainsi que l'incertitude associée, et ce, à partir des données de la cohorte Enfant Scanner. L'atteinte de ce double objectif pose plusieurs difficultés. Tout d'abord, s'il existe réellement, le risque radio-induit recherché est faible, rendant plus difficile tout test d'hypothèses ou toute sélection de modèles visant à le mettre en évidence. Par ailleurs, les variables réponses d'intérêt (i.e., âge au diagnostic du cancer) sont très fortement censurées à droite. Enfin, les paramètres d'entrée du modèle déterministe implémenté dans NCICT 1.2 sont incertains, rendant le calcul de la dose à l'organe lui-même incertain. Une non prise en compte de ces incertitudes peut mener à des estimateurs de risque biaisés, à une déformation des relations dose-réponse estimées ainsi qu'à une sous-estimation de l'incertitude associée aux estimations de risque. Nous présenterons tout d'abord les différents modèles hiérarchiques que nous proposons, basés sur des modèles de survie avec covariables dépendantes du temps, pour décrire l'association potentielle entre l'âge observé au diagnostic du cancer, le coefficient de risque sanitaire d'intérêt et la dose à l'organe, en tenant compte explicitement des incertitudes inhérentes au calcul de la dose. Nous mettrons en évidence les avantages à l'utilisation de l'approche statistique bayésienne pour mener l'apprentissage des différents modèles proposés-de grande dimension-à partir des données de la cohorte Enfant Scanner. Nous insisterons plus particulièrement sur la possibilité de faire de l'apprentissage par transfert, indispensable dans notre cas, pour quantifier les incertitudes de dose à partir d'un échantillon de données externes. Nous proposerons un retour d'expériences quant à l'utilisation du package RStan pour mener l'apprentissage bayésien des modèles hiérarchiques proposés via un algorithme de type Monte-Carlo hamiltonien. Enfin, en partant des résultats obtenus sur données réelles, nous discuterons des avantages et des limites à l’utilisation du LOOIC (Leave-One-Out Cross-Validation Information Criterion) pour comparer les capacités prédictives des différents modèles hiérarchiques proposés en insistant plus particulièrement sur la problématique de sélection de modèles précédemment évoquée
RENEB Inter-Laboratory Comparison 2021: The Dicentric Chromosome Assay
No full textInternational audienceAfter large-scale radiation accidents where many individuals are suspected to be exposed to ionizing radiation, biological and physical retrospective dosimetry assays are important tools to aid clinical decision making by categorizing individuals into unexposed/minimally, moderately or highly exposed groups. Quality-controlled inter-laboratory comparisons of simulated accident scenarios are regularly performed in the frame of the European legal association RENEB (Running the European Network of Biological and Physical retrospective Dosimetry) to optimize international networking and emergency readiness in case of large-scale radiation events. In total 33 laboratories from 22 countries around the world participated in the current RENEB inter-laboratory comparison 2021 for the dicentric chromosome assay. Blood was irradiated in vitro with X rays (240 kVp, 13 mA, ∼75 keV, 1 Gy/min) to simulate an acute, homogeneous whole-body exposure. Three blood samples (no. 1: 0 Gy, no. 2: 1.2 Gy, no. 3: 3.5 Gy) were sent to each participant and the task was to culture samples, to prepare slides and to assess radiation doses based on the observed dicentric yields from 50 manually or 150 semi-automatically scored metaphases (triage mode scoring). Approximately two-thirds of the participants applied calibration curves from irradiations with γ rays and about 1/3 from irradiations with X rays with varying energies. The categorization of the samples in clinically relevant groups corresponding to individuals that were unexposed/minimally (0–1 Gy), moderately (1–2 Gy) or highly exposed (>2 Gy) was successfully performed by all participants for sample no. 1 and no. 3 and by ≥74% for sample no. 2. However, while most participants estimated a dose of exactly 0 Gy for the sham-irradiated sample, the precise dose estimates of the samples irradiated with doses >0 Gy were systematically higher than the corresponding reference doses and showed a median deviation of 0.5 Gy (sample no. 2) and 0.95 Gy (sample no. 3) for manual scoring. By converting doses estimated based on γ-ray calibration curves to X-ray doses of a comparable mean photon energy as used in this exercise, the median deviation decreased to 0.27 Gy (sample no. 2) and 0.6 Gy (sample no. 3). The main aim of biological dosimetry in the case of a large-scale event is the categorization of individuals into clinically relevant groups, to aid clinical decision making. This task was successfully performed by all participants for the 0 Gy and 3.5 Gy samples and by 74% (manual scoring) and 80% (semiautomatic scoring) for the 1.2 Gy sample. Due to the accuracy of the dicentric chromosome assay and the high number of participating laboratories, a systematic shift of the dose estimates could be revealed. Differences in radiation quality (X ray vs. γ ray) between the test samples and the applied dose effect curves can partly explain the systematic shift. There might be several additional reasons for the observed bias (e.g., donor effects, transport, experimental conditions or the irradiation setup) and the analysis of these reasons provides great opportunities for future research. The participation of laboratories from countries around the world gave the opportunity to compare the results on an international level
Chapitre 31. Rayonnements ionisants
No full textInternational audienceLes rayonnements ionisants ont toujours fait partie de notre environnement, du fait de la présence d’éléments radioactifs sur la Terre. Depuis la fin du XIXe siècle, la découverte de la radioactivité et le développement de ses nombreuses utilisations (industrielles, médicales diagnostiques et thérapeutiques, militaires) ont engendré de nouvelles sources d’exposition de la population aux rayonnements ionisants.2Nous sommes ainsi tous exposés en permanence, à de faibles doses, aux rayonnements ionisants, naturels (expositions environnementales au radon et aux rayonnements d’origine cosmique et tellurique) et artificiels (expositions médicales, professionnelles et environnementales)
Etude des arythmies cardiaques et troubles de la conduction après radiothérapie pour le cancer du sein
No full textRadiotherapy is a major treatment for breast cancer; however, it can be associated with a medium to long-term (>5-10 years) increase in the risk of cardiac complications.Specific knowledge regarding the risk of cardiac arrhythmias and conduction disorders among these cardiac complications was limited.In this context, the objective of this work was to study the association between radiotherapy for breast cancer and the risk of developing cardiac arrhythmias and/or conduction disorders, as well as to explore the dose-response relationship between this risk and the absorbed dose by the heart and its sub-structures.Based on medico-administrative data from the French health insurance, this study demonstrated that breast cancer patients treated with radiotherapy had an increased risk of pacemaker implantation and ablation procedures for arrhythmia compared to the general population (SIR=2.18 and 3.55, respectively, p0.20).This thesis work has thus revealed a potential risk of arrhythmias and conduction disorders after radiotherapy for breast cancer and contributes to opening interesting research directions to better quantify the dose-response relationships with the aim of developing prevention strategies.La radiothérapie constitue un traitement majeur pour le cancer du sein, cependant elle peut être associée à une augmentation à moyen ou long terme (>5-10 ans) du risque de complications cardiaques. Parmi ces complications cardiaques, les connaissances spécifiques concernant le risque d'arythmies cardiaques et de troubles de la conduction étaient limitées.Dans ce contexte, ce travail de thèse avait pour objectif d'étudier l'association entre la radiothérapie pour le cancer du sein et le risque de survenue d'arythmies cardiaques et/ou troubles de la conduction ainsi que d'explorer la relation dose-effet entre ce risque et la dose absorbée par le cœur et les sous-structures.En s'appuyant d'abord sur les données médico-administrative de l'assurance maladie française, ce travail a montré que les patientes traitées par radiothérapie pour leur cancer du sein présentaient un risque accru d'implantation de pacemaker et de procédure d'ablation pour le traitement d'une d'arythmie supra-ventriculaire que la population générale (SIR=2,18 et 3.55 respectivement, p0,20). Ce travail de thèse a ainsi mis en évidence un risque potentiel d'arythmies et troubles de la conduction après une radiothérapie pour un cancer du sein et contribue à ouvrir des pistes de recherche intéressantes pour mieux quantifier les relations dose-réponse dans le but de développer des stratégies de prévention
Use of machine learning and deep learning to predict particulate 137Cs concentrations in a nuclearized river
No full textInternational audienceCesium-137, discharged by nuclear installations under normal operations and deposited in watersheds decades. Thus, modelling of 137 Cs concentration in rivers have been developed based on geochemical approaches and equilibrium assumptions (solid/liquid ratio) as this radionuclide has moved into rivers and oceans due to soil erosion. Recently a new approach is possible to model these concentrations with the popularization of data-driven models based on data acquired in the environment by monitoring networks. In this study, the concentrations of particulate cesium-137 measured near the mouth of the Rhône River (France), a highly nuclearized river, are simulated using two data-driven models, a Hierarchical Attention-Based Recurrent Highway Networks (HRHN) and a Random Forest Regressor (RF). The data-driven predictions were done using only hydrological data (water discharge and suspended solid fluxes) and industrial input of 137 Cs. Although the data-driven models provided a better prediction than a recent empirical model, the best prediction (R² = 0.71) was obtained with HRHN, a model that considers the temporal aspect of the monitoring data. The most important predictors were the hydrological data at the monitoring station and of the tributary that generate the most sediment flux (Durance River). In fact, the concentration of 137 Cs in the perimeter of this study was more related to hydrology than to nuclear release, as there were few events with high 137 Cs concentrations (concomitant nuclear release and low water discharge). However, the HRHN approach, which is more complex to implement than RF, can predict the concentrations of such events correctly despite their low representation of these events. The results of this study demonstrate the usefulness of data-driven models to assist monitoring programs by filling in gaps or helping to understand observed concentrations
COAL experiments investigating the reflooding of a 7 X 7 rod bundle during a Loss Of coolant Accident: Effect of a partially blocked area with ballooned rods
No full textInternational audienceDuring a loss of the coolant of the primary circuit (LOCA) in a pressurized water reactor, the drying of the fuel assemblies may lead to the fuel temperature increase and deformation of the fuel rod claddings. In addition to the restriction of the flow area, the fragmented irradiated fuel relocation within the ballooned zone leads to an increase of the local residual power. The COAL experiments will focus on the coolability issue of a partially deformed fuel assembly during water injection with the safety systems using a 7x7 bundle of electrically heated rods. These experiments are part of the PERFROI project launched by IRSN with the support of the french "Agence Nationale pour la Recherche" (ANR), EDF and the US-NRC. The effect of the flow blockage {intact geometry up to long ballooning (100 to 300 mm) with different blockage ratios (80 to 90%)} will be evaluated for various power, mass flow rates and different pressures representative to Large (LBLOCA at 0.3 MPa) and Medium break size (MBLOCA : 0.5 to 3 MPa) configuration. Relocation of fragmented fuel in the balloons are taken into account by a local increase of the power by a factor of 1.5. This paper presents the thermal hydraulics parameters and the main results of the experiments performed in a facility of the STERN Laboratories (Canada). The presence of the balloons increases significantly the Peak Cladding Temperature. These results will be used to improve and validate the heat exchange models of thermal hydraulics codes dealing with the complex reflooding processes in such configuration
Health effects of ionising radiation in paediatrics undergoing either cardiac fluoroscopy or modern radiotherapy (The HARMONIC project)
No full textInternational audienceThe use of ionising radiation (IR) for medical diagnosis and treatment procedures has had a major impact on the survival of paediatric patients. Although the benefits of these techniques lead to efficient health care, evaluation of potential associated long-term health effects is required. HARMONIC aims to better understand the increased risk of cancer and non-cancer effects after exposure to medical IR in children with cancer treated with modern external beam radiotherapy (EBRT) – radiation energy in MeV range – and in children with cardiac defects diagnosed and treated with cardiac fluoroscopy procedures (CFP) – radiation energy in keV range. The project investigates, among survivors of paediatric cancer, potential endocrine dysfunction, cardiovascular and neurovascular damage, health-related quality of life and second (and subsequent) primary cancer (SPC). The cardiac component builds a pooled cohort of approximately 90 000 paediatric patients who underwent CFP during childhood and adolescence to investigate cancer risk following exposure to IR and explore the potential effects of conditions predisposing to cancer. HARMONIC develops software tools to allow dose reconstruction in both EBRT and CFP to enable epidemiological investigations and future optimisation of treatments. With the creation of a biobank of blood and saliva samples, HARMONIC aims to provide a mechanistic understanding of radiation-induced adverse health effects and identify potential biomarkers that can predict these effects
Review of the A1 and A2 values: final curtain ?
No full textInternational audienceThe A1 and A2 radioactive transport limit values of the Q System described in the advisory material SSG-26 have been developed to provide the maximum allowable contents in packages not designed to withstand accidents, with the objective to limit the accidental exposure of persons below an effective dose of 50 mSv and a skin equivalent dose of 500 mSv. Current values were determined in 1996 according to specific scenarios for five exposure pathways. Since then, the ICRP has published revised radiological data. In addition, progress in computer hardware and software allow the implementation of new Monte Carlo based calculation methods, which are more representative of the physical processes. An international working group involving NRA, PHE, GRS and IRSN was created in 2013 to discuss the improvement of calculation methods described in the Q System. This group later became part of the IAEA TRANSSC Technical Expert Group (TTEG) on Radiation Protection. The first findings and results were presented during the PATRAM 2016 conference, and the progress of the review was described during PATRAM 2019. While most trends on the potential changes in A1 and A2 values were presented, further discussions aimed at consolidating hypotheses and calculation methods were necessary to complete the review and propose to the TRANSSC Member States an update of the Q system consistent with the latest ICRP recommendations and methodologies. This paper describes the work that has been performed since 2019-especially regarding inhalation, contamination, ingestion, alpha and neutron considerations, explains the main changes in the calculation methods as well as the tools that have been developed to evaluate the Q values for any radionuclide, and shows results that could be implemented in the future revision of the IAEA SSR-6 regulations