Institute for Radiation Protection and Nuclear Safety (IRSN)
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Targeted nuclear irradiation with a proton microbeam induces oxidative DNA base damage and triggers the recruitment of DNA glycosylases OGG1 and NTH1
No full textInternational audienceDNA is the major target of radiation therapy of malignant tumors. Ionizing radiation (IR) induces a variety of DNA lesions, including chemically modified bases and strand breaks. The use of proton beam therapy for cancer treatment is ramping up, as it is expected to reduce normal tissue damage. Thus, it is important to understand the molecular mechanisms of recognition, signaling, and repair of DNA damage induced by protons in the perspective of assessing not only the risk associated with human exposure to IR but also the possibility to improve the efficacy of therapy. Here, we used targeted irradiation of nuclear regions of living cells with controlled number of protons at a high spatio-temporal resolution to detect the induced base lesions and characterize the recruitment kinetics of the specific DNA glycosylases to DNA damage sites. We show that localized irradiation with 4 MeV protons induces, in addition to DNA double strand breaks (DSBs), the oxidized bases 7,8-dihydro-8-oxoguanine (8-oxoG) and thymine glycol (TG) at the site of irradiation. Consistently, the DNA glycosylases OGG1 and NTH1, capable of excising 8-oxoG and TG, respectively, and initiating the base excision repair (BER) pathway, are recruited to the site of damage. To our knowledge, this is the first direct evidence indicating that proton microbeams induce oxidative base damage, and thus implicating BER in the repair of DNA lesions induced by protons
Chapter 11 - Detection of radiation-induced senescence by the Debacq-Chainiaux protocol: Improvements and upgrade in the detection of positive events
No full textInternational audienceSenescent cells are blocked in the cell cycle but remain metabolically active. These cells, once engaged in the senescence process, fail to initiate DNA replication. Due to the shortening of telomeres, replicative senescence can be triggered by a DNA damage response. Moreover, cells can also be induced to senesce by DNA damage in response to elevated reactive oxygen species (ROS), activation of oncogenes, cell-cell fusion or after ionizing radiation. There are multiple experimental ways to detect senescent cells directly or indirectly. Senescence-associated cellular traits (SA β-Gal activity, increase in cell volume and lysosome content, appearance of γ-H2AX foci, increase of ROS and oxidative damage adducts, etc.) can be identified by numerous methods of detection (flow cytometry, confocal imaging, in situ staining, etc.). Here, we improved an existing flow cytometry protocol and further developed a new one specifically tailored to ionizing radiation-induced endothelial senescence. Thus, we have upgraded the Debacq-Chainiaux protocol and added improvements in this protocol (i) to better detect positive events (ii) to offer a compatibility to simultaneously analyze various intracellular molecules including phosphorylated signaling proteins and cytokines, whether related or not to senescence processes
Effects of temperature on the delayed behavior of biaxially prestressed concrete
No full textInternational audienceThe delayed deformations of prestressed concrete structures under sustained loading exhibit a non-linear progression over time, impacting tension in the prestressed tendons and causing a subsequent decline in compression within containment vessel walls of nuclear power plants. Maintaining compression within these walls is critical for ensuring tightness under various operational conditions. Design codes provide analytical formulas for assessing these deformations, primarily based on tests involving prestressed concrete in a single direction, such as bridge decks. However, discrepancies between on-site measurements and analytical formulas arise in the case of biaxially prestressed structures such as containment vessels. Moreover, the impact of temperature on the kinetics of measured delayed deformations is overlooked in Eurocode 2 formulas. This study is a part of the European project ACES (Assessment of safety performance of Civil Engineering Structures), aiming to assess the analytical formulas of fib model code 2020 to address effects like biaxial prestressing, temperature, loading history on the evolution of concrete strains over time. The planned experimental program includes various Thermo-Hydro-Mechanical configurations, enriched by a few additional ones from other ACES project studies. It comprises two types of creep tests, uniaxial and biaxial loading, on small concrete slabs. These samples are instrumented with fiber optic sensors to measure strains in the three directions throughout the test period. The presented results pertain to temperatures of 20°C and 38°C in water conditions and are compared with those from databases of other studies from literature. Comparing experimental measurements with fib model code formulas will guide modifications to account for temperature effects, particularly in bi-axially prestressed structures
Ecosystem approaches in radioecology: ICRER 2024 – refresher Course
No full textInternational audienceThe presentation titled "Ecosystem Approaches in Radioecology" by Rodolphe Gilbin explores the evolution of radioecology from human-centric studies to a more ecosystem-based perspective. It emphasizes integrating ecological, radiobiological, and environmental sciences to address complex interactions and cumulative impacts of ionizing radiation. The document outlines challenges like multi-stressor interactions, the need for predictive modeling, and data integration across biological scales. It advocates for an ecosystem services approach, aligning with sustainability goals, to improve environmental and human protection frameworks. Finally, it stresses policy implications and calls for interdisciplinary collaboration for holistic impact assessments.La présentation intitulée « Approches écosystémiques en radioécologie » de Rodolphe Gilbin explore l’évolution de la radioécologie depuis les études centrées sur l’humain vers une perspective plus écosystémique. Elle met l’accent sur l’intégration des sciences écologiques, radiobiologiques et environnementales pour traiter les interactions complexes et les impacts cumulatifs des rayonnements ionisants. Le document décrit les défis tels que les interactions multi-stresseurs, la nécessité d’une modélisation prédictive et l’intégration des données à toutes les échelles biologiques. Il préconise une approche des services écosystémiques, alignée sur les objectifs de durabilité, pour améliorer les cadres de protection de l’environnement et de l’humain. Enfin, il souligne les implications politiques et appelle à une collaboration interdisciplinaire pour des évaluations d’impact holistiques
Measurement of the Prompt Decay Constant in a Zero Power Reactor Using a Novel 3D Detector System
No full textInternational audienceAnalyzing neutron noise in zero power reactors is a valuable tool for gaining insights into integral parameters, such as the prompt decay constant α. This information can be used to validate codes that predict said parameters, or time-dependent behavior, particularly reactor transients. The zero-power research reactor CROCUS has been widely used for conducting noise experiments and has recently been enhanced with a new detection system, SAFFRON. This system includes an array of 150 miniature neutron detectors evenly dispersed throughout the core, allowing for 3D spatial detection capabilities. We conducted a neutron noise experiment using the 3D array to test this new system to determine the prompt decay constant α. Our results, obtained using the Rossi-α method, showed agreement with Serpent 2 Monte Carlo code (using the LLNL FREYA library for fission) predictions within 1σ of the estimated uncertainties. We notably observed that, based on previous experiments, using all 150 detectors did not achieve the levels of detection efficiency (i n co unts pe r fission) necessary to observe the fission chain decay - yet we still observe the decay with comparatively high statistical significance. We therefore show experimentally, that the spatial extent of the detection system is an important parameter in the prediction of neutron noise technique success. The results also indicate that SAFFRON is a powerful measurement tool that can be expanded for use in active perturbation experiments, 3D flux maps, and other high-fidelity reactor physics experiments
Chapter 4 : The Economic Costs of a Nuclear Accident
No full textInternational audienceThis chapter provides a brief overview of the various costs of a nuclear accident and the methods by which they can be assessed. The study of the costs of nuclear accidents began after the Chernobyl accident in Ukraine in 1986. Each economic study is defined by the objectives it seeks to accomplish, with the costs to be taken into account in the analysis varying based on the objectives pursued in the cost study. Thus, in a situation in which an accident has occurred, the objective of nuclear accident cost studies is to optimize the contamination remediation strategies. The optimization of post-accident management strategies is the historical use of economic evaluations of nuclear accident costs. The assessment of the costs of a nuclear accident is complicated in the case of the Fukushima incident by the presence of three interrelated events: the earthquake, the tsunami and the nuclear disaster
High Burn-up Code Results Intercomparison on a Research Reactor Assembly Numerical Benchmark
No full textInternational audienceThe work presented in this paper aims at comparing the results of various depletion codes at high burn-up on a research reactor numerical benchmark proposed by TechnicAtome. This paper proposes to perform a comparison between TRIPOLI-4®, COCONEUT-2D, VESTA 2.2 and SERPENT2. This is carried out on a standard fuel plate-type assembly with burnable poison, used by TechnicAtome to set new methodologies. Parameters such as reactivity, and isotopic concentrations are studied on a burn-up calculation reaching around 150 GWd/tU. The results obtained with the different codes show some deviations that increase at high burn-up rates. The explanation identified relies in the energy deposition models for the power calculation performed by the different depletion codes
Thermoresponsive gel embedding extracellular vesicles from adipose stromal cells improves the healing of colonic anastomoses following irradiation in rats
No full textInternational audienceAnastomotic leak occurrence is a severe complication after colorectal surgery. Considering the difficulty of treating these leaks and their impact on patient care, there is a strong need for an efficient prevention strategy. We evaluated a combination of extracellular vesicles (EVs) from rat adiposederived stromal cells with a thermoresponsive gel, Pluronic® F127 (PF-127) to prevent anastomotic leaks. The pro-regenerative and immunomodulatory potencies of EVs are assessed in vitro. In vivo efficacy are assessed in rat with a colonic anastomosis model after irradiation. Endoscopic, anatomical and histological data show a consistent effect of EVs + gel on the healing of colonic anastomosis. These results are illustrated by a smaller anastomotic ulcer size, less fibrosis and less inflammatory infiltrations in the EVs + gel group. This multi-modal investigation is the first to point-out the translational potential of EVs combined with PF-127 for the healing of high-risk colorectal anastomosis.The incidence of rectal cancer worldwide is 732,210 per year 1 . Neoadjuvant chemoradiotherapy supplemented by surgery with a low colorectal or colo-anal anastomosis is recommended in locally advanced disease 2 . Despite years of research, the incidence of anastomotic leak after rectal surgery remains high, ranging from 3 to 21% 3,4 and is associated with increased morbidity, mortality, and cancer recurrence 5 . Furthermore, anastomotic leaks are associated with an increased healthcare burden due to the higher costs of management and the use of resources for remedial care 6 . It is known that anastomotic leak etiology is multifactorial. Excluding technical failures, there is accumulating evidence pointing at anastomotic leak as the result of a complex, dynamic interplay of several factors and biological processes 7-9 . This includes host genetics, gut microbiome, inflammation, and the immune system 10 . The occurrence of anastomotic leak might also be linked to TNM stage and patient nutritional status 11 , along with treatment-related factors. Indeed, while preoperative chemoradiotherapy for rectal cancer improves local</div
Potential Effect of Saline Solution on Fission Products Mitigation by Pool Scrubbing
No full textInternational audienceThe potential release of fission products (FPs) to the atmosphere during an hypothetical severe accidents on nuclear facilities is a main issue in nuclear safety. Accurate estimation of these releases is crucial for risk assessment and implementation of appropriate measures. To this end, IRSN studies the mitigation of FPs transported in a carrier gas injected through a liquid pool. This process, referred to 'pool scrubbing', can occur in various accident situations in Pressurized Water Reactors (PWRs), such as Filtered Containment Venting Systems (FCVS) or with the Steam Generator Tube Rupture (SGTR), as well as in nuclear-powered submarines or in new Small Modular Reactors (SMRs) with pressurized water. Experiments dealing with characterization of bubbles hydrodynamics and trapping of iodine compounds (decontamination factors measurements) are currently conducted. In this objective, a dedicated facility named TYFON (Trapping and hYdrodynamics for FissiON products behaviour in pool scrubbing) at IRSN enables to perform hydrodynamics and iodine retention tests for different carrier gas injection rates (characterized by Weber number). In this context, advanced results have been obtained on hydrodynamics in the injection zone and CsI aerosol retention. In line, a new study focused on the impact of a saline solution on these phenomena and on bubble plume modelling has been launched. In the long term, all the experimental data collected, including hydrodynamics and the decontamination factor (DF), will be used to improve the modelling of pool scrubbing phenomenon in the ASTEC code developed by IRSN
L'AOP dans le contexte de la radioécologie: défis et perspectives
No full textInternational audienceThe definition of reference levels for radiological protection of the environment is dependent on the methodologies and applicability domains considered by the relevant expert groups (ICRP, IAEA, ERICA European Consortium). However, these methodologies share common limitations regarding the derived reference levels, mainly due to the use of available data, coming from laboratory experiments with the observation of biological endpoints that are not necessarily representative of the wildlife chronically exposed to various sources and levels of ionising radiation. Furthermore, the potential presence of other pollutants and stressors (abiotic parameters, etc) that interact with radionuclides makes it challenging to assess the risk to wildlife in realistic exposure scenarios. The Adverse Outcome Pathways (AOP) framework appears to be a valuable tool that helps to structure a sequence of causally linked events at different biological levels (Molecular Initiating Event, Key Events (KE), and Adverse Outcome (AO)). In the context of ecological risk assessment, AOP provide a way of linking molecular data, usually obtained in laboratory conditions, to ecological levels, i.e., community and ecosystem, for which the definition of relevant key events is still challenging. In addition, AOP networks can be proposed to help to compare effects between different types of stressors; to deconvolute biological effects in the context of exposures to multiple stressors. AOP provides an efficient summary of existing data through a clear and standardized framework accessible via the open access database AOP-KB, shared by research and regulators communities.This work proposes a review of the challenges of developing AOP for radioecology. A few guidelines are proposed to overcome some of the identified challenges. These include the assessment of possible relevant ecological endpoints regarding ionising radiation for AOP development, proposal of integrated and multidisciplinary approaches to fuel AOP development, and discussions of AOP applications to inform ecological risk assessment