Institute for Radiation Protection and Nuclear Safety (IRSN)
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ASTEC core degradation calculations in support of Level-2 Probabilistic Safety Assessment for 1300MWe French reactors: Methodology and preliminary results
No full textInternational audienceThe Institute for Radiation Protection and Nuclear Safety (IRSN) in France has updated its Level-2 Probabilistic Safety Assessment (L2 PSA) for the French 1300MWe Pressurized Water Reactors (PWRs) as part of the decennial safety reevaluation for these specific reactor units. This study was particularly underpinned by computations performed using the IRSN ASTEC V2.2 code. ASTEC, which stands for Accident Source Term Evaluation Code, is the reference integral code employed by IRSN for modeling and predicting the progression of severe accidental sequences. Within this framework, IRSN has conducted a total of 554 simulations of accidental sequences, for both conditions of 100% Nominal Power and of reactor shutdown. These accidental sequences have been defined based on the ASNR results of Level-1 PSA. They encompass the entire spectrum of events starting from initiating event to the point of vessel rupture. Furthermore, these simulations implement state-oriented Emergency Operating Procedures (EOPs) and Severe Accident Management Guidelines (SAMGs). This paper presents the different calculations carried out, outlines the methodology used to define them and the primary outcomes derived
Modeling of the decomposition of iodine oxides aerosols (IOx) in the containment -Consequences on the understanding of volatile iodine behaviour in the containment
No full textInternational audienceIodine oxides aerosols (IOx) are fine aerosol particles that are formed in a reactor containment in case of severe accident. Their stability was studied under irradiation in representative conditions of the containment. Under the influence of the temperature, humidity and irradiation they are found to be unstable. Their decomposition kinetics and stability are studied in EPICUR facility thanks to the STEM, STEM2 and MIRE projects. An IOx decomposition model is set up in ASTEC-SOPHAEROS code (version 3.1). It considers the influence of the humidity, the temperature, and dose rate. Its application to the PHEBUS FPT-0/1/2/3 tests lead to (1) an improved modeling and understanding of the inorganic iodine volatility in the FPT-3 containment all along the transient and to (2) an improved modeling after the washing when the gaseous temperature increases (FPT-0 and FPT-1) and ( 3) before the washing when the humidity decreases (FPT-2) as long as a relevant molar gaseous iodine fraction coming (x I2_RCS ) from the reactor coolant system (RCS) is set up for FPT-0/1/2. A sensitivity analysis indicates that values of x I2_RCS up to ≈30% would be needed to improve the modeling of iodine volatility before the washing for FPT-0/2. A fraction of 10% would be more appropriate for FPT-1. A complementary approach is on-going to quantify the influence of the uncertainties of each chemical model developed in ASTEC-SOPHAEROS code within the objective to identify which chemical phenomena are the most influent on iodine volatility in the PHEBUS containment
Activities of ISO Working Group 18: Biological and Physical Retrospective Dosimetry
No full textInternational audienceBiological and physical retrospective dosimetry for ionizing radiation exposure is a rapidly growing field and several methods for performing biological and physical retrospective dosimetry have been developed to provide absorbed dose estimates for individuals after occupational, accidental, intentional, and incidental exposures to ionizing radiation. In large-scale radiological/nuclear incidents, multiple retrospective dosimetry laboratories from several countries may be involved in providing timely dose estimates for effective medical management of several thousands of exposed individuals. In such scenarios, the harmonization of methods among participating laboratories is crucial for consistency in data analysis, dose estimation and medical decisionmaking. In this regard, ISO documents ensure that these practices are standardized globally across the laboratories by providing quality assurance and quality control documentation that guide laboratories in maintaining high-quality performance for consistency. With the intent of bringing standardization and harmonization of biological and physical retrospective dosimetry methodologies across national and international laboratories, the ISO working group 18 (WG18) was established under ISO/TC85/SC2 (Technical Committee 85, Subcommittee 2-Radiation Protection) in 1999. This manuscript summarizes some of past, current and future activities of WG18 on biological and physical retrospective dosimetry
Morphological parameters investigation of deposits formed on pleated filters using DLA
No full textInternational audiencePleated filters are widely used as they offer a greater filtration area leading to lower pressure losses. However, their geometry impacts the air flow fields inside their pleats, which can evolve as more aerosol matter accumulates. This leads to different behavior between flat and pleated filters with respect to pressure loss evolution with both filtration velocity and deposited mass. To study the effect of streamlines inclination on deposit morphology the possibility of producing numerical deposits is here investigated. A custom DLA (Diffusion Limited Aggregation) code is used which can handle both poly-dispersed particles population and streamline tilt for spherical particles. The morphological parameters here considered are the porosity, the contact angle distribution and the coordination number distribution. The DLA approach, by accounting for stochastic and deterministic forces, is well-suited for simulating nanoparticle behavior where Brownian motion is significant. It provides detailed insights into deposit microstructures and the influence of pleat geometry and flow incidence angles, offering a powerful tool for advancing both theoretical models and practical applications in aerosol filtration systems. Computations were carried to reproduce experimental results on porosity obtained with mono-dispersed PSL (Polystyrene Latex) and poly-dispersed CsCl particles. Comparison show good agreement between the experimental porosities and the ones computed using the custom DLA code. Contact angles and coordination number distributions give physically coherent results. Theoretical probability density functions for the contact angle distributions in both the diffusion and ballistic regimes were obtained and shown to agree with the distributions numerically obtained. Based on the adequacy between simulation results and experimental data, the effect of streamlines tilt on deposit porosity was investigated. In the simulations carried out, inclination of gas flow direction increases the limiting porosity in the ballistic regime when the tilt is higher than 45o with respect to capture plane normal vector
New experimental insights into two-phase air-water bubbly and intermittent flow in large duct and cross-flow configurations
No full textInternational audienceThis study focuses on the characterization of two-phase air–water cross-flow in a tube bundle with square pitch configuration, and of the upward flow in the free duct region upstream of the bundle. Two measurement techniques were used: a wire mesh sensor and a dual optical probe. The research focuses on analyzing void fraction, gas velocity, gas–liquid interface/bubble shape and size, and two-phase flow regime transitions. Bubbly flow and intermittent flow regimes were investigated, by varying the gas flow rate for a fixed liquid flow rate. The intermittent flow showed a periodic generation of large gas structures in the central region of section. The frequency of these structures was obtained and found not to vary significantly between the free duct region downstream of the tube bundle, the region within the tube bundle and the region downstream of the bundle. Gas velocities could be measured as a function of the size of the gas structures. The profiles of void fraction and gas velocity at different positions within the tube bundle were measured and analyzed
Same-day discharge strategy in a heart rhythm management clinic: The patient-reported experience
No full textInternational audienceBackground: Same-day discharge (SDD) has been adopted for interventional cardiology procedures, however, data on patient experience are scarce.Aims: To investigate patient-reported experience after various SDD electrophysiology procedures. Methods: Consecutive patients undergoing electrophysiology procedures, who fulfilled pre-defined eligibility criteria for SDD, completed the questionnaire before discharge. Procedures suitable for SDD included non/minimally-invasive (e.g. electric cardioversions, tilt tests) and invasive procedures (e.g. cardiac device replacements, catheter ablations). The questionnaire assessed patient experience before and during the procedure, satisfaction with the provided information and understanding of the discharge instructions.Results: The questionnaire was completed by 501 patients (57.5% men). Invasive procedures accounted for 56.7% of SDD procedures. Most patients (88.9%) described SDD as a good or quite good experience, while 95.3% would not hesitate to undergo a second SDD procedure if necessary. A direct interview with a healthcare team member was the preferred method of obtaining information. At discharge, a considerable number of patients were unsure about the provided instructions, including those related to anticoagulation. Patient-reported satisfaction did not differ between invasive and non/minimallyinvasive procedures (P = 0.06). However, after an invasive procedure, patients had a better understanding of discharge instructions (59.5% vs 41.9%; P < 0.001). Most patients who underwent a procedure under general anaesthesia reported a good or quite good experience (87.7% vs 84.2% of sedation patients; P = 0.16).Conclusion: SDD was generally a positive experience for patients undergoing invasive or non/minimallyinvasive procedures. However, discharge instructions and patient understanding require improvement
The impact of hydrogen flakes on the uniaxial and biaxial fracture toughness of a forged ferritic steel
No full textInternational audienceThis work focuses on the effects of hydrogen flakes on the fracture toughness of forged ferritic steel under uniaxial or biaxial loading conditions. The fracture toughness under uniaxial loading was investigated on CT specimens and cruciform specimens were used for the biaxial loading conditions representative of a thermal shock in a Reactor Pressure Vessel. The observed decrease in fracture toughness in the flaked material was related to the higher carbon content near the hydrogen flake. Moreover, the nature of the initial defect (fatigue crack or hydrogen flake) did not significantly affect the fracture toughness. The cruciform specimen exhibited higher fracture toughness compared to CT specimens, even in the presence of flakes. This confirmed the conservatism of standard fracture analyses used for structure integrity assessment based on a lower bound fracture toughness curve obtained from CT specimens
La réponse gouvernementale en cas d’urgence radiologique
No full textInternational audienceL’utilisation de la radioactivité, que ce soit dans le domaine médical, de l’industrie ou de la recherche, nécessite des précautions au regard des effets sur la santé que la radioactivité peut générer en cas d’usage inapproprié, d’accident ou d’acte malveillant. Dans ces situations d’urgence, l’enjeu est de limiter l’exposition aux rayonnements ionisants autant que cela est raisonnablement possible au travers, d’une part, de la mise en place de mesures de protection, d’autre part, d’une prise en charge adaptée des personnes susceptibles d’être exposées à la radioactivité. Dans tous les cas, les décisions et les actions doivent prendre en compte le contexte de l’évènement, sans oublier, le cas échéant, la primauté de l’urgence médico-chirurgicale sur l’urgence radiologique
Experimental investigation at reduced scale of the effect of a ceiling on the burning rate of a pool fire
No full textInternational audienceThis study examines the influence of the proximity of a ceiling on the burning rate of a fire in enclosures. The parameters included the pool diameter, distance to the ceiling and fuel type. The analysis focused on the average mass loss rate. The results confirmed the increase in mass loss rate with the elevation for all fuel types. This increase in the mass loss rate appears from a distance to the ceiling that is correlated with the flame height. It is caused by an increase in the heat flux emitted by the flame, which changes shape, and the temperature of the ceiling, which increases with the fire elevation. A correlation is proposed to predict the increase in mass loss rate as a function of the enthalpy ratio Δ H/ Lv and flame height. A comparison of the results with previous experimental studies demonstrated consistency between the different tests