Institute for Radiation Protection and Nuclear Safety (IRSN)
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ASTEC validation of sfp dewatering using results from the denopi project
No full textInternational audienceLoss of cooling in a Spent Fuel Pool (SFP) of a nuclear power plant can lead to the melting of fuel assemblies and to strong radiological consequences to the environment. In order to study the first phases of such accidents, up to the fuel assemblies uncovery, the DENOPI project was launched by the French Institute for Radiation Protection and Nuclear Safety (IRSN) supported and funded by the French Government and partners. Among the different facilities developed in the project, the MIDI facility aims at studying the complex thermal-hydraulics phenomena occurring in a large water pool heated from the bottom by electrical rods arranged in dedicated racks. MIDI is scaled by homothety to a typical French SFP. Different assembly arrangements (loading patterns) have been tested at different power levels, with either uniform power repartition, or hot and cold cells. In each test, the water level and temperatures at different elevations are followed, as well as mass flow rate entering each fuel rack. These experimental results also provide relevant data for the analysis and understanding of large natural convection loops that are expected in immersed passive heat removal systems of Small Modular Reactors. The forthcoming OECD/NEA POLCA project aims to extend such results database, in particular to assess the capability of thermal-hydraulics codes to reproduce the main tendencies of these experimental results. The ASTEC code developed by IRSN is a system code dedicated to the simulation of major accidents in nuclear facilities that may lead to the release of radiological material. Recent works within the MUSA European project have shown the importance of reducing models uncertainties in the first phases of the accident, during the pool dewatering. In this paper, first simulations of MIDI tests are performed with ASTEC in order to assess and improve the capability of ASTEC to simulate the dewatering of a large water pool such as a SFP during a loss-of-cooling accident. Simulations are performed for a selection of MIDI tests with different heating patterns and power levels. Different models of subcooled boiling models from the literature are tested in ASTEC, stressing the key role of these models for an accurate prediction of the experimental flow
Isotopic effect of oxygen on the Raman mapping of a polycrystalline uranium dioxide UO2
No full textInternational audienceUranium dioxide UO2 is a widely studied material due to its use as fuel in Pressurized Water Reactors (PWR) and Raman spectroscopy is a technique of choice to characterize the evolution of its microstructure. UO2 crystallizes in a fluorite CaF2 (space group Fm-3m) structure that gives rise to a unique Raman signature, the T2g band. However, several other bands are often detected whose attribution remains unclear. The present study gives new insights on the Raman spectrum of UO2 thanks to the combination of isotopic labelling with 18 O and Raman imaging. In addition to the expected T2g, U2 (LO), 2LO and U3 bands, we have detected a doublet at 885 and 925 cm -1 , a U* band at 555 cm -1 in some specific areas and 2 bands located at 367 and 1196 cm -1 . All Raman bands shift under the effect of the replacement of 16 O by 18 O, excepting for the U* band that could not be detected anymore. The isotopic shift ratio could be determined for 20% and 30% 18 O labelling. No discrepancy in band position is observed between grains and grain boundaries, except for the U2(LO) band. We also evidence a difference between the U defect bands and the 885 and 925 cm -1 doublet bands evolution under labelling, although the latter also seems to be connected to the presence of defects in the material
Numerical Modelling of the Behaviour over 60 Years of a Nuclear Power Plant Containment Vessel Submitted to an Internal Swelling Reaction
No full textInternational audienceIn France, the extending of nuclear power plant service life from 40 to 60 years is an actual issue. Due to the number of nonlinear and concomitant concrete phenomena, such structure needs a reliable tool to ensure and predict their behavioural evolution. In this work, a thermo-hydro-chemo-mechanical model considering passive reinforcements in a distributed manner is applied to the calculation of a containment vessel with ISR. Shrinkage, creep, ISR swelling and induced damage are strongly coupled to each other, and all depend on thermal and humidity environmental conditions. The calculation is based on the available basic mechanical characteristics, the passive reinforcement ratios, the tensioning kinetic data of the prestressing cables and the structure’s geometry. The results show a good correlation with the multiaxial strains of the structure on the in-situ data. The model is used to make predictions over the next 30 years. Two scenarios of maximum swelling are considered. Cracking, which is an essential information for these containment structures, is compared between 30 years and 60 years. The prediction at 60 years shows that the pathology, with a hypothesis of rapid evolution, does not have a deleterious effect on the structure
Introduction to neutron transport
No full textIntitulé de la formation : Master Nuclear Energy, option Nuclear Reactor Physics and EngineeringMaste
Studies on the retrospective thoron measurements by CDs/DVDs: A posteriori calibration and influence of environmental factors
No full textInternational audiencePast exposure to indoor thoron poses a significant risk for lung cancer. A method based on home-stored CDs/DVDs allows the estimation of past exposure through retrospective thoron measurements. However, these measurements are significantly affected by the geometry of the CD-case. In this paper, an improved a posteriori calibration procedure is proposed that mitigates the CD-case effect, enabling the estimation of the disk's calibration factor with uncertainty better than 20%. The influence of the environmental temperature, pressure and humidity on the thoron measurements is also studied. It is observed that these parameters have influence within 30%. Thus, retrospective thoron measurements with uncertainty better than 50% can be conducted. The CD method overcomes a major source of error in evaluating the past thoron exposure related to the yearly changes in indoor thoron that could even reach an order of magnitude
An investigation of lunar dust simulant adhesion using a centrifuge system under high vacuum and UV irradiation conditions
No full textInternational audienceIt is well known that lunar dust contamination is of paramount concern for space agencies currently planning complex missions to the moon. The fine, sharp particles are known to damage mechanisms, cause wear, and deposit on surfaces thereby compromising optics, crippling power supplies, and causing thermal dysregulation. The adhesion of lunar dust is, however, not a well understood phenomenon. Lunar dust particles adhere through several mechanisms, including electrostatic forces due to the radiative environment.This study aimed to produce realistic adhesion values from high-fidelity environment testing, whilst investigating the impact of various parameters. Two different lunar dust simulants (LMS-1, Exolith Labs and JSC-1A, ETSimulants/Orbitec) sieved to 30 µm) depending on the adhesion to the substrate. Whilst dependencies on substrate were observed, adhesion forces were found to be largely independent of particle size for this size range.Further investigations are ongoing to test the behavior of more simulants and materials, as well as the introduction of VUV radiation during centrifugation in order to clarify the effects of photoemission on adhesion in this system. Both dielectric and conducting substrates will be used. Tests shall also be carried out using a simpler powder material (e.g. glass spheres), in order to corroborate the accuracy of experimental results
A new certified reference material IAEA-465 for radionuclides in Baltic Sea sediment
No full textInternational audienceCertified reference material (CRM) for natural (40K,210Pb,210Po,226Ra,228Ra,228Th,230Th,232Th,234U,235U,and 238U) and anthropogenic (137Cs,239+240Pu, and241Am) radionuclides in marine sediment from the Baltic Sea (IAEA-465) has been developed. Information values are given for 238Pu,239Pu and240Pu. Altogether 27 laboratories participated in this exercise. Radiometric (alpha-spectrometry, gamma-spectrometry and beta counting, as well as mass spectrometry (ICP-MS and AMS) techniques were applied in measurements. The CRM is intended to be used for Quality Assurance/Quality Control of radionuclide analyses, for the development and validation ofanalytical methods, for the development of reference methods and for training purposes
A new physiological manikin to test and compare ventilation devices during cardiopulmonary resuscitation
No full textInternational audienceBackground : There is a lack of bench systems permitting to evaluate ventilation devices in the specific context of cardiac arrest. Objectives: The objective of the study is to assess if a new physiological manikin may permit to evaluate the performances of medical devices dedicated to ventilation during cardiopulmonary resuscitation (CPR). Methods : Specific CPR-related features required to reproduce realistic ventilation were implemented into the SAM (Sarthe Anjou Mayenne) manikin. In the first place, the manikin ability to mimic ventilation during CPR was assessed and compared to real-life tracings of airway pressure, flow and capnogram from three out of hospital cardiac arrest (OHCA) patients. In addition, to illustrate the interest of this manikin, ventilation was evaluated during mechanical continuous chest compressions with two devices dedicated to CPR: the Boussignac cardiac arrest device (B-card − Vygon; Ecouen France) and the Impedance Threshold Device (ITD − Zoll; Chelmsford, MA). Results : The SAM manikin enabled precise replication of ventilation tracings as observed in three OHCA patients during CPR, and it allowed for comparison between two distinct ventilation devices. B-card generated a mean, maximum and minimum intrathoracic pressure of 6.3 (±0.1) cmH2O, 18.9 (±1.1) cmH2O and −0.3 (±0.2) cmH2O respectively; while ITD generated a mean, maximum and minimum intrathoracic pressure of −1.6 (±0.0) cmH2O, 5.7 (±0.1) cmH2O and −4.8 (±0.1) cmH2O respectively during CPR. B-card allowed to increase passive ventilation compared to the ITD which resulted in a dramatic limitation of passive ventilation. Conclusion : The SAM manikin is an innovative model integrating specific physiological features that permit to accurately evaluate and compare ventilation devices during CPR
Radiation-induced gastrointestinal and cutaneous injuries: understanding models, pathologies, assessments, and clinically accepted practices
No full textInternational audiencePurpose: A U. S. and European joint effort fostering the development of medical countermeasures (MCMs) operable in case of radiological or nuclear emergencies. Methods: Based on the joint engagement between the U.S. National Institute of Allergy and Infectious Diseases (NIAID) and the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN), a Statement of Intent to Collaborate was signed in 2014 and a series of working group meeting were established. In December 2022, the NIAID and IRSN hosted a five-day, U.S./European meeting titled ‘Radiation-Induced Cutaneous and Gastrointestinal Injuries: Advances in Understanding Pathologies, Assessment, and Clinically Accepted Practices’ in Paris, France. The goals of the meeting were to bring together U.S. and European investigators to explore new research avenues for the medical management of skin and gastrointestinal injuries, including specific diagnostics for each organ system, animal models, and promising medical countermeasures (MCMs) to mitigate radiation damage. There was also an emphasis on exploring additional areas of medicine and response to understand best practices from other emergency scenarios, which could be leveraged to improve radiation preparedness, and the importance of accurate dosimetry in preclinical work. Results: Subsequent to the workshop, seven collaborative projects, funded by both organizations, were established on topics ranging from MCMs and predictive biomarkers, and using physical methods to assess cutaneous radiation injuries, to mechanistic studies to understand radiation-induced damage in multiple organ systems. The importance of accurate dosimetry in preclinical works was highlighted and two recently published U.S./European commentaries that focus on the need for dosimetry standardization in the reported literature had their origins in this meeting. This commentary summarizes the workshop and open discussions among academic investigators, industry researchers, and U.S. and IRSN program representatives. Conclusions: Given the substantive progress made due to these interactions, both groups plan to expand out these meetings by incorporating high-level investigators from across the globe, while endeavoring to maintain the informal setting that was conducive to in-depth scientific discussion and enhanced the state of the science in radiation research
A Neural Style Transfer Data Augmentation Strategy as Applied to Total Focusing Method Images: A Classification Task Perspective
No full textInternational audienceThis paper focuses on the use of total focusing method (TFM)-based ultrasonic (UT) imaging inspection for coarse-grained materials such as cast austenitic stainless steel (CASS) in the nuclear industry and addresses the challenges of performing inversion tasks such as defect detection, classification, and localization. The problem of detecting small (e.g., millimeter) defects in thick tubes is not straightforward due to the size of the specimens and the high scattering noise induced by the inspection of CASS, which can potentially hide the presence of defects. This work proposes a machine learning (ML) based framework that utilizes both simulations and experimental data to address the scarcity of experimental signatures and the weak representativeness of simulations when the specimen's microstructure is unknown. The paper suggests a preliminary analysis based on the use of neural style transfer paradigm to enhance the realism of simulated data using experimental pristine and flawed TFM images. This method aims at increasing the quantity and quality of flawed samples using both numeric simulation data and pristine experimental images taken during the inspection of one CASS pipe. The paper discusses the evaluation of the proposed framework in terms of ML-based defect detection