Institute for Radiation Protection and Nuclear Safety (IRSN)
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Modeling the transfer of radionuclides in aquatic environments
No full textInternational audienceThe transfer of radionuclides in aquatic environments (lakes, rivers, oceans) is controlled by known physicochemical processes, but which remain, sometimes, difficult to reproduce correctly in numerical models. However, a good understanding and prediction of these transfers is essential because these environments have a high risk of being impacted during an accident, since all nuclear power plants are installed at the water's edge. If the effect of radioactive contamination of water on humans would be less than compared to that of a terrestrial environment, the consequences can be strong for the effects on ecosystems and the use of water (drinking water, irrigation, …). Likewise, remediation possibilities are much more complicated for sediments than for soils.IRSN has developed several types of numerical models to respond to this challenge. They make it possible to simulate the fate of dissolved and particulate radionuclides in rivers or at sea, as well as their transfer to some organisms.The presentation will describe the main processes taken into account in these models and will be based on various examples of work performed by the researchers from IRSN. They will cover a large spatial scale, from soil inputs in the watershed to sediment deposition at sea. Current studies to integrate new processes or adapt to crisis or monitoring needs will be discussed
Numerical simulations of bubbly turbulent convection in cubical geometries
No full textInternational audienceIn this work we present numerical results of pool boiling flow in a turbulent Rayleigh-Bénard convection configuration, using our in-house code in a cubical geometry. The problem in hand is encountered in various natural phenomena as well as in industrial applications. An Eulerian-Lagrangian approach is developed for the mixture of liquid water and vapor bubbles. The liquid mean temperature is close to the saturation temperature and is governed by the quasi-incompressible Navier-Stokes equations that are solved using DNS standards. The motion and growth/shrinkage of each individual vapor bubble is modeled and the backward effect of the bubbles on the fluid is accounted via momentum and energy exchanges between the two phases (two-way coupling), as well as variations in fluid phases volumetric fractions (volumetric coupling). In such pool configuration the non-dimensional parameters governing the flow are both those relative to Rayleigh-Bénard convection, namely Rayleigh number, Prandtl number and aspect ratio, and those to boiling, namely the overall vapor volumetric fraction, the bubble size based Reynolds number, the degree of superheat of the liquid scaled by the overall temperature difference, and the Jakob number (sensible heat to latent heat ratio). At first, we describe the model used and its corresponding validation, involving natural convection, isolated bubble dynamics and coupling between bubbly and bulk flows. In the second part, we consider the study of the relationship between heat transfer through the pool (Nusselt number) and the flow topology for different settings of the bubbly configurations
Liposomal formulations of bisphosphonate molecules for the treatment of internal Strontium/Cobalt contamination
No full textInternational audienceIn the event of nuclear/radiological incidents or accidents involving internal contaminations with radioactive cobalt or strontium compounds, the current recommended therapeutic options (calcium salts of DTPA and calcium gluconate respectively) have been shown to be of low specificity, and their effectiveness remains modest. The main health risk resulting from internal contamination is irradiation of the target organs for retention of the radionuclides considered (skeleton, liver, kidney), which can cause long-term deleterious effects that can lead to the development of malignant diseases. There is therefore a crucial need to develop new decorporation agents to improve the medical care of patients exposed to such events. To address this question, the experimental strategy adopted was to use a class of pharmaceutical molecules (Biphosphonates or BPs) that already have marketing authorisation and whose complexation properties with divalent cations are strongly suspected. The first step consisted of assessing the affinity of BP molecules with the cations of interest. To this end, we set up an analytical method based on capillary electrophoresis. Several charged metal-ligand complexes have been identified. During the next step, we developed new liposomal formulations to deliver strontium/cobalt potential chelating agents to the main radionuclide retention organs (bone, liver, and kidneys). In vivo evaluation of the decorporation efficiencies of both free and liposome-encapsulated molecule were then performed in a rodent model. The results showed a clear interaction between the radionuclides and the ligand and unexpected data concerning reference treatments. For now, BP-based treatments do not fulfil all the necessary conditions to constitute a decorporating agent. The results obtained thus highlight the need to continue efforts to find an effective, efficient chelating treatment and the importance of taking care of victims as soon as possible after exposur
Central nervous system tumours and occupational ionising radiation exposure: a nested case–control study among the ORICAMs cohort of healthcare workers in France
No full textCorrection: central nervous system tumours and occupational ionising radiation exposure: a nested case-control study among the ORICAMs cohort of healthcare workers in France BMJ Open 2024;14:e084285.corr1. doi: 10.1136/bmjopen-2024-084285.corr1International audienceObjective This study aimed at investigating the relationship between occupational exposure to external ionising radiation and central nervous system (CNS) tumours mortality in healthcare workers working in France. Design and setting The Occupational Radiation-Induced Cancer in Medical staff (ORICAMs) nested case–control study was conducted based on the dosimetric records of the national register of occupational dosimetry (Système d’information de la surveillance de l’exposition aux rayonnements ionisants). Participants and methods 33 CNS tumour deaths occurred between 2002 and 2012 among the ORICAMs cohort composed of 164 015 healthcare workers. Each case was matched to five controls alive at the time of the corresponding case’s death, based on sex, year of birth, date of enrolment in the cohort and duration of follow-up. All participants were badge monitored for external radiation exposure, expressed in H p (10). Conditional logistic regression was used to analyse the dose–response relationship between radiation dose and CNS mortality. Results Cases were exposed to a mean cumulative career radiation dose of 5.8±13.7 (max: 54.3) millisievert (mSv) compared with 4.1±15.2 (142.2) mSv for controls. No statistically significant association was found between CNS tumour mortality and cumulative whole-body career dose (OR=1.00, 95% CI 0.98 to 1.03), duration of exposure (OR=1.03; 95% CI 0.95 to 1.12) or age at first exposure (OR=0.98; 95% CI 0.91 to 1.06). Conclusion We found no evidence of an association between external radiation exposure and CNS tumour risk in healthcare workers. Limitations of the study include low statistical power and short duration of follow-up
Stress Release–Induced Suction in Unsaturated MX80 Bentonite Pellet and Powder Mixtures
No full textInternational audienceIn this study, a series of suction-control oedometer tests were conducted on unsaturated and saturated MX80 bentonite pellet/powder mixtures. The mixture samples were imposed with various suctions from 0 to 113 MPa under a low vertical stress (0.1 MPa). Then, the mixture samples were loaded in steps with controlled suction until reaching three different target stresses σv (0.1, 3.2, and 12.8 MPa) and instantaneously unloaded. The microstructure of unloaded samples was observed with mercury intrusion porosimetry (MIP) and microcomputed tomography (μCT), together with the determination of suction, water content, void ratio, and saturation degree. Results showed that the water-retention behavior of bentonite pellet/powder mixture was rather characterized by pellets instead of powder. Due to the stress release, the measured suction after unloading sme was larger than the imposed suction sim. The suction difference Δs between sme and sim depended on both suction and load. Under a given σv, the suction effect was characterized by an increase of Δs when sim decreased from 113 to 4.2 MPa, but by a noticeable decrease of Δs when sim further decreased to zero. This was found to be related to the changes of the slopes of soil-water retention curves (SWRCs): the slope was decreasing with suction increases after 4.2 MPa suction, but was increasing with suction increases before 4.2 MPa suction. As far as the stress effect was concerned, a larger Δs was identified at a higher σv for a given sim. The narrowing difference between Δs and the reduction of mean stress of pellet Δppellet with increasing load was because of the decrease of larger pores due to loading. The total mixture void ratio emixtureT was highly dependent on suction and vertical stress, whereas the total pellet void ratio epelletT was only dependent on suction in the stress range considered
Enhanced beams and plates models incorporating the steel-concrete interface behavior for large-scale reinforced concrete structural applications
No full textInternational audienceConsidering the interaction between concrete and steel reinforcement in numerical simulationsof reinforced concrete structures is crucial for accurately capturing the concrete cracking process. This is particularly interesting when studying structures fulfilling functions that go beyondtheir simple mechanical resistance, such as waterproofing functions. While three-dimensional(3D) volumetric finite element modeling offers detailed insights into structural behavior,its computational intensity becomes prohibitive for large-scale structures. In such contexts,adopting beam and plate elements formulations proves computationally more efficient, dueto their reduced number of degrees of freedom. This paper presents a kinematic enhancementtechnique designed to integrate steel-concrete interface behavior into beam and plate finiteelement formulations. The approach combines classical beam or plate elements representingconcrete behavior, conventional beam or truss elements modeling steel reinforcement, and theincorporation of bond stresses at the interface. The paper provides comprehensive explanationsof this enhancement technique along with a curated selection of numerical validation andapplication examples. These examples are supplemented by a comparison with experimentaldata, illustrating the efficiency of the proposed enhancement approac
The TANDEM Euratom project: Context, objectives and workplan
No full textInternational audienceThe TANDEM project is a European initiative funded under the EURATOM program. The project started on September 2022 and has a duration of 36 months. TANDEM stands for Small Modular ReacTor for a European sAfe aNd Decarbonized Energy Mix.Small Modular Reactors (SMRs) can be hybridized with other energy sources, storage systems and energy conversion applications to provide electricity, heat and hydrogen. Hybrid energy systems have the potential to strongly contribute to the energy decarbonization targeting carbon-neutrality in Europe by 2050. However, the integration of nuclear reactors, particularly SMRs, in hybrid energy systems, is a new R&D topic to be investigated. In this context, the TANDEM project aims to develop assessments and tools to facilitate the safe and efficient integration of SMRs into low-carbon hybrid energy systems. An open-source “TANDEM” model library of hybrid system components will be developed in Modelica language which, by coupling, will extend the capabilities of existing tools implemented in the project. The project proposes to specifically address the safety issues of SMRs related to their integration into hybrid energy systems, involving specific interactions between SMRs and the rest of the hybrid systems; new initiating events may have to be considered in the safety approach.TANDEM will study two hybrid systems covering the main trends of the European energy policy and market evolution at 2035's horizon: a district heating network and power supply in a large urban area, and an energy hub serving energy conversion systems, including hydrogen production; the energy hub is inspired from a harbor-like infrastructure. TANDEM will provide assessments on SMR safety, hybrid system operationality and techno-economics. Societal considerations will also be encased by analyzing European citizen engagement in SMR technology safety.The work will result in technical, economic and societal recommendations and policy briefs on the safety of SMRs and their integration into hybrid energy systems for industry, R&D teams, Technical Safety Organizations, regulators, Non-Governmental Organizations and policy makers. The TANDEM consortium will involve 17 partners from 8 European countries (Belgium, Czech Republic, Finland, France, Germany, Italy, Spain, Ukraine).The TANDEM project has the ambition to become a pioneer initiative in Europe in gathering efforts and expertise around development of SMRs integration into hybrid energy systems. The dissemination and the exploitation of the project outcomes as well as the proposed Education & Training activities shall serve as a basis for a number of new R&D and innovation projects addressing the safety issues of SMRs and their integration into hybrid energy systems
Evaluation of the speciation and availability of Cu, Sn, Bi and U from lacustrine sediments influenced by former mining activities
No full textInternational audienceManaging reservoir sediments remains challenging due to their propensity to significantly sequestrate trace elements. Moreover, many artificial reservoirs were located downstream of former mining sites. However, the knowledge of the exact trace element speciation and its fate in sediments submitted to reoxidation and drying events, such as dredging operations, is still limited.In this study, we examined the degree of contamination and solid speciation of trace elements and radionuclides in case of lake sediments dredging influenced by former mining activities. Finally, to assess the consequences such management i.e., dredging, by mimicking drying and oxidizing conditions, Toxicity Characterizing Leaching Procedure (TCLP) tests combined with parallel chemical extractions and mineralogical analyses were performed.Our results showed enrichments for Cu, Sn and Bi related to the former extractions activities of Charrier Cu–Sn mining site, as well as an enrichment for U partially due to the Bois-Noirs-Limouzat U mining site, in lake sediments. Moreover, the reoxidation and drying of initially anoxic sediments led to metal solid speciation dominated by: (i) Cu and Bi inherited sulfide minerals such as chalcopyrite, (ii) Cu, Bi and U associated with natural organic matter, and (iii) large grain-size refractory cassiterite SnO2 crystals. Additionally, results from the TCLP indicated a limited leachability of the studied elements, confirming the significant stability of U, Cu and Bi associated with natural organic matter. Finally, Cu and U concentrations extracted by TCLP are lower than threshold values indicating that these sediments are not considered as hazardous regarding these elements
Modèles de rein 2D et 3D in vitro pour étudier la réponse néphrotoxique à l'exposition à l'uranium
No full textInternational audienceAs a heavy metal and alpha emitter, uranium presents chemical and radiological toxicity risks, accumulating preferentially in the kidneys, specifically in proximal convoluted tubules. The biological mechanisms and pathways impacted by uranium exposure can be formulated into an adverse outcome pathway (AOP) (https://aopwiki.org/aops/447), allowing us to identify the different steps and gaps between an initiating event to the kidney toxicity. Using in vitro models of renal proximal tubule epithelial cells (hRPTEC TERT1) or induced kidney organoids (iKO), this study aims to reinforce and contribute to the development of the AOP of kidney toxicity. After identifying the U(VI) concentrations that induce adverse outcomes (apoptosis or necrosis), key events linked to oxidative stress, apoptosis, survival, inflammation, and renal damage are studied at the gene and protein levels. Apoptosis (Casp 3/7, Bax/Bcl2, cytochrome C) is significantly induced starting from exposure to 300 µM for hRPTEC and from 500µM for iKO, and necrosis (LDH) from 500 µM for both models. A time-dependent rise in ROS production and an antioxidant response -increased HO-1, NQO-1, GCLC- are observed in hRPTEC cells. Whereas SOD2, NQO-1 are augmented in iKO but GCLC, CYP2E1 and CAT are diminished in iKO. Uranium concentrations >300µM induced a marked inflammatory response in both models, with increased levels of TNFα, IL-6 and IL-18 in hRPTEC cells and only TNFα in iKO. The study of renal damage markers revealed a slight increase in KIM-1 at 500 µM and a decreased of Collagen IV in both models and an increased level of Calbindin in iKO. In conclusion, this work provides an insight into the key events in the AOP of uranium-induced renal failure featuring a human phenotype of proximal tubule epithelial cells and kidney organoid model, while considering the dose-dependent effect
Artificial Radionuclides In Coastal Marine Ecosystems
No full textInternational audienceThis chapter presents various models used to predict and study the fate of artificial radionuclides in the coastal marine environment. The two major sources of artificial radionuclides to the environment are from past atmospheric nuclear weapons testing and nuclear facilities, whether civil or military, through controlled or accidental releases. Radionuclides in the ocean are divided into dissolved or particulate forms and are therefore present in both the water column and sediment. Exchanges between these forms are mainly dependent of their physico-chemical properties, and their dispersion is governed by hydrodynamic and hydrosedimentary processes. They are also transferred to living organisms through processes that can be simple such as adsorption and direct absorption from seawater by external surfaces (skin, gills) or more complex via ingestion and subsequent transfer in trophic webs. Several modelling, empirical or mechanistic approaches have been developed since the 1960s to account for and predict the behavior of these contaminants in various equilibrium or dynamic situations. They are presented here, with examples of modelling applications mainly focusing on the Fukushima accident which led to the most important release of artificial radionuclides to the ocean