Institute for Radiation Protection and Nuclear Safety (IRSN)
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Timescale of radium and alkaline earth cations ascent in the trees: Use of isotopic (228Ra/226Ra) ratio
No full textInternational audienceDue to its short-lived progeny, including gaseous radon isotopes that can be inhaled and its significant transfer into vegetation, radium poses a substantial concern in radiation risk assessment. Although the transfer of Ra from soil to plants has been previously documented, the distribution and speciation of radium within the plant tissues, particularly within trees, remain unclear. The temporal dimension of Ra transfer is also poorly known. Therefore, the transfer of radium and others alkaline earth cations in beech trees was investigated through the analysis of fine (<2 mm) roots and leaves corresponding to tree organs with a life cycle limited to one season. This study was conducted at the experimental Montiers (INRAE-Andra site, France) and Strengbach watershed (OHGE site, France) beech-forested site. The activity of 226 Ra and the isotopic ratio ( 228 Ra/ 226 Ra) were measured in roots and leaves using gamma spectrometry. Additionally, the concentration of alkaline earth cations (Mg, Ca, Sr, and Ba) was measured, to better constraint the mechanism of alkaline earth cation transfer through the xylem. The retention of these cations within the trees increases with the mass of the element, following the order Mg < Ca < Sr ≈ Ba < Ra, i.e.: light alkaline earth cations are more efficiently transferred from roots to leaves than heavy one. Our results suggest that these cations maintain their hydration shell during their ascent in stems and a low pH ion-exchange process rather than a complexation process with carboxylic group occurs.The decay of the ( 228 Ra/ 226 Ra) isotopic ratio over time during transfer within the trees allows us to quantify the slow Ra translocation from roots to the leaves, ranging from 1 to more than 16 years. This duration increases with the age of the trees. Hence, radioactive decay of Ra provides particularly valuable timescale information that is usually difficult to assess for Ca or other alkaline earth cations.</p
Transfer functions for QA/QB international regulatory limits for the safe transport of radioactive materials
No full textInternational audienceThis paper presents a proposed revision of the International Atomic Energy Agency transport regulations, related to the A 1 and A 2 limit values used to determine the radioactive transport classification. Based on the ‘ Q system’, a novel methodology was introduced to derive Q A and Q B values related to scenarios involving external exposure from a distant source. These values are key parameters that respectively represent the total effective dose and total equivalent dose to the skin, from all primary and secondary particles contributing to radiation exposure. The International Working Group (WG A 1 / A 2 ) is established and associated with the TRANSSC Technical Expert Group on Radiation Protection. A review of the A 1 and A 2 values is performed in response to identified limitations within the existing Q system. The followed approach is based on Monte Carlo simulations that enabled the development of transfer functions aimed at reducing computational time and increasing the flexibility of dose evaluations for any radionuclide with known particle emission spectra. This method allows updating the Q A and Q B values to account for future data evolutions (decay data, fluence-to-dose conversion coefficients) and standardizing the calculation of regulation limits across all referenced radionuclides and scenarios related to external exposure. The transfer functions are established using three Monte Carlo simulation codes—FLUKA, Geant4, and MCNP—and address the previous limitations of the ‘ Q system’, reflecting the latest International Commission for Radiation Protection recommendations and improvements in calculation techniques. The results of the WG show consistent agreement across the codes, with minor discrepancies observed at low primary energies due to statistical uncertainties and different handling of stopping power for electrons/positrons in the codes. This revised approach aligns with current standards and recommendations, ensuring that the radiological consequences of transport accidents are acceptable for the new A 1 and A 2 limits from a radiological protection perspective
Radiological injuries under low energy x-rays in mice depending on dose and protocol: comparative characterization of lesion severity and impact of the in vivo bone response on retrospective dose estimations
No full textInternational audienceObjective . To improve our knowledge about the biological effects of over exposures involving low-energy x-rays, we developed and characterized a preclinical mouse model allowing to mimic different lesion severity degrees induced by 80 kV x-ray depending on the dose and protocol (single or repeated exposure). Approach . Mice were locally exposed (paw) to 80 kV x-rays in a single (15, 30 or 45 Gy in K air ) or repeated exposition (2 × 15 or 3 × 15 Gy in K air ) to assess different degrees of lesion severity. Six post-irradiation euthanasia time points (0, 7, 14, 21, 42, and 84 days) were determined to follow up the evolution of lesions based on the lesion score, weighing and cutaneous blood perfusion. The bone dose was estimated at the different time points by electron paramagnetic resonance (EPR) spectroscopy. Main results . The monitoring of the lesion severity allows to classify the exposure protocols according to their severity. EPR spectroscopy measurements allow to determine the bone dose on the day of irradiation which is 7 times higher than the initial dose for single protocols. However, the initial signal measured at the end of the repeated exposure was 27% lower than the signal measured for a single dose. The study of the kinetics of EPR signal showed a decrease of the EPR signal which is dependent on the exposure protocol but not on dose highlighting the impact of bone physiology on the bone dose estimation. Significance : the preclinical model developed allows to assess the impact of the dose and protocol on the lesion severity induced by low-energy x-ray. For the first time, the dynamics of free radicals have been quantified in an in vivo model, highlighting that the doses actually administered can be underestimated if samples are taken weeks or even months after exposure
L’Observatoire des Sédiments du Rhône (OSR) - Réseau de suivi des MES et contaminants associés sur le Rhône et ses affluents
No full textAdaptation of the PIRT methodology to the Severe Accident domain
No full textInternational audienceSevere Accidents (SAs) dominate the risk associated with the commercial production of nuclear energy. Despite the major achievements made in their understanding, upcoming new technologies such as Advanced Technology Fuels (ATFs) and Small Modular Reactors (SMRs), more stringent safety requirements, optimization of SA management, and other factors, point the need for an efficient use of research resources in the years to come. The SEAKNOT project (SEvere Accident research and KNOwledge managemenT for LWRs), coordinated by CIEMAT, was born to address this need in all and every aspect. The present article describes how the PIRT (Phenomena Identification and Ranking Table ) approach has been adapted to the entire SA domain to prioritize forthcoming research. A 13-step methodology aimed at source term (ST) release to the environment or its potential prevention/mitigation is outlined with particular emphasis on the challenges addressed while adapted. At the time this article is being written, the phenomena ranking process has already started
Probabilistic fault displacement Hazard analysis in an extensional setting: Application to a strategic Dam and methodological implications
No full textInternational audienceWe present a Probabilistic Fault Displacement Hazard Analysis (PFDHA) for a strategic dam located in the Upper Tiber Valley (Northern Apennines of Italy) claimed to be sited on a supposed capable fault (Montedoglio fault).We verify the seismic capability of the Montedoglio fault through detailed geological and geophysical analyses. We find no evidence for considering the Montedoglio fault as an active and capable structure, the fault being constituted by a system of discontinuous parallel faults, apparently inactive since more than 56 ± 3 ka, and likely unable to nucleate strong surface rupturing earthquakes. Since the dam lies on the hanging wall of the closest major active fault of the area (Anghiari normal fault, ~1.5 km away), we investigate the likelihood of having distributed faulting at the dam’s site in case of a strong surface-rupturing earthquake occurring on the Anghiari fault. We apply a probabilistic approach to obtain hazard curves of exceedance of vertical displacement at the dam’s site for different rupture scenarios. We show that the mean hazard curve is always below an annual frequency of exceedance of 1 × 10− 5 , corresponding to displacement values below 1 cm over 100,000 years of return period. The study highlights several weaknesses and uncertainties in using PFDHA with state-of-the-art models, suggesting the need for improvements to enhance their applicability in earthquake engineering geology practice
Un atelier sur l'avenir de la radioprotection
No full textNational audienceA workshop on the future of radiological protection was jointly organised by the Institute for Radiological Protection and Nuclear Safety (IRSN) , the Nuclear Protection Evaluation Centre (CEPN) and the International Commission on Radiological Protection (ICRP) in March 2024. The aim was to present recent developments within the ICRP and to exchange views with representatives of the French radiological protection community on the review and revision of the System of radiological protection. This article presents a summary of the main points discussed during the workshop.Un atelier sur l’avenir de la radioprotection a été organisé conjointement par l’Institut de radioprotection et de sûreté nucléaire (IRSN), le Centre d’étude sur l’évaluation de la protection dans le domaine nucléaire (CEPN) et la Commission internationale de protection radiologique (CIPR) en mars 2024. L’objectif était de présenter les développements récents au sein de la CIPR et d’échanger avec les représentants de la communauté française de la radioprotection sur l’examen et la révision du Système de protection radiologique. Cet article présente une synthèse des principaux points de discussion abordés durant cet atelier
Synthesis of Source Term Assessments for a Loss-of-Cooling Accident in a Spent Fuel Pool: Insights from Uncertainty and Sensitivity analyses and potential benefit of water injection by spray system
No full textInternational audienceThe recently completed Horizon-2020 project on “Management and Uncertainties of Severe Accidents(MUSA)” has applied uncertainty and sensitivity analysis in the assessment of Severe Accidents (SA),particularly in predicting the radiological source term of reactor and Spent Fuel Pool (SFP) accidentscenarios. For SFP, the two main objectives were: 1/ to determine the main uncertainties affecting theaccident progression and fission product release during an accident in a SFP and 2/ to assess the possiblebenefits, in terms of source term reduction, of water injection by spray systems. The target of this paper isto describe the main achievements at the end of the 4 years’ project, regarding SFP accident scenario. Theuncertainty and sensitivity analyses were performed by eleven participants thanks to the propagation of theuncertainties of the input parameters to the output uncertainties of severe accident codes. A SFP accidentalscenario was selected, uncertainty sources in models and input parameters were identified and key targetvariables were chosen as Figure of Merits (FOMs). It was found that spreading in SA code responses comingfrom the uncertainty quantification done by each participant was relatively small when compared to thevariability between reference computations of all participants. It reveals that important uncertainty sources,such as the lack of modeling or the nodalization, have not been taken into account in the uncertaintyquantification. The sensitivity analysis, based on statistical correlation coefficients and supported by theanalysis of scatter plots, has put in light that uncertain parameters linked to aerosol phenomena in thebuilding significantly affect the source term. It has also revealed that the relationship between the sourceterm and uncertain parameters linked to degradation is not straightforward, due to the non-linear nature ofthe phenomena in play and due to cliff-edge effects. Concerning the benefits of spray systems, the massflow rate and the injection time that can prevent cladding failure, and thus Fission Product (FP) release weredetermined by seven participants, thanks to ASTEC, RELAP/SCDAPSIM and MELCOR calculations. Theresults obtained are very preliminary and should not be considered as demonstrative, since SA codes aregenerally not validated to compute the cooling of an assembly by spray injection. It is thus mandatory tocarry out a validation work of the thermal hydraulics and the POLCA OECD project would be anopportunity for this
Evaluation of Various Correlations for Direct-Contact Heat Transfer in Dispersed Flow Film Boiling Using the DRACCAR Code
No full textInternational audienceFollowing the core uncovery after a hypothetical loss of primary coolant accident (LOCA), a flow of steam with dispersed droplets forms downstream of the quench front. This flow is crucial for cooling nuclear fuel rods that are not in direct contact with water, representing a typical Dispersed Flow Film Boiling (DFFB) scenario. Depending on accident severity, fuel rod deformation may partially block subchannels, diverting steam towards less deformed areas and potentially impacting cooling. As a result, characterizing heat transfer under such conditions is essential to enhance the nuclear reactor safety during accidents like LOCA. The COLIBRI experimental loop was designed to assess the heat flux released by steam/droplet flow in intact and deformed fuel rod subchannels. Experimental results obtained with this facility helped evaluate various correlations for direct-contact heat transfer calculations in DFFB within the DRACCAR code. In this article, the DRACCAR code is used to compare different correlations for heat transfer due to droplet impacts onto the wall calculation. This comparison was made on four COLIBRI experiments, involving two different droplet mass flow rates (5 kg/h and 11.5 kg/h) and two levels of subchannel deformation (intact and 90% blocked)
Long-term biological effects after acute 131 I-administration of two rat models (with and without thyroid)
No full textInternational audiencePurpose: Radioiodine-131 (RAI or iodine-131) is one of the most frequently used radionuclides fordiagnosis and therapy of thyroid diseases (90% of all therapies in nuclear medicine). In order tooptimize the patient protection, it is important to evaluate the long-term biological effects of RAItherapy on non-target organs.Materials and methods: An experimental animal model has been adopted, it consists on mimingRAI therapy. An activity of RAI has been administrated in two models of Wistar rats: the first modelwith an intact thyroid gland (Thy + model), and the second one was thyroidectomized (Thy- model).For each model, 6 rats were orally contaminated with a solution 18.5 ± 1MBq of [131I]NaI and 6others rats were used as controls. The 24 rats have been placed in individual cages for a period of08 months then they were euthanized. The blood was collected by cardiac puncture and all organswere immediately removed. A fraction of thyroid, liver, kidneys and testicles was put in vialscontaining formaldehyde (10%) for histological investigation.Results: Histological observations show some liver disorders more accentuated in the case of theThy- model, the appearance of kidney tissue effects (hemosiderin deposits, fibrosis and glomerularnecrosis) for both models and an absence of any anomaly for the testicles slides. The disturbanceof blood parameters specific to each organ has been revealed.Conclusions: Long-term biological effect of 131I-administration shows the appearance of varioushistological disorders confirmed by disturbances in hepatic and renal functions