Institute for Radiation Protection and Nuclear Safety (IRSN)
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Quantification de la fraction remise en suspension de simulant d'oxyde de plutonium dans un dispositif de dégradation thermique à petite échelle
No full textInternational audienceAn IRSN programme, named FIGARO, focuses on glovebox fires with the aim of quantifying aerosol releases. This paper summarises the methodology developed in this project to quantify the aerosol resuspension through the measurement of the aerosol release fraction in a small-scale experimental facility of the IRSN (Saclay, France). The facility allows thermal degradations to study aerosol airborne resuspension by fire. The resuspension is characterized by the quantification of the aerosol release fraction from glovebox wall slabs. Investigations were carried out to identify surrogate and tracer particles. The contamination of the wall slabs was realised with a specific, qualified contaminating system
An introduction to Spent Nuclear Fuel decay heat for Light Water Reactors: a review from the NEA WPNCS
No full textInternational audienceThis paper summarized the efforts performed to understand decay heat estimation from existing spent nuclear fuel (SNF), under the auspices of the Working Party on Nuclear Criticality Safety (WPNCS) of the OECD Nuclear Energy Agency. Needs for precise estimations are related to safety, cost, and optimization of SNF handling, storage, and repository. The physical origins of decay heat (a more correct denomination would be decay power) are then introduced, to identify its main contributors (fission products and actinides) and time-dependent evolution. Due to limited absolute prediction capabilities, experimental information is crucial; measurement facilities and methods are then presented, highlighting both their relevance and our need for maintaining the unique current full-scale facility and developing new ones. The third part of this report is dedicated to the computational aspect of the decay heat estimation: calculation methods, codes, and validation. Different approaches and implementations currently exist for these three aspects, directly impacting our capabilities to predict decay heat and to inform decision-makers. Finally, recommendations from the expert community are proposed, potentially guiding future experimental and computational developments. One of the most important outcomes of this work is the consensus among participants on the need to reduce biases and uncertainties for the estimated SNF decay heat. If it is agreed that uncertainties (being one standard deviation) are on average small (less than a few percent), they still substantially impact various applications when one needs to consider up to three standard deviations, thus covering more than 95% of cases. The second main finding is the need of new decay heat measurements and validation for cases corresponding to more modern fuel characteristics: higher initial enrichment, higher average burnup, as well as shorter and longer cooling time. Similar needs exist for fuel types without public experimental data, such as MOX, VVER, or CANDU fuels. A third outcome is related to SNF assemblies for which no direct validation can be performed, representing the vast majority of cases (due to the large number of SNF assemblies currently stored, or too short or too long cooling periods of interest). A few solutions are possible, depending on the application. For the final repository, systematic measurements of quantities related to decay heat can be performed, such as neutron or gamma emission. This would provide indications of the SNF decay heat at the time of encapsulation. For other applications (short- or long-term cooling), the community would benefit from applying consistent and accepted recommendations on calculation methods, for both decay heat and uncertainties. This would improve the understanding of the results and make comparisons easier
TEX-MOX experiments: final design of critical experiments to mimic MOX fuel in low moderation conditions
No full textInternational audienceThe goal of TEX-MOX experiments is to fill the gaps in the criticality safety validation basis in intermediate energy range. 3 experiments were designed to answer this purpose to be executed at NCERC (National Criticality Experiments Research Center) in USA on the Planet vertical lift machine. These experiments were designed to provide a high keff sensitivity to 239Pu and 240Pu in the intermediate energy range, comparable to the real case sensitivities, corresponding to the criticality safety validation needs in French nuclear facilities. The decay heat produced by the mixed uranium-plutonium metallic plates to be used in the experiments challenged the mechanical design that was adopted to handle this issue. Final design of the experiments will be presented in this paper along with the main characteristics as expected uncertainties, keff sensitivities and mechanical design of the cooling system
Induced polarization of clay-rich materials — Part 5: Influence of hyperalkalinity in bentonites
No full textInternational audienceA total of 54 new core samples were built by mixing smectite-rich MX80-bentonite and Fontainebleau (silica) sand to study the effect of a hyperalkaline pore solution (including the presence of potassium) on the induced polarization properties of these mixtures. Two types of experiments were performed. In the first set of experiments, we performed induced polarization measurements 10 minutes after the preparation of the core samples (static experiments) for a broad variety of water contents and saturations. The second set of experiments was performed for over 1000 hours to study the potential effect of illitization upon the induced polarization properties (time-lapse experiments). Indeed, in the presence of potassium in the hyperalkaline pore solution favors the transformation of smectite into illite. Furthermore, we expect cation replacement (sodium replaced by calcium and potassium) in the smectite interfoliar pore network. For the static experiments, the relationships developed in the previous papers of this series regarding the dependence of the in-phase and quadrature conductivities on the water content and saturation remain valid. For the time-lapse experiments, we observed a decrease of the in-phase and quadrature conductivities over time. These trends can be fitted by a decaying exponential function. This behaviour is explained by the kinetics of the illitization process and its effect on the cation exchange capacity of the material. Induced polarization appears therefore as a promising technique to monitor the effect of hyperalkaline solutions associated with the leaching of concrete and permeating a bentonite seal in Deep Geologic Disposal facilities that could be potentially used for high-level and long-lived radioactive wastes
Pump and probe wave mixing for imaging nonlinear features embedded into a massive concrete block
No full textInternational audienceNonlinear ultrasonic parameters are known to be highly sensitive to the presence of damage in materials, and numerous methods have already been reported. This study proposes a way to image a nonlinear defect embedded into a nonlinear medium. The nonlinear defect is mimicked by a Berea sandstone sphere (high nonlinearity). It is placed into a large concrete block (average nonlinearity) during casting. The proposed pump and probe propagating wave interaction method allows imaging the presence of the highly nonlinear region. The image contrast is magnified by a factor 8 in the defective zone. The results are validated using a model and the individual mechanical properties of both concrete and Berea Sandstone. These findings open perspectives for application to civil engineering concrete structures such as the assessment of durability distresses involving internal swelling
Site-specific cancer mortality after low level exposure to ionizing radiation: Findings from an update of the International Nuclear Workers Study (INWORKS)
No full textInternational audienceA major update to the International Nuclear Workers Study was undertaken that allows us to report updated estimates of associations between radiation and site-specific solid cancer mortality. A cohort of 309,932 nuclear workers employed in France, the United Kingdom, and United States were monitored for external radiation exposure and associations with cancer mortality were quantified as the excess relative rate (ERR) per gray (Gy) using a maximum likelihood and a Markov chain Monte Carlo method (to stabilize estimates via a hierarchical regression). The analysis included 28,089 deaths due to solid cancer, the most common being lung, prostate, and colon cancer. Using maximum likelihood, positive estimates of ERR per Gy were obtained for stomach, colon, rectum, pancreas, peritoneum, larynx, lung, pleura/mesothelioma, bone and connective tissue, skin, prostate, testis, bladder, kidney, thyroid, and residual cancers; negative estimates of ERR per Gy were found cancers of oral cavity and pharynx, esophagus, and ovary. A hierarchical model stabilized site-specific estimates of association, including for lung (ERR per Gy=0.65; 95% credible interval [CrI]: 0.24, 1.07), prostate (ERR per Gy=0.44; 95% CrI: -0.06, 0.91), and colon cancer (ERR per Gy=0.53; 95% CrI: -0.07, 1.11). The results contribute evidence regarding associations between low dose radiation and cancer
Chemo-mechanical characterization of a low-pH model cement paste in magnesium bearing environment
No full textInternational audienceIn contact with natural waters, concrete can be exposed to the action of magnesium. Mg-attack on the cement paste leads to dissolution of cementitious phases and formation of brucite, hydrotalcite and/or magnesium silicate hydrates (M-S-H). The knowledge of the properties of the latter is limited. In binders with supplementary cementitious materials, M-S-H formation is favoured over that of brucite because of the lower contents of portlandite. To investigate the effects of a magnesium attack on such binders, a low Ca/Si model cement paste was immersed in a 5 mmol/L MgCl2 solution for several months. Energy-dispersive spectrometry analyses coupled with X-ray diffraction and electron probe microanalyses showed Ca leaching, Si preservation and Mg enrichment of the altered zones of the pastes corresponding to the dissolution of C-S-H and formation of M-S-H and amorphous silica. The Mg-enriched zone showed a lower residual Young's modulus than the sound zone as measured by microindentation
Cancer therapy-related cardiac dysfunction after radiation therapy for breast cancer: results from the BACCARAT cohort study
No full textInternational audienceBackground Radiation therapy (RT) for breast cancer (BC) can result in subtle cardiac dysfunction that can occur early after treatment. In 2022, the European Society of Cardiology (ESC) published the first guidelines in cardiooncology with a harmonized definition of cancer therapy-related cardiac dysfunction (CTRCD). The aim of this study was to evaluate CTRCD occurrence over 24 months of follow-up after RT in BC patients and to analyze the association with cardiac radiation exposure. MethodsThe prospective monocentric BACCARAT study included BC patients treated with RT without chemotherapy, aged 40-75 years, with conventional and 2D Speckle tracking echocardiography performed before RT, 6 and 24 months after RT. Based on ESC cardio-oncology guidelines, CTRCD and corresponding severity were defined with left ventricle ejection fraction and global longitudinal strain decrease, occurring at 6 or 24 months after RT. Dosimetry for whole heart, left ventricle (LV) and left coronary artery (left anterior descending and circumflex arteries (CX)) was considered to evaluate the association with CTRCD, based on logistic regressions (Odds Ratio -OR and 95% confidence interval -95%CI). Youden index based on receiver operating characteristic curve analysis was used to identify the optimal threshold of dose-volume parameters for predicting CTRCD. ResultsThe study included 72 BC patients with a mean age of 58 ± 8.2 years. A total of 32 (44%) patients developed CTRCD during follow-up: 20 (28%) mild CTRCD, 7 (9%) moderate CTRCD, and 5 (7%) severe CTRCD. Cardiac radiation doses were generally higher among patients with CTRCD rather than non-CTRCD. Dose-response relationships were significant for mean CX dose (OR = 2.48, 95%CI (1.12-5.51), p = 0.02) and marginally significant for V2 of LV (OR = 1.03 95%CI (1.00-1.06), p = 0.05). V2 of LV ≥ 36% and mean CX dose ≥ 1.40 Gy thresholds were determined to be optimal for predicting CTRCD. ConclusionFor BC patients treated with RT without chemotherapy, CTRCD can be observed in an important proportion of the population over 24 months after treatment. Left ventricle and circumflex coronary artery exposure were found to be associated with CTRCD and could be used for the prediction of such cardiotoxicity. Further research remains needed to confirm these results.</div
Residential radon exposure during childhood and late health effects at adult age, in the CONSTANCES cohort
No full textInternational audienceRadon exposure is an established risk factor for lung cancer. Over the recent decades, a growing number of epidemiological studies have investigated other possible health effects of radon exposure, but results are inconsistent. No study has focused on radon exposure during childhood and health outcomes at adult age. The objectives of this project are: 1/ to carry out a reconstruction of residential radon exposure from birth until 2019 in a large cohort; 2/ to estimate the risks of cancers and other chronic diseases at adult age potentially associated with radon exposure and doses to specific organs, especially during childhood. Methods Individuals were selected from the French CONSTANCES population-based adults cohort recruited between 2012 - 2017. We included in our study participants with a completed residential history since birth, and who gave their consent to the use of data concerning them from the French national health system (SNDS). Radon exposure was reconstructed by linking residential histories with a map of indoor radon concentrations by municipalities. Incident case of chronic diseases were identified over the period 2010-2021. Cancer and non-cancer risks will be estimated using survival models. Results Initially 58,697 participants provided a residential history since birth, and 57,571 (46% males) of them were identified in the SNDS. Mean age at recruitment was 48.8 years. The median annual radon exposure during childhood (0 -15 years) was 59 Bq/m3. At this stage, incident cases for the following diseases have been identified: 104 lung, 406 colorectal, 1251 breast and 735 prostate cancers, 612 strokes, 291 heart failures, and 1703 coronary heart diseases. Discussion Statistical analyses adjusting for potential confounders will be undertaken to investigate the relationships between these diseases and radon exposure as well as related organ doses, especially during childhood but also considering the influence of doses at later ages
An experimental study of the thermal-hydraulics of a spent nuclear fuel pool under loss-of-cooling accident conditions. Part II: a first interpretation of the MIDI tests
No full textInternational audienceThis article provides a first interpretation of the MIDI tests that were conducted in the frame of the IRSN’s DENOPI project. A first-level phenomenological analysis is detailed here. It is shown that the actual phenomenology mostly complies with the one that was envisioned by the community right after the Fukushima-Daiichi nuclear accident. Next, the diverse modes of water vaporization that may come into play during a spent nuclear fuel pool loss-of-cooling accident are quantified for each achieved test, by means of a proposed analytical model of the vapor diffusion process taking place on top of the liquid pool free surface. Then, a so-called vaporization regimes map is reconstructed on the basis of the test data. This map allows predicting the most likely dominant vaporization mode, given the pool level and total heat power. At last, the obtained data is reduced through the form of a set of dimensionless correlations, involving some of the classical numbers in heat and mass transfers. In doing so, the free surface evaporation, degassing of dissolved gaseous species and bubbles release processes are all modeled by means of a simple mathematical formulation