Institute for Radiation Protection and Nuclear Safety (IRSN)
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The Plutonium Temperature Effect Program
No full textInternational audienceVarious theoretical studies have shown that highly diluted plutonium solutions could have a positive temperature effect, but up to now, no experimental program has confirmed this effect. The French Plutonium Temperature Effect Experimental Program (or PU+ in short) aims to effectively show that such a positive temperature effect exists for diluted plutonium solutions. The PU+ experiments were conducted in the “Apparatus B” facility at the CEA VALDUC research center in France. It involved several sub-critical approach-type experiments using plutonium nitrate solutions with concentrations of 14.3, 15, and 20 g/L at temperatures ranging from 20 to 40 °C. Fourteen (five at 20 g/L, four at 15 g/L, and five at 14.3 g/L) phase I experiments (consisting of independent sub-critical approaches) were performed between 2006 and 2007. The impact of the uncertainties on solution acidity and plutonium concentration made it difficult to demonstrate the positive temperature effect, requiring an additional phase II experiment (with a unique plutonium solution) from 22 to 28 °C that was performed in July 2007. This phase II experiment has shown the existence of a positive temperature effect of ~+5.17 pcm/°C (from 22 to 28 °C for a plutonium concentration of 14.3 g/L). It has recently been possible to confirm the results of this program with MORET 5 calculations by generating thermal scattering data S(α,β) at the correct experimental temperatures. This paper finally presents a fully documented experimental program highlighting the Plutonium Temperature Effect theoretically described in the literature. Its high level of precision and its “one-step” approach to criticality allowed it to show a significant positive temperature effect for a rather small variation of temperature (+6 °C). The order of magnitude of the effect was confirmed with Monte Carlo calculations using thermal scattering data for hydrogen in the solution produced by IRSN for the purpose of the comparison
Influence of ambient light on the radiation-induced attenuation of germanosilicate optical fibers in the visible and near-infrared domains
No full textInternational audienceWe investigated the influence of the ambient light on the Radiation-Induced Attenuation (RIA) of Ge-doped optical fibers measured at the telecommunication wavelengths when exposed to a 60 Co source, and in the visible and Near-InfraRed (NIR) domains when exposed to X-rays. From our results, it is possible to observe that this class of optical fibers are sensitive to the ambient light. Indeed, in all cases, their RIA value changes depending on the illumination conditions. In particular, the γ-ray irradiations revealed jumps in the measured RIA when changing the lamp of the irradiation chamber, whereas the X-ray irradiations reported that the relative photobleaching effect caused by the ambient light increases with the wavelength, up to ~1300 nm. The spectral study revealed no direct correlation between the absorption bands of the known Ge-related point defects and the external photobleaching phenomenon
Reflections on the future developments of research in retrospective physical dosimetry
No full textInternational audienceElectron paramagnetic resonance, thermoluminescence, and optically stimulated luminescence, with biological tissues and inert materials are well established physical methods for retrospective dosimetry in acute accidental exposures. The objective of this article is to provide a view of the questions still open, the current challenges and the needed solutions. As research on emergency response methods is encountering increasing difficulties in terms of financial and human resources in many countries, it is essential to identify the research priorities and pay attention to cost-effective research paths. The intention of the paper is to stimulate discussion in the scientific community and to encourage collaboration among laboratories toward goals that address the real needs in retrospective dosimetry for acute exposures
Comportement viscoplastique d’un polycristal : modélisation micromécanique et application au durcissement d’un acier irradié
No full textInternational audienceLe contexte de ce travail est relatif au vieillissement de la cuve dans les réacteurs nucléaires à eau pressurisée. Durant sa vie en réacteur, la cuve reçoit une dose d'irradiation neutronique qui induit des défauts à l'échelle atomique. Ces défauts cristallins ont tendance à modifier le comportement mécanique de l'acier de cuve, avec un durcissement et une fragilisation. L'objectif de ce travail est de proposer un nouveau modèle de comportement viscoplastique à l'échelle du polycristal, capable d'utiliser une loi de comportement cristalline adaptée à un acier de cuve irradié. Tout d'abord, une loi de plasticité cristalline, à base physique et dédiée au comportement élasto-viscoplastique des aciers de cuve irradiés (basée sur [1]), a été implémentée dans un code de calcul à base de FFT appelé CraFT (présenté dans [2]). Ensuite, une campagne de simulations numériques en champs complets a été menée, avec le code CraFT, sur des microstructure polycristallines. Les résultats numériques obtenus ont été comparés avec des résultats expérimentaux existants. Enfin, la partie relative à l'homogénéisation a été abordée, sur la base de l'approche "Fully Optimized Second-Order" [3].[1] Monnet G., Vincent L., Gélébart L., "Multiscale modeling of crystal plasticity in Reactor Pressure Vessel steels: Prediction of irradiation hardening", Journal of Nuclear Materials 514 (2019) 128-138.[2] Suquet P., Moulinec H., Castelnau O., Montagnat M., Lahellec N., Grennerat F., Duval P. et Brenner R., "Multi-scale modeling of the mechanical behavior of polycrystalline ice under transient creep". Procedia IUTAM (2012) 76-90.[3] Ponte Castañeda P., "Fully optimized second-order variational estimates for the macroscopic response and field statistics in viscoplastic crystalline composites", Proc. R. Soc. A 471: 20150665 (2015)
Dosimetric evaluation of the benefit of deep inspiration breath hold (DIBH) for locoregional irradiation of right breast cancer with volumetric modulated arctherapy (VMAT)
No full textInternational audienceIntroduction:Right-lateralized cardiac substructures can be substantially exposed during right breastcancer (R-BC) radiotherapy. The cardiac benefit of deep inspiration breath hold (DIBH) is established incombination with volumetric modulated arctherapy (VMAT) for left breast cancer with regional nodeirradiation but is unknown for R-BC. This study evaluated the dosimetric benefit of DIBH for locore-gional irradiation of R-BC with VMAT.Material and Methods:All patients treated for R-BC with adjuvant locoregional DIBH-VMAT in theDepartment of Radiation Oncology of the Institut Curie (Paris, France) until December 2022 wereincluded, corresponding to 15 patients. FB- and DIBH-VMAT plans were compared both for a normo-fractionated regimen (50Gy/25fx) used for treatment and a replanned hypofractionated regimen(40Gy/15fx). Dose to the heart, cardiac substructures (sinoatrial node (SAN), atrio-ventricular node(AVN), right coronary artery, left anterior descending coronary artery, left ventricle), ipsilateral lung andliver were retrieved and compared.Results: Mean heart dose (MHD) was 3.33 Gy with FB vs. 3.10 Gy with DIBH on normofractionated plans (p¼0.489), and 2.58 Gy with FB vs. 2.41 Gy with DIBH on hypofractionated plan (p¼0.489). Thebenefit of DIBH was not significant for any cardiac substructure. The most exposed cardiac substruc-ture were the SAN (mean dose of 6.62 Gy for FB- and 5.64 Gy for DIBH-VMAT on normofractionatedplans) and the RCA (mean dose of 4.21 Gy for FB- and 4.06 Gy for DIBH-VMAT on normofractionatedplans). The maximum benefit was observed for the RCA with a median individual dose reduction of0.84 Gy on normofractionated plans (p¼0.599). No significant dosimetric difference were observed forright lung. Liver mean dose was significantly lower with DIBH with median values decreasing from2.54 Gy to 0.87 Gy (p¼0.01).Conclusion:Adding DIBH to efficient cardiac-sparing radiotherapy techniques, such as VMAT, is notjustified in the general case for locoregional R-BC irradiation. Specific R-BC patient subpopulationswho could benefit from additional DIBH combination with locoregional VMAT are yet to be identified
Development of an accurate method for the on-line noble gases (Xe, Kr) concentrations measurements and their trapping by MOF in dynamic breakthrough experiments in nuclear context
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Feasibility study of using earbuds and wireless headphones for retrospective dosimetry
No full textInternational audienceLuminescence dosimetry could be an essential tool in retrospective dosimetry for assessing an absorbed dose after a radiological overexposure. Mobile phone components could be useful proxies for measuring the amount of dose an individual has received. Different research groups have extensive experience in characterising different elements of mobile phones (i.e. electronic components, display or touch screen glass) for physical retrospective dosimetry. However, so far these techniques are frequently destructive and alternative materials need to be sought for further research on cheaper electronic devices. Earbuds and wireless headphones have become quite popular and are often carried closely to the body or may be found in personal bags. These low-budget electronic devices might potentially be better accepted by the general population compared to high-price objects, such as an expensive smartphone. On the circuit boards of these items, electronic components (SMDs) were found. The results of a dose recovery test after x-ray irradiation using a standardized luminescence measurement protocol developed for resistors extracted from mobile phones are presented. The estimated doses from the sampled SMDs were overestimated by a factor up to 2.1 following this initial experiment. Further investigations showed that the signal stability of some SMDs was significantly different from that of mobile phone resistors. The use of a fading correction specific to these SMDs improved the dose reconstruction results. Generally, these low-budget electronic devices are potentially suitable for dose assessment and an alternative fortuitous retrospective dosimeter
Influence of the water content on the complex conductivity of bentonite
No full textInternational audienceCompacted bentonite is considered as a potential buffer material for deep geological disposals of high-level nuclear wastes. Methodologies to non-intrusively monitor the water content of such sealing materials are important in the context of the safety of these storage facilities and for various engineering applications as well. Induced polarization is a non-intrusive geophysical method sensitive to the water content of porous media. We investigated the complex conductivity spectra of 69 samples made of 2 distinct MX80 bentonites, one in the form of powder from crushed pellets (Type I) and the other in the form of a granulated bentonite mixture (GBM, type II). The samples are prepared at different compaction states and saturations. The pore water conductivity of the porous samples is estimated to be ~2.5 S m− 1 (25 ◦C) by two different methods. The complex conductivity spectra were obtained at room temperature (25 ± 2 ◦C) in the frequency range 1 Hz-45 kHz. In-phase and quadrature conductivities reflect conduction (electromigration) and polarization processes, respectively. At a given frequency, both the in-phase and quadrature conductivities increase with the water content along a trend that is independent of the compaction state. An induced polarization model based on the dynamic Stern layer model is used to explain these results. The first Archie’s exponent m is inferred from the formation factor F using the in-phase conductivity data versus the pore water conductivity data at different salinities (NaCl, 25 ◦C). The dynamic Stern layer model applied to polarization correctly predicts the dependence of the in-phase conductivity, quadrature conductivity, and normalized chargeability with the water content and the Cation Exchange Capacity (CEC). This petrophysical work can easily be applied to time-domain induced polarization data collected in field conditions to monitor hydraulic barriers
Assesment of covariance processing with GAIA for nuclear data uncertainty propagation
No full textInternational audienceNuclear data uncertainties are provided as covariance matrices in standard nuclear data libraries and propagating them trough neutronics simulations helps quantify the associated uncertainties on the final result. However, processing these matrices often poses challenges. Currently, the IRSN nuclear data processing code GAIA processes cross sections via several modules like DOP (Reconstruction and Doppler), TOP (URR), and SAB (TSL), but lacks the capability to process covariances. This paper introduces a new module named COP (COvariance Processing). The COP module aims to process covariance matrices comprehensively, including cross section (File 33), angular distribution (File 34), and resonance parameters (File 32). The preliminary results obtained using the COP module of GAIA in comparison with the ERRORR module of NJOY and PUFF module of AMPX are presented
OECD/NEA-ARC-F project: Unit1 and Unit3 hydrogen explosion analysis Lessons learned and perspectives
No full textInternational audienceOn March 11, 2011, the earthquake of magnitude 9.0 and subsequent tsunami led to a multi-unit severe accident at the Fukushima Daiichi Nuclear Power Station (Daiichi). As a result of high temperature oxidation of the core materials a large amount of hydrogen had been produced and released from the N2 inerted containments, and in case of Unit 4 -due to transfer through a common ventilation system from Unit 3 to Unit 4, leading to explosions that damaged the reactor buildings of three reactor units (Units 1, 3 and 4). Even though efficient hydrogen counter measures have been considered by the inertisation of the containment atmosphere with N2, the explosions outside the containments in the reactor buildings could not be prevented, as these buildings were not provided with mitigation measures. This underlined the challenges caused by hydrogen and other combustible gas accumulation to the building's integrity in general and the need to further improve the hydrogen/combustible gas mitigation measures within the containment (if nothing was implemented so far) as well as in surrounding reactor building. Under the OECD/NEA/BSAF and BSAF2 programs, analyses of the Fukushima accident were performed using various severe accident tools with the goal of improving understanding of the accident progression and providing relevant information on the condition of the reactor buildings and containment. As follow up of the BSAF2 project, the ARC-F project aims to address the remaining issues, as hydrogen explosion analysis and its consequences. For this purpose, dedicated Task-group, composed of representatives from IRSN, CEA (France), IBRAE (Russia), NRA and JAEA (JAPAN), has been charged with providing information on the analysis of hydrogen transport and combustion. This paper summarizes the results and lessons learned from the analyses performed by the Task-group members for gas explosions that occurred in Unit 1 and Unit 3