Quentin Auzoux | Commissariat à l'Energie Atomique (CEA) (original) (raw)

Papers by Quentin Auzoux

Journal of Nuclear Materials, 2014

calculations showed these half thickness blisters should grow in only a few days in PWR condition... more calculations showed these half thickness blisters should grow in only a few days in PWR conditions. Eventually, the Diffusion Equilibrium Threshold (DET) was defined as a criterion that limits the blister growth, and emphasizes that the hysteresis in the hydrogen solubility limit in zirconium must be taken into account to model hydrogen thermo-diffusion in zirconium alloys.

Journal of Nuclear Materials, 2014

This study is focused on the impact of rapid Reactivity Initiated Accident (RIA) representative s... more This study is focused on the impact of rapid Reactivity Initiated Accident (RIA) representative strain rates (about 1 s -1 [1]) on the behavior and fracture of unirradiated Cold Work Stress Relieved Zircaloy-4 cladding tubes. Uniaxial ring tests (HT) and plane strain ring tensile tests (PST) were performed in the 0.1 to 10 s -1 strain rate range, at 25 °C. The local temperature increase due to plastic dissipation was measured with a high-speed infrared camera.

Procedia Materials Science, 2014

The influence of hydride blister on cold worked stress relieved Zircaloy-4 cladding tubes fractur... more The influence of hydride blister on cold worked stress relieved Zircaloy-4 cladding tubes fracture toughness at room temperature was studied using hoop tensile tests and plane strain tensile tests. The experimental macroscopic fracture stress and strain values and an elastic-plastic finite element analysis of the mechanical tests with the CAST3M code were used to calculate the J-integral and estimate the fracture toughness for several blister depths from 120 to 240 μm.

Materials Science and Engineering: A, 2014

Two optimizations of the Expansion Due to Compression (EDC) test, which induces a near uniaxial l... more Two optimizations of the Expansion Due to Compression (EDC) test, which induces a near uniaxial loading, were proposed and developed to reach higher biaxiality ratios (ratio between mechanical quantities in axial and in circumferential direction). The first optimization, named HB-EDC for High-Biaxiality EDC, allowed to reach transverse plane strain conditions. The second optimization, named VHB-EDC for Very High Biaxiality EDC, was designed to reach higher loading biaxiality ratios. These optimized EDC tests were performed * at 25 • C, 350 • C and 480 • C on unirradiated hydrided Cold Worked Stress Relieved (CWSR) Zircaloy-4 samples. First, samples unhydrided or uniformly hydrided up to 1130 wppm were tested. Secondly, samples hydrided at 310 wppm with a hydride blister were tested. A large ductility reduction is induced by the increase in biaxiality level in absence of a hydride blister or with small blisters (<50 µm deep). The fracture strain decreases quickly with the blister depth at 25 • C, but more progressively at higher temperature. An equation that quantifies the fracture strain reduction with the blister depth is proposed. Eventually, one of the tests developed in the present study, the HB-EDC test, was proven to be a good compromise between the test complexity and the stress state reached. It is a good candidate to characterize the mechanical behaviour of irradiated cladding.

Journal of Nuclear Materials, 2013

This study is focused on the hydrogen-induced dimensional change or "growth" of zirconium alloys.... more This study is focused on the hydrogen-induced dimensional change or "growth" of zirconium alloys. Dilatometric experiments were performed on samples taken from a unirradiated Zircaloy-4 (Zy-4) fuel cladding loaded up to 940 wppm hydrogen. Samples were taken in the axial direction of the tube or at 45 • to the axial and transverse directions. The results indicate that hydrogen-induced expansion is anisotropic. Theoretical expansion calculations were carried out considering the partition of hydrogen in solid solution and hydrides together with the material crystallographic texture. Hydride-induced expansion was calculated using two different assumptions reported in the literature, namely "Pure Lattice Transformation Strains" (PLTS) and "Pure Shear Transformation Strains" (PSTS). Calculations based * on the PSTS hypothesis satisfactorily predicted the anisotropy observed in the dilatometric curve. Under this assumption, the contribution of hydrides to the axial growth of high-burnup Zy-4 cladding is limited to 12%. This study shows it is important to consider the respective contribution of hydrogen in both states, together with the material crystallographic texture, to understand the dilatometric behavior of hydrided zirconium alloys.

Journal of Nuclear Materials, 2014

calculations showed these half thickness blisters should grow in only a few days in PWR condition... more calculations showed these half thickness blisters should grow in only a few days in PWR conditions. Eventually, the Diffusion Equilibrium Threshold (DET) was defined as a criterion that limits the blister growth, and emphasizes that the hysteresis in the hydrogen solubility limit in zirconium must be taken into account to model hydrogen thermo-diffusion in zirconium alloys.

Polymer, 2003

The influence of pre-shearing on the crystallisation of a conventional Ziegler -Natta catalysed a... more The influence of pre-shearing on the crystallisation of a conventional Ziegler -Natta catalysed and a metallocene catalysed linear lowdensity polyethylene (LLDPE) samples was studied by a rheo-optical method, coupling light scattering and steady shear flow. Experiments were performed on a high-temperature shearing cell, with a pair of parallel quartz plate windows. The polymers were sheared at a melt temperature T s (ranging from 190 to 150 8C) at a constant shear rate ð _ gÞ for a duration time t s . After cessation of shear (at a given deformation of _ gt s unit), the sample was maintained at the selected melt temperature for a waiting time t w (ranging from 0 to 10 min) before it was cooled down to 90 8C. Small-angle light scattering (SALS) patterns were recorded during the whole process. It was shown that the pre-shear history thus investigated has no measurable influence on crystallisation of the linear metallocene LLDPE. For the Ziegler -Natta sample, the influence of pre-shear on its crystallisation is larger when the shear rate ð _ gÞ and strain ð _ gt s Þ are large, the waiting time t w is smaller or the temperature T s is lower. The consequence of shear is giving ellipsoidally deformed spherulites, elongated in the flow gradient direction, which originate from oriented nuclei. Crystallisation, following flow in particular, is shown to be a very good probe of chain orientation and it turns out to be more sensitive than classical linear rheological methods. It can detect if the sheared sample is in a steady state or if all chains have relaxed after a flow. For example, it is surprisingly shown that chain orientation for the Ziegler -Natta sample requires a large amount of shear deformation, in the order of 1000 strain units, to reach a steady state. q

Journal of Nuclear Materials, 2014

calculations showed these half thickness blisters should grow in only a few days in PWR condition... more calculations showed these half thickness blisters should grow in only a few days in PWR conditions. Eventually, the Diffusion Equilibrium Threshold (DET) was defined as a criterion that limits the blister growth, and emphasizes that the hysteresis in the hydrogen solubility limit in zirconium must be taken into account to model hydrogen thermo-diffusion in zirconium alloys.

Journal of Nuclear Materials, 2014

This study is focused on the impact of rapid Reactivity Initiated Accident (RIA) representative s... more This study is focused on the impact of rapid Reactivity Initiated Accident (RIA) representative strain rates (about 1 s -1 [1]) on the behavior and fracture of unirradiated Cold Work Stress Relieved Zircaloy-4 cladding tubes. Uniaxial ring tests (HT) and plane strain ring tensile tests (PST) were performed in the 0.1 to 10 s -1 strain rate range, at 25 °C. The local temperature increase due to plastic dissipation was measured with a high-speed infrared camera.

Procedia Materials Science, 2014

The influence of hydride blister on cold worked stress relieved Zircaloy-4 cladding tubes fractur... more The influence of hydride blister on cold worked stress relieved Zircaloy-4 cladding tubes fracture toughness at room temperature was studied using hoop tensile tests and plane strain tensile tests. The experimental macroscopic fracture stress and strain values and an elastic-plastic finite element analysis of the mechanical tests with the CAST3M code were used to calculate the J-integral and estimate the fracture toughness for several blister depths from 120 to 240 μm.

Materials Science and Engineering: A, 2014

Two optimizations of the Expansion Due to Compression (EDC) test, which induces a near uniaxial l... more Two optimizations of the Expansion Due to Compression (EDC) test, which induces a near uniaxial loading, were proposed and developed to reach higher biaxiality ratios (ratio between mechanical quantities in axial and in circumferential direction). The first optimization, named HB-EDC for High-Biaxiality EDC, allowed to reach transverse plane strain conditions. The second optimization, named VHB-EDC for Very High Biaxiality EDC, was designed to reach higher loading biaxiality ratios. These optimized EDC tests were performed * at 25 • C, 350 • C and 480 • C on unirradiated hydrided Cold Worked Stress Relieved (CWSR) Zircaloy-4 samples. First, samples unhydrided or uniformly hydrided up to 1130 wppm were tested. Secondly, samples hydrided at 310 wppm with a hydride blister were tested. A large ductility reduction is induced by the increase in biaxiality level in absence of a hydride blister or with small blisters (<50 µm deep). The fracture strain decreases quickly with the blister depth at 25 • C, but more progressively at higher temperature. An equation that quantifies the fracture strain reduction with the blister depth is proposed. Eventually, one of the tests developed in the present study, the HB-EDC test, was proven to be a good compromise between the test complexity and the stress state reached. It is a good candidate to characterize the mechanical behaviour of irradiated cladding.

Journal of Nuclear Materials, 2013

This study is focused on the hydrogen-induced dimensional change or "growth" of zirconium alloys.... more This study is focused on the hydrogen-induced dimensional change or "growth" of zirconium alloys. Dilatometric experiments were performed on samples taken from a unirradiated Zircaloy-4 (Zy-4) fuel cladding loaded up to 940 wppm hydrogen. Samples were taken in the axial direction of the tube or at 45 • to the axial and transverse directions. The results indicate that hydrogen-induced expansion is anisotropic. Theoretical expansion calculations were carried out considering the partition of hydrogen in solid solution and hydrides together with the material crystallographic texture. Hydride-induced expansion was calculated using two different assumptions reported in the literature, namely "Pure Lattice Transformation Strains" (PLTS) and "Pure Shear Transformation Strains" (PSTS). Calculations based * on the PSTS hypothesis satisfactorily predicted the anisotropy observed in the dilatometric curve. Under this assumption, the contribution of hydrides to the axial growth of high-burnup Zy-4 cladding is limited to 12%. This study shows it is important to consider the respective contribution of hydrogen in both states, together with the material crystallographic texture, to understand the dilatometric behavior of hydrided zirconium alloys.

Journal of Nuclear Materials, 2014

calculations showed these half thickness blisters should grow in only a few days in PWR condition... more calculations showed these half thickness blisters should grow in only a few days in PWR conditions. Eventually, the Diffusion Equilibrium Threshold (DET) was defined as a criterion that limits the blister growth, and emphasizes that the hysteresis in the hydrogen solubility limit in zirconium must be taken into account to model hydrogen thermo-diffusion in zirconium alloys.

Polymer, 2003

The influence of pre-shearing on the crystallisation of a conventional Ziegler -Natta catalysed a... more The influence of pre-shearing on the crystallisation of a conventional Ziegler -Natta catalysed and a metallocene catalysed linear lowdensity polyethylene (LLDPE) samples was studied by a rheo-optical method, coupling light scattering and steady shear flow. Experiments were performed on a high-temperature shearing cell, with a pair of parallel quartz plate windows. The polymers were sheared at a melt temperature T s (ranging from 190 to 150 8C) at a constant shear rate ð _ gÞ for a duration time t s . After cessation of shear (at a given deformation of _ gt s unit), the sample was maintained at the selected melt temperature for a waiting time t w (ranging from 0 to 10 min) before it was cooled down to 90 8C. Small-angle light scattering (SALS) patterns were recorded during the whole process. It was shown that the pre-shear history thus investigated has no measurable influence on crystallisation of the linear metallocene LLDPE. For the Ziegler -Natta sample, the influence of pre-shear on its crystallisation is larger when the shear rate ð _ gÞ and strain ð _ gt s Þ are large, the waiting time t w is smaller or the temperature T s is lower. The consequence of shear is giving ellipsoidally deformed spherulites, elongated in the flow gradient direction, which originate from oriented nuclei. Crystallisation, following flow in particular, is shown to be a very good probe of chain orientation and it turns out to be more sensitive than classical linear rheological methods. It can detect if the sheared sample is in a steady state or if all chains have relaxed after a flow. For example, it is surprisingly shown that chain orientation for the Ziegler -Natta sample requires a large amount of shear deformation, in the order of 1000 strain units, to reach a steady state. q