Search results for "nuclear experiment"
showing 10 items of 7971 documents
Infrared Spectroscopy of Ruthenium Tetroxide and High-resolution analysis of the v3 band
2015
International audience
On-line measurements of RuO$_4$ during a PWR severe accident
2015
International audience; After the Fukushima accident, it became essential to have a way to monitor in real time the evolution of a nuclear reactor during a severe accident, in order to react efficiently and minimize the industrial, ecological and health consequences of the accident. Among gaseous fission products, the tetroxide of ruthenium RuO$_4$ is of prime importance since it has a significant radiological impact. Ruthenium is a low volatile fission product but in case of the rupture of the lower head by the molten corium, the air entering into the vessel oxidizes Ru into gaseous RuO$_4$, which is not trapped by the Filtered Containment Venting Systems. To monitor the presence of RuO$_4…
Sensing ruthenium tetroxide Emissions : a spectroscopic study
2015
International audience; After the Fukushima accident, it became essential to have a way to monitor in real time the evolution of a nuclear reactor during a severe accident, in order to react efficiently and minimize the industrial, ecological and health consequences of the accident. Ruthenium is a low volatile fission product but in case of the rupture of the vessel lower head by the molten corium, the air entering into the vessel oxidizes Ru into a gaseous form RuO$_4$. To monitor the presence of RuO4 allows making a diagnosis of the core degradation and quantifying the potential release into the atmosphere. RuO$_4$ is of prime importance since it can have a significant radiological impact…
Etude de l'interface et de l’adhésion combustible-gaine dans les réacteurs à eau pressurisée
2017
National audience
3D simulation of a 500kg UO$_2$ melt in a cold crucible induction furnace
2017
International audience; In the field of severe accident studies for nuclear generation reactors 2, 3 and 4, the Plinius-2 project aims to build a new facility to perform experiments of corium interactions tests at a large scale until 2020. In this context, the project in collaboration with ECM Technology has to define and build a furnace able to melt up to 500 kg of simulated corium of various compositions (mix of UO$_2$ ,ZrO$_2$ , steel or concrete). The work presented in this article is a 3D dimensional simulation of a large load of UO$_2$ melts in a cold crucible, including turbulence modelling, induction heating and stirring. Solidification of the oxide near the cold wall of the crucibl…
Influence of the slag content on the hydration of blended cement
2015
International audience; Slag is increasingly used for replacing a part of clinker. The addition of slag modifies the hydration process and so the physico-chemical properties (such as porosity, transport properties) of cementitious materials. Indeed the evolution of the physico-chemical properties are determined by the hydration kinetics of the anhydrous phases and the composition of the hydrated phases. The hydration process of slag blended cement is still under investigation due to the complex interactions between clinker and slag. The aim of this work is to link the evolution of slag blended cement properties (such as bound water, chemical shrinkage, mineralogy, porosity) to the hydration…
Influence of boric acid on the hydration of magnesium phosphate cement at an early age
2015
International audience; Magnesium phosphate cements (MPCs) are receiving increasing attention because of their outstanding properties of fast setting and hardening, good volume stability and excellent bonding to old concrete structures. Their main area of application is thus rapid repair works, but they may also offer prospects for the stabilization / solidification of deleterious waste.The main constituents of MPCs are magnesium oxide (calcined, or hardburnt, magnesia) and a water-soluble acid phosphate, which is most often diammonium hydrogen phosphate (NH$_4$)$_2$HPO$_4$. To avoid the release of noxious gaseous ammonia during the hardening process, potassium dihydrogen phosphate (KH$_2$P…
Shape coexistence at the proton drip-line: First identification of excited states in 180Pb
2010
Excited states in the extremely neutron-deficient nucleus, 180Pb, have been identified for the first time using the JUROGAM II array in conjunction with the RITU recoil separator at the Accelerator Laboratory of the University of Jyvaskyla. This study lies at the limit of what is presently achievable with in-beam spectroscopy, with an estimated cross-section of only 10 nb for the 92Mo(90Zr,2n)180Pb reaction. A continuation of the trend observed in 182Pb and 184Pb is seen, where the prolate minimum continues to rise beyond the N=104 mid-shell with respect to the spherical ground state. Beyond mean-field calculations are in reasonable correspondence with the trends deduced from experiment.
Charge radius of the short-lived $^{68}$Ni and correlation with the dipole polarizability
2020
We present the first laser spectroscopic measurement of the neutron-rich nucleus $^{68}$Ni at the \mbox{$N=40$} subshell closure and extract its nuclear charge radius. Since this is the only short-lived isotope for which the dipole polarizability $\alpha_{\rm D}$ has been measured, the combination of these observables provides a benchmark for nuclear structure theory. We compare them to novel coupled-cluster calculations based on different chiral two- and three-nucleon interactions, for which a strong correlation between the charge radius and dipole polarizability is observed, similar to the stable nucleus $^{48}$Ca. Three-particle--three-hole correlations in coupled-cluster theory substant…
Decay and Fission Hindrance of Two- and Four-Quasiparticle K Isomers in 254Rf
2015
International audience; Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73) mu s have been discovered in the heavy (254)Rf nucleus. The observation of the shorter-lived isomer was made possible by a novel application of a digital data acquisition system. The isomers were interpreted as the K-pi = 8(-), nu(2)(7/2(+)[624]; 9/2(-)[734]) two-quasineutron and the K-pi = 16(+), 8(-)nu(2)(7/2(+)[624]; 9/2(-)[734] circle times 8(-)pi(2) (7/2(-)[514]; 9/2(+)[624]) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomer…