[en] A research program regarding the consequences of a Reactivity Initiated Accident occurring in PWRs is at present time carried out at the Nuclear Protection and Safety Institute (IPSN). It is specially devoted to the study of the behaviour of highly irradiated fuel during fast power transients such as control rod ejections. The study progresses in two fronts: (1) an experimental program will be performed in the CABRI facility, (2) a computer code, namely SCANAIR, is being developed. After validation on the available tests, this code must allow a reliable extrapolation to the reactor case. Both SCANAIR code and CABRI program and first results are presented

[en] We propose a numerical method to calculate unsteady flows of Bingham fluids without any regularization of the constitutive law. The strategy is based on the combination of the characteristic/Galerkin method to cope with convection and of the Fortin-Glowinsky decomposition/coordination method to deal with the non-differentiable and non-linear terms that derive from the constitutive law. For the spatial discretization, we use low order finite elements, with, in particular, linear discretization for the velocity and the pressure, stabilized by a Brezzi-Pitkaeranta perturbation term. We illustrate this numerical strategy through two well-known problems, namely the hydrodynamic benchmark of the lid-driven cavity and the natural convection benchmark of the differentially heated cavity. For both, we assess our numerical scheme against previous publications, for Newtonian flow or in the creeping flow regime, and propose novel results in the case of Bingham fluid non-creeping flows

[en] SCANAIR is a computer code simulating Reactivity Initiated Accidents, such as control rod ejections, in PWRs. The structural mechanics module of the code is described: it uses 1^1/2 D modelling; the fuel deformation laws deal with thermal expansion, fuel swelling due to gaseous fission products, elastic, plastic strains, and a cracking strain simulating the fuel expansion induced by the presence of cracks. To solve the resulting highly non-linear equilibrium equations, a particular numerical method has been implemented, which gives good results. An example of application (calculation of a japanese NSRR experiment) is given. (author). 11 refs., 6 figs

No abstract available

[en] [1-¹⁴C]Glycolate metabolism was examined in leafy shoots of soybean plants (Glycine max (L.) Merr., var. Adepta). Only small amounts of ¹⁴C were incorporated into evolved carbon dioxide and glucidic compounds. Free and protein glycine was labelled but higher levels of radioactivity were found in free serine. Changes in the distribution of ¹⁴C with time showed that metabolic conversion glycollate → glycine → serine occurred very early and serine biosynthesis was more important in the shoot than in the leaves. Carbon dioxide labelling was always slight compared to serine labelling. These data suggest strong relations between glycollate and nitrogen metabolism

[en] A research program aimed at the modelling of the corium ex-vessel behaviour is in progress in IPSN (Institut de Protection et de Surete Nucleaire) since 1994, to assess the safety of future PWRs core catchers. The resulting code, named CROCO, is briefly presented here under its first version mainly devoted to the spreading phase. The numerical procedure has been verified on academic problems (namely dam break problems) exhibiting analytical solutions. Moreover, validation tests have been successfully performed against CORINE experiments using glycerol and non-eutectic Bismuth-Tin alloy simulant, KATS tests using high temperature simulants and the first real material VULCANO test. Both verification and validation tests show a satisfactory agreement between CROCO V1.0 computations and reference results. (orig.)