[en] The production of muons in atmospheric showers initiated by gamma rays with energies below 10 TeV is calculated using the Monte Carlo code FLUKA. The simulations as well as various general properties of the muons reaching sea level and of their ancestors in the cascade are discussed

[en] Studies on the highly improbable serious accidents which might occur in reactors (e.g. core meltdown) are currently carried out by the designers and operators of nuclear power plants. The coordinated research and development actions undertaken in France, which aim at better knowing these phenomena, are dealt with in this issue, some of which might lead to practical applications in the current of future nuclear power plants. This dossier comprises 14 papers dealing with: the safety of water reactors and the severe accidents; the point of view of Electricite de France (EdF); the consideration of severe accidents in the design of the European pressurized water reactor (EPR); the probabilistic safety studies of level 2; the source term: the confinement of fission products; a huge international program - Phebus PF; the possibilities of corium keeping inside the vessel; the corium recovery outside the vessel; the hydrogen risk; the steam explosion risk; MAEVA, a scale model at Civaux for confinement evaluation in accidental situation; the exploitation of R and D by the direction of studies and researches of EdF; the study of alternative solutions for the management of severe accidents in PWRs (the goals of the CEA program 'innovation-future reactors'); the contribution of international collaboration programs. (J.S.)

[en] Creep mechanisms for metals, ceramics and rocks, effect of pressure and temperature on deformation processes are considered. The role of crystal defects is analysed, different models of creep are described. Deformation mechanisms maps for different materials are presented

[en] The FLUKA Monte Carlo program is used to calculate the effects of hadroproduction by primary gamma rays incident upon the Earth's atmosphere; for the results presented in this paper, only primary angles at 0^o from zenith are considered. The FLUKA code is believed to be quite accurate in reproducing experimental photon hadroproduction data in the 1 GeV to 10 TeV energy range studied. The charged pions which are so produced can decay to muons with sufficient energy to reach ground level. The number of these muons and their radial and energy distribution are studied for incident gamma ray energies from 1 GeV to 10 TeV. The number of these muons is not negligible; they can, in certain circumstances, be used to study potential sources of gamma rays such as gamma ray bursts. It is found, for example, that a 10 TeV incident primary gamma ray produces, on average, 3.4 muons which reach ground level; the gamma ray energy which produces the maximum number of muons at ground level depends on the spectral index of the primary gamma spectrum, a constant which describes how the primary gamma flux rises with decreasing primary energy. For example, for a differential spectral index of 2.7, there is a broad maximum number of muons coming from ∼30 GeV primary gamma ray energy

[en] The following tests were carried out on high porosity (40 to 70%) sintered nickel: tensile tests, compression tests, diametral crushing tests, using strain gauges and extensometers. Results were obtained on the relationship elastic properties - porosity, Poisson coefficient in relation to deformation, variations of yield strength, and breaking stress. these various properties were also studied in relation to the sintering methods and the properties of the powders used

[en] Radiation effects on metals or alloys used in fast reactor core components are examined in the papers presented at this conference, the accent being put on swelling and irradiation creep of steels and nickel alloys

[en] The temperature and stress dependence on the secondary creep rate of the Cd+26.5Zn eutectoid in the superplastic domain was studied in constant-stress compression creep. Experiments were performed in the following ranges of temperature, stress and grain size: 170C< T<227C, 112, 1<10μm. In all cases secondary creep was established after a strain approximately equal to 4%. For temperatures higher than 200C all the techniques yielded the same value for m (m=0.49+-0.03) in the whole investigated range of stresses. For T=170C a lower value of m was found (m=0.33). The activation energy was determined and found equal to 25Kcal/mol. Micrographic examinations were performed on sectioned samples at several stages of deformation. The grain size was found to be identical for various conditions of temperature and stress and very stable with respect to deformation. The experimental results of the creep tests are discussed in relation with the microstructural aspects

[en] In this conference are presented papers dealing with swelling of metals and alloys, (and specially ferritic steels), structural evolution and stability under irradiation, modifications of mechanical properties, consequences on the behaviour of fuel elements and the optimization of materials selection, and irradiation creep

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