[en] A burnable poison rod is described which minimizes the displacement of the moderator coolant, thereby increasing the core moderation and burnable poison depletion. This is accomplished by arranging annular pellets of burnable poison in the rod and permitting reactor coolant to flow up through the annular inner bore. (author)

[en] The invention deals with a method to produce nuclear reactor fuel rods which contain the fuel in a cladding tube and in which an alkali metal is put in the space between the fuel and cladding for better heat transfer from the fuel to the cladding. The bubble-free filling-in of the alkali metal causes difficulties; the invention suggests to carry out the filling-in of fuel and alkali metal in a horizontal position of the cladding to rinse through the free space firstly with alkali metal, then to fill with fuel and then with the alkali metal taking account of necessary space for the fission gas volume. Equipment to carry out this process in which all operations are carried out in a vacuum box is described. (UWI)

[en] The heat exchange surfaces are located in revolution symmetry around an axis. The flow directions of the media are parallel to this axis. The object of the invention is to reduce the overall height and the consumption of material at unchanged heat transfer area. In application of the heat exchanger in an evaporation apparatus additional height will be saved by locating the expansion chamber centrally within the heat exchanger. The mentioned improvement is achieved by locating the heat exchange surfaces in an annular space around the axis. (O.S.)

No abstract available

[en] A Large Eddy Simulation (LES) is performed for the turbulent flow in an annular tube. The continuity and momentum equations are solved with the cylindrical coordinate. The common Smagorinsky model is employed and the nonslip conditions is applied on the solid wall. Some preliminary calculations are made with different combinations of mesh size in axial and azimuthal directions. A large number of grid number is required especially in the azimuthal direction, because the spanwise mesh becomes inevitably large in the outer region with the cylindrical coordinate. Three radius ratios, 0.1, 0.04 and 0.02, are calculated. The asymmetric velocity profile and the turbulent intensities are well reproduced by the present calculation. The vortical structures over both outer and inner rods are examined. A structure over the thicker inner is quite similar to the one over the plain surface. The streaks are found even over the thin rod of R1/R2=0.02. (orig.)

[en] The invention concerns an insulating structure for protecting a wall against a high temperature atmosphere. This structure has the advantage of being adaptable to the shape of the area to be protected, particularly in an annular space. It applies in particular where the wall to be protected is in an aerosol or liquid metal vapour atmosphere (sodium in particular) inside a fast neutron reactor vessel. To this end, the structure considered is built of numerous components joined together, each formed of two long angle bars, inter-slotted with reduced play between their parallel faces, these two angle bars themselves enclosing a soft metallic filling. The soft filling is formed of a stack of metal cloth, netting or knitting or stuffed with wool or chippings

[en] In 1991 Llibre and MacKay proved that if f is a 2-torus homeomorphism isotopic to identity and the rotation set of f has a non-empty interior then f has positive topological entropy. Here, we give a partial converse theorem. We show that the interior of the rotation set of a 2-torus C^1+α diffeomorphism isotopic to identity of positive topological entropy is not empty, under the additional hypothesis that f has a suitable finite covering that is topologically transitive. We also give examples that show that these hypotheses are necessary

No abstract available

[en] The transmission probabilities T⁰¹ and T⁰⁰ for annular cylindrical regions are computed. T⁰¹ is the probability that a neutron incident uniformly and isotropically on the outer surface of the annular region will be transmitted through the inner surface. T⁰⁰ is the probability that a neutron incident uniformly and isotropically on the outer surface of the annular region will be transmitted through the outer surface. Here T⁰⁰ has been divided into two integrals T⁰⁰¹ and T⁰⁰² (T⁰⁰ = T⁰⁰¹-T⁰⁰²). T⁰⁰¹ is related with the escape probability for solid cylinders and can be expressed in terms of polynomial for nonreentrant geometries (Raghav, 1981). Polynomials for nonreentrant geometries have been expressed in terms of the average chord length of the body. Average chord length in this case is R 4 VΣ/S, where V is the volume, S is the surface of the body and Σ is the total cross section in the region. For reentrant, i.e. annular cylindrical geometry, average chord length for each integral is evaluated here. T⁰¹ and T⁰⁰² are obtained by Bonalumi's analytical (P-L approximation) and by a similar polynomial mentioned above. The division of T⁰⁰ in two integrals T⁰⁰¹ and T⁰⁰² is found to give good results for T⁰⁰. (author)

No abstract available