[en] FRAGEMA has developed most types of inspection equipments to work on irradiated fuel assemblies and on single fuel rods during reactor outages with an efficiency compatible with the utilities operating priorities. In order to illustrate this statement, two specific examples of inspection equipments are shortly described: the on-site removable fuel rod assembly examination stand, and the fuel assembly multiple examination device. FRAGEMA has developed techniques for the identifiction of the leaking fuel rods in the fuel assembly and the tooling necessary to perform the replacement of the faulted element. These examples of methods, techniques and equipments described and the experience accumulated through their use allow FRAGEMA to qualify for offering the supply of the corresponding software, hardware or both whenever an accurate understanding of the fuel behaviour is necessary and whenever direct intervention on the assembly and associated components is necessary due to safety, operating or economical reasons

[en] The design of a prototype safeguards instrument for determining the number of irradiated fuel assemblies leaving an on-power refueled reactor is described. Design details include radiation detection techniques, data processing and display, unattended operation capabilities and data security methods. Development and operating history of the bundle counter is reported. (U.S.)

[en] It is well known that the oxidation of a defected fuel element by steam gives rise to an increase in O/U ratio with a consequent lowering of the incipient melting temperature. Concurrently, the hyperstoichiometry reduces the thermal conductivity thereby raising the centerline fuel pellet temperature for a fixed linear power. The development of fission products soluble in the UO₂ phase or, more important, the deliberate introduction of additive oxides in advanced CANDU fuel bundle designs further affects and generally lowers the incipient melting temperature. For these reasons, the modeling of the molten (hyperstoichiometric) UO₂ phase containing several solute oxides (ZrO₂, Ln₂O₃ and AnO₂) is advancing in the expectation of developing a moving boundary heat and mass transfer model aimed at better defining the limits of safe operating practice as burnup advances. The paper describes how the molten phase stability model is constructed. The redistribution of components across the solid-liquid interface that attends the onset of melting of a non-stoichiometric UO₂ containing several solutes will be discussed. The issues of how to introduce boundary conditions into heat transfer calculations consistent with the requirements of the Phase Rule will be addressed. The Stefan problem of a moving boundary associated with the solid/liquid interface sets this treatment apart from conventional heat and mass transfer problems. (author)

No abstract available

[en] The service range covers technical and shipment implications in the transport of fresh and spent fuel elements. The paper discusses the transport volume, the number of transports required and the transport cost resulting for the NPPs. (DG)

[en] The loading pond for loading and unloading a transport container for the fuel element of a PWR has a separate area. In this area, the decontamination of the surface of the transport container by means of jets and flushing liquid can be carried out. The part basin equipped for cooling and decontamination is devided by means of a flexible wall made of plastic plates and a boron insert between the transport container lid and a surrounding edge in the loading basin. (DG)

[en] A core for a nuclear reactor of high specific power output is provided with an arrangement of fuel bundles in which at least some bundles incorporate tubular pencil elements mounted between end plates, having coolant flow restricting means secured to the bundle to control the balance of coolant flow between external flow along the outsides of the pencils and internal coolant flow within the hollow pencils. 4 claims, 6 drawing figures

[en] To model thermal mechanical bundle deformation behaviour under high temperature conditions, several factors need to be considered. These are the sources of loads, deformation mechanisms, interactions within bundle components, bundle and pressure tube (PT) interaction, and boundary constraints on the fuel bundles under in-reactor conditions. This paper describes the modelling of the following three processes: Bundle slumping due to high temperature creep-sag of individual elements and endplates; Differential element expansion and fuel element bowing; and, Bundle distortion under axial loads. To model these processes, a number of key mechanisms for bundle deformation must be considered, which include: 1) Interaction of fuel elements in a bundle with their neighbours, 2) Endplate deformation, 3) Fuel elements lateral deformation under various loads and mechanisms, 4) Interaction within a fuel element, 5) Material property change at high temperatures, 6) Transient response of a bundle, and 7) Bundle configuration change. This paper summarises the new models needed for the mechanistic modelling of the key mechanisms mentioned above and provides an example to show how an endplate plasticity model is developed with results. (author)

[en] The neutron radiography installations of Saclay using collimated neutron sources from reactors for non-destructive testing of nuclear fuels and components of the nuclear industry are described. The first installation in a pool for experimental devices before, during and after irradiation near the core allowing imaging of highly radioactive materials. The second, a dry installation, is used for monitoring active fuel elements. The last is used for inactive materials coming from industry

[en] It is stated that one type of fuel element assembly used in a sdoium cooled fast reactor comprises a hexagonal bundle of slender fuel elements enclosed by a casing, termed a 'wrapper'. The fuel elements are each helically wrapped with wire to brace them apart and prevent bowing and vibration and to ensure efficient cooling. The width of the gap between the fuel bundles and the 'wrapper' is mainly governed by the height of the wire wraps of the outer fuel elements, and the edge channels resulting from the wire wraps of the same size tend to cause overcoolinf of the outer elements. Allowance may be necessary for differential growth under irradiation. The transverse growth of the fuel bundle is greater than between the ends of the bundle and is greater than the 'wrapper'. The resuling bundle to 'wrapper' gap which must be allowed involves a coolant flow path that is much less restrictive than that over the inner elements of the bundle, so that the outer elements are greatly overcooled and the mean outlet temperature of coolant from the assembly is reduced. Furthermore the fuel elements can vibrate in the clearance and suffer damage. An expedient that has been adopted to reduce overcooling of the outer elements is to insert a 'filler' in the form of a ribbed plate within the gap, thereby reducing the cross-sectional area of the coolant flow path. In the arrangement described at least one collapsible filler is located within the gap, the filler being longitudinally convoluted to follow the transverse contour of the bundle. This substantially eliminates vibration of the bundle and restricts the cross-sectional area of the gap. The filler can collapse during irradiation to accommodate differential irradiation growth of bundle and 'wrapper'. A preferred construction of collapsible filler comprises two spaced membranes forming a longitudinally convoluted envelope, one membrane being slit and deformed to provide leaf springs that react on the wrapper. (U.K.)