No abstract available

No abstract available

[en] A definition of the effective number density of lumped isotope chains is proposed and its physical interpretation discussed. As the first integral of the system of depletion equations, it is claimed to be the most consistent argument in terms of which the pseudo-isotopes effective group cross-sections should be tabulated. (author)

[en] Efforts exist to increase the burnup of fuel to be replaced (recharged) in the reactor. Extension of the recharging cycle makes the operation more economical. However, this calls for increasing the²³⁵U enrichment above 5%. This brings about problems in the various parts of the fuel cycle, which must be analyzed. The article outlines major barriers to reactor operation with fuel with enrichment over 5%, which must be addressed before this operating mode is approved. (author)

[en] An analysis has been completed which indicates that the consideration of spent fuel histories ('burnup credit') in the criticality design of spent fuel shipping casks could result in significant public risk benefits and cost savings in the transport of spent nuclear fuel. Capacities of casks could be increased considerably in some cases. These capacity increases result in lower public and occupational exposures to ionizing radiation due to the reduced number of shipments necessary to transport a given amount of fuel. Additional safety benefits result from reduced non-radiological risks to both public and occupational sectors. In addition, economic benefits result from lower in-transit shipping costs, reduced transportation fleet capital costs, and fewer cask handling requirements at both shipping and receiving facilities

[en] This report provides a technically based gas sampling frequency strategy for the High Burnup (HBU) Confirmatory Data Project. The evaluation of: 1) the types and magnitudes of gases that could be present in the project cask and, 2) the degradation mechanisms that could change gas compositions culminates in an adaptive gas sampling frequency strategy. This adaptive strategy is compared against the sampling frequency that has been developed based on operational considerations.

[en] The MOX fuel rods irradiated in the frame of Belgonucleaire's R and D program behaved satisfactorily and at least as well as UO₂ rods, up to burn-ups beyond 60000 MWd/t. From the results so far, one may conclude that additional data should be obtained to better predict and understand the fission gas release behavior of the present industrial MOX fuel pellets obtained by the MIMAS (Micronization of a Master blend) process. In particular, more data are needed on: high burn-up behavior of MIMAS fuel (above 40000 MWd/t); understanding of the influence of the fuel microstructure (including the type and characteristics of UO₂ powder) on the in-pile (mainly thermal) behavior; MOX fuel chemistry behavior at high burn-up, in relation to cycling, fission gas release and internal cladding corrosion; helium production and release in MOX rods and contribution to the internal pressure. The good understanding of the MOX behavior will not only allow improvements in the models used for its prediction and licensing but also in the fabrication process and the design characteristics. Core data will also be complemented by new basic experiments on representative MOX fuel from a neutronic point of view, needed to improve models and computational aids. 3 figs., 1 tab

No abstract available

[en] An attempt to formulate the multigroup burn-up equations of the fuel in nuclear reactors is presented. The introduction of the pseudoproducts and the collapsing of multigroup cross sections are considered too. Finally, a comparison of the derived formulae with those of the one-group case is given. (author)

[en] The numerous steps of the fuel cycle each have their own technicalities and for each of them safety evaluations have been conducted. However, the fuel cycle should be seen as a whole, i.e. as one single ''system'', not only as a sequence of steps