Application of the feedback model for the history base using DRAGON

We present here a new model for cross sections parametrization. This model allows us to generate a coherent set of the nuclear cross sections for a CANDU cell as a function of the concentration of the various isotopes in the core, moderator and coolant density and temperatures (fuel, coolant and moderator). Simple physical considerations lead us to determine the law of variations of the mean cross sections as functions of these parameters. They permit the computation of the cross sections for each state of the reactor core, using a unique library for each type of cell and containing the nuclear cross sections computed at rated (nominal) conditions and feedback coefficients. (author). 3 refs