On the calculation of the flux fine distribution in PWR fuel assemblies by the response matrix method

We develop a procedure for the pin wise group flux distribution calculation in a typical PWR fuel assembly, based on the response matrix method. Using a variational procedure and standard perturbation theory as well, we obtain the response matrices for the heterogeneous fuel assembly. A first-order approximation for the perturbed group fluxes is obtained in terms of unperturbed direct and adjoint group fluxes. Two approximation were used: high-order Fourier expansion, and adaptation of Kirchoff's formula. Our method was tested for a PWR fuel assembly with 20 control rods inserted and the results showed that this first-order approach is accurate for the analysed case. (author). 28 refs., 6 figs., 6 tabs