Ex-vessel dosimetry at WWER 440

Dosimetry experiments were performed at a WWER-440 unit to investigate the neutron exposure of the reactor pressure vessel. The study included analysis of several sets of activation detectors, irradiated in the pressure vessel cavity at five azimuthal and ten axial positions. The evaluation of the measurements was carried out with the newly-developed adjustment code COSA1 based on the generalized least squares method. Because of the broad response region covering the full energy region of radiation damages, the reactions 93Nb(n,γ) and 93Nb(n,n') are especially well suited to reactor dosimetry. The experiments revealed that the available neutron transport calculations are conservative as compared with the measurements. (author). 5 figs., 2 tabs., 10 refs