Neutron Spectral Analysis of the Caorso Boiling Water Reactor Cavity and Sacrificial Shield Penetrations and Comparison with the Irradiation Experiment Results

An analysis of the neutron transport in the region around the Caorso [a 2600-MW(thermal) boiling water reactor] reactor pressure vessel and the streaming through three penetrations of the sacrificial shield, located at various distances from the reactor core midplane, was performed. The DOT 4.2 and MORSE codes were used to evaluate the neutron flux levels and spectra in several locations, some of which are very far from the neutron source. The calculational methodology used for this analysis is described, and the results are compared with those of some measurements carried out at the Caorso power station during the second cycle of operation using the multiple foil activation technique. A comparison shows that the agreement is good from both the neutron total flux and energy distribution points of view. Possible reasons for some observed discrepancies are discussed.