Time Behavior of the Neutron Flux at the Vessel Boundary of a Boiling Water Reactor Power Plant

The results of a recent measurement of the neutron fluence at the vessel outer boundary of the Caorso Nuclear Power Plant show that the neutron flux per unit power was not constant during the reactor operation. This effect, usually not mentioned, may induce serious errors in the results of neutron dosimetry by the multiple foil activation technique.