Reactor pressure vessel (RPV) dose assessments for UK PWR plant have been performed using the AEA Technology Monte Carlo radiation transport code MCBEND.
Monte Carlo models of the plant are validated against fast neutron activation measurements performed on flux monitor wires from surveillance capsules removed at the end of each cycle. These monitors have a range of time and spectrum dependencies. A computationally efficient method has been developed that calculates dosimeter activation values in a single calculation per reaction. This utilizes MCBEND's advanced acceleration techniques as well as an innovative treatment of neutron source data. The method employs plant validated, three-dimensionsal (3D) time-dependent neutron source data obtained from the UK reactor physics code PANTHER.
Mean ratios of calculation (C) to experiment (E) obtained for the surveillance capsules removed to date are 1.02, 0.99 and 1.04.
RPV dose distributions in axial, azimuthal and radial detail are obtained with a single calculation per reactor octant. Normalization to mean C/E provides best estimate dose data for the RPV inner surface and quarter thickness. A similar calculation provides dose data for the RPV top weld.