Analysis of PWR Pressure Vessel Surveillance Dosimetry with McBend

Fast fluences received by four surveillance capsules in two 900-MWe PWR have been calculated with the Monte Carlo transport program MCBEND and compared with values estimated from activation measurements. First comparisons between calculation (C) and experiment (E) gave C/E values equal to 0.98/0.97/0.98/0.90. The original experimental values were based on saturation activation rates obtained from the measured activities and from the reactor power history, assigning at each operation cycle a contribution proportionnal to its time-integrated power production. A revision was then carried out in order to inlcude the effects of the fuel loadings (low leakage or out-in) in the contribution of each cycle. The revised experimental values led to C/E equal to 0.98/1.00/1.00/0.99, thus considerably reducing the scatter, and confirming the suitability of MCBEND to provide an essentially unbiassed approximation of the fast flux at the level of the surveillance capsules.