3-DIMENSIONAL NEUTRON-FLUX CALCULATIONS FOR THE VVER PRESSURE-VESSEL

The neutron flux values at the sites important for the pressure vessel s of the VVER-1000 and VVER-440 reactors have been calculated by the t hree-dimensional TORT code and the synthesis method approximation. The synthesis method is widely used now for neutron fluence routine calcu lations in metal embrittlement surveillance. The three-dimensional neu tron flux evaluation by the synthesis method is based on the two-dimen sional and one-dimensional solutions of the transport equation. The co mparison of the results obtained by both methods confirms the good con sistency within 3% for integral neutron flux,vith energy >0.5 MeV; use d for metal damage estimation, according to Russian reactor standards. Further investigations on the calculation validity will be based on c omparisons with measurements of the threshold detector activities, mon itored in the air shell behind the reactor pressure vessels of the Koz loduy nuclear power plant.