Alkhadzh-Ali S. The fast neutron fluences for weld metal regions of WWER-1000 reactor pressure vessel

Subject of inquiry - the neutron-physical parameters that influence on the capacity for work of the elements of the reactor primary circuit. The investigation aims were the methodology design and practical determination of neutron fluences with energies above 0.5 MeV on the reactor welds located opposite the reactor core. The research methods - neutron transport calculations within reactor near-vessel space by the Monte-Carlo simulation of multigroup neutron transport problems and the determination of neutron field characteristics at the outer pressure vessel surface by neutron-activation method. Equipment - gamma-spectrometer. The calculational-experimental methodology for the determination of neutron fluences on WWER-1000 pressure vessel welds is designed. Space-energy characteristics of the fast neutron field at the outer reactor pressure vessel surface for the weld regions were investigated for the first time. The azimuth distributions of fast neutron fluences within 60-degree core symmetry sectoro n the inner surface and in the depth of 1/4 and 3/4 thickness of WWER-1000 pressure vessel upper shell welds were obtained for the first time. It was shown that azimuth distributions of fluence values have delineated maxima and minima in which the values are differed almost 3 times. The designed calculational-experimental methodology is used at Khmelnitskaya NPP Unit 1 for the determination of neutron fluences on the reactor pressure vessel welds. It may be used at NPPs with WWER-1000 reactors without any restrictions.