Calculation of the neutron flux density distribution in WWER 440 reactor pressure vessel using MCNP5

One of the limiting factors in terms of nuclear power plant lifetime is reactor pressure vessel condition. Its radiation embrittlement causes especially fast neutrons. We are focused on describing methodology of the neutron flux density, inhere in reactor WWER-440/V-213 pressure vessel area with simulation in code MCNP 4C2 in this work. Computer simulation of selected neutron-physical parameters will be verified for a consideration of the data from ionization chamber, received from mode department of nuclear power plant in Bohunice and Mochovce. Condition of reactor pressure vessel is usually monitored by surveillance specimen program. Between the irradiation channel which contain surveillance specimen and the reactor pressure vessel is large area containing water with boric acid and structural steel parts. This environment influence density of neutron flux in pressure vessel area and energy spectrum of neutrons. The goal of this work is improve assessment of reactor WWER-440/V-213 pressure vessel radiation degradation and following valuation possibility of its lifetime. (Authors)