Stress analysis of nuclear power plants reactor components

During the nuclear reactor operation, one of the most important limiting factors in fuel element duty is the mechanical iteraction of fuel and clad. This interaction produces cyclic stresses and strains in the cladding, and these in turn consume clad fatigue life. It is expected, that compressive hoop stress at the clad ID reaches 14500 psi (100 MPa=MN/m2, ie. 1000 bar). Tensile stresses could be created once the clad has come in contact with the fuel pellet, approximately after 15000 hours in the reactor core. Reactor pressure vessel is also being exposed to high mechanical load and to an intensive neutron flux irradiation. During the life time of the NPP, this leads to a gradual deportant in the event of LOCA (Loss of Coolant Accident) with action of ECCS (Emergency Core Cooling System), and thus with an instant vessel temperature drop. The reactor containment has to comprise relatively high pressure developed during the accidental fluid release from the reactor piping. The steel structure is additionally loaded by a crane circular rail under the dome, and the strength and stability analyses prove to be very difficult. (author)