Reactor Dynamic Model
Reactor dynamic model development is necessary for analyzing seismic stability, vibration and dynamic response of the reactor at the maximum design accident as it allows us to analyze the "whole system", to evaluate the strength of the support elements and the possibility of collision of individual parts of the model. First of all, estimated partial frequencies of individual reactor elements exceeding 30 Hz, its allow us the schematization of spatial elements of the reactor as rigid bodies on elastic supports. The initial stress raises natural frequencies, but the shell forms of vibrations are dominant especially for the Reactor Internals. The lowest bending natural frequencies found for the fuel assemblies (TVS).
By schematizing the individual rigid elements of the reactor as a lumped mass, and the support elements and relatively flexible parts of the reactor as springs, IPP Center Ltd. developed a dynamic reactor model. The peculiarity of this model is to take into account:
nonlinearities of contacts, the possibility of contact breaks and the occurrence of bumps between individual parts of the model ;
the elasticity of the coolant located between the elements, and significantly affect the dynamic characteristics;
the presence of pipes of the main circulating pipeline, which can be interpreted as additional elastic elements.
Using the developed model, we obtained the natural forms and frequencies a of the reactor, and then using the linear-spectral method of calculation the distribution of forces in the elements of the model, in particular, in the supporting elements of the reactor, the Reactor Internals supports, etc., was obtained.
Using the finite element method and the response spectrum, the individual elements of the reactor were calculated in more detail.