Reactor core structure in FBR type reactors

Purpose: To improve the seismic-proofness of a reactor core without increasing the pitch and the bending load of reactor components. Constitution: In the reactor core of FBR type reactors, reactor components of fuel assemblies exhibit group vibration behaviors and upper and intermediate pat portions are destructed due to the colliding force in the vibrations to possibly reduce the integrity of the reactor components. In view of the above, a wrapper tube as the reactor components disposed to the outside of the reactor core are made so as to have substantially identical outer diameter with the wrapper tubes for other reactor components and made thicker than the wrapper tubes for other reactor components. In this way, the strength of the wrapper tubes for the reactor components disposed to the outside of the reactor core is increased and the earthquake proofness of the reactor core can be improve without increasing the pitch and the bending load thereof. (Takahashi, M.)