Plastic deformation of the neutron absorbing rod containing a swelling powder core

The neutron adsorbing rods consist of stainless steel shell containing powder swelling core. They are used in a reactor control and protection system. A mathematical model of the powder compressible material is developed for application in an inelastic behavior modeling of the irradiation swelling powder core. The model represents the phenomenological mechanisms of plastic compressibility due to hydrostatic stress loading and plastic shear deformation. The volume plastic compression results in hardening related to plastic shear strain. Some examples of plastic loading are considered. Plastic deforming of stainless steel cylindrical shell containing boron carbide powder core is investigated using the proposed model. When compressing the swelling powder core, the shell plastic radial expansion occurs. The results of plastic deforming numerical simulation by means of finite element method are presented for both rod structure components.