[en] Analysis of TOPAZ thermionic reactor moderator block have been carried out to study strength under unhomogenous deformation. The moderator block works under unhomogenous and unsteady temperature and neutron fields, which cause swelling of moderator material (zirconium hydride). One of the main demand which moderator block of the reactor must satisfy is cracking absence during lifetime. From mathematical point of view the simulation of moderator material behavior is the solution of boundary-value problem of thermomechanics (with receiving temperature, displacement, stress and strain fields). For solution of non-linear and (or) unsteady boundary-value thermomechanics problem was made a two-dimensional finite-element code FEMINA. The problem is solved with consideration of swelling and creep-strain of the zirconium hydride under unhomogenous and displacement, stress and strain fields is shown. Quantitative strength estimates of the moderator block have been made. (author)