The concrete biological shield (CBS) is a critical component of nuclear reactors, providing long-term attenuation of neutron radiation from the active zone. During decades of operation, neutron irradiation triggers radiation-induced volumetric expansion (RIVE) of concrete aggregates, generating internal restraint stresses that accumulate over time, initiate cracking, and may ultimately degrade structural integrity and shielding performance. As direct in-situ assessment remains highly limited due to inaccessibility during operation, numerical simulations are a crucial tool for evaluation. This contribution presents development of a 3D nonlinear finite-element model of a non-lead-bearing CBS of the WWER-440/213 nuclear reactor in ATENA software to simulate its mechanical response under irradiation-driven loading over a 60-year service period. RIVE is introduced as an isotropic eigenstrain field derived from neutron exposure. ATENA uses a verified fracture-plastic material model for concrete, which allows us to focus on investigation of crack initiation and propagation. First cracking occurs in the early stages of the reactor’s operation, and after 60 years of the lifespan, the dominant crack propagates up to several millimeters. The conclusion also suggests improvements to the presented model such as including concrete creep or the operational temperature – humidity field. However, the model proves that the presented approach can provide a basis for long-term service-life assessment of CBS structures under irradiation.