Abstract: CITP-Ⅱ irradiation device, which is specially designed for fusion tritium breeder research, works in a thermal neutron reactor. With lithium orthosilicate as the breeder, the safety analysis was done to work out the device’s influence on physical parameters of the reactor and get the breeder’s temperature distribution and thermotechnical features in the n-γ field. The stiffness and strength were checked, and also the safety characters of the device were assessed. The feasibility of gap gas regulating the temperature and gas refueling the breeder was demonstrated. The calculation and analysis results provide data for comprehensive performance assessment.