Nuclear power is the rapidly developing branch of the global energy sector as nuclear-based electric power generation is 11 percent of total electricity production in the world. However, any mistake during the nuclear power plant maintenance may lead to technological disaster. In order to provide technological safety at the nuclear power plant it is necessary to carry out video diagnostics of nuclear reactor. Although modern optoelectronic systems have good light sensitivity, reactor walls illumination is too low, so diagnostic video systems need artificial light source to provide the necessary signal-tonoise ratio. There are special requirements to the light sources radiation tolerance, lighting uniformity, spectral characteristics Thermal stability, dimensions and weight characteristics are also of great importance. Light-emitting diodes (LED) based luminaire with radioactive shielding and heat removal system seems to be the good way to perform the task of illuminating the walls of nuclear reactor. The advantages of the LED based luminaires in comparison with other light sources are their relative energy efficiency, stability and long lifetime. The aim of the paper is to design the LED luminaire to perform the tasks of nuclear reactor video diagnostics, considering the high radiation and temperature level when choosing the materials and design. The computer modeling is carried out and its results are discussed.