A 10-MW high-temperature gas-cooled test reactor, the High-Temperature Reactor-10 (HTR-10), being built at the Institute of Nuclear Energy Technology of Tsinghua University, is a type of modular high-temperature gas-cooled reactor. The design features of the HTR-10 are studied in terms of five important sources of airborne radioactive materials released to the environment. These sources are activation of the air in the reactor cavity, leakage of the primary coolant, release of radioactively contaminated helium from the regeneration of the helium purification systems, release of radioactively contaminated helium from the gas evacuation subsystem of the fuel load and unload systems, and leakage of the vapor from the water/steam loops. On the basis of the HTR-10 design parameters, the amount of radioactivity released to the environment per year is calculated, and the dose to the public is calculated as it relates to the HTR-10 site.