To assess internal exposure due to inhalation of radioactive aerosols and gases generated in high-energy accelerator facilities, physicochemical properties such as particle size of aerosols and chemical form of gases are important information. We measured the particle size distribution and concentration of aerosols to coexist with radionuclide formed by high-energy radiation emission in the target room of LINAC and estimated the long term variation of particle size and concentration of radioactive aerosols in high-energy acceleration facilities by a simple model. The estimated concentration and size distribution of aerosols were relatively consistent with the experimental results. We also calculated the time variation of the particle size distribution of radioactive chlorine aerosols from the measured particle size of non-radioactive aerosols. These results suggest that the diameter of aerosols generated at accelerator facilities grow to about 500 nanometers under conditions of continuous operation.