Radioactive aerosol particles released from a pneumatic irradiation system in a nuclear research reactor

Abstract

Particle size distribution of activity was investigated with an impactor for airborne particles released from a pneumatic irradiation system of a research reactor. Airborne radioactivity released from the pneumatic tube of the reactor was identified as 24Na, 38Cl, and 56Mn and various fission products of which origin was uranium impurity in aluminum used in the part of the pneumatic tube. The AMAD (activity median aerodynamic diameter) of 24Na and 56Mn that were produced through (n,γ) reactions was ca. 1 μm, while that of fission products was ca. 0.4 μm. It was suggested that radioactive particles of ca. 1 μm were due to activation of aluminum dust in the pneumatic tube, and that the particles of ca. 0.4 μm were formed by attachment of recoiled fission products to radiation-induced airborne particles.