SYSTEM FOR NOSE-ONLY INHALATION EXPOSURES OF SMALL ANIMALS TO (RUO4)-RU-106

Ruthenium-106 and 103Ru are major fission products with high probability of release as RuO4. Ruthenium tetroxide exists as a vapor, diffuses rapidly through air and porous barriers, and is rapidly reduced to the dioxide form by an organic material. It was necessary to design production and animal inhalation exposure systems that would minimize reduction of RuO4 during the production and the exposures. Ruthenium-106 tetroxide was produced in an all-glass generating system by oxidizing 106RuCl3 to 106RuO4. This was collected in glass flasks cooled by dry ice. The crystalline 106RuO4 was subsequently sublimated and passed into an all-glass exposure system for the nose-only inhalation exposure of rats to the 106 RuO4 vapor. The 106RuO4 inhaled by rats was deposited mainly on the external nares and in the upper respiratory tract. The initial body burdens ranged from 4.1 to 15 μCi and the initial lung burdens ranged from 0.05 to 0.4 μCi when 250 μCi of 106Ru were sublimated. No releases of 106RuO4 to the laboratory environment occurred during the use of this system. © 1979.