A group of Professor Chitaro Takahashi of Kyoto University and others took out radioactive palladium, which may be mixed in a trace amount with the precious metal palladium extracted from high-level radioactive waste, from the radiation controlled area and used it in a normal living environment. The world's first trial calculation and announcement of a clearance level that can be said to be safe.
High-level radioactive waste contains useful elements such as palladium and zirconium.In particular, palladium, a platinum group element, is a precious metal used in automobile exhaust gas catalysts, and if it can be recovered and reused, it is good news for Japan, which has few resources.However, the problem is that a small amount of radioactive palladium remains in the recovery.Therefore, it is necessary to clarify the standard (clearance level) that the concentration of residual radioactive palladium does not affect the human body and that it can be taken out of the radiation controlled area and used in a general living environment. There is.
In this research, we investigated in detail the flow of palladium from raw materials to products, usage patterns, disposal status, etc., estimated the route and amount of palladium taken up by the human body, and evaluated each radiation exposure dose.As a result of estimation based on this, the clearance level of radioactive palladium was about 3000 becquerels per gram.This estimated value is considerably higher than the clearance level for radionuclides such as radioactive cobalt and radioactive cesium in the waste materials discharged from the reactor facility, but radioactive palladium is a chemically stable individual and emits beta rays. Since it is extremely weak, there is no effect on the human body or the environment at this concentration.
In the future, we will verify this research and consider clearance levels such as zirconium, which are also valuable for reuse.
