Summary of countermeasures for reduction of radiation exposure from radioactive corrosion products(CPs) deposited on fuel cleaning system of "JOYO"

not registered; Ito, Hideaki; Okubo, Toshiyuki; not registered

Many subassemblies have been washed by water in the fuel cleaning system of JOYO, and a large amount of radioactive corrosion products(CPs) was removed from the surface of the subassemblies. These CPs deposited on the wall of piping and components in the system cause radiation exposure of personnel at operation and maintenance of the system. Following countermeasures for the reduction of radiation exposure have been conducted from 1991 to 1994. (1)ldentification of radiation source points by a Radiation image Display(RID). (2)Shielding of components in the system. (3)Rearrangment of water drain lines. (4)Replacement of water circulation piping. (5)lnstallation of a mist trap to the argon gas circulation line. (6)Installatlon of drain piping to valves of the argon gas circulation line. The dose rate in the fuel cleaning equipment room(A-212) was reduced to about one third after conducting the countermeasures. This report discribes the result of the countermeasures for the reduction of radiation exposure of personnel at operation and maintenance of the fuel cleaning system in "JOYO".