Short Review of Sodium Removal Experience in PNC

摘要

Experiences in the removal of sodium from fuel assemblies and other reactor components are shortly reviewed. The experiences were obtained from the operation of the FBR ''JOYO'' and at the research work facilities in the O-arai Engineering Center, PNC. As for JOYO, many dummy fuel and blanket fuel sub-assemblies and dummy control rods have been sent to the Fuel Cleaning Facility for sodium removal. Steam and demineralized water have been used for the process. Sodium removal from the grapples of the fuel handling machines was done after a certain time of service in sodium. For this process, alcohol has been used. Sodium removal from the mechanical sodium pump of the primary coolant system was done with steam-nitrogen and water. At the research work facilities, on the other hand, sodium removal tests were performed for various components, such as the secondary mockup pump of JOYO, 1 MW steam generator, sector model of the intermediate heat exchanger of JOYO, and mockup isolation valves. From these experiences, it was found that sodium removal from small crevices by conventional methods was difficult. In order to improve this situation, saturation boiling process was designed, and the experiment using test pieces has been initiated. This process is modification of the water charging process, in which water is charged into the process cell or tank and the inside pressure is adjusted so that boiling of the water is initiated and the formation of hydroxide film is prevented. (Atomindex citation 11:497059)