On the trial manufacture of small sodium loop and study on the sodium corrosion of explosive plugged part

2 1/4 Cr-1 Mo steel is used for the material of tube plate and tubing of evaporator, and SUS 321 stainless steel is used for the material of them of super heater, in steam generator of fast breeder reactor ''Monju''. Supposing the case in which leakage takes place in evaporator or super heater of fast breeder reactor, the explosive plugging method was developed by Japan Welding Engineering Society etc. It was indicated by the researchers that this method is effective to the purpose. It is not yet known whether the plugged parts keep the stable strength or not, during the long service period in the environment of fast breeder reactor. The corrosive property of explosive plugged part in secondary sodium circuit in the reactor is studied. For this purpose, it is necessary to make the sodium loop apparatus which provides the corrosion environment which resembles that of F.B.R. as much as possible. In this study, because of practical restriction, we are obliged to aim the qualitative comparison between the corrosion characteristics of explosive bonded part in liquid sodium and that of base metal. A small and simple sodium loop is made for trial, and the soaking experiments are conducted. A small and simple sodium loop is designed first of all. In order to model the environment of secondary sodium circuit of F.B.R., testing temperature, testing period, flow rate of Na, and material of loop are decided, respectively. Because testing specimen for explosive bonded part can not been cut out at the explosive plugged part, a special clad plate is made. The specimen is cut out at the clad plate. Testing result shows that explosive bonded boundary is somewhat weaker than base metal in the resistance to the sodium attack under the testing condition employed. (author)