Study on the Strength of Explosive Plugged Part under the Environment of Steam Generator

Supposing the case in which leakage takes place in tubing of steam generator, 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 steam generator.Under the above consideration, following three tests on plugged part are conducted.1. Thermal Shock Test2. Stress Corrosion Cracking Test3. Liquid Sodium Corrosion TestTesting results are grained as follows.1. Peeling occures immediately after beginning of thermal shook test. Cracking occures after 150-200 thermal cycles in SH, 200-400 thermal cycles in EV and 1000 thermal cycles in SG.2. Residual stress in tube plate near the plug is compressive. SCC does not occur in the tube plate there. It occures on the inner surface of plug.3. The susceptibility to SCC of explosive bonded boundary is lower than that of base metal due to martensite in bonded boundary.4. Explosive bonded boundary is somewhat weaker than base metal in the resistance to the sodium attack under the testing condition employed in liquid sodium corrosion test.