A study on the thermal shock of an explosive plugged part of a steam generator

If leakages are discovered in the heat exchanger tube of a super heater or evaporator by an in-service inspection, and they are found to be unsuitable for further service, the plugging must be applied in that tube and effectiveness of the plant kept. To apply this method to ''Monju'' and PWR, characteristics of many plants must be researched, and original techniques developed. Supposing the thermal shock which takes place in the heat-exchanger is due to mis-operation of the valves, the thermal shock test of the explosive plugged part is conducted under severer condition than that in service. Microscopic examination (x 200) of a section of the specimen after a thermal shock test, ultrasonic inspection and observation of acoustic emission during testing are conducted to detect peeling of the boundary and cracking in the material. SUS 321 steel, 2 1/4Cr-1Mo steel and SUS 304 steel are used as testing materials, supposing that they are the materials for the super heater, the evaporator of FBR and steam generator of PWR. Low detonation velocity explosive and a reverse detonation method are used for the plugging of specimens. (author)