Investigation of an on-line pipe wall thinning monitoring using a high accuracy sensor

Tagawa, Akihiro ; Fujiki, Kazunari*; Yamashita, Takuya

Until now, in Japan, the safety of nuclear power plants (NPP) has been secured by performing a time based maintenance. However, recently, NPPs were taking into consideration a new procedure using a condition based maintenance, aiming to improve both reactors safety and reactors operation ratio. Therefore, it is needed to develop new sensors that can monitor in the same time, during reactor operation, the integrity of both piping system and pressure vessel. Two measurements techniques have been employed using a new developed sensor, depending on the required purpose. The 1st technique is based on the Pulse echo method. The 2nd technique is based on EMAR that is usually used for a material fatigue assessment. The developed sensor measures at 200 degrees C a minimum plate thickness 5mm 0.03mm using pulse echo, and 2mm 0.003mm using EMAR.