Ultrasonic imaging technologies for decommissioning of the Fukushima Daiichi Nuclear Power Plant

The decommissioning of the Fukushima Daiichi Nuclear Power Plant (1F) is underway, but various problems are hindering progress on the first experience for mankind. All kinds of new technology must be introduced to solve the problems we are facing with. We believe that ultrasonic measurement also can contribute to the decommissioning of 1F. Our research group participates in the research program, JAEA Nuclear Energy S&T and Human Resource Development Project through concentrating wisdom, and is working on two projects: one is a remote detection technique for deposits inside pipes, which will be used to confirm the absence of radioactive materials in the pipes before cutting them. The second is the measurement of debris shape under poor visibility. During fuel debris removal, ultrasonic waves are expected to be used as a technique to visualize the debris under poor visibility due to the fracturing process. Since it is difficult to use an optical camera due to the high radiation dose, we are developing spatial visualization using ultrasonic phased-array technology as an alternative method.