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Successful improvement of a high energy X-ray CT technique which takes the world�s highest resolution imagesMar. 23 , 2010Researchers at the Japan Atomic Energy Agency (JAEA, President Toshio Okazaki) have succeeded in taking the world�s highest resolution X-ray CT images using a high energy X-ray CT technique developed at JAEA. This non-destructive technique enabled us to allow observation of the irradiation-induced changes of fuel pellets in a fuel pin without destructive examination. Additionally, this technique can be applied not only to nuclear reactor fuel but also industrial structural materials and other dense objects. In order to measure the fuel pin position in an irradiated fuel assembly, the X-ray CT apparatus shown in Fig. 1 was developed in 1999 in the O-arai Research and Development Center. In this X-ray CT system, the 12 MV X-ray pulse was used in synchronization with the switch-in of the detector to minimize the effects of the gamma ray emissions from the irradiated fuel assembly. In the present study, this X-ray CT apparatus was upgraded to obtain high resolution X-ray CT images for observing the irradiation behavior of fuel pellets in the fuel pins. To obtain these images, the number of X-ray detectors has been increased from 30 to 100, and the collimator equipped with a slit of 0.1mm width was utilized. These improvements made it possible to observe the inner condition of the fuel pins as shown in Fig.2. In addition, this technique was applied to a fuel assembly irradiated in the experimental fast reactor �JOYO�, and high resolution X-ray CT images were successfully obtained of the fuel pellets and fuel pins as shown in Fig.3. The fuel pellets, with their central voids, claddings and wrapping wires can be clearly distinguished from each other. A large number of data can be obtained in a short time and applied to the analyses of fuel performance, which leads better safety analyses of fuel assemblies and fuel pins. It is expected that this X-ray CT technique can be applied to the inspection of structural and other dense materials such as lithium-ion batteries of electric vehicles and cast metal products, etc. Fig.1 Outline of X-ray CT system Fig.2 X-ray CT images of dummy fuel assembly Fig.3 High resolution X-ray CT image of the irradiated fuel assembly |
