Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : September 03, 2017 - September 06, 2017
The distribution of boron in the fuel debris is one of the massive concern for the Fukushima Daiichi NPS decommissioning mainly because its distribution affects the hardness of the debris and possibility of the re-criticality. The distribution might be partially determined by the relocation behavior of the B4C control blade. Thus, it is important to clarity the dominant factor for the variety of the relocation behavior. In particular, this study focuses on the initiation of the relocation in terms of the influence of the B4C/SS mass ratio and SS clad thickness. The B4C-control-rod simulant which consists of the real materials was melted and its relocation behavior was observed in a time-resolved manner with varying the experimental conditions. As a consequence, mainly two relocation modes were found depending on the B4C/SS mass ratio and SS clad thickness. In the first mode, the B4C/SS eutectic melt covered the surface of the specimen and large portion of the B4C kept intact. In the second mode, the eutectic melt formed a large droplet while the specimen collapsed and large portion of B4C was consumed for eutectic melting or enclosed in the droplet.
