Sample analysis at the Fukushima Daiichi NPS. Results of analysis with a focus on U-containing particle

This paper introduced the state and results of analysis of the samples collected from inside the primary containment vessels (PCVs) and their surroundings, which have been carried out to date at Fukushima Daiichi NPS Units 1-3 reactors. The following six types of samples have been analyzed so far: (1) Unit 1 PCV bottom deposit, (2) Unit 2 traversing in-core probe (TIP) pipe blockage, (3) Unit 2 operating floor curing sheet, (4) Unit 2 PCV internal survey device deposits (on the control rod drive mechanism rail), (5) Unit 2 PCV internal survey device deposits (camera section), and (6) Unit 3 PCV internal survey device deposits. By observing the samples with SEM-EDS, it was considered that U-containing fine particles were detected in some samples. With a focus on radioactive fine particles, the following particles were analyzed: (1) particles that may be derived from molten core, (2) particles that may have undergone evaporation/condensation process, (3) amorphous U-containing particles that contain a considerable amount of Zr, or spherical U-containing particles that hardly contain Zr, and (4) particles that contain Fe as a main component. (A.O.)