Step-by-step challenge of debris characterization for the decommissioning of Fukushima-Daiichi Nuclear Power Station (FDNPS)

The present article reviewed the step-by-step attempts on debris characterization after severe accident of Fukushima-Daiichi Nuclear Power Station (FDNPS). It was rather difficult to investigate reactor inside in first few years. Distribution degraded core materials, i.e. fuel debris, investigated by a muon tomography and damaged status preliminarily predicted from analysis. In parallel, literature review carried out for generated Three Mile Island unit 2 simulated previously examined nuclear safety research. Since 2017, remote investigations have been out, which is gradually clarifying damage status. sample analysis has accumulated useful knowledge characterization. Furthermore, several out-of-pile tests reflected unique conditions at FDNPS conducted mainly Japan, including ex-vessel formation mechanism metal-rich corrosion seawater materials. To establish proper method suitable samples also extremely important. These data compiled as database 'debrisWiki' includes maps, investigation results inside, probable scenarios, so on. Various international collaborations were launched continued decommissioning use relevant improving safety.