Fukushima Nuclear Power Plant No. 1 machine found suspected nuclear fuel debris for the first time, TEPCO: Fruitful

From February 8 to 10, Japan's Tokyo Electric Power Company conducted an internal survey of the reactor containment of Unit 1 at the Fukushima Daiichi Nuclear Power Plant and found a large amount of accumulation. On February 13, TEPCO said the buildups might be nuclear fuel debris. This is the first time that Unit 1 has found or is a substance of fuel debris.

Accumulations of fuel debris found in or as fuel debris during an internal survey of the reactor containments of Unit 1 of the Fukushima Daiichi Nuclear Power Plant.

According to Kyodo News Agency reported on February 13, the head of TEPCO commented that "considerable results have been achieved." However, the report pointed out that even if the fuel debris is currently found, it is only a small part, and it is still very far from the target of full removal. This is the first time that material has been found or fragmented from nuclear fuel at Unit 1 of the Fukushima Daiichi Nuclear Power Plant. The deposits found were bumpy, blackened, rock-like masses near the opening in the base that supported the reactor's pressure vessel containing nuclear fuel from below. Some analysts believe that almost all the nuclear fuel in Unit 1 melts down after penetrating the pressure vessel, and the fuel fragments flow outward from the base opening and spread. If the lumps found this time are nuclear fuel fragments, this analysis may be corroborated.

At the bottom of the reactor containment of Unit 1, which was investigated, there was about 1.8 meters of standing water, and the lump was photographed by a remotely operated underwater robot, and the size and hardness of the lump were not known. However, the robot's original task was to install metal rings called "guide rings" at 4 sides of the containment to avoid the subsequent robot cables actually responsible for the investigation from hanging objects inside the reactor. In a March 2017 investigation, TEPCO found flat-distributed buildup at the bottom of the containment, but at that time TEPCO judged that it was not fuel debris based on the amount of radiation in the surrounding area, etc. According to the plan, TEPCO will invest five robots in the future to investigate the thickness, distribution and radiation volume of the accumulation in detail.

Kyodo News Agency previously reported that TEPCO began investigating the inside of the fukushima 1 reactor containment on February 8. In the investigation, TEPCO used underwater robots to collect information about the build-up at the bottom of the containment and the molten nuclear fuel (i.e., nuclear fuel fragments) below it. This is the first related survey since March 2017. According to the footage captured by the camera mounted by the robot at that time, the bottom of the containment was uneven, and it was suspected that there was a large amount of debris accumulated. TEPCO said that of the units 1 to 3, only unit 1 detected the substance.

On March 11, 2011, a magnitude 9.0 earthquake occurred in the waters off northeast of Japan and caused a special tsunami, which was affected by both earthquakes and tsunamis, and a large amount of radioactive materials leaked from the Fukushima Daiichi Nuclear Power Plant, resulting in a serious nuclear accident.