26 Juillet 2017
July 23, 2017
Melted nuke fuel images show struggle facing Fukushima plant
By KOHEI TOMIDA/ Staff Writer
Images captured on July 22 of solidified nuclear fuel debris at the bottom of a containment vessel of the crippled Fukushima No. 1 nuclear power plant show the enormity of decommissioning of the facility.
Plant operator Tokyo Electric Power Co. said it will closely study the images from the No. 3 reactor's containment vessel to determine the spread and amount of nuclear fuel debris.
After analysis, TEPCO will decide on a policy to retrieve the fuel debris.
The government and TEPCO plan to start the retrieval process in one of the three crippled reactors at the plant from 2021.
It will be a formidable task, given that a method of recovering debris that is stuck to the floor has yet to be considered.
The recent images were taken by a submersible robot, which was sent into the containment vessel on July 19, 21 and 22.
The No. 3 reactor's containment vessel is filled with water to a depth of 6.4 meters.
On the final day, the remote-controlled robot was dispatched to the deepest part of the containment vessel.
The images showed that pieces that fell from the structure and deposited material accumulated to a height of about 1 meters at the bottom of the containment vessel.
In particular, what is believed to be nuclear fuel debris is scattered in the form of rocks in the area directly beneath the pressure vessel.
The latest investigation has confirmed TEPCO’s assumption made through analyses that most of the reactor’s nuclear fuel melted through the pressure vessel and accumulated at the bottom of the containment vessel.
It also discovered that the nuclear fuel debris has spread throughout the containment vessel.
The images marked the first confirmation through a robot probe of a large amount of nuclear debris in any of the embattled No. 1 through No. 3 reactors.