The location of the fuel debris inside the three reactors at the Fukushima No. 1 power plant is of critical importance to officials with Tokyo Electric Power Company Holdings Inc. (TEPCO), reports the Japan Times.
Finding and removing the radioactive fuel is the most critical and dangerous part of the decommissioning process. TEPCO has attempted to use remote-controlled robots to see inside the reactors since they began the clean-up after the meltdowns following a massive earthquake and tsunami in March 2011.
But even using remote-controlled robots proved futile because of the extremely high level of radiation inside the reactors. In February, a TEPCO spokesman said the problems with the robots breaking down due to the radiation underscore the “challenges” of decommissioning the plant. And inadequate cleaning, high radiation levels, and structural damages could hinder any subsequent probes into the reactor.
The Mini Manbo swimming robot
Toshiba Corp. and the International Research Institute for Nuclear Decommissioning, or IRID, a government-funded consortium, co-developed the underwater robot, named “Mini Manbo” (miniature sunfish). Toshiba demonstrated the loaf-of-bread-sized robot for the news media at a company test site near Tokyo on Thursday, reports CTV News Canada.
The robot is mounted with lights and maneuvers through the water using tail propellers, collecting data with two cameras and a dosimeter. All the information is sent back to the surface through a cable. “The fuel debris will be a challenge,” said Dale Klein, a former U.S. Nuclear Regulatory Commission chief, who now serves as an outside adviser to the Tokyo Electric Power Co., the plant’s operator.
Klein says it may take six months to a year to obtain all the necessary information and data before deciding how to remove the radioactive fuel.
“They will have to identify where it is, then they will have to develop a capability to remove it. No one in the world has ever had to remove material like this before. So this is something new and it would have to be done carefully and accurately,” Klein said.
The Unit 3 primary containment vessel
Unit 3 has the highest level of water inside, estimated to be about 6.0 meters (19.6 feet) in depth. It is believed that the fuel debris inside has melted through the pressure vessel and settled at the bottom of the primary containment vessel.
“Until today, no one has seen the situation inside reactor 3,” said Tsutomu Takeuchi, senior manager at Toshiba’s Fukushima Restoration and Fuel Cycle Project Engineering Department, speaking at the demonstration of the new robot on Thursday.
TEPCO is hoping to use the Mini Manbo for the first time in mid-July. The new robot will join a large corral of robotic machines that are being used to decommission Fukushima. Japan hopes the fuel can be located and if so, they plan on starting the removal of the fuel from the reactors after the Tokyo 2020 Olympics Games.
