Toshiba Corp. and the International Research Institute for Nuclear Decommissioning (IRID) have developed a submersible robot (an underwater ROV), 13cm in diameter, that is small enough and resilient enough to enter and inspect the damaged primary containment vessel (PCV) of Fukushima Daiichi Nuclear Power Station Unit 3.
The robot will be deployed in summer 2017, following operator training.
An Oct. 20, 2015 survey by Tokyo Electric Power Co. found the PCV of Unit 3 flooded with coolant to a depth of about 6 meters. In determining how to best advance the plant’s clean-up, fuel and other debris submerged in the coolant must be located and mapped.
However, the penetration hole giving access to the PCV is only 14cm in diameter, limiting the size of any robot that can be deployed.
Toshiba and IRID build a radiation-hardened robot. At 30cm long it provides a platform for front and rear-facing video cameras and their LED lights. The robot is powered and remotely controlled via wire, and operators can control its progress through the coolant and the PCV with five thrusters, four rear mounted and front mounted.
It will deliver a video feed that will clarify damage to the PCV interior and information on how best to retrieve fuel debris.
“We have already developed remotely operated robots for inspections at Fukushima,” said Goro Yanase, General Manager of Toshiba’s Nuclear Energy Systems & Services Div.
Manufacturers and utilities have used a number of robots at Fukushima Daiichi Nuclear Power Station to inspect the distribution of fuel debris. IRID and Toshiba developed a small robot reminiscent of a scorpion to inspect the interior of the Unit 2 PCV in February 2017.
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