Swimming robot ‘little sunfish’ to inspect crippled Fukushima plant
Japan has unveiled a small swimming robot that will inspect the damage at the crippled Fukushima nuclear power plant. The device weights 2kg, is 13cm in diameter and will be able to swim deep into the melted reactor, its developers say.
The Japan-based International Research Institute for Nuclear Decommissioning (IRID) unveiled the robot, dubbed ‘mini manbo’ (little sunfish) in the media, together with Toshiba group on Thursday.
The robot “is small enough and resilient enough to enter and inspect the damaged primary containment vessel [PCV] of Fukushima Daiichi Nuclear Power Station Unit 3,” a statement from the IRID said, adding that the device will be deployed this summer.
The device is equipped with two cameras and can be remotely controlled via a wire, while operators can record its progress through the coolant. ‘Little sunfish’ will deliver a video feed that “will clarify damage to the PCV interior and information on how best to retrieve fuel debris,” the IRID added.
The major advantage of the robot is that it “can avoid various obstacles,” Tsutomu Takeuchi, a senior manager at the nuclear energy division of Toshiba, told AP. The company is tasked with helping to clean up the damaged plant.
The device was created for inspection of the primary containment vessel (PCV) of Unit 3 of the crippled plant. Unit 3 was flooded with coolant to a depth of about 6 meters (20ft) and in order to make a proper clean-up, such a coolant must be located and mapped, according to the IRID.
“The penetration hole giving access to the PCV is only 14cm in diameter, limiting the size of any robot that can be deployed,” the IRID added.
Thus, the newly-presented robot seems ideal for the job.
The robot’s radiation resistance is approximately 200 Sievert (Sv), according to its characteristics. For comparison, an exposure of about 1 sievert can cause biological damage to living tissue, according to the International Atomic Energy Agency (IAEA).
“Scientists developed ‘mini manbo’ with the aim of operating in a highly radioactive environment,” Goro Yanase, general manager of Toshiba’s Nuclear Energy Systems & Services Division, said.
“We succeeded in developing a small robot with high-level radiation resistance, and through its deployment we expect to get information that will support the advance of decommissioning,” he added.
The Fukushima Daiichi nuclear power plant suffered a blackout and subsequent failure of its cooling systems in March 2011, when it was struck by an earthquake and tsunami. Three of the plant’s six reactors were hit by meltdowns, making the disaster the worst since the Chernobyl catastrophe in the USSR in 1986.
Japanese authorities have repeatedly sent robots to inspect the contained area of the crippled plant but the devices either broke down or the missions were aborted. In February, such an attempt ended in failure as a clean-up robot stopped working two hours after it was sent to the inactive Reactor 2 at the nuclear complex.
Following the failure, Naohiro Masuda, president of Fukushima Daiichi Decommissioning, said that more creativity was needed to produce robots that can find and assess the condition of melted fuel rods at the high-level radiation site.
Toshiba unveils submersible video robot to probe reactor 3 at Fukushima No. 1 plant
YOKOSUKA, KANAGAWA PREF. – Toshiba Corp. unveiled on Thursday a submersible robot to take live video of reactor 3 at the Fukushima No. 1 power plant to confirm whether fuel debris is sitting at the bottom of a pool of radioactive water inside.
The location and condition of the fuel in the three reactors hit by core meltdowns is critical information for Tokyo Electric Power Company Holdings Inc., which runs the plant. Removing the fuel debris is considered the most difficult part of decommissioning the complex.
Unit 3 has the highest level of water inside at 6 meters. The fuel debris inside is presumed to have melted through its pressure vessel and settled at the bottom of its 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.
“If we can observe the situation inside the reactor, that would be a huge leap in our ongoing effort to extract the debris” and eventually shut down the wrecked plant, he said during a demonstration of the robot at the Port and Airport Research Institute in Yokosuka, Kanagawa Prefecture.
Co-developed with the International Research Institute for Nuclear Decommissioning, the cylindrical 30-cm robot, dubbed the “mini manbo” (miniature sunfish), has a camera that can move 180 degrees vertically on its front and a fixed camera on its rear, allowing it to crawl through the water while capturing images.
Tepco plans to send the remotely controlled robot into the reactor as early as mid-July. A camera inserted into the reactor in October 2015 was unable to reach the bottom of the containment vessel.
No probe has been able to confirm the location or condition of the nuclear debris in any of the three crippled reactors.
Tepco sent a scorpion-shaped robot developed by Toshiba and the institute into reactor 2 in February, but it broke down before reaching its target under the pressure vessel after a tire got stuck.
In March, Tepco’s five-day robot-based investigation failed to capture an image of what was thought to be fuel debris in reactor 1.
A separate Tepco probe in January found black lumps in reactor 2’s pressure vessel but couldn’t immediately confirm they were fuel.
In December, the government estimated that the total cost of the Fukushima disaster would reach ¥21.5 trillion, including ¥8 trillion for decommissioning. That was almost doubled the initial estimate of ¥11 trillion.
Takeuchi of Toshiba did not reveal how much it cost to develop mini manbo.
Tsutomu Takeuchi, senior manager at Toshiba’s Fukushima Restoration and Fuel Cycle Project Engineering Department, shows off a robot it claims can probe water-filled reactor 3 at the defunct Fukushima No. 1 nuclear plant.
Swimming and wriggling robots unveiled for Fukushima clean-up
University and industry scientists have demonstrated new robots specialised for moving through and searching scenes of destruction that are impossible or dangerous for humans to enter.
Hardy, agile, remote-controlled robots will be vital for the decommissioning of power plants, particularly in the case of the Fukushima Daiichi Nuclear Power Plant, which suffered a meltdown in 2011 following a devastating tsunami and earthquake.
Robots can spend hours or days in environments so highly radioactive that a human worker would be killed in seconds.
The Japanese government hopes to start the challenging task of removing hundreds of tonnes of melted fuel after the Tokyo 2020 Olympics, potentially beginning work in 2021. For this to be possible, engineers need to know the exact location of the fuel, and understand the extent of the structural damage to the reactors.
Among other efforts, a snake-like robot was used in 2011 to explore the reactors, but was trapped repeatedly by obstacles and its camera was blocked. A “scorpion” inspired crawling robot also failed to navigate the site and was abandoned inside.
Years later, a new version of the snake-like robot has been revealed by Japanese scientists, including a team from Tohoku University in Sendai: a region severely affected by the tsunami and earthquake.
The robot stretches to eight metres in length, has a camera attached to the front and can move at speeds of up to 10cm per second.
It wriggles in a serpentine motion, propelled by the vibrations of the brush-like hairs that cover its body. Unlike any other robot, it can also “rear” its tip like the head of a snake, shooting a small jet of air to lift it. This allows it to climb over obstacles – such as debris in a disaster zone – up to 20cm in height.
According to Professor Satoshi Tadokoro of Tohoku University, the robot could search for people trapped in collapsed homes following earthquakes, and test the structural safety of damaged buildings. The researchers hope to have it ready to assist in search and rescue operations and other tasks within three years of durability testing.
Meanwhile, an alternative disaster relief robot has been unveiled by Toshiba and the public International Research Institute for Nuclear Decommissioning. This swimming robot is the size of a loaf of bread is and fitted with lights, camera and tail propellers.
It is designed specifically to inspect meltdown damage at the Fukushima nuclear plant, and will enter the primary containment vessel of Fukushima’s Unit 3 this summer to locate melted fuel in radioactive water.