Since the Fukushima Daiichi nuclear accident in 2011, the plant has been a symbol of the risks of nuclear power. The 9,0 magnitude earthquake that hit Japan, followed by a devastating tsunami, severely damaged the plant's reactors, causing partial meltdowns and leaving behind an estimated 880 tons of nuclear fuel. Advanced robots have since been developed to enter the reactors and perform tasks that humans cannot do because of the deadly radiation.
Robot Challenges in Fukushima
At the start of the nuclear plant decommissioning work, TEPCO engineers developed multiple specialized robots to enter the damaged reactors. However, one of the biggest problems these robots face is extreme radiation. The moment they get too close to the core, their wiring and electronic components are severely affected, rendering them useless in a short time.
Robots, which are essential for mapping and removing debris from reactors, often 'die' due to the power of the radiation. Temperatures and radiation levels inside the reactor are so high that even the most advanced devices cannot operate on a sustained basis.
Despite these challenges, robots continue to play a crucial role. Some can 'swim' in highly radioactive water, navigate obstacles or inspect areas that would be lethal to humans. However, their lifespan is woefully short, and each robot can take years to develop.
The current state of the plant and the leaks
One of the biggest concerns at the Fukushima site is the continued leakage of radiation into groundwater that drains into the Pacific Ocean. For the first few years after the accident, continued leaks posed a global threat. To mitigate this problem, an underground “ice wall” was built, intended to stop the flow of radioactive water.
Although the construction of this wall has reduced leaks, the radiation leak has not been completely stopped. Authorities have reported that, although progress has been made, the problem persists. It is expected to take decades more to reduce these radiation levels to acceptable levels. The thousands of tanks holding radioactive water, a number that continues to grow, represent a logistical and environmental challenge.
In addition to the nuclear fuel residue, highly radioactive water has also been detected at levels sufficient to be harmful even to robots specifically designed for this purpose.
New developments and technological advances
In recent years, technology has advanced significantly in efforts to dismantle the plant. New robots such as the model dubbed “Telesco,” developed by TEPCO, can extend up to 22 meters, allowing them to reach previously unexplored areas inside the reactors. Equipped with lights, cameras and grippers to collect samples, these robots have been key to obtaining crucial information about the melted fuel remnants.
One of the main goals is to remove samples of the melted fuel for analysis and to better understand its composition and state. These advanced robots are the first to reach the bottom of the reactors and extract small amounts of radioactive material, a crucial achievement toward the eventual total decommissioning of the plant.
In addition to ground robots, tiny drones are planned that will fly through the reactors' narrowest ducts and tunnels. At Unit 1 of the plant, for example, drones will provide high-resolution images and create a detailed map of the state of materials inside the reactor. Such technology is vital for planning the removal of fuel waste in the coming years.
Progress in decommissioning: milestones reached and future challenges
Despite the obstacles, some tangible progress has been made. Since 2013, more than 1.300 spent fuel rods have been successfully removed from one of the cooling pools at reactor number 4 at the plant. In October 2024, another key mission began with the aim of removing the remaining rods from the other reactors.
As more advanced technologies are developed, new avenues are also opening up for addressing the most damaged reactors, such as Unit 3. Although challenges are expected, research into melted fuel at the Fukushima nuclear plants is critical to learning how to prevent future nuclear disasters and developing safer methods of operating and maintaining reactors.
In addition, the scientific community has pointed out that the decommissioning of the Fukushima reactors may offer unique information for future nuclear decommissioning projects elsewhere in the world, including sites such as Three Mile Island in the United States.
In the coming years, new technologies, including improvements in robotics and advanced sensors, are expected to enable decommissioning crews to do their work more safely and efficiently. It has been estimated that it will take 30 to 40 years to complete the decommissioning process of the Fukushima Daiichi plant, although some experts believe it could take even longer due to technical challenges and the constant buildup of radioactive water.
The decommissioning of Fukushima not only marks a step toward cleaning up a highly contaminated site, but also raises crucial questions about the future of nuclear energy in Japan and around the world. The 2011 nuclear accident dramatically altered public perception of the safety of nuclear power, prompting most countries to pause and reassess their energy policies.
The use of robots to decommission Fukushima has been vital to managing the risks associated with extreme radiation. Although these robots face significant challenges, they remain the best option for moving forward in such a dangerous environment. Continued advances in robotic and sensor technology will be key to achieving safe and effective decommissioning of the plant.