Meltdown Maneuvers: Advanced Robotics for Safer Nuclear Cleanup

Robots have long been used to handle radioactive material at nuclear disaster sites and decommissioned power plants. Ongoing advancements in remote-controlled equipment and containment designs are taking the application to new heights, as evidenced in two recent demonstrations.

One case study involves removing radioactive debris from a reactor at Japan’s Fukushima Daiichi Nuclear Power Station, while the other is testing a mixed-reality telerobotic system for nuclear cleanup in the U.S.

This robotic arm was designed to retrieve radioactive debris at Japan’s Fukushima Daiichi Nuclear Power Station. Image used courtesy of the International Research Institute for Nuclear Decommissioning

Robots Aid in Fukushima Cleanup 13 Years After Disaster

Tokyo Electric Power Company (TEPCO) is deploying a remote-controlled robot to extract melted fuel debris from Unit 2 of its Fukushima Daiichi nuclear plant. The facility has been offline since 2011 when a 9.0 earthquake and subsequent tsunami caused outages disabling three reactors’ cooling systems. For Unit 2, TEPCO could not shut down the reactor by inserting control rods, and a hydrogen explosion in the adjoining building further damaged the reactor’s walls, making containment even more difficult.

Over a decade later, TEPCO plans to employ radiation-hardened robotics to remove some 880 tons of melted fuel inside three reactors. For years, TEPCO has been busy retrieving spent fuel from Units 3 and 4, investigating damage from Units 1 and 2, and dismantling and rebuilding plant portions for further cleanup activities. Later this year, the company will begin removing radioactive fuel debris for the first time with an extendable pipe robot venturing into Unit 2’s primary containment vessel.

Top: Mock-up of the robot arm taking samples from the reactor’s primary containment vessel. Bottom: The real-world testing setup. Images used courtesy of the International Research Institute for Nuclear Decommissioning

Initially, the machine will remove under 3 grams of material before scaling up for future decommissioning work. TEPCO demonstrated the process last month, lowering the robot from a pipe as it picked up a debris piece.

The retrieval plan at Unit 2 involves inserting a 72-foot, 4.6-ton arm of high-strength stainless steel and aluminum through the same route accessed during a previous investigation using a telescopic arm.

The tongs-like extensions will collect small deposits using a metal brush and vacuum container. The arm is designed to extend through a cylindrical structure leading to the reactor pedestal’s bottom. An extension pipe is inserted up to a replacement rail that TEPCO installed in place of the control rod drive unit. Below the arm, a guide pipe serves as a ramp to the rail. The robot then enters the access route through a tilting motion.

A presentation slide shows TEPCO’s planned steps for Unit 2’s trial retrieval. Image used courtesy of TEPCO

National Labs Test Digital Twin-Operated Telerobotics

Meanwhile, in the U.S., Argonne National Laboratory has demonstrated a remote-controlled telerobotic system for handling radioactive materials inside a hot cell.

Wearing a virtual reality headset and haptic gloves, an operator directs a dual-arm robot to handle nuclear waste. Image used courtesy of Argonne National Laboratory

Testing took place over a week in a nonradioactive mock environment at Oak Ridge National Laboratory’s radiochemical processing site. A dextrous, dual-arm robot successfully opened a canister of hazardous materials, inspected and sorted the contents, and closed the containers. Behind the wheel, a human operator guided the machine’s movements via a virtual reality headset and haptic gloves.

The demonstration used Argonne’s mixed-reality digital twin platform, which combines sensory displays, virtual models, and hardware controls to form a digital representation of tangible objects. In this case, the operator remotely controlled the robot’s arms from a digital workstation.

According to Argonne, the technology could replace conventional radioactive material handling methods. Historically, the process relied on hot cells consisting of shielded concrete and mechanical manipulators accessible through sealed gloveboxes. However, these techniques rely on obsolete manual equipment that can be difficult to deploy on-site.

Argonne’s augmented telerobotics development. Image used courtesy of Argonne National Laboratory

Argonne’s telerobotics solution addresses these gaps with a mobile hot cell system controlled by augmented devices and digital twin software. After some technical improvements to the hot cell structure, the laboratory plans to conduct another demonstration later this year.

Once completed, the robot is expected to help the Department of Energy clean up 107 nuclear sites.