A Nuclear Decommissioning Manipulator with Novel Variable Impedance Actuator

With the ageing of nuclear facilities such as those in the Sellafield nuclear site in the UK, or the relatively recent disaster that occurred in the Fukushima Daiichi power plant in Japan, nuclear decommissioning is a major challenge that needs to be addressed in the 21st century. Innovative decommissioning technologies can assist in minimizing the risks and costs in tackling these complex challenges. More particularly, robotics solutions have already shown their potential, through several exploration missions, to monitor the conditions in Fukushima and mapping radiation sources in the Sellafield nuclear site. However, only a few dedicated robotic manipulators have been developed to contribute to the decommissioning tasks. Due to the radiation and the environmental uncertainties, standard robotic manipulators used in industrial applications are unsuitable for decommissioning scenarios.

In this project, we propose a robotic solution to aid in the clean-up of the primary containment vessel in Fukushima, and dismantling and decommissioning operations in Sellafield. We will develop a robotic manipulator based on a novel Variable Impedance Actuator (VIA) and employ artificial intelligence techniques for efficient exploration and decommissioning in nuclear environments. In contrast to existing VIAs which require sensors in the region of interaction and use feedback control strategies to modify the robot's impedance, we propose a novel Continuously Variable Transmissions(CVT) based Variable Impedance Actuator for an inherently collision-safe manipulator that can adapt to uncertain environments without additional interaction sensors. To fully capitalize on the manipulator's ability to change its impedance, new navigation and control strategies will be developed to perform remote handling tasks and a dedicated impedance controller will be designed to adapt the dynamic interaction behaviour of the robot according to the situation. The VIA, the manipulator and associated control strategies will finally be validated in realistic use-case scenarios representative of the Sellafield and Fukushima challenges.

This robotic solution will help to address the challenges associated with limited sensor availability due to radiation hazards and will allow us to safely conduct tasks in sensitive environments owing to the inherent collision safely offered by the VIA. This solution also offers resilience in events of communication and sensor failure or during mis-operation in teleoperation protocols, further de-risking robotic manipulation in the clean-up and decommissioning tasks in Fukushima and Sellafield respectively.