Our laboratory has been actively working on robotics for nuclear environments since the Fukushima nuclear accident in 2011. I’ll introduce some of the projects I’ve been involved in.
Radiation Source Estimation
The first step in decommissioning the Fukushima Daiichi nuclear power plant is to reduce radiation levels at the site so that workers can stay longer and be safer. Therefore, it is important to determine the distribution of radiation sources and to decontaminate the estimated radiation sources. Due to high radiation levels, it is desirable to install radiation detectors on a robot, and the robot will autonomously explore the site to estimate the radiation sources.
We developed a path planning method to localize the radiation sources. This method determines the next measurement point based on previous measurements, allowing for autonomous exploration. By utilizing principal component analysis of the simple back-projection results, the robot automatically moves towards the radiation sources and circles around to accurately localize the radiation sources. Please refer to the paper here.
We also have improved the radiation source estimation by utilizing filtered back-projection. Please refer to the paper here.
If you are interested in radiation source estimation using non-directional detectors such as Geiger counter, please check out the paper here as well.
Gamma Ray Irradiation Experiment On Camera
Radiation affects not only people but also electronic equipment. Therefore, we need to consider the effects of radiation on the electronic equipment of robots for nuclear applications. Firstly, electronic devices will malfunction if they are exposed to radiation for a long time, which is called the total ionising dose (TID) effect.
Sometimes the critical components can be protected by heavy metals such as lead or moved away from high levels of radiation, but cameras are one of the components that are difficult to protect from radiation.We have carried out several gamma ray irradiation tests on commercial off-the-shelf cameras to investigate the TID effect. Also, we investigated the image noise caused by gamma radiation. Please refer to the paper here.
Best Viewpoint For Operator to Control Robot Arm
For the decommissioning of the Fukushima Daiichi nuclear power plant, we need to retrieve the nuclear fuel debris that remains inside the primary containment. One approach would be to use the teleoperation of a robotic arm. The viewpoints provided to the operator are carefully selected to achieve efficient teleoperation. Therefore, we are woking on viewpoint selection for robot teleoperation. Please refer to the papers here and here for further explanation.
Navigation and Control For Robot Arm
We are also working on the navigation and control algorithm of a robotics manipulator for nuclear fuel debris retrieval. This is an ongoing joint project with the University of Sussex.