Scientists monitoring the ruins of the Chernobyl nuclear power plant in Ukraine have seen a surge in fission reactions in an inaccessible chamber within the complex. They are now investigating whether the problem will stabilise or require a dangerous and difficult intervention to prevent a runaway nuclear reaction. The explosion at Chernobyl in 1986 brought down walls and sealed off many rooms and corridors. Tonnes of fissile material from the interior of a reactor were strewn throughout the facility and the heat it generated melted sand from the reactor walls with concrete and steel to form lava-like and intensely radioactive substances that oozed into lower floors. One chamber, known as subreactor room 305/2, is thought to contain large amounts of this material, but it is inaccessible and hasn't been seen by human or robotic eyes since the disaster.

Boston Dynamics' Spot robot is expanding to its resume every day, and the quadruped can add nuclear power plant exploration and radiation monitoring to the list. Engineers from the University of Bristol recently tested Spot around the Exclusion Zone territory of the Chernobyl Nuclear Power Plant. The Exclusion Zone covers approximately a 1,000-square-mile area in Ukraine surrounding the Chernobyl Nuclear Power Plant, where radioactive contamination is highest and public access and inhabitation are restricted. According to the State Agency for Exclusion Zone Management, this is the first time Spot has been tested there. Spot helped create a 3D map of the distribution of nuclear radiation around the Chernobyl Nuclear Plant.