These materials are a low-radioactivity version of what we think the fuel debris is like, which can now be used to learn more about their chemical properties and behaviour so we can begin to design safe strategies to remove the real degraded fuel. Our team at the University of Sheffield, UK, has developed new materials that are a safe simulation of the degraded fuel materials that remain both in Chernobyl and Fukushima. However, despite these huge challenges, there is hope that we can safely decommission both disaster sites, and this hope has been boosted by a major breakthrough in the world of materials science. Such an event would spread contamination throughout the reactor and significantly hamper the clean-up operation. In Ukraine, there is a pressing need to remove the LFCM from the reactor building of Unit 4 before the sarcophagus, hastily-erected in the aftermath of the accident, collapses. Controversially, this tritium-contaminated water is destined for release into the sea. If left at the plants, they could remain a hazard for decades, even millennia, unless something can be done to stabilise or remove them.Īt Fukushima, as long as the MCCI material remains, it requires continual cooling, generating millions of cubic metres of radioactive water. The degraded nuclear fuel materials present a highly dangerous risk to personnel and the environment in the surrounding areas of Ukraine and Japan. Without understanding their chemical make-up, it is challenging to design safe strategies to remove, store, or dispose of degraded nuclear fuel, and this is slowing down efforts to decommission both sites – 11 years on from Fukushima and 36 years since Chernobyl. This means that only a few samples have been collected from Chernobyl, and none from Fukushima, resulting in us knowing very little about the substances and their chemical properties. These degraded nuclear fuel substances – known at Chernobyl as Lava-like Fuel Containing Materials (LFCMs), and as Molten Core Concrete Interaction (MCCI) products at Fukushima – are highly radioactive and too dangerous for humans and even some robots to get close to, even with the most protective nuclear safety equipment. It is thought to comprise melted mixed oxide fuel – containing plutonium as well as uranium – zircaloy cladding, boron carbide fuel rods, stainless steel, as well as a high-sand-content concrete. In Fukushima, the exact composition of the degraded nuclear fuel material residing in the three damaged nuclear reactors is still unknown. This flowed through the nuclear power plant and has solidified into large masses such as the infamous Elephant’s Foot – a large mass of corium and other materials formed underneath the plant, composed primarily of silicon dioxide, with traces of uranium, titanium, zirconium, magnesium and graphite. In the case of Chernobyl, the mixture of molten fuel, cladding, steel and concrete, combined with sand, which was used in an attempt to extinguish the fire in the reactor at the time of the accident, formed nearly 100t of highly radioactive glass-like lava. Due to the intense heat, the materials melted together and formed a lava-like substance that has since solidified and remains at the bottom of the stricken reactors. The incidents, particularly in the case of Chernobyl, may seem long ago now, but the most dangerous radioactive materials they produced still very much remain and are slowing down efforts to clean up the sites.ĭuring both nuclear accidents, a loss of cooling caused uranium fuel to melt together with zircaloy cladding and all the materials used to build the nuclear reactors, including concrete and steel. Professor Claire Corkhill, Chair in Nuclear Material Degradation, explains.īoth Chernobyl in Ukraine and Fukushima in Japan stunned the world when their nuclear power stations went into meltdown. The Chernobyl power station, Ukraine, with its safe confinement roof installed in 2016 In recovery – safely removing radioactive debrisĮxtremely dangerous radioactive debris remains at the world’s largest nuclear disaster sites, new materials developed by scientists at the University of Sheffield, UK, could pave the way for its safe removal.
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