The RBMK is a type of nuclear reactor designed and used primarily in the former Soviet Union. It stands for "Reaktor Bolshoy Moshchnosti Kanalny," which translates to "High Power Channel Reactor." This reactor uses graphite as a moderator and water as a coolant, allowing it to operate on low-enriched uranium fuel. One of the most notable RBMK reactors is the one located at Chernobyl, which was involved in the catastrophic Chernobyl disaster in 1986. The design of the RBMK has several safety concerns, including a positive void coefficient, which can lead to unstable reactor conditions under certain circumstances.