Corium (nuclear reactor) from the pre-meltdown reactor or be due to spontaneous fission of reactor-created actinides. In the absence of adequate cooling, the materials inside of the reactor vessel overheat and deform as they undergo thermal expansion, and the reactor structure fails once the temperature reaches the melting point of its structural materials. The corium melt then accumulates at the bottom of the reactor vessel. In the case of adequate cooling of the corium melt, the melt can solidify and the spread of damage is limited to the reactor itself. However, corium may melt through the reactor vessel and flow out or be
Fukushima Daiichi nuclear disaster (Unit 1 Reactor) Fuel Pool Cooling (FPC) line. On 10 August, the spent fuel pool was switched from the water-injection system – that functioned some 5 months – to a circulatory cooling system. For the first time since the 11 March disaster, all four damaged reactors at the plant were using circulatory cooling systems with heat-exchangers. Fukushima Daiichi nuclear disaster (Unit 1 Reactor) The was a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the Tōhoku earthquake and tsunami on 11 March 2011. It is the largest nuclear disaster since the Chernobyl