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
Nuclear reactor heat removal total heat produced in the nuclear reactor is: formula_5 where formula_6 is the mean neutronic flux and V is the fuel volume (normally measured in formula_7). Recovery of this amount of heat is achieved by using cooling fluids whose temperature at the entrance to the reactor channel formula_8 will increase with the distance traveled in the channel. The thermal balance of the channel is expressed by the relationship: formula_9 where formula_10 is the flow rate of the cooling agent, formula_11 is the specific heat at constant pressure, formula_12 is the increase in the temperature of the fluid after passing a