If you look at this picture you will get cancer!

http://en.wikipedia.org/wiki/Generation_IV_reactor

Degradation of the whole fuel element

Water and zirconium can react violently at 1200 °C, at the same temperature the zircaloy cladding can react with uranium dioxide to form zirconium oxide and a uranium/zirconium alloy melt.

http://en.wikipedia.org/wiki/Behavior_of_nuclear_fuel_during_a_reactor_accident

http://en.wikipedia.org/wiki/Corium_%28nuclear_reactor%29

http://en.wikipedia.org/wiki/Zirconium

http://en.wikipedia.org/wiki/High_temperature_corrosion

[...]It is black and yellow.[...]

http://en.wikipedia.org/wiki/Chernobylite