What is the worse thing that could happen, from a nuclear meltdown in a power station.?

The 'China Syndrome' refers to the most drastically severe meltdown a nuclear reactor could possibly achieve. In this case, the reactor would reach the highest level of supercriticality for a sustained period of time, resulting in the melting of its support infrastructure. The uranium in the core would behave in a similar manner to a delta-cl fire, self-sustaining temperatures in excess of 2000�C. Since these temperatures would melt all materials around it, the reactor would sink due to gravity, effectively boring a hole through the reactor compartment's floor.