Nuclear Power Engineering
Commercial power generation from fusion reactor is not yet possible, because

It is difficult to control fusion reaction
Quantity of fuel required for initiating fusion reaction is prohibitively high
The fuel required (e.g. deuterium and tritium) is scarce
It is difficult to initiate fusion reaction

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Nuclear Power Engineering
Molten sodium (as a coolant in fast breeder reactor)

Is highly radioactive at elevated temperatures and can cause explosion, when it comes in contact with air or water
Can't attain high temperature at normal pressure
Is not at all corrosive, even at a higher temperature
None of these

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