What is meant by thermonuclear reactions and why are they so called ? Why are these reactions not useful for peaceful purposes ?

Explanation

Those nuclear reactions which acquire very high temperature `(gt10^(6)K)` are called thermonuclear reactions, `e.g.,` fusion reactions are referred to as thermonuclear reactions.
Till date it has been possible to produce a fusion reaction only if a fusion reaction is used to generate the high temperature. A fusion explosion is triggered by an atom bomb which generates the high temperature needed for the fusion reaction. As yet it is not possible to control fusion process, therefore these reactions are not useful for peaceful.