[FairOpinion]

plutoinic/megatn(a)/((-)(-))

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Plutonium is used in some nuclear bombs.

Megaton is a way of measuring the strength of a nuclear explosion. I think it comes from it would be equivalent to the amount of TNT, e.g, it would take 1 Megaton (1,000,000 tons) of TNT to cause the equivalent explosion of a "1 Megaton" nuclear bomb.

[Axenolith]

Nothing terrorist originated will have a yield over ~40 kilotons (Kt), and that would be a long shot in hell in and of itself...

Megatonnage (Mt) is indicative of thermonuclear weapons, the biggest purely fission weapon was a few hundred Kt yield.