A modern thermonuclear weapons usually contains both plutonium and highly enriched uranium.
Typically, these warheads have a mass
of about 200 - 300 kg and a yield of hundreds of
kilotons of chemical explosive, which corresponds
to about one kilogram per kiloton of explosive
yield. For comparison, the nuclear weapons that
destroyed Hiroshima and Nagasaki weighed 300 kg
From IPFM, Global Fissile Material Report 2011
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