At the end of last year Japan owned 31.8 tons of fissile plutonium. Apparently 6.6 tons of that is actually in Japan while the rest is held abroad under terms of various nuclear waste reprocessing deals.

That’s a lot of fissile plutonium. You can use it, for instance and if you really wanted to (not that you would being a lovely reader of Nuclear Reaction), as the naughty bit in nuclear weapons. In the case of 31.8 tons of the stuff, that’s a lot of naughty bits in nuclear weapons. Let’s have a little rough fun with the numbers.

There was around six kilogrammes of plutonium in the ‘Fat Man’ atomic bomb that exploded over Nagasaki on August 9 1945 killing 80,000 people by the end of that year. Japan currently owns enough fissile plutonium to make 4,500 replicas of ‘Fat Man’. ‘Fat Man’ exploded with the force of 21,000 tons of TNT (21 kilotons). Japan’s current stockpile of fissile plutonium has the potential explosive force equivalent to a mountain of TNT weighing 94,500,000 tons (94,500 kilotons) – that’s around a fifth of the total explosive force expended by all the nuclear weapons tests in history (510,000 kilotons).

We told you it was a lot of fissile plutonium. We do hope someone’s keeping a close eye on it all.