I heard that NK’s NUK Test was 5, or so, times the one set off at Hiroshima!
It only take 5-10 lbs. of U-235 to make a massive bomb!
And U-235 is made from centrifuges, starting with ‘Yellow Cake’ (normal uranium found in the ground).
Remember Einstein’s equation: E = MC2
Put in 5 lb of U-235 times the speed of light squared!
That’s a massive amount of energy!
The Norks use Plutonium.
It was likely a boosted fission blast, where an atomic bomb causes isotopes of hydrogen to fuse. So, it may have been a hybrid.
Actually only a fraction of the fission material (uranium or plutonium) is converted into energy. But it still results in a massive amount of energy!
Remember. It does “only” take that amount of U233 U235 to create the critical mass for a fission nuclear bomb. But only a very tiny amount of the fissionable material actually reacts. The rest (around the central exploding mass) is simply blown away with the blast.
More importantly, the equation actually is: energy = difference in mass x c^2.
It’s the DIFFERENCE in the mass of the nuclei (the difference between original mass of U235 and the sum of the masses of all of the fission products and neutrons afterwards) that is multiplied by c^2
So the exploding mass DOES react according to Einstein’s energy. But most definitely you do not multiply the 20 pounds of original U235. Only a “few grams” of U235 react to create the blast equivalent of 10,000 tons of chemical explosives.