Of course, unlike the bombs dropped on Japan modern thermonuclear weapons burn large amount of U328 with the fast neutrons created from fusion, resulting in large amounts of fallout. They may not cause many radiation deaths from their explosion but the fallout they create will endanger people downwind for a long time after the initial explosion.
That depends, some use U-238 for this purpose to about double the yield, some don't, like the 50 Mt Tsar Bomba in its one test: https://en.wikipedia.org/wiki/Tsar_Bomba
I don't have words to convey how much I hope we never see those weapons used in anger.
Nothing that I know about human nature suggests that they'll again never be used in anger, it's only a question of when. Hopefully not any time soon.
The replaced the U-238 in the Tsar Bomba test with lead when they tested it at the cost of halving its power, you're right. But sadly I've never heard of that being done with a deployed thermonuclear weapon.
That depends, some use U-238 for this purpose to about double the yield, some don't, like the 50 Mt Tsar Bomba in its one test: https://en.wikipedia.org/wiki/Tsar_Bomba
I don't have words to convey how much I hope we never see those weapons used in anger.
Nothing that I know about human nature suggests that they'll again never be used in anger, it's only a question of when. Hopefully not any time soon.