Yes, but the initial nuclear charge is comparatively small (1.5MT), and dispersed over a large area, since the bomb is detonated pretty high above the ground. To my knowledge there is only one such charge in this bomb. If its yield weren't limited to 50MT, there'd be two such stages. Andrei Sakharov suggested not using U238, replacing it with some passive material in the secondary module. The yield was limited because if it weren't, there _would_ be a lot of radioactive contamination, and the fireball would touch the ground, exacerbating the problem.
Wow, I never realized Tsar Bomba was scaled down. Wiki link says with U238 it would have yielded over 100MT. Also confirms that it was a very clean bomb, with over 97% of the energy coming from fusion.
97% energy coming from fusion is in no way proof of this being clean bomb. 3% from fission is still many times more than Hiroshima or Nagasaki bomb. We also don't know how much fissile material there was (and how much was dispersed in environment). Because the bomb was detonated high up there wouldn't be hotspots on the ground but the release was still there, dispersed for all humanity for decades to come.
Calling the bomb clean would be like calling somebody's vomit clean because it was diluted in large amount of water and then sprayed on all walls so there are no large concentrations of it.
Everything's relative. Of course it generated more radioactivity than Hiroshima's measly fifteen kilotons, but for a fifty megaton bomb it was pretty darn clean.
Well, that lake your city draws their drinking water from? I guarantee someone vomited, peed and shat into it. The issue is the concentration. Remember that because this was 4KM above ground, the resulting fallout was spread over tens of thousands of square kilometers.
Sure, but that radiation is dispersed over much, much greater distances and you need less radiation to give the effect intended. The end result is that the explosion zone is not nearly as radioactive as either Hiroshima or Nagasaki.
Also, there is vomit all over the pavements and walls of your city. Just in low concentrations.
https://ru.wikipedia.org/wiki/%D0%A6%D0%B0%D1%80%D1%8C-%D0%B...
https://www.atomic-energy.ru/files/books/Ukroschenie%20yadra...