In your argument as to when a nuclear power plant kills people, as I see it, you consider the period too short. It may be that few or no one dies from the direct explosion, but the worst thing about the accidents is the immense amount of gamma radiation. Radiation deaths often do not occur immediately, but only after some time. It is therefore difficult to estimate how many deaths are due to radiation from nuclear catastrophes, but to estimate it with one death is definitely too low in my opinion. The number of deaths from nuclear power is certainly not comparable to solar or wind power due to its magnitude.
“Overall, based on statistical modelling of the radiation doses received by workers and local residents, a total of 4000 deaths will eventually be attributable to the Chernobyl accident”(Pflugbeil, S. (2006). Chernobyl – Looking back to go forwards: the September 2005 IAEA Conference. Medicine, Conflict and Survival, 22(4), 299–309. https://doi.org/10.1080/13623690600945230) “Environmental fallout from the accident affected cropland, forests, rivers, fish and wildlife, and urban centres. In the three countries most affected, nearly 800 000 ha of agricultural land was removed from service, and timber production was halted on nearly 700 000 ha of forest.”(Pflugbeil, S. (2006). Chernobyl – Looking back to go forwards: the September 2005 IAEA Conference. Medicine, Conflict and Survival, 22(4), 299–309. https://doi.org/10.1080/13623690600945230) “Studies have found that exposed populations had anxiety levels twice as high as normal, with a greater incidence of depression and stress symptoms.”(Pflugbeil, S. (2006). Chernobyl – Looking back to go forwards: the September 2005 IAEA Conference. Medicine, Conflict and Survival, 22(4), 299–309. https://doi.org/10.1080/13623690600945230)
I’m sorry but I didn’t have the time to find the values for Fukushima as well. There are a lot of different numbers, but I think these are also validated by the UN and WHO and are pretty informative