So i'm currently researching nuclear power and nuclear energy as it is a topic that has always interested me, but when researching nuclear fission waste, and hearing about waste that has a half life of 1000s of years, I cant help but wonder, if a nuclear material is dangerous because of its emission when an atom decays, if you have two substances of the same mass, one with a short half life and one with a greater half life, surely the latter is significantly less dangerous? It has less decays per second, so less ionising radiation, therefore, why do we have to secure it SO tightly, if when compared to materials that take <100 years it emits less harmful particles?
If the half life was super fast, ie. 10s of years, the radioactivity is high, but you could store it for a relatively short time and it would become safe rapidly.
If the half life was very long, ie. 10s of thousand years, the radioactivity is small, so its not really a big problem to begin with.
The complicated situation is when the lifetimes are in the 100s - 1000s of years regime, where they are still very active, but wont decay rapidly, so storage is an issue.