40B will not be enough to clean up the mess left behind by nuclear planets AND take care of radioactive waste for 100.000+ years.
The total economic damage caused by Chernobyl is estimated to be 235 billion dollars (but who really knows).
Cleaning up after a disaster isn't the same as cleaning up a plant's stored waste.
I could as well say that I've calculated that 42 dollars will be enough to take care of all the leftover nuclear waste forever.
The fund has $40 billion, but there are 60 commercial plants in the US. Even with the optimistic $2 billion per plant and ignoring scientific plants and interim storage facilities and Fukushima situations, there are still about $80 billion that are not yet internalized into nuclear power production costs.
Decommissioning is paid for by plant-specific trust funds that are also paid into throughout the life of the plant.
In general, it's looking to be slightly cheaper than expected to decommission plants, and so there's a bit of a gold rush to access these funds. That's why you see stuff like this: https://www.ipsecinfo.org/2018/11/23/holtec-seeks-approval-t...
This is another element in the equation of why nuclear plants are shutting down early.
The obvious alternative are renewables, though, not fossil fuel plants.