I would certainly agree that nobody should actually try to put a year's generation of dangerous nuclear waste in 3 shipping containers. It'd be hazardous and the shipping containers couldn't be moved without breaking (probably do some damage to them even without moving them). The point is more that we're dealing with a volume of material that is - for an industrial society - tiny. There is a reason that in practice it is ignored it despite the braying crowd of people insisting that it is an unsolved problem that we can't ignore. It is an extremely ignoreable problem on the scale of benefits that nuclear power provides.
You may dedicate whole container to transport just a few kg of highly radioactive items.
> Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel that has already been cooled in a spent fuel pool for at least one year and often as much as ten years. Casks are typically steel cylinders that are either welded or bolted closed. The fuel rods inside are surrounded by inert gas. Ideally, the steel cylinder provides leak-tight containment of the spent fuel. Each cylinder is surrounded by additional steel, concrete, or other material to provide radiation shielding to workers and members of the public.
https://en.m.wikipedia.org/wiki/Dry_cask_storage
There’s also a lot of low level nuclear waste which is a pain to deal with (make sure you pick the right brand of kitty litter…)
https://www.npr.org/sections/thetwo-way/2015/03/26/395615637...