Making the box of salty radiation medicine an order of magnitude cheaper and shoving a bit of hydrogen in a salt cavern solves the storage problem (which is already far smaller than you're pretending) entirely.

Fissions reactors that don't have incredibly strict and expensive regulation are already pretty unreliable, and they're operating within the bounds of known materials rather than an order of magnitude outside of them.

Even the mythical 100% uptime nuclear reactor still needs just as much storage for abritrage because it is so much more expensive.