There is $450m nuclear insurance available on the market. Perhaps you could work out proportional reinsurance using that plus the reactor maker insurance guarantee. Price-Anderson already incentivizes nuclear quite a bit by the US Gov acting as a backer. It doesn't help because nuclear is too risky for the benefit. Same as hydro-electric. Too dangerous for the money.
Reinsurance is a method to pool insurance resources so that a smaller insurance company can assert the ability to cover a hundred billion dollar claim to begin with. It doesn't solve the time value of money issue, it only moves it around.
Carrying that amount of insurance is prohibitively expensive independent of the risk. Require the oil companies to carry enough insurance on every well to cover a claim the size of Deepwater Horizon and see how fast it destroys them.
