Reporting on the Japanese Dai-ichi nuclear situation, this blog emphasized the risk from the spent fuel pool in building #4.
While the large risk from the Dai-ichi spent fuel pool at building #4 has been reduced significantly, the risk of spent fuel pools at reactors in general is ongoing. The U.S. has many spent fuel pools perched high in reactor buildings, where under massive natural disasters, some might possibly lose water and begin significant nuclear emissions if not addressed quickly.
The safe storage solution, for up to 100 years or more, is to move spent fuel out of pools and into dry casks in concrete bunkers.
This is an existing technique, already proven in use.
The only obstacle? Cost. A cost that is moderate compared to the size of the industry and the market value of the electricity it produces.
Potentially larger costs are currently imposed on all of us already in the form of risk, to the profit of the plant operators. By avoiding this safety expense, they impose a risk of much greater costs onto the public at large, onto you and me. Correctly placing this cost back onto the plant operators would raise electric prices only a tiny amount, and make little difference on your monthly bill ($7 bn is an amount consumers of electricity from these plants pay for power over about 5 months, but that cost could be amortized over 10-20 years). This relatively modest cost could save much larger costs someday. It's akin to whether automobile seat belts are worth the money.