I agree with the above poster, Trying to create an uncontrolled fission reaction in the fuel rod containment using a nuclear trigger would simply result in a a very tiny amount actually being fission into lighter isotopes, which would still be radioactive The rest would be vaporized and spread mostly into the pacific ocean and western north America It is an insane idea.

The solution is to remove the fuel rods and bury them deep in a geologically table area encased in concrete and separated from each other. It won't be cheap and there will be hundredths of people that die in the process of removing the fuel rods, but the alternative is possibly the contamination of the entire northern hemisphere of the planet with nucleotides that have half lives in the thousands of years.