Apparently when you extract plutonium for making nuclear bombs, as the North Koreans appear to be doing, you also get krypton:

On Sunday, reports quoted US government officials as saying that elevated levels of krypton-85 had been discovered in the air above the North Korean border. This is a gas with a half-life of 10.7 years that is created along with plutonium by the fission of uranium fuel in a reactor. The fuel is reprocessed to separate out the plutonium by dissolving it in acid, but this also releases the krypton-85.

This would seem to suggest that Dear Leader might be more powerful that Superman since Dear Leader can take that krypton, smash it, and make kryptonite. Which is why the Green Lantern is the most powerful superhero of all time [furious debate among comic nerds may now begin].