Craving reliable energy that doesn’t come with a big side order of carbon, the United States is taking a new look at nuclear power.

But even as they hail President Barack Obama’s announcement last month that the government would back $8 billion in loans for new nuclear power plants, some engineers also are urging a new look at an alternative to the uranium fuel those plants will inevitably use.

Thorium, they say, provides all the carbon-free energy of uranium – about 300 times more, actually – with almost none of the guilt.

Thorium plants cooled with molten fluoride salt would leave a fraction of the nuclear waste compared to the uranium-fueled, water-cooled plants in use today. In addition, thorium plants can’t melt down and don’t produce reliable fuel for bombs.

“What’s not to love?” asked Kirk Sorensen, a NASA rocket scientist in Huntsville, Ala., who is earning his doctorate in nuclear engineering…