In my last post, I imagined Bush administration Strangeloves testing nuclear weapons in the Grand Canyon. No, they don't really want to do that. But they do want to start testing nukes again where they used to, in Nevada, as early as 2005. This would end a testing moratorium imposed by Poppy Bush in 1992, as USA Today's lead story reminds us.

The current Bushies love the idea that "bunker-buster" nukes can magically, cleanly neutralize deeply buried chemical and biological weapons. Alas, it's not that easy:

The limitations of physics mean even the best-designed bunker-busters can burrow only 30 to 50 feet before exploding. The explosion triggers shock waves that travel down toward buried targets and destroy them.

Critics say that means nuclear bunker-busters wouldn't be able to burrow deep enough before exploding to contain the fallout they would create. Sidney Drell, a Stanford University physicist, determined that destroying a target dug 1,000 feet into rock would require a nuclear weapon with a yield of 100 kilotons — more than six times that of the Hiroshima bomb. The explosion of a nuclear bomb that big would launch enormous amounts of radioactive debris into the air and contaminate a huge area.

To contain fallout for a one-kiloton bomb, the warhead would have to penetrate an estimated 220 feet underground, many times the depth achievable by any current earth-penetrator warhead. The challenge scientists face is to find some way to get the bomb deep enough so that the explosion harms only what's underground — not people on the surface.

Critics say the evidence against battlefield use of nuclear weapons is spread all over the Nevada Test Site. Most notable is Sedan Crater, 1,280 feet across and 320 feet deep. It is the largest crater at the test site, the result of a 104-kiloton device that was exploded 635 feet underground in 1962.

The idea was to see whether nuclear weapons could be used for such peaceful purposes as creating new harbors. The blast threw 12 million tons of radioactive earth 290 feet into the air, where it became airborne fallout. That was the end of the idea of digging harbors with nuclear bombs.

Until now, apparently.