Clean Bomb

The nuclear bomb, although a powerful weapon, is frowned upon both by tacticians and politicians for its unwanted side effects. From a completely strategic point of view, a nuke makes for a poor offensive weapon. While its primary can and will flatten any man-made target, the affected area is unsuitable for occupation. The only good strategic use of a nuke is to use it as a fail-safe. Say that your forces defending a key position such as a bridge or port is hopelessly outnumbered and enemy troops are already moving in to occupy the position, your best choice of options includes a unscheduled sunrise a few kilometers over that port, flattening out the remaniants of your forces and the bulk of the enemy, while making the key position unusable.

But to make such a dirty device something suitable for offensive operations is rather easy. Most of the radioactive fallout comes from unreacted primary stage fissile material (uranium or plutonium). Most fission bombs (a-bombs) only have one stage where the conventional explosives crush a fissile stage, and much of the fissile fuel is unreacted and created fallout. In fusion bombs (h-bombs), the energy from a fission bomb is harvested to crush and heat hydrogen to the fusion temperature, which in turn reacts more of the fissile material, creating less fallout.

What I propose is to create a three stage fission bomb using four layers of conventional explosives and three layers of fission fuel. Stage one is located at the center of the bomb and consists of a thin shell of fission material sandwiched by a conventional core and outer shell, its detonation occurs first.The second stage is located at the outside of the device, and the layout is similar to the first stage, consisting of a thin shell of fissile fuel sandwiched between two shells of conventional explosives. The final stage is simply a thick shell of fissile fuel.

What happens when the timer goes off is the first and second stage detonates, creating two nuclear scale explosions to either side of the final stage, crushing it with more force and duration than any conventional explosive, reducing fallout without reducing yield. The leftover fissile material from the first stage also has no where else to go other than to the hot little reaction occurring at its neighboring third stage, and the crumbs leftover are given a second chance to fizz, reducing fallout yet again while probably increasing the yield.