Nuclear bomb fallout

[Marlin]

The neutron bomb is commonly known to be the most efficient nuclear weapon. Its blast is just twice the size of the largest conventional bomb but produced very high radiation emmisions. It was designed to counter the large number of Russian tanks in Eastern Europe but not devastate the European country side with minimal blast damage and fallout.

There is a nuclear weapon that that per kiloton was much more effective in reducing fallout. What was this weapon?

[Nuclear Renaissance]

the fusion-driven "Bassoon" design?

[Marlin]

The specific weapon is a multi-stage device.

[Nuclear Renaissance]

The "bassoon" design gave birth to the TX-41 "Poplar" shot, which was 95% fusion. I can't recall anything cleaner than that....

[Marlin]

The device I am looking for was 97%.

[Preciousblue1965]

I think a better question would be......

Where in the Ham-Sammich do you get all this stuff?

[Marlin]

Teller-Ulam

Nope, this device has another unique distinction as well.

[Nuclear Renaissance]

Well, per kiloton, the Soviet Tsar Bomba is probably the highest percent fusion. But, your original question asked for an "effective" reduction of fallout, and that's not really effective, because to get to the high 90-percent range, you have to chain together a reallly big bomb (and thus a lot of fallout anyway).

[Adam Grundleger]

Yep, Tsar Bomba was 97% fusion in a three stage fission-fusion-fission reaction with a non-fissile reflector.  It was the largest by yield (50-100 Mt) device ever tested, yet was remarkably clean with regard to fallout. The 4000m height of the airburst helped minimize fallout as well.

[Marlin]

The answer is Tsar Bomba and not only was it the cleanest bomb but the largest ever tested. If the lead shileding had not been installed it would have been 100 mega tons not just 50.

The device offically designated RDS-220, known to its designers as Big Ivan, and nicknamed in the west Tsar Bomba (and referred to as the Big Bomb by Sakharov in his Memoirs [Sakharov 1990]) was the largest nuclear weapon ever constructed or detonated. This three stage weapon was actually a 100 megaton bomb design, but the uranium fusion stage tamper of the tertiary (and possibly the secondary) stage(s) was replaced by one(s) made of lead. This reduced the yield by 50% by eliminating the fast fissioning of the uranium tamper by the fusion neutrons, and eliminated 97% of the fallout (1.5 megatons of fission, instead of about 51.5 Mt), yet still proved the full yield design. The result was the "cleanest" weapon ever tested with 97% of the energy coming from fusion reactions. The effect of this bomb at full yield on global fallout would have been tremendous. It would have increased the world's total fission fallout since the invention of the atomic bomb by 25%.

http://nuclearweaponarchive.org/Russia/TsarBomba.html