[cynwoody]

We don't have any [100 mt nukes] and never did.

In 1961, the Soviets came within a factor of two, with a 58-megaton bomb. It was supposed to yield 100 megatons, but they decided to replace the U-238 tamper with lead, in the interest of reducing fallout, which was already becoming a world opinion issue. In the event, 97% of its yield was from fusion, and it produced very light fallout, having exploded at an altitude of 13,000 feet.

Tsar Bomba Video

[Nathan Zachary]

The Bassoon device fired in Zuni was the first test ever of a three stage thermonuclear design. Surprisingly, this substantial innovation was also the first successful thermonuclear device design ever fired by Lawrence Livermore (then known as UCRL, now LLNL). The configuration fired in this test was a "clean" (low fallout) version that used a lead tamper around the thermonuclear third stage. Only 15% of the energy yield was from fission. A "dirty" version of this design, the Bassoon Prime device, was later fired in Redwing Tewa. The predicted yield for Zuni was 2-3 Mt.

The Bassoon device was 39 inches in diameter, and 135.5 inches long. It weighed 12,158 lb. Crater dimensions were 2330 feet wide, 113 feet deep.

This design was later developed into the Mk-41 bomb, the highest yield (25 Mt) weapon ever deployed by the U.S.

http://nuclearweaponarchive.org/Usa/Tests/Redwing.html