The two-stage shrimp device detonated during the Bravo test became the largest nuclear detonation ever conducted by US. The significance of the Bravo test was
greatly enhanced by the fact that it was the first actual test of a dry (solid) fuel nuclear weapon built by the Teller-Ulam scheme. The test results were more than
successful from a military standpoint and Bravo basically defined the future of thermonuclear weapons. Other than that Bravo test was a disaster. There were serious miscalculations
and problems during this test series leading to human casualties.
The shrimp was a fairly large cylinder, measuring 179.5 inches long and 53.9 inches wide. Relatively lightweight as well for the nuclear weapon, it weighed only 23,500lb. The fuel consisted of up to 40% enriched Li6 deuteride. The rest of it was inexpensive Li7 isotope that played a significant and unexpected role during the explosion. All that was encased in a Uranium tamper. One more novelty was the exterior casing that was aluminum rather than steel in Ivy-Mike's Sausage, which significantly reduced the weight of the overall assembly.
Bravo's 15 Megaton explosion ripped the crater, which was 6510ft in diameter, with a depth of 250 ft. The fireball was 4 miles in diameter. The mushroom at its peak was 130,000ft (40+ km) high, 322,500ft (100 km) diameter with a stem of 22,500ft (7km).
The projected yield for the shrimp device was 6 mgt, with a of range 4-8 mgt. The practical yield was as much as 2.5 times higher. The reason for this unpredicted boost was the Li7 isotope. Inert by itself it reacted with the high energy neutrons produced by the tritium-deuterium fusion. Collision between the neutron and Lithium atom would produce tritium and helium atoms. Tritium is a highly reactive and efficient thermonuclear fuel, hence the dramatic increase in the weapon's total yield.
Unexpectedly, the high yield in conjunction with bad weather conditions produced the worst radiological catastrophe in US nuclear testing history. The whole Bikini atoll was contaminated and eventually the Green Zone was increased to 850Mi diameter circle. A number of US personnel, Marshallese and Japanese fishermen were exposed to dangerous levels of radiation.