Trinity Site by United States Department of Energy

Lying next to the entrance of the chain link fence that still surrounds Trinity Site are the rusty remains of Jumbo. Jumbo was the code name for the 214-ton Thermos shaped steel and concrete container designed to hold the precious plutonium core of the Trinity device in case of a nuclear mis-fire. Built by the Babcock and Wilcox Company of Barberton, Ohio, Jumbo was 28 feet long, 12 feet, 8 inches in diameter, and with steel walls up to 16 inches thick.

The idea of using some kind of container for the Trinity device was based on the fact that plutonium was extremely expensive and very difficult to produce. So, much thought went into a way of containing the 15 lb. plutonium core of the bomb, in case the 5, 300 lbs. of conventional high explosives surrounding the core exploded without setting off a nuclear blast, and in the process scattering the costly plutonium (about 250 million dollars worth) across the dessert. After extensive research and testing of other potential containment ideas, the concept of Jumbo was decided on in the late summer of 1944.