Moving "Jumbo" at the Trinity test site

The U.S. Nuclear Weapons Cost Study Project was completed in August 1998 and resulted in the book Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940 edited by Stephen I. Schwartz. These project pages should be considered historical.

Caterpillar tractors haul "Jumbo" across the New Mexico desert, May 1945

As preparations for the first nuclear weapon test — code-named Trinity — proceeded in 1944, General Leslie Groves, the head of the Manhattan Project, began to worry about what would happen if the test was a failure. With a very limited supply of plutonium then available, a failure could scatter tens of millions of dollars of the precious element across the New Mexico desert. To avoid this problem, a massive steel vessel to contain the explosion was built at a cost of $142 million. Nicknamed "Jumbo," the container weighed 214 tons, was 25 feet (6 meters) long, 12 feet (3.7 meters) wide, and had walls 14 inches (36 centimeters) thick. As the reactors at the Hanford Reservation (Site W) began to produce greater quantities of plutonium and calculations lessened the chance of a fizzle, Jumbo was abandoned (it was exposed to the July 16, 1945, Trinity test and came through unscathed). Jumbo was at the time the heaviest item ever shipped by rail; several of the trestles between the plant in Ohio where it was manufactured and the Trinity site were damaged by its great weight and had to be rebuilt.

Credit: Los Alamos National Laboratory