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.
This converted B-36 bomber (designated the NB-36H) carried an operating nuclear reactor to study how to build a nuclear-powered aircraft
Between 1946 and 1961, the Air Force and the Atomic Energy Commission spent more than $7 billion trying to develop a nuclear-powered aircraft. Although no airplane ever flew under nuclear power, the Air Force converted this B-36 bomber, known as the Nuclear Test Aircraft, to carry an operating three-megawatt air-cooled reactor to assess operational problems (it made 47 flights over Texas and New Mexico between July 1955 and March 1957). The NB-36H carried the reactor in its aft bomb bay and incorporated a new nose section, which housed a 12 ton lead and rubber shielded crew compartment with 10-12 inch (25-30 centimeters) thick leaded-glass windows. Water pockets in the fuselage and behind the crew compartment also absorbed radiation (due to weight constraints, nothing was done to shield the considerable emissions from the top, bottom or sides of the reactor).
One idea for an operational nuclear-powered aircraft involved detachable reactor modules that could be replaced as needed. In this artist’s conception, the pilots were in the section forming part of the tail, which could be detached in cases of emergency.
Credit: San Diego Aerospace Museum (top), U.S. Air Force (bottom)