W47 - Reliability Controversy

Reliability Controversy

The history of the W47 warhead had a serious series of reliability problems with the warhead design. 300 of the EC-47 production prototype model were produced from April 1960 through June 1960, and were all promptly retired in June 1960 due to reliability concerns. Production of Y1 and Y2 models then proceeded in 1960 through 1964. A total of 1060 Y1 and Y2 models were produced, but they were found to have so many reliability problems that no more than 300 were ever in service at any given time. In 1966, 75% of the stockpiled Y2 warheads were thought to be defective and unusable. Repair programs continued for some time.

A number of the Polaris warheads were replaced in the early 1960s, when corrosion of the pits was discovered during routine maintenance.

Failures of the W45, W47, and W52 warheads are still an active part of the debate about the reliability of the US nuclear weapons force moving into the future, without ongoing nuclear testing.

A one-point safety test performed on the W47 warhead just prior the 1958 moratorium failed, yielding a 100-ton explosion. As the test ban disallowed testing needed for inherently safe one-point safe design, a makeshift approach with a boron-cadmium wire folded in the pit during manufacture, and pulled out by a small motor during the warhead arming. The wire had a tendency to become brittle during storage, and break or get stuck during arming, preventing complete removal and rendering the warhead a dud. It was estimated that 50-75% of warheads would fail. This required a complete rebuild of the W47 primaries. The oil used for lubricating the wire also promoted corrosion of the pit.