As of February 6, 1996 the total quantity of plutonium was 66.1 metric tons, including Department of Defense quantities. Pantex still has Category I/II quantities of special nuclear material (SNM), which is in the form of plutonium pits. The plant is authorized to stage up to 20,000 plutonium pits. Currently, approximately 14,000 are in interim staging at Pantex.
Almost all plutonium at the Pantex Plant is weapons grade and in the form of pits, the plutonium assemblies that serve as a primary nuclear component of a weapon. A pit consists of a plutonium metal shell surrounded by a hermetically sealed outer metal shell that is usually stainless steel. For interim storage, pits are packaged in AL-R8 storage containers. The total quantity of plutonium at Pantex is large. In July 1994, Pantex had over 6,000 pits and sealed sources.
A significant vulnerability at Pantex Plant is total reliance on the outer metal shell of a pit as the only barrier to prevent plutonium oxidation and release. The pits have not been tested and qualified for extended storage, which begins after the service life of a weapon. Some pits have weaknesses in joint materials and design, making them vulnerable to failure and consequent plutonium release during handling and storage.
The oldest pits at the Pantex Plant are over 33 years old. Aging and environmental effects may cause or contribute to a wide variety of pit failures. Daily warming and nightly cooling of pit storage magazines may lead to crack initiation and growth in aluminum welds in some pits. Chemical contaminants introduced during testing, cleaning, and packaging may also initiate crack growth over extended periods of time. Almost all pits are stored in magazines in AL- R8 containers. Being unsealed, the AL-R8 containers do not keep out airborne contaminants and would not completely contain plutonium released from a failed pit.
The Pantex Plant surveillance program uses relatively simple methods to identify failed pits but does not address underlying failure mechanisms or their causes. Normal Pantex Plant operations involve only sealed forms of plutonium. Any incident exposing plutonium at the Pantex Plant would be handled as an abnormal event by trained personnel.
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