Pit Lifetime Appendix: Simple Simulations of Rossi-alpha Processing Distortions.; JSR-05-330A

15 pages (per the report documentation page). Wraps. Formulae. Figures. This is a JASON report, Distribution authorized to U.S. Government agencies and their contractors. It is understood that with the passage of time and the general diffusion of knowledge into the public sector that there is no current distribution limitation. JASON is an independent group of elite scientists who advise the United States government on matters of science and technology, mostly of a sensitive nature. The group was created in the aftermath of the Sputnik launch as a way to have the nation's preeminent scientists help the government with defense problems, similar to the way that scientists helped in World War II. It was established in 1960 and has somewhere between 30 and 60 members. Its work first gained public attention as the source of the Vietnam War's McNamara Line electronic barrier. Most of its research is military-focused. It has been estimated that plutonium pits have a minimum lifetime of at least 100 years, and a Lawrence Livermore National Laboratory study found that samples artificially aged to 150 years still performed as designed. This is because the alloy used in modern pits degrades slowly, and independent scientific reviews, including a JASON report, have concluded that most types of pits have a credible lifetime of at least a century. Aging issues are primarily a concern for the plutonium itself, which is stabilized by the addition of a small amount of another material to its alloy to prevent it from degrading. JASON studies (2007 and earlier) concluded that most plutonium pits have a minimum lifetime of at least 100 years. LLNL study (2012): Researchers at Lawrence Livermore National Laboratory found that plutonium samples artificially aged to 150 years continued to perform as designed. They also noted that the aged plutonium continued to "age gracefully" with no unexpected aging issues appearing. Other studies: The National Nuclear Security Administration (NNSA) has a 10-year research plan to further study plutonium pit aging to better predict lifetimes for each nuclear weapon system in the U.S. stockpile, as reported by the U.S. Government Accountability Office. In addition to the plutonium itself, other components of the pit, such as the non-nuclear materials, have also shown remarkable stability over the years. While plutonium pits are not expected to age significantly within the first 100 years, they are still a concern for some officials who believe that 80 or more new pits per year are needed to replace the aging pits in the U.S. arsenal. Presumed First Edition, First printing of this Appendix.…