Jeffrey Lewis3 Studies Show Pu Pits Age Well

NNSA has a very helpful press release explaining those studies showing plutonium ages better than Sophia Loren.

Unfortunately, it doesn’t seem to be online … until now:

Recent studies by Lawrence Livermore and Los Alamos National Laboratories show that the aging of plutonium in U.S. nuclear weapons will not affect reliability over the next several decades. The classified studies were done for the Department of Energy’s National Nuclear Security Administration (NNSA) and have taken five years to complete.


The classified studies looked at pits in each nuclear weapon type and gave specific information on plutonium properties, aging and other information. Overall, the weapons laboratories studies assessed that the majority of plutonium pits for most nuclear weapons have minimum lifetimes of at least 85 years.


The scientific process used in the assessment of plutonium aging on pit lifetimes was peer reviewed by the JASON panel, an independent scientific panel of academics with experience in nuclear physics and the nuclear weapons program. The JASON study concludes that most plutonium pit types have credible lifetimes of at least 100 years, while other pit types with less than 100 years of projected stability have mitigations either proposed or being implemented. The JASON review was congressionally mandated by the Defense Authorization Bill for fiscal year 2005, and was submitted to Congress today.

So three studies: Los Alamos, Livermore and JASON.

Late Update: The JASON report is online.


  1. Mason Lowe (History)

    The JASON panel report is available online at:

  2. Meteor Blades (History)

    I guess this is good news?

  3. not trying to be critical

    As far as I know, the JASONs didn’t do a study but rather a peer review

  4. Jeffrey Lewis

    No worries, the unclassified version is online here, so …

  5. Jacobo (History)

    So what are the implications for former Soviet weapons? It seems that the certain degradation of old Soviet devices has received considerable attention in non-proliferation discussions. Are there certain maintenance requirements for long-lived plutonium pits that the Russians have not been following?

  6. Haninah

    Unlike safety and security issues, reliability has been strictly left out of US-Russia collaboration on nuclear issues, so what the technical issues are regarding the reliability of Soviet warheads is not an easy question to answer from the open literature. There is some consensus, though, that unlike us the Russians can, and probably do, regularly remanufacture their legacy designs, so that physical aging of the plutonium components is less of a concern for them. (They also may or may not have had signifincantly larger performance margins to begin with – there’s some debate about that.)

    Generally, the Russians are much more concerned about the aging of their delivery vehicles, the slow pace with which retired vehicles are being replaced, and the fact that START (while it’s still alive) prevents them from compensating for those problems by up-MIRVing their more robust vehicles.

  7. Jacobo (History)

    Thanks, Haninah; good explanation.

  8. Haninah

    My pleasure. For more information on Russia’s stockpile stewardship and remanufacturing activities, see more information on START and Russia’s delivery vehicle problems, see