Plutonium in Warhead Cores (“Pits”) Stable to 150 Years
December 6, 2012
Aging Tests at Nuclear Weapons Lab Extend Earlier Results, Increasing Confidence
Results Highlight Lack of Need for New Pit Production Facility
Scientists at Lawrence Livermore National Laboratory (LLNL), using peer-reviewed protocols, have determined that plutonium in the fissile core of nuclear weapons is stable for at least 150 years.
A short description of these studies and their policy context can be found in this month’s issue of LLNL’s Science and Technology Review (“Plutonium at 150 Years: Going Strong and Aging Gracefully <https://str.llnl.gov/Dec12/chung.html> ,” by Arnie Heller, pdf).
The article was brought to our attention this morning by our colleagues at Princeton’s Program on Science and Global Security <http://www.princeton.edu/sgs/> , with whom we have closely collaborated on pit policy issues this past decade.
The peer review for the protocols used in these continuing experiments, as well as the widely-cited interim results showing that U.S. pits last at least 85 years, can be found in a November 20, 2006 review by the JASON defense consultants (“Pit Lifetime,” <http://www.lasg.org/JASONs_report_pit_aging_ocr.pdf> pdf, JSR-06-335, The Mitre Corporation).
These new conclusions, like those of 2007, are based on multiple methodologies: naturally aged plutonium samples, artificially aged plutonium samples, and theory. Accelerated pit aging experiments began in 1997 in response to concerns expressed by the JASONs and many other parties, including the Los Alamos Study Group.
The Study Group requested clarification of pit aging phenomena and their implications for reliability and infrastructure investment in a letter to Secretary O’Leary in October of 1996, given the statements made to us that year by senior Los Alamos National Laboratory (LANL) officials that ““LANL has found no aging phenomena which would significantly decrease pit performance in the first few decades of pit life, assuming there are no design errors or manufacturing defects.””
In 1996, as we wrote then, “”the first few decades”” was the outer envelope of confident pit life. By 2002 it was 45-60 years. By 2007 it was at least 85 years. Now it is 150 years.
While pits contain other shell(s) made of other materials, some of which could in principle corrode or otherwise degrade, only the two plutonium hemishells need be manufactured and joined in a plutonium facility. Pits can be otherwise assembled and the more peripheral components exchanged in far less expensive facilities, as was done at the Rocky Flats Plant. (As far as we know, no such pit repairs are needed or planned. The Pantex nuclear weapons plant near Amarillo, TX, has a pit requalification work station in which the outer layer of the pit can be removed for inspection and replaced if needed.) Thus it is the aging of the plutonium components themselves, not anything else, which is germane to plutonium infrastructure decisions.
Study Group Director Greg Mello: “Taken together with other information, this new finding has a number of important implications. These include:
· The probability of prior results being mistaken (despite the extensive peer review they had) and therefore of acute pit failure, is now lower than ever.
· Pit production for the stockpile is not needed, unless somehow a grossly uneconomical scheme is devised in which the present inventory of roughly 5,000 backup pits, beyond the roughly 5,000 pits now in the nuclear stockpile, is deemed insufficient. [For stockpile pit inventory and other details see U.S. Plutonium "Pit" Production: Additional Facilities, Production, Restart are Unnecessary, Costly, and Provocative <http://www.lasg.org/CMRR/Mello_pit_recommendations_2Mar2010.pdf> , pdf. Extensive further resources can be found at http://www.lasg.org/CMRR/open_page.htm.]
· Such a cockamamie scheme indeed has been devised. It is the so-called W78/W88 Life Extension Project, including a large build of new “hedge” warheads. It may not endure, politically or managerially. Let us hope not.
· Barring such artificial, created “needs,” no large new plutonium pit manufacturing capability is needed to maintain an extremely large, diverse nuclear stockpile for the foreseeable future — for generations.
· For sound reasons, the U.S. has signed a binding treaty promising complete nuclear disarmament: the Treaty on the Non-Proliferation of Nuclear Weapons (NPT).
· It would be counterproductive to plan or design for such a large facility now because the planning and design bases would change so much prior to any necessity for construction that the effort would need to be updated again and again.
· In today’s world, national security threats from other sources have eclipsed the unique and nearly absolute claim nuclear weapons once had on appropriations. In our view, the most important of these is climate change and the severe weather, heat, and drought it is bringing. Whatever one’s views regarding threats may be, misallocation of tens of billions of dollars — which is what a program of pit production and fielding of new-pit warheads involving new-made plutonium pits would cost — would have very serious national security impacts.
· These results are being reported by LLNL, not LANL, and they are only being reported now. Until this year, LANL was to financially benefit from $6 billion in new construction primarily justified for its role in supporting pit production. LANL still seeks billions in new plutonium infrastructure investment, beginning later this decade.
· We very much doubt LANL’’s ability and willingness to reveal important national security science results that do not support LANL’s financial bottom line.
· The plutonium laboratory which is producing these results is slated to be downgraded from a secure nuclear facility under current National Nuclear Security Administration (NNSA) plans. This would leave LANL as the sole arbiter of pit aging.
· These results have been generated continuously. We have inquired about them, and congressional staff who have requested briefings on them have told us that the results of these continuing aging experiments were more than confirmatory of the reported 2007 findings. Why were these evolving results withheld until now, instead of being released, say, annually?
· It cannot be emphasized enough that rising threats to our very survival require our full political and fiscal attention. Livermore’s scientists have done the nation a great service by publishing these results, belated though they be.”