The Jasons Report on Plutonium Pits
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Photo Credit LANL
This is very much down in the weeds, but I think it’s worth noting for the nuke nerds.
The Jasons have issued a report on the plutonium in nuclear weapons. The Jasons are a group of experts convened by the Department of Energy to consider various issues. They have been primarily focused on nuclear weapons, but they also have considered “Havana Syndrome” (cricket sounds) and global warming (real). Most of their work is classified.
In 2010, they seemed to have found a problem in the aging of plutonium pits in nuclear weapons. They didn’t say what the problem was or how bad it was –classified, but it was clear that they felt there was something wrong.
In this latest report, they feel that the problem has been fixed.
The performance of a pit can degrade over time due to effects of the radioactive decay of the Pu-239 nuclei. Before 2010, tests of Pu at the age in the stockpile did not show evidence of degradation of properties relevant to weapons performance. This is in part because annealing processes in materials like Pu partially counteract the damage caused by radiation. After 2010, some aging effects began to be observed in stockpile-age and artificially aged Pu. In response, in 2021 the National Nuclear Security Administration (NNSA) created a 10-year Research Plan for Pu and Pit Aging (the “Plan”) that was implemented at its Laboratories. Many significant achievements were made in the first five years of the Plan including: property measurements that directly compare new with aged Pu, advances in materials characterization using newly developed tools at NNSA facilities, and simulation tools with enhanced calibration based on new experimental results. Overall, the results from the first five years of the Plan show that there are gradual changes in Pu material properties as a function of age, at a level that do not call into question present weapons performance.
They still want more work on the problem, though. The data is used for projections of the lifetime of nuclear weapons – how long they can go without major refurbishing and the probability that they might be a dud for targeting.
It appears that a facility for obtaining more data on the issue has been delayed. The ECSE will be underground at the National Nuclear Security Site in Nevada, along with a number of other very costly instruments. There’s a fair bit of information at that link, for those who want to get even further into the weeds.
The Proposed Updates incorporate new information learned in the first five years of the Plan, as well as changes to address delayed availability of the Enhanced Capability for Subcritical Experiments (ECSE). The Updated Plan includes a number of different experiments to directly explore weapons-relevant trajectories to improve assessments. The updated Plan also includes preparation for experiments with ECSE when it comes online. If appropriately funded, focused, prioritized, and scheduled, the Updated Plan should further reduce uncertainties in weapons performance due to Pu aging.
As with any report released by the Trump administration, we must ask whether this is truthful or what the boss wants. I’ll guess that the Jasons retain a truth-telling ability. I knew one of them and can’t imagine it otherwise for him.
Cross-posted to Nuclear Diner