Tracking Pit Production

, Washington representative and senior analyst | June 25, 2012, 11:01 am EST
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UCS recently obtained a copy of the March 2012 “Quarterly Pit Production Report” produced by the National Nuclear Security Administration (NNSA). What follows is a little history and some of the interesting tidbits that can be teased out of the report.

In 1989, the Rocky Flats Plant in Colorado was shut down due to environmental and health concerns. As this was the country’s major plutonium handling facility, this stopped production of plutonium “pits” for nuclear warheads. Also known as “triggers,” pits are the fissile material for the first-stage fission reaction that creates the energy to initiate the explosion of the second stage of a hydrogen bomb. For about a decade after Rocky Flats first suspended and then shut down production, the United States did not try to make new pits. With the end of the Cold War, there was more interest in cutting the size of the weapons stockpile and learning how to maintain it than in building new warheads.

But, motivated by the desire to regain a pit production capacity and to maintain the number of W88 warheads deployed on Trident missiles (more on that below), the United States decided in the mid-1990s to restart pit production where the first ones were built, at Los Alamos National Laboratory in New Mexico.

For eight years, between 1998 and 2006, Los Alamos produced 20 W88 pits that were basically dress rehearsals. Called “Engineering Development Units” or “Production Development Units,” they were intended to allow workers at Plutonium Facility 4 (PF-4) to figure out the process of how to make a pit—any pit—and in particular the W88 pit.

The W88 was selected because, unlike other warheads in the stockpile, almost all of the 400 or so that were initially built are deployed, with very few in reserve. In 2004, apparently only one pit remained in the reserve, so any destructive testing of pits (something that was done on a more or less annual basis) would lead to reductions of the number of deployed W88 warheads.

Thus, in 2007, with a production process in place, efforts to produce a stockpile-quality W88 pit begin in earnest. The first two attempts didn’t make the grade and were scrapped. The third attempt achieved the “Diamond Stamp” seal of approval that is required for entry into the nuclear stockpile.

Through 2011, 39 more W88 pits were produced. Of those, 29 received the Diamond Stamp: 18 ended up in the war reserve stockpile, seven went to shelf life testing, two were set aside for destructive testing, and two were spares. An additional six pits were scrapped (for eight total), and four more were “Production Development Units.” That should have completed the production run but because the second-to-last pit produced (#60) had to be scrapped, PF-4 produced one additional pit in 2012 that will likely be a spare should it meet certification requirements.

In total, 62 W88 pits were built, and 29 or 30 will end up with the Diamond Stamp.

At this point, there is no near-term requirement for the production of more pits of any kind. The next planned production is for W87 pits, but according to the March 2012 quarterly pit production report they are not needed until the FY2019-FY2020 timeframe.

Although it does not say so, the likely reason to produce W87 pits is for use in the upcoming life extension program (LEP) for the W78. In the 2010 Nuclear Posture Review (NPR), the administration indicated that it was considering the development of one warhead to be deployed on both air- and sub-launched missiles. NNSA has been hot on the trail of this “common warhead” for the W78 and W88 warheads (the latter next in line for a LEP after the W78).

NNSA would also like to add insensitive high explosives (IHE) to every weapon in the enduring stockpile. Neither the W78 nor the W88 have IHE, but the W87 does. By using a version of the W87 primary in these warhead LEPs, they achieve both those goals.

That is, if Congress will let them. Swapping out one primary for another has not been done before and Congress has not supported recent efforts to make significant changes to warheads the stockpile. (Congress shut down the “Robust Nuclear Earth Penetrator” and the seemingly irresistible “Reliable Replacement Warhead” programs.)

Another tidbit of interest in the pit production report is the reference to scaled experiments. Among its FY12 accomplishments, it states “Continuing production support of the scaled experimental pit that will be used in early FY13 at the Nevada Test Site.” Scaled experiments use miniaturized versions of warheads, including a plutonium pit, but without enough fissile material to generate a sustained reaction (and thus produce no nuclear explosion). There is some dispute about whether the United States has conducted a scaled experiment with a plutonium pit since the 1980s; this revelation seems to mean that they have not, given the noteworthiness of the accomplishment.

As we’ve noted before, scaled experiments are somewhat controversial.

One of the problems with scaled experiments is the lack of diagnostic equipment to learn the right lessons from the test. Congress has asked the independent science advisory group JASON to weigh in before NNSA conducts a scaled experiment. Apparently NNSA thinks the results will be in its favor—or it would not be working to produce a scaled experimental pit.

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