Questions about projected U.S. plutonium pit production capability

by Greg Mello

During her 8 February 2018 Senate confirmation hearings as President Trump's nominee to be the new National Nuclear Security Administration (NNSA) administrator, Lisa Gordon-Hagerty said her "number one" priority would be building up the US capacity to produce plutonium cores (pits) for nuclear weapons, with a target of making at least 80 pits a year by 2030.

The United States currently has some pit production capability at Los Alamos National Laboratory (LANL), centered in LANL's main plutonium facility at Building PF-4 in TA-55. PF-4 was build 40 years ago for the purposes of research, surveillance, and prototyping, not production. Despite hundreds of millions in ongoing structural and mechanical renovation, it has been dogged with persistent safety problems and has operated only sporadically for all activities involving pits since 2013. NNSA estimates that PF-4 will come to the end of its life around 2039.

Since 1992 NNSA has invested billions of dollars in pit production at LANL, but this investment has failed to create the reliable pit production capability NNSA repeatedly said LANL already had once. According to NNSA's November 2017 "Plutonium Pit Production Analysis of Alternatives (AoA) Results and Next Steps," the agency expects to invest a further $3 billion in pit production at LANL over the coming eight years--$1 B for operations and $2 B for facility renovation and new equipment. The goal of this effort is to establish a 30 pit per year capacity in existing facilities by 2026.

Achieving an enduring post-2030 80 pit per year capacity will be even more costly. NNSA is currently considering two options. The first (and so far preferred, on bases of schedule and cost), involves repurposing all or part of the partially-completed Mixed-Oxide Fuel Fabrication Facility (MFFF) at the Savannah River Site (SRS) in South Carolina. The alternative option involves construction of new pit production facilities at LANL.

NNSA's pit production AoA document says the 80 pits per year requirement derives from "pit aging estimates and planned production schedules to meet military requirements." These requirements are also mentioned in the February 2018 Nuclear Posture Review (NPR), which stated, accurately enough, that "[t]oday, the U.S. capability to produce plutonium pits is limited to research and development pits unsuitable for stockpile use" and affirmed that "DoD requires NNSA to produce at least 80 plutonium pits per year by 2030." The report, however, contains no reference to any current or proposed warhead or warhead program which requires new pits.

The 2014 "Assessment of Nuclear Weapon Pit Production Requirements" notes that "in 2008, the Nuclear Weapons Council (NWC) ... established the requirement for 50-80 pits per year" by 2031. This 2008 justification is now a decade old and has not been re-examined in any detail in public. The only changes are the target date that has moved forward by one year from 2031 to 2030 and the production target that has increased from "50-80" pits per year to "no fewer than 80" pits per year.

The current US stockpile consists of approximately 4,018 warheads and bombs, each with a pit. This number does not include approximately 2,600 intact-but-retired weapons of recent vintage. In addition, there are in storage for possible reuse an unknown but large number of "National Security Asset" pits.

In 2008, the Department of Energy (DOE) and the Department of Defense (DoD) wrote that "depending on warhead type, the best estimate of minimum pit life is 85-100 years." The oldest pits in the stockpile were made in 1978 and therefore are 40 years old as of 2018. These oldest pits will therefore be useable, according to DOE and DoD, until at least the 2063 to 2078 period. The newest pits were made in early 1989 and will be useable until at least the 2074 to 2089 period. This means that the earliest date that replacement of today's stockpile pits would need to start is 2063, and the earliest date that replacement would need to conclude is 2074.

Discounting for the moment whatever flexibility is available from pit reuse across warhead type and other compensatory measures (including partial pit rebuild), a stockpile of the same size as today's would require 50 years to fully replace at an average production rate of 80 pits per year. Production that began in 2030 at that rate would completely replace today's stockpile by 2080.

The FY 2018 Stockpile Stewardship and Management Plan shows NNSA has no stockpile pit production scheduled at all until 2023, when just one pit is required, followed by 10, 20 and 30 pits in 2024, 2025, and 2026 respectively. Additionally, the FY 2015 National Defense Authorization Act (NDAA, Sec. 4219) required achieving a 90-day production demonstration of 80 pits per year in 2027, with up to a two-year grace period. It is not clear how NNSA expects to achieve the almost three-fold jump in pit production from 30 pits per year in 2026 to 80 pits per year in 2027. Given that NNSA's pit production Analysis of Alternatives asserts a maximum production rate in PF-4 of 30 pits per year, meeting the 2027 deadline implies bringing additional facilities into operation by that time. NNSA states that achieving this goal is unlikely but possible, though not at LANL.

Under the previous administration, the proposed Interoperable Warhead (IW-1) was the only Life Extension Program (LEP) to require new pits until 2041, when an "IW-3" was to begin production, also said to require new pits. The 2018 Nuclear Posture Review contains no reference to any interoperable warhead, except as a possible concept exploration for the future.

There is clearly a need to re-examine and publicly justify infrastructure strategies and pit production requirements. The FY18 NDAA (Sec. 3141) required NNSA to submit an analysis of alternatives regarding plutonium production capabilities and identify the preferred course of action. The report should have been submitted to the congressional defense committees in January 2018. The discussion of alternatives should focus on a number of key questions that will determine the future of U.S. pit production capability:

Is there really a need for any new pits between now and mid-century? How is the projected need in pit production capability dependent on stockpile size and composition? Where--at what site, in what facilities--should pit production take place, and with what capacity, starting when?

In practice, questions about management risk, facility age, institutional suitability, workforce training and skills, potential expansion capacity, and supporting infrastructure will loom large in NNSA's pit production decisions.

At no time since the dawn of the nuclear age has the United States been able to produce pits both safely and reliably. Can this really be done, and if so how? The United States has not been able to successfully build a plutonium handling facility since 1978. What lessons can be drawn from prior failures? Could such a facility be built and safely operated today?

Pit production decisions are intertwined with decisions about the disposition of surplus plutonium, so much so that firm decisions about the former may not be possible prior to firm decisions about the latter. Will there be a surplus plutonium disposition mission at MFFF, what will it be, and could pit production occur there as well?

Or, if the pit production mission is to stay at LANL indefinitely, how will it become institutionally compatible? Can it ever succeed? Given PF-4's advanced age, what replacement facilities will be required?

None of these questions are easy or going away soon, no matter what NNSA decides.

For more background about these issues, see US Pit Production: Background and Issues (PDF).