Los Alamos to share plutonium pit production with Savannah River facility

A partially completed, billions-over-budget facility for transforming surplus weapons plutonium into fuel for commercial reactors will be repurposed to manufacture plutonium cores for nuclear weapons, the US Departments of Energy and Defense announced on 10 May. Under the new plan, the Savannah River Site in South Carolina will produce more than half of the 80 plutonium pits per year that the agencies have said will be needed for the nuclear weapons stockpile by 2030. Los Alamos National Laboratory (LANL), which had previously been designated as the sole pit production facility, will be responsible for fabricating at least 30 pits annually.

In a joint statement , Lisa Gordon-Hagerty, administrator of DOE’s National Nuclear Security Administration, and Ellen Lord, undersecretary of defense for acquisition and sustainment, said NNSA’s two-pronged approach “represents a resilient and responsive option” to meet Defense Department requirements. They said the plan provides flexibility and redundancy by not relying on a single site, and it meets the requirements set forth in the Trump administration’s February Nuclear Posture Review , which advocates building at least 80 pits per year.

When a weapon is detonated, high explosives implode the grapefruit-size pit, causing the plutonium to fission and produce radiation that drives the weapon’s secondary fusion stage. The nuclear weapons complex has lacked the capacity to produce substantial numbers of the plutonium pits since the closure of the Rocky Flats Plant near Denver, Colorado, in 1992. Since then, LANL’s World War II–era PF-4 facility has been the only site in the country with pit fabrication capabilities. The watchdog group Nuclear Watch New Mexico says that a total of 29 pits for refurbished submarine-launched missile warheads were produced at LANL from 2007 to 2011, in addition to an unknown number of prototypes. No pits have been fabricated since 2012.

The Mixed Oxide Fuel Fabrication Facility (MOX) at the Savannah River Site was designed to adapt weapons plutonium for peaceful energy purposes (see Physics Today, July 2017, page 28 ). The US agreed to employ the MOX fuel disposal pathway in a 2000 agreement with Russia under which each side agreed to shed 34 metric tons of the fissile material. Amid deteriorating bilateral conditions, Russia suspended that agreement in 2016. In addition, NNSA has concluded that the plutonium could be disposed of more rapidly and at far less cost by diluting it with inert material for permanent geological storage as low-level transuranic nuclear waste (see Physics Today, July 2014, page 24 ). But the South Carolina congressional delegation, led by Senator Lindsey Graham (R), has steadfastly opposed DOE’s attempts to terminate MOX plant construction.

A preliminary NNSA estimate puts the cost of repurposing the MOX plant at as much as $4.6 billion, but an agency spokesperson says a formal baseline won’t be provided until the new design is 90% complete. The timeline will depend on congressional appropriations. In 2016, NNSA estimated that completing the MOX plant for its original purpose would cost more than $11 billion, in addition to the $4.6 billion that had already been spent. At LANL, it will cost about $3 billion over five years to upgrade the infrastructure and train additional workers to produce 30 pits or more annually there starting in 2026, the NNSA spokesperson says.

A report by NNSA released last October identified the dual-site, repurposed MOX plant option as the best bet to meet the 80-warheads-per-year requirement by 2030. The agency said that producing more than 30 pits per year at LANL would lead to “regulatory milestones historically difficult to navigate,” such as complying with environmental laws and meeting quality assurance standards. The analysis acknowledged that there would be cost and schedule risks involved in reconfiguring the half-finished MOX plant to a completely new mission.

Some in the environmental and disarmament communities question whether new pit production capability is required at all. A 2008 report by JASON, a group of scientists who advise the government on defense matters, said the minimum estimated lifetime of a pit is 85–100 years. Since the oldest warheads in the current stockpile were placed into service beginning in 1968, that means pit replacements wouldn’t be required until at least the early 2050s. Another 2012 study by LANL and Lawrence Livermore National Laboratory found no unexpected decay-related issues in plutonium whose age had been accelerated to an equivalent of 150 years.

But LANL director Terry Wallace says he “disagrees significantly” with the analysis that was the basis for the minimum 85-year lifetime. The study reviewed only one pit type, which he says was probably the simplest one. “The certainty that plutonium can age forever is happy-speak,” Wallace says. Moreover, he notes that a pit is made of more than just plutonium. The functionality of a warhead could be impacted by factors including radiolysis from plutonium’s decay and the element’s interactions with other materials in the weapon.

In a joint statement , New Mexico’s congressional delegation, all Democrats, said it was pleased that LANL will retain its R&D and limited production roles with a new, multibillion-dollar investment. But the lawmakers warned that “halting the long-planned modular expansion of LANL’s facilities for plutonium pit production will set back our military’s life extension programs and stretch the lab’s existing facilities and workforce to its limits.”