By Frank von Hippel, June 12, 2020
The National Nuclear Security Administration (NNSA), the organization within the Energy Department that is responsible for producing and maintaining US nuclear warheads, is moving forward with a plan to build a plutonium-pit-production factory at DOE’s Savannah River Site in South Carolina. “Pits” are the form of the plutonium in the fission trigger “primaries” of US two-stage nuclear warheads.
The primary motivation for this move is lack of confidence in the pit-production capacity at Los Alamos National Laboratory, which has been responsible for preserving US pit production expertise since production at the Rocky Flats Plant outside of Denver shut down at the end of the Cold War. There are also political motivations, including filling the jobs gap at the Savannah River Site resulting from the collapse of NNSA’s effort to build a Mixed-oxide Fuel Fabrication Facility there to process some of its excess Cold War plutonium pits into power reactor fuel.
NNSA’s rush forward may result in a debacle on top of a debacle. If the experts at Los Alamos can’t manage pit production there, why does NNSA think that they can design and train the staff to operate a pit-production facility at the Savannah River Site?
Also, the United States need for pits is unclear at the moment. In 2007, the pits produced at Rocky Flats—now 30 to 40 years old—were pronounced to be good for at least a century and, in 2012, the Lawrence Livermore National Laboratory upped the durability estimate to 150 years. NNSA did not support the necessary research to solidify this conclusion, however—an oversight that it now promises to remedy.
The NNSA also claims that it needs to produce new pits for two types of safer primaries for two new nuclear warheads, but there seem to be enough already-existing pits for one of the warheads, and the design for the second has not yet been decided.
Thus, there are multiple arguments for delaying a decision on the proposed second pit-production facility for a decade or so. By then, Los Alamos should have mastered the production of pits, the longevity of the legacy pits will be better established, and the need for pits not available in the legacy stockpile should be clarified.
The purpose of insensitive high explosive is not to reduce the probability of an accidental nuclear explosion. Other elements of the safety design are supposed to do that, and, to date, no warhead accident has resulted in a nuclear yield.
The benefit from the use of insensitive high explosive would be to reduce the number of accidents in which the chemical explosive around a pit is detonated and plutonium is dispersed. There were many such accidents involving aircraft-carried warheads prior to the decision not to fly nuclear-armed aircraft in peacetime. The most famous was the collision of a nuclear-armed B-52 strategic bomber with its refueling tanker over Spain in 1966, which resulted in a large area of plutonium contamination on the ground, requiring 1,600 US military personnel to be deployed for up to 12 weeks, working with minimal protection, gathering contaminated dirt and crops into barrels for shipment back to the US for burial on the Savannah River Site. The Navy has had no such accidents with its SLBM warheads, however, and believes that reducing the risk significantly would require redesigning its Trident missile as well as their warheads. It therefore has in the past not been willing to invest in adapting new insensitive high explosive warheads to its missiles, a process that would include flight tests.
We can wait for another decade before we decide on whether the United States requires two pit production facilities. Indeed, we can wait for another decade before we decide on whether we need any new pits at all.