Interoperability requirements for the core of nuclear warheads under the National Nuclear Security Administration’s (NNSA) “3+2” modernization strategy may lead to trade-offs and complications for the U.S. nuclear stockpile, according to a report by the independent science advisory group JASON.
The NNSA publicly released the executive summary of the January 2015 report this week. The report was mandated by Congress in fiscal 2014 appropriations to assess the technical issues and risks associated with the nuclear warhead strategy.
The “3+2” modernization strategy will ultimately transition the seven existing deployed warhead types into three types to be used for the land- and sea-based legs of the nuclear triad, and two types for the air-carried leg. The land- and sea-based re-entry legs of the triad will feature an interoperable nuclear explosive package – the core of the warhead that includes both nuclear and non-nuclear components.
The NNSA’s fiscal 2016 stockpile stewardship and management plan said the strategy, expected to take at least 30 years to fully implement, would allow for a “smaller stockpile, increasing interoperability, and reducing the number of warhead types, while providing the flexibility required to hedge against geopolitical surprise.” Existing missile warheads are not currently adaptable to different delivery systems.
However, the JASON report says that while the 3+2 strategy decreases the number of types of nuclear explosive packages, it would lead to more warhead assembly types, as each package would be deployed in two types of aeroshells. This means the strategy “results in six (not three) total types of [re-entry vehicles] and [re-entry body] warhead assemblies,” the report notes. Moreover, each of these assemblies would then need to be independently tested, it says.
Stephen Young, a senior analyst for the Union of Concerned Scientists, wrote in a critique of the NNSA’s new stockpile plan that the 3+2 term is therefore misleading and that “the NNSA’s plan should be called 6+2.”
However, NNSA spokeswoman Francie Israeli said by email that “it is too soon to tell how many [warhead assembly types] there will be. The NNSA and the Department of Defense are examining a variety of options that include the use of common ‘warhead assemblies.’”
The JASON report also says designing and qualifying a nuclear explosive package for two delivery platforms – rather than one – is more difficult and could result in a common design that “may be sub-optimal for each platform.”
“Commonality does lead to fewer total component types, which provides advantages during development, qualification, production, and potentially, surveillance,” the report says. “These advantages must be weighed against increased complexity and potentially sub-optimal performance.”
Israeli said that while the warheads under the strategy may indeed change performance for specific delivery platforms, NNSA “must develop and ultimately demonstrate that each weapon meets both DOD military requirements and NNSA requirements for safety and surety.”
The report points to potential trade-offs associated with commonality, performance, security, and other features. Making the nuclear explosive package interoperable “may force a reduction in primary yield margins, for example,” it says. The primary yield initiates the chain reaction that ignites fissionable materials in the core of the nuclear weapon, and is therefore critical for warhead reliability.
The report also finds program instability a threat to NNSA capabilities, as “stopping and re-starting efforts is wasteful of limited resources and introduces risk,” and notes the lack of “compelling analysis” of the cost, schedule, and risk consequences of the 3+2 strategy’s commonality requirements.
The report recommends that NNSA “maintain stable and predictable” program execution while commissioning more studies on issues of commonality and the number of warhead types.
This assessment, Young said, indicates that “JASON seems unconvinced of the value of the 3+2 plan as currently laid out, and believes much more study is required.”
Israeli said the NNSA regularly incorporates the findings and recommendations of JASON reports into its programs “and will do so in this case as we prepare to deliver the first ballistic warhead from this program in 2030.”
