Ensure the safety, security, and effectiveness of the nuclear weapons stockpile through well-managed scientific research, technology development, and advantageous international collaborations.
The Office of Defense Science is responsible for managing the Science Campaign which conducts new scientific research and combines it with existing data from stockpile surveillance, past nuclear tests, and computer simulations to improve NNSA’s models of nuclear weapons performance and physics. Advances in the understanding of weapon physics, combined with improved computing power, lead to higher-fidelity predictive models that allow the NNSA complex to confidently conduct annual assessments, develop new technologies for Life Extension Programs (LEPs), and support non-stockpile national security missions.
The Office aims to permanently remove any technical motivation for a return to underground testing while maintaining capabilities that would be needed in the unlikely event of a return to underground nuclear testing, as mandated by Presidential directive. Its specific priorities in the coming years are meeting the requirements laid out in the Nuclear Posture Review Report (April 2010), especially the development of advanced surety systems and options for reuse in LEPs, providing expertise and experimental platforms for assessing the stockpile, and applying its knowledge and experimental tools to assessments of emerging nuclear threats. Over the longer term, the Office is working steadily to replace empirical parameters in models of nuclear weapons performance (i.e., those determined by UGTs), with an ab initio understanding of the physics, so the weapons complex can confidently predict performance for decades into the future while avoiding technological surprise. The principal technical activities of the office are:
Primary Assessment Technologies
Primary Assessment Technologies (PAT) provides capabilities needed to strengthen assessment of stockpile primaries, develop a broad range of options for future LEPs, and underwrite improvements in weapons safety and security. PAT leads the Office’s efforts to support development of reuse and enhanced surety options. It is also the home of the Office’s work to support non-stockpile national security missions. It applies NNSA’s expertise, models and experimental capabilities to national security problems so the Nation can better understand and respond to emerging nuclear threats.
Advanced Radiography develops the sources, targets and detectors used to diagnose hydrodynamic and other experiments that subject materials to strong shock and high strains, including those that study plutonium properties. These transformational technologies advance and improve the quality of scientific results at facilities such as the Dual Axis Radiographic Hydrodynamic Test Facility (DARHT), Site 300, Z, Nevada National Security Site (U1a), and pRad at the Los Alamos Neutron Science Center. The main focus for the out-years is the development of radiographic requirements and advanced analysis of radiographic information so that the Science Campaign will have the tools necessary for the requirements of future hydrodynamic experiments.
Secondary Assessment Technologies
Secondary Assessment Technologies (SAT) strengthens evaluation and assessment of stockpile secondaries. It supports evaluation of the reliability and performance of potential future and/or modified configurations that may enter the stockpile without nuclear testing, thus supporting a broad range of options for future LEPs. SAT also develops the predictive capabilities to quantify weapon output and its interaction with the surrounding environment. SAT has a strong programmatic coupling with the high energy density (HED) facilities supported by both the Science Campaigns and the Office of Inertial Confinement Fusion, including the National Ignition Facility, Omega Laser Facility at the University of Rochester Laboratory for Laser Energetics, and the Z Machine at Sandia National Laboratories in New Mexico.
Nuclear Experiments supports the Stockpile Stewardship Program by conducting experiments with special nuclear material, as well as surrogate hydrodynamic experiments. It is responsible for executing experiments at the Nevada National Security Site, DARHT and other firing sites. Its particular focus is on hydrodynamic and sub-critical plutonium experiments that are part of the Dynamic Materials Properties, Advanced Certification, and Primary Assessment subprograms. These experiments provide vital data on plutonium performance and, in the case of hydrodynamic experiments—high explosive-driven experiments in weapons geometry—provide a platform for investigating integrated performance of weapons subsystems and physics without nuclear explosive testing. It is also responsible for maintaining operations of experimental platforms that perform plutonium experiments such as the Large Bore Powder Gun and advanced platforms for measuring plutonium properties, such as the Joint Actinide Shock Physics Experimental Research gas gun, facilities at TA-55, Proton Radiography Facility at the Los Alamos Neutron Science Center, the Z Machine, and National Criticality Experiments Research Center at the Device Assembly Facility. Nuclear Experiments works on the long-range development of advanced radiographic and other diagnostic techniques and is responsible for oversight of the DOE-DoD Joint Munitions Program (JMP). JMP is a joint research and development program with the Department of Defense that aims to improve nonnuclear munitions technology.
The Advanced Certification subprogram provides the integrating approach for the Science Campaign. Recent internal and external studies have highlighted areas for improvement in how the design laboratories certify and assess stockpile systems in the absence of integrated nuclear testing. This Science Campaign subprogram responds to those studies with activities to improve the weapons assessment and certification process through expanded, independent peer review mechanisms and refined computational tools and methods. Advanced Certification also includes the advancement of the physical understanding of surety mechanisms and their impacts on assessment and certification, further exploration of failure modes, assessments of the effects of (new) manufacturing on material properties, understanding near-neighbors and anticipating technological surprise.
Dynamic Materials Properties
The Dynamic Materials Properties (DMP) develops the models that describe and predict the behaviors of weapons materials in the extreme conditions of nuclear weapon operation. DMP conducts an experiment-centered research program emphasizing materials response under high-pressure, high-temperature, high-strain, and high-strain-rates (i.e., rapid material deformation). Its efforts also include developing new experimental and diagnostic platforms capable of providing the needed data and supporting its interpretation. NNSA ultimately uses these models to predict material response and performance in the nuclear explosive package for assessments of performance, safety, surety and reliability.