Lawrence Livermore National Laboratory (LLNL) has conducted an experiment at the National Ignition Facility (NIF) to assess the ability of U.S. nuclear weapons to survive encounters with adversary missile defenses and reach their targets. This experiment demonstrated a new capability to analyze nuclear materials under extreme conditions, advancing stockpile modernization.
For the first time, weapons-grade plutonium samples were exposed to intense, pulsed thermonuclear neutron radiation in a safe and controlled laboratory setting at NIF. The experiment recreated some of the conditions that a U.S. weapon could encounter from enemy missile defense systems. The results provide data to assess the resilience of strategic weapons such as the W87-1 warhead in hostile threat environments. This is essential to the National Nuclear Security Administration's (NNSA) ongoing efforts to modernize the U.S. nuclear deterrent and ensure its reliability and effectiveness.
"This experiment demonstrates how cutting-edge science drives nuclear weapon design and production," said LLNL Deputy Director for Strategic Deterrence Brad Wallin. "By providing first-of-its-kind data on plutonium performance, NIF gives us the insight we need to modernize the stockpile and ensure the nation's deterrent remains credible for the future."
The October experiment delivered 2.065 megajoules (MJ) of laser energy to its target, producing a fusion yield of 3.6 MJ - about 1.7 times more energy than was delivered to the target. Since first achieving fusion ignition in December 2022, the NIF team has performed successive experiments in support of stockpile modernization. The most recent results show the consistency of the ignition platform and demonstrate its use as an intense neutron source for survivability studies.
"This is exactly the kind of work that NIF was built to enable. After multiple successful ignition experiments we have made significant progress in using this incredible capability to advance our mission," said Laboratory Director Kim Budil. "By directly exposing these plutonium samples to extreme environments that are only possible at NIF, we are producing unmatched scientific data that will guide the future of the deterrent."
A plutonium pit is a core component of a nuclear warhead. For this experiment, researchers used small samples from a legacy W87-0 warhead pit produced in the late 1980s and a newly manufactured W87-1 pit produced at Los Alamos National Laboratory. The gram-quantity samples were securely sealed within specialized hardware and safely subjected to a high-fluence 14 MeV neutron environment. Following the experiment, the samples were removed and analyzed under strict safety protocols.
"As one of the NNSA's premier experimental facilities to support the nuclear weapons stockpile, NIF is fully delivering on its mission," Budil said.
Advancing survivability science
Central to this experiment was the cryogenic-compatible X-ray, neutron and blast snout (CryoXNBS), a diagnostic enclosure that safely positions materials near the igniting capsule. Built to endure the intense conditions of an ignition shot, the CryoXNBS features a 22-kilogram steel case that protects against X-rays and debris, allowing researchers to expose materials and electronics to the highest thermonuclear fusion neutron fluences available. Inside, containment vessels securely hold the material samples and instruments.
The CryoXNBS also integrates real-time diagnostics that provide nearly instant indications of shot performance. After each experiment, the system is retracted for safe disassembly and sample analysis, expanding what researchers learn from every experiment. Collected data will refine predictive models and inform how nuclear components perform under the combined stresses of heat, shock and radiation.
Successfully executing this experiment required years of preparation and coordination across many teams throughout the nuclear security enterprise.
"It was truly a tour de force for LLNL and our partners," Budil said. "Every aspect was carried out with an uncompromising focus on safety and scientific rigor."
