Defense Experimentation and Stockpile Stewardship

A primary mission of the NNSS is to help ensure that the nation’s nuclear weapons stockpile remains safe, reliable, and secure from our enemies. To accomplish this, Stockpile Stewardship deploys a wide range of science and technologies, focused on experiments in weapons science and the potential for weapons dismantlement.
Since the U.S. no longer conducts full-scale nuclear tests, (the U.S. voluntarily ended underground nuclear testing in 1992), Stockpile scientists and engineers now obtain data from breakthrough scientific experiments, engineering audits and analysis, high-tech computer simulations, and world-class diagnostic measurement systems. To keep existing warheads reliable, secure, and safe, every aspect of a weapon’s performance is meticulously studied so that the national laboratories can predict not only what will happen during an explosion (measurements within billionths of a second), but also measure what will happen to a device as it changes and ages over time (the nuclear arsenal is now more than 50 years old).
NNSS has a number of unique facilities and capabilities that directly contribute to the continued certification of the nuclear deterrent.
Stockpile Stewardship Fact Sheet
Device Assembly Facility
At the Device Assembly Facility (DAF), using the most modern assembly cells in the nuclear weapons enterprise, scientists work on Special Nuclear Material (SNM), Radiation Test Objects, and high-explosives in support of experiments for Stockpile Stewardship and other programs.  DAF is poised to perform nuclear weapons operations such as alterations, modifications, and dismantlement.  Operations also include receipt, repackaging, staging, and on-site transportation of SNM.  DAF is secured by a 24-hour guard force and state-of-the-art security alarm systems for this 100,000-square-foot complex. 
Device Assembly Facility Fact Sheet
National Criticality Experiments Research Center
The new National Criticality Experiments Research Center (NCERC) facility at the DAF is a centerpiece for innovative methods in the development of treaty verification technologies.  Here, personnel are rigorously trained in nuclear materials management and criticality safety.  These operations have a host of applications:  emergency response to terrorism, nuclear nonproliferation (in accordance with domestic and international agreements), nuclear criticality investigations for Stockpile Stewardship and other programs, and numerous levels of training activities to maintain and advance expertise within the nuclear materials community.
National Criticality Experiments Research Center Fact Sheet
U1a Complex
The U1a Complex, an underground experimental facility and tunnel complex at the NNSS, is home to a wide range of unique capabilities.  Experiments range from measuring the properties of plutonium under weapons-like conditions to state-of-the-art diagnostic development and X-ray radiography.  The Complex hosts subcritical experiments (SCEs) to collect data from plutonium when it is subjected to high pressures and shocks, mimicking environmental conditions of a nuclear explosion.  SCEs are essential to the collection of data to support the national weapons laboratories in maintaining the safety, security and reliability of the U.S. nuclear weapons stockpile.  These experiments work below the criticality threshold (hence the label "sub" critical) and are consistent with the U.S. nuclear testing moratorium.  The U1a drift complex is 963 feet underground - a major advantage for safety and security. 
U1a Complex Fact Sheet
Joint Actinide Shock Physics Experimental Research
Joint Actinide Shock Physics Experimental Research (JASPER) is a two-stage light-gas gun. It is used to study the behavior of plutonium and other materials under high pressure, temperatures, and strain rates. Understanding the behavior of materials such as plutonium at high pressures is essential for predicting weapon performance. JASPER is capable of accelerating projectiles at 8 km/sec so that, upon impact with a small sample of plutonium, strong shock waves can be studied in actual weapons material.  This creates precise equation-of-state measurements that help experts assure the safety and viability of the nation's nuclear weapons stockpile. 
JASPER Fact Sheet  
Big Explosives Experimental Facility
The Big Explosive Experimental Facility (BEEF) is a high-explosive testing facility that provides data to support Stockpile Stewardship and other national security programs.  The facility consists of a control bunker, a camera bunker, a gravel firing table, and associated control and diagnostic systems.  At BEEF, conventional high-explosives experiments are safely conducted using a test bed that provides sophisticated diagnostics such as high-speed optics and x-ray radiography on the firing table.  BEEF is certified for up to 78,000 lbs. of high explosives and is a remote 10-acre fenced compound capable of classified work.
BEEF Fact Sheet
Dense Plasma Focus
The Dense Plasma Focus (DPF) machines at NNSS are currently the largest and most powerful in the world.  These machines instantaneously compress ionized gasses (plasmas) raising their temperature and pressures similar to those in the interior of the sun.  In the process, they emit bursts of neutrons that are used in a variety of scientific experiments.  The DPF fusion process lasts for less than a millionth of a second.  The development of detection systems for finding nuclear material, pulsed power research, physics measurements, and advanced diagnostics development are just a few of the ongoing activities supported by these powerful sources.