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NNSA Improves Capability To Certify Nuclear Weapons Stockpile

DARHT Second Axis Is Ready for Operation

DARHT accelerator cellsWASHINGTON, D.C. – The ability to continue to assess and certify the aging U.S. nuclear weapons stockpile without underground nuclear testing took a major step forward today as a senior official announced that the Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility is now fully operational.

"DARHT is an incredible scientific and engineering achievement and is extremely important to certifying the nuclear weapons stockpile," said Robert Smolen, the National Nuclear Security Administration's (NNSA) deputy administrator for defense programs.  "U.S. nuclear weapons are 20 to 30 years old, and this high-tech machine allows us to look at how changes made to fix age-related and technical defects may affect weapon performance – all without conducting an underground nuclear test."

DARHT, located at NNSA's Los Alamos National Laboratory, produces four-frame x-ray movies of very rapid events, like explosions, which take place in millionths of a second.  It produces x-ray (or radiographic) images from two perpendicular angles (making it "dual-axis" and allowing for a three dimensional picture) of a nuclear weapons component as it is subjected to the extreme pressures of an implosion in a hydrodynamic test.  (Hydrotests are high-explosive-driven experiments that assess the performance and safety of nuclear weapons.  Under these test conditions, the behavior of solid materials becomes similar to liquids, hence the term "hydrodynamic.")

Los Alamos National Laboratory teamed with Lawrence Livermore National Laboratory, Lawrence Berkeley National Laboratory and private industry to make DARHT's second axis achieve this new capability.

The United States has not produced new nuclear weapons since 1991, and has not conducted an underground nuclear test since 1992 when President George H.W. Bush ordered a voluntary moratorium be put in place.   

To ensure the nation's nuclear weapons remain safe, secure and reliable beyond their original design life of roughly 10-20 years, the stockpile stewardship program was implemented.  As part of this program, DARHT's pictures allow NNSA scientists to thoroughly examine and predict how a particular weapon component from the current stockpile will react during a nuclear explosion.

"NNSA has been able to continually assure the reliability of the nuclear weapons stockpile without returning to underground nuclear testing," Smolen said.  "As these weapons age, doing so becomes increasingly challenging.  DARHT is an enormous help to our national security mission."

DARHT's second axis, or DARHT 2, underwent extensive reconstruction and testing, performed better than planned, and is now complete.  It joins the first axis, known as DARHT 1, which is a single-pulse accelerator and has been making important contributions to the stockpile since 1999.  The two axes combined now represent a world leading radiographic capability.

The complete system will now be put through a series of readiness tests, to ensure it can be operated safely, and the first combined hydrodynamic test is scheduled to be conducted this summer.  The data from DARHT, when combined with data from both historical underground  tests and present day hydrodynamic experiments at NNSA's Nevada Test Site and Lawrence Livermore National Laboratory, allow NNSA to maintain the safety and reliability of the stockpile.

Established by Congress in 2000, NNSA is a separately organized agency within the U.S. Department of Energy responsible for enhancing national security through the military application of nuclear science. NNSA maintains and enhances the safety, security, reliability and performance of the U.S. nuclear weapons stockpile without nuclear testing; works to reduce global danger from weapons of mass destruction; provides the U.S. Navy with safe and effective nuclear propulsion; and responds to nuclear and radiological emergencies in the United States and abroad.

Media contact(s):
NNSA Public Affairs (202) 586-7371