The most recent NNSA quarterly summary of experiments conducted as part of its science-based stockpile stewardship program is now available here .
The quarterly summary for the 1st quarter of FY2012 prepared by NNSA’s Office of Defense Programs  provides descriptions of key NNSA facilities that conduct stockpile stewardship experiments. These include some of the most sophisticated scientific research facilities in the world including, the Dual Axis Radiographic Hydrodynamic Test  (DARHT) facility at Los Alamos National Laboratory, National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, and the Z machine  at Sandia National Laboratories. The summary also provides the number of experiments performed at each facility during each quarter of the fiscal year.
The U.S. Stockpile Stewardship Program is a robust program of scientific inquiry used to sustain and assess the nuclear weapons stockpile without the use of underground nuclear tests. The experiments carried out within the program are used in combination with complex computational models and NNSA’s Advanced Simulation and Computing (ASC) Program  to assess the safety, security and effectiveness of the stockpile. An extraordinary set of science, technology and engineering (ST&E) facilities have been established in support of the stockpile stewardship program.