Others are “pin shot” experiments that use hundreds of fiber optic, electrical or other types of “pins” emanating from a center to determine features of the plutonium pit or a surrogate pit as it implodes (see image). Some IWEs involve “core punches” that use powerful radiographic imaging equipment to photograph the interior of nuclear weapon or surrogates’ components. IWEs are used to validate modern weapon baseline models (the tested warhead designs) and are the most comprehensive tool for validating computer codes based on past nuclear weapon tests. They can address many performance-related questions in one test.
Integrated Weapons Experiments (IWEs) use a rough approximation of an actual War Reserve warhead configuration, minus the special nuclear material. The tests vary greatly in scale and purpose (and there is some overlap) but fall into two overall categories: Integrated Weapons Experiments (IWEs) and Focused Experiments (FEs).Ī model of a pin shot hydrodynamic experiment. Hydrodynamic tests using small amounts of plutonium are conducted underground at the U1a facility at the Nevada National Security Site (NNSS, formerly the Nevada Test Site), while others using surrogate materials occur at the Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory in New Mexico, and the Contained Firing Facility at Site 300 of the Lawrence Livermore National Laboratory in California.
The device is then fired, revealing information on the design’s behavior from the high-explosive detonation to the beginning of the nuclear chain reaction.Ī hydrodynamic test of the W76 warhead design is conducted at the Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory in 2005. In one type of hydrodynamic test, researchers build a full-scale primary-the first stage of a modern nuclear weapon-but the plutonium is replaced with a metal that has similar density and weight, but is not fissionable. The term “hydrodynamic” is used because material is compressed and heated with such intensity that it begins to flow and mix like a fluid, and “hydrodynamic equations” are used to describe the behavior of fluids. In tests, conventional high explosives are set off to study the effects of the explosion on specific materials. The public justification is to “improve confidence in predictive capabilities and help validate simulation codes,” but part of the reason is also that those codes will become less reliable if NNSA changes the warhead designs by adding new safety and security features during the Life Extension Programs.Įvery year, the United States conducts “hydrodynamic” experiments designed to mimic the first stages of a nuclear explosion. The SSMP and other documents describe an interest in a type of hydrodynamic test called a “scaled experiment,” which uses more special nuclear material and more closely resembles actual warhead designs. (Special nuclear material refers to highly enriched uranium and plutonium, which are key components of a nuclear weapon.) And as the stockpile ages “ and modernization design options become more complex,” the Stockpile Stewardship and Management Plan (SSMP) states, “subcritical experiment that include special nuclear material will become more important” (emphasis added). nuclear warheads has been successfully validated using a wide range of simulation experiments, such as the compression of fissile material in hydrodynamic tests. Note: This is the third of four posts analyzing the FY 2012 Stockpile Stewardship and Management Plan, each jointly produced by the Federation of American Scientists and Union of Concerned Scientists.
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