First 3-D Simulation Of Nuclear Weapons Trigger<%pubplace name%> 07 Feb 00Modern nuclear weapons consist of two main components: the "primary," or trigger, and the "secondary," which produces most of the energy, or yield, of a nuclear weapon. Demonstrating the ability to computationally visualize and analyze what happens to each of these components is a critically important step in simulating an entire nuclear weapon's explosion in three dimensions. In addition to the accomplishment at the Department's Livermore Lab, the Energy Department's Los Alamos National Laboratory has also demonstrated significant progress toward this goal using a different computational method in a fully integrated simulation on the SGI Blue Mountain computer. "This three-dimensional simulation is a key advance in our science-based work to secure the safety and reliability of America's nuclear deterrent without underground testing," said Secretary Richardson. "The same advances in computing that make this possible will also allow for important advances infields ranging from medical and pharmaceutical research to aerospace, combustion and global climate modeling. I want to express my appreciation for this notable accomplishment and the hard work that went into it." The simulation required about 300,000 megabytes of random-access memory (RAM). For comparison, a conventional desktop computer is equipped with only a few hundred megabytes of RAM. Even with the supercomputer, calculations ran for more than 20 days. A desktop would have taken 30 years to accomplish the same task. The Department of Energy joined with computer manufacturing companies to develop computers with unprecedented speed and capacity. Before ASCI supercomputers, none of the world's computers have been able to meet the speed required by the 3-D simulation, nor did they have the capacity for handling such complex calculations. It is now routine for Department of Energy's Lawrence Livermore, Los Alamos, and Sandia national laboratories, with the help of U.S. computer industry partners IBM,SGI, Intel and others, to do stockpile stewardship simulations that would have been impossible with previous computing capabilities. DOE's Stockpile Stewardship Program has three primary areas of emphasis: science, manufacturing capabilities and weapon inspection activities.The scientific foundation has five basic parts: hydrodynamics, materials properties, high-energy- density physics, microsystems engineering and computational capabilities.Taken together, these elements will enable the Department of Energy to meet its stewardship responsibilities over the coming decade and beyond. To do that, the program's capabilities must continue to advance to meet the challenges of the milestones ahead. For example, ongoing hydrodynamic testing, subcritical experiments and high temperature research will continue to produce data that DOE scientists will need to simulate the complete operation of all components of a nuclear warhead. Aging and manufacturing variations as well as phenomena such as hydrodynamics, high explosive detonation, and radiation transport are all part of the three-dimensional reality that must be replicated and analyzed through carefully integrated scientific experiments and computer simulation. For example, in November, the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory successfully performed its first hydrodynamic test to allow Los Alamos researchers to study how materials behave and interact in weapons. This facility is a very advanced, massive x-ray machine built to provide freeze-frame photos of materials imploding at speeds more than10,000 miles an hour which allows scientists to study solids and metals that flow like liquids, thus becoming "hydrodynamic" when driven by the detonation of high explosives. In another example, subcritical experiments at the Nevada Test Site are yielding previously unknown scientific and technical information on the effects of aging and behavior of nuclear weapon materials. The understanding of these material processes derived from these experiments are incorporated into the computer codes that enable scientists to simulate these processes computationally.
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