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May 2001

The Laboratory
in the News

Commentary by
Jeff Wadsworth

Uncovering
Hidden Defects
with Neutrons

The Human in the Mouse Mirror

The NIF Target Chamber—Ready
for the Challenge

Indoor Testing Begins Soon at
Site 300

Patents

Awards


 

 

IMAGINE, if you can, some 3,100 cubic meters of concrete and over 2,000 metric tons of reinforcing steel. "ThatŐs enough concrete and steel to build the frame of a 16- by 18-meter, 60-story office building," says Rick Visoria, project manager for the new Contained Firing Facility (CFF) at Site 300, Livermore's experimental test site. "Those are the quantities we used to build the firing chamber at the CFF, which is also 16 by 18 meters. But, it's only 10 meters high."
Those huge amounts of materials for a relatively small structure say a lot about the thickness of the firing chamber's concrete walls, the denseness of its reinforcing steel, and the thickness of its steel liners. Those thicknesses and densities are needed for tests inside that will use as much as 60 kilograms of high explosives—enough explosive to demolish that hypothetical 60-story building frame.
The inside surfaces of the firing chamber are protected by 50-millimeter-thick steel plates from a spray of shrapnel traveling as fast as 1.5 kilometers per second—that's three times the speed of a bullet. The chamber's main structural elements are designed to remain elastic when blasted by explosives, so that repetitive firings are possible.
The CFF, including the firing chamber, support area, diagnostic equipment area, and new offices and conference room, adds almost 3,200 square meters to Bunker 801 at Site 300. Bunker 801 houses the Flash X Ray—one of the most powerful x-ray machines in the world—and other diagnostic tools that have been used for many years to examine weapon components during hydrodynamic and other tests (see S&TR, March 1997, Site 300's New Contained Firing Facility, and March 1999, Site 300 Keeps High-Explosives Science On Target).
Construction of the firing chamber and its support facilities began in April 1999 and was virtually complete by the end of 2000. Acceptance testing of the building and its many new systems is under way. During construction, Bunker 801 has been unusable, but by fall, its real work is expected to begin. The project's goal was to limit bunker downtime to 28 months. Says Visoria, "We'll be coming in almost exactly on schedule, and on budget, too."
The CFF will be an essential tool of the Department of Energy's Stockpile Stewardship Program to assure that our nation's nuclear arsenal remains safe and reliable as weapons age beyond their designed lifespan. Computer modeling provides considerable information about how a nuclear weapon will behave, but test data are needed to validate the codes used in modeling.

Why Indoors?
Site 300 has been used since 1955 to perform experiments that measure variables important to nuclear weapon safety, conventional ordnance designs, and possible accidents (such as fires) involving explosives. To date, these experiments have been performed in the open air. The CFF will dramatically reduce emissions to the environment and minimize the generation of hazardous waste, noise, and blast pressures. While emissions from open-air testing at Site 300 are within current environmental standards, use of the CFF ensures that testing can continue even if environmental requirements change. Future residential development not far from Site 300 will also benefit from these environmental precautions.
Visoria says, "Indoor testing will allow experimenters to perform tests at virtually any time and in any kind of weather, offering greater flexibility in scheduling and better control of the testing environment. Setting up experiments will also be easier on a steel floor rather than on an outdoor gravel firing table."

 

Testing a Test Facility
The completed construction project is being subjected to an array of tests to assure that all systems are in working order. For example, tests are planned to assure that the CFF can withstand huge explosions of sometimes hazardous materials while remaining a safe place to work.
After construction was completed, Livermore personnel and the construction contractor, Neilsen Dillingham Builders Inc. of Pleasanton, California, conducted site acceptance tests of the CFF's state-of-the-art mechanical, electrical, safety, and process control systems. These tests culminated in the Firing Sequence of Operations, an integrated system test that checked out all the steps associated with firing an experiment. Several Firing Sequence of Operations tests were run, sometimes under irregular conditions, such as when power to the facility was abruptly shut down.
The next step was the Structural Qualification Test Series to examine the integrity of the overall structure and the firing chamber in particular. A series of five high-explosive shots was conducted. The shots ranged from 25 to 125 percent of the explosive weight of 60 kilograms of high explosives. Data on the structural integrity tests are preliminary but indicate that all is well.
A spherical firing chamber structure would have been best for resisting blast effects. But a sphere is difficult to design and build because it does not use conventional construction methods. Engineering tests in the mid-1990s on a one-quarter-scale model of the firing chamber demonstrated that a rectangular, conventionally reinforced, concrete structure would have the structural strength to contain the blast effects of a high-explosive detonation. An essential requirement was that the chamber exhibit an almost totally elastic response to detonations within it, meaning that the chamber would not incur any permanent changes to its size or shape over time. Strain gauges installed in the thick walls, floor, and ceiling of the firing chamber are supplying the data needed to show that the full-scale facility meets the specified structural strength and elasticity response.
The last tests prior to putting Bunker 801 back to work will take about a month. They will assure that new CFF systems and those in the existing bunker are properly integrated.

(a) Aerial view of firing chamber construction on August 31, 1999, just prior to pouring the floor slabs for the firing chamber. This pour required deliveries by more than 100 concrete trucks. The protruding end of the Flash X Ray bullnose can be seen in the upper right. (b) The final concrete pour was for the roof slab of the firing chamber. Note the denseness of the reinforcing steel in both photos.

Back to Work
The CFF is the largest explosives chamber in the world. That means that no one at the Laboratory or anywhere else is experienced in bringing such a large indoor testing facility on line.
Lloyd Multhauf, a deputy division leader in the Defense and Nuclear Technologies Directorate, which will be using the CFF, says, "Our first task will be to learn how to work with hazardous materials indoors. We will begin with less hazardous test shots and work up to those with more hazardous materials."
To purge the air in the firing chamber after a shot, the chamber is equipped with an air intake and exhaust system that can perform 10 air changes in half an hour. Exhaust air goes through a series of filters before being released into the atmosphere.
Personnel who then enter the firing chamber will be fully suited up to protect against any remaining hazardous materials. After removing the remains of the experiment, they will turn on a wash water system as necessary to remove any particulate matter from the walls and floor.
Says Multhauf, "Anyone entering the chamber will be in full personal protective equipment until we know for sure that the protective systems we've installed really operate properly."
There is much important work to do once Bunker 801 is fully operational. The Department of Energy recently assigned Livermore to perform work required to extend the lifespan of the W80 nuclear weapon, which was originally designed by Los Alamos National Laboratory. This effort will be similar to the W87 Life Extension Project that Livermore is completing. As design and engineering get under way to make the weapon more robust and able to withstand a longer time in the stockpile, hydrodynamic tests in the CFF will be numerous. But this time around, they will be indoors and much quieter.

—Katie Walter

Key Words: Contained Firing Facility (CFF), hydrodynamic testing, Site 300, Stockpile Stewardship Program, W80 Stockpile Life Extension Project.

For For further information contact Rick Visoria (925) 423-0939 (visoria1@llnl.gov).

 

 

   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



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UCRL-52000-01-5 | May 25, 2001