X-Ray Machine Zaps Itself

By John Fleck, Albuquerque Journal Staff Writer

A $350 million nuclear weapons X-ray machine at Los Alamos — already years overdue and millions of dollars over budget — inadvertently damaged one of its internal components last week, causing at least another three-month delay in the project.

A powerful beam of electrons used to create the machine's X-ray pulse vaporized a piece of graphite inside, fouling a vacuum chamber that needs to be ultraclean, according to lab spokesman Kevin Roark.

Seventeen of the X-ray machine's 74 massive doughnut-shaped power cells will need to be taken apart and cleaned, Roark said.

No one was injured and there was no damage other than the mess to the machine, known as the Dual-Axis Radiographic Hydrotest Facility, or DARHT, Roark said.

DARHT has been plagued by problems.

When it was proposed 21 years ago, the managers of the U.S. nuclear weapons program called it "essential." With a redesign midway through the project's development and repeated delays, its cost grew from an initial $30 million estimate to at least $260 million.

Then, when it was completed in 2003, lab scientists found that it did not work. They had to completely tear it apart and rebuild it, adding $90 million to the cost.

In May, the National Nuclear Security Administration declared the reconstruction a success, and lab officials said the machine would be ready for its first full-scale nuclear weapons test by September or October.

That test will now be delayed until early 2009, Roark said Monday.

Last week's accident, first reported on the "LANL: The Rest of the Story" blog, happened during tuning of the machine in preparation for the first weapons test, according to Roark.

DARHT generates two powerful X-ray beams. The first beam was completed in the 1990s and has been used successfully ever since. The problems, including the most recent incident, involve the second X-ray beam.

Fired at right angles into a target, they can create a three-dimensional image. The X-rays are powerful enough to penetrate metal, allowing nuclear weapons designers to study mock nuclear weapons as they are being detonated.

The pictures allow weapons designers to study the details of the early stages of a weapon's explosion without conducting a full nuclear test.

The machine works by firing a powerful electron beam, which in turn creates a burst of X-rays. Last week's accident happened when the electron was inadvertently focused on a piece of graphite.

Under normal conditions, the piece of graphite acts as a sort of window shade, allowing routine testing of the electron beam without actually using it to X-ray anything. But for reasons that are not yet clear, the electron beam was too tightly focused, burning off a piece of graphite, according to Roark.

"It was an unexpected result," he said.

Roark said cleaning up the mess can be done within the project's current budget.