Lab Conducts First X-Ray Test on Mock Weapon

By John Fleck, Albuquerque Journal Staff Writer
Saturday, December 05, 2009

Los Alamos National Laboratory on Thursday evening took the first ever three-dimensional X-ray movie of a mock nuclear weapon detonation, a milestone two decades in the making.

The test at the lab's Dual Axis Radiographic Hydrodynamic Test Facility, known as "DARHT", used the world's most powerful X-ray machines to take pictures of the inner workings of a W78 nuclear warhead, said Dave Funk, head of the lab's hydrodynamics experiments division.

The 6:09 p.m. test, with more than 60 Los Alamos staff in attendance, was a success, yielding good data on the W78's behavior, Funk said in a telephone interview Friday.

The massive X-ray machine is part of the National Nuclear Security Administration's suite of test equipment and computer simulations used to maintain U.S. nuclear weapons without underground test blasts.

Garrett Harencak, a senior National Nuclear Security Administration official overseeing the lab's weapons work, issued a statement calling the test "an important development in the NNSA's stockpile stewardship mission."

"I applaud LANL for reaching this important milestone. DARHT will help ensure a safer and more secure stockpile without testing," Sen. Jeff Bingaman, D-N.M., said in a statement.

The test ends an embarrassing episode for the weapons program. DARHT was originally planned in 1988 with a price tag of $30 million to $54 million, but a series of delays because of litigation by environmentalists, design changes and design flaws dragged out the project, and pushed the final price tag over $300 million.

For the first five decades of the U.S. nuclear program, weapons were actually detonated to test them, first above ground and then underground beginning in the 1960s. "You got the answer, right? It worked or not," Funk explained.

The United States abandoned full test blasts in 1992, establishing a program of small-scale experiments and computer simulations instead.

In a nuclear weapon, high explosives are used to squeeze plutonium to create a critical mass, yielding its nuclear blasts.

DARHT tests allow weapons designers to X-ray a mock nuclear weapon during the early stages of that blast, to compare the weapon's performance to predictions made by the lab's supercomputer simulations, Funk explained. Without the explosive plutonium, there is no nuclear yield, and the blast can be contained with a big steel vessel, according to Funk.