The nearly 50-year history of the country’s single most powerful nuclear weapon is coming to an end.

By Anna M. Tinsley

The nearly 50-year history of the country’s single most powerful nuclear weapon is coming to an end.

Workers at the nation’s only nuclear weapon assembly and disassembly facility will spend less than an hour today doing the final work to dismantle the last B53 — the United States’ most destructive weapon — which weighs about 10,000 pounds and is roughly the size of a minivan.

This weapon was deployed at the height of the Cold War and was targeted at Russia. “This was a big part of our Cold War strategic plan,” said Steve Erhart, the top federal official at the Pantex weapons plant, about 17 miles northeast of Amarillo.

“Its dismantlement is a key point in history,” he said. “It takes … a lot of destructive power off of the earth.”

Officials from the Energy Department and the National Nuclear Security Administration will be among those gathering at Pantex today to mark the end of the B53. They will watch as workers, who have already done the bulk of the work to take apart the weapon, take the final steps to dismantle it.

Pantex officials said in a statement that this “ensures that the Cold War system will never again be part of the U.S. nuclear weapons stockpile.”

B53s, described as “high yield strategic thermonuclear bombs,” were first introduced around 1962.

They were designed to be dropped from a B-52 bomber as a “bunker buster,” sending shock waves similar to an earthquake through the ground to collapse deep underground shelters near Moscow where high-ranking officials might be. The bomb could burrow underground and destroy everything in its path — and then some.

Ultimately, the bomb, which contained about 300 pounds of high explosive around a uranium core, had a yield of 9 megatons, making it about 600 times more powerful than the bomb that destroyed Hiroshima, Japan, during World War II, according to the Federation of American Scientists.

Because of the bomb’s size and age, officials said dismantling the weapon “did present some challenges,” Erhart said. “We had to engineer solutions to safely handle a bomb that size.”

Some early versions of the weapon were retired in the 1960s, and the U.S. began to disassemble some in the 1980s. The remaining B53s were retired from the country’s active arsenal in 1997.

President Barack Obama has called on the U.S. to reduce the number of nuclear weapons, saying in 2009 that “to put an end to Cold War thinking, we will reduce the role of nuclear weapons in our national security strategy and urge others to do the same.” Last year, the National Nuclear Security Administration gave Pantex the authority to begin dismantling the B53 weapons system.

For years workers have studied the best way to dismantle the fewer than 50 B53s, especially trying to anticipate the “unknowns with how this weapon system has aged,” said John Woolery, general manager of Pantex. “Before touching it, we had to spend about three years … identifying a safe process to disassemble it.”

Once the work is finished, Pantex workers “can be quickly retrained to work on any other [weapon] we have a need for,” Woolery said. “It’s a matter of where the priorities are.”