the last of the B-53's

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NPR | MICHELE NORRIS, host: The United States is taking one of its nuclear options off the table today. The B-53 is a 10,000-pound relic of the Cold War days. A bomb so big it could have obliterated a big city in a single blow. Well, now near Amarillo, Texas, the last B-53 is being dismantled.

And Hans Kristensen joins us now to talk about that. He directs the Nuclear Information Project at the Federation of American Scientists. So glad you came into the studio.

HANS KRISTENSEN: Thanks for having me.

NORRIS: Can you tell us a little bit more about the B-53, how did it compare to other weapons? And how was it intended to be used?

KRISTENSEN: It was a city buster, literally. In its first incarnation, it was a warhead on the tip of a long-range ballistic missile called the Titan. And it was designed to blow-up cities. And a later version was converted into a gravity bomb, which is the one that we now see being taken apart. That was built for the B-52 long-range bomber.

And, of course, over the years the mission changed that delivery vehicles became more accurate. And so, instead of being a city-busting weapon, it turned into a bunker-busting weapon, where it was designed to literally dig up underground command and control facilities in the Soviet Union, later Russia.

NORRIS: So, facilities perhaps in the side of mountains and things like that.

KRISTENSEN: Correct. They can be under a, you know, great big granite formation to protect better or they can just be very deep in general.

NORRIS: What does this thing look like?

KRISTENSEN: Well, it's a size of a little car. I've been standing right next to one of them and it's humongous. And it's so big that the large B-52 bomber could only carry two of them in its belly. I mean, one in each bomb bay, and it was full.

NORRIS: How do you dismantle a monster bomb like this?

(SOUNDBITE OF LAUGHTER)

KRISTENSEN: Well, it's like taking a car apart except you do it much more carefully. The, you know, nuts and bolts, the glue - you name it. I mean, it's just peeling apart layer by layer. And there are very strict manuals on exactly what you have to do, how much pressure can you apply to each screw, what kind of glue holds the chemical high explosives together around the spear of uranium - highly enriched uranium, in this case. Also, how to handle it because you don't want to drop some of this stuff.

The high explosives are not what we have in the most modern weapons that are called insensitive high explosives. These are sort of conventional high explosives. And if you drop them they can explode. And so, they take these weapons apart in these weapons bays, as they call them, that are underground hardened concrete-steel structures that can contain a blast if these high explosives go off.

NORRIS: This is part of a global effort to step away from the Cold War and the machinery of the Cold War. In your estimation, how much progress has been made in that effort? How much is yet to be done, not just here but around the world?

KRISTENSEN: Well, as everything, it depends on when you compare it to. Because, I mean, we had arsenals on our side at a peak somewhere around 32,000 weapons in our stockpile. Today, we're down to 5,000. On the Soviet side, they had at their peak some 45,000 weapons in their stockpile. And they're now down to perhaps eight. So, a big job has been done.

But, as you can imagine, five and 8,000 weapons is still an enormous amount of overcapacity for the kind of world we live in today. These large arsenals, they were built, you have to remember, to battle, to fight nuclear wars - large arsenals against large arsenals. So, now we're struggling with how to drawdown these big arsenals and make them more applicable to the kind of world we live in today.

NORRIS: I've been speaking with Hans Kristensen about the dismantling of the last B-53 bomb. He's the director of the Nuclear Information Project at the Federation of American Scientists. Thanks so much for coming in.

KRISTENSEN: Thanks for having me.