assembled in them, he explained. But with the end of the Cold War, thousands of bombs had been dismantled there, the nuclear components put in cold storage. It remained a full-time job.
The distinctive name came from the twenty-foot mound of compacted gravel heaped over the blast-resistant concrete roofs.
“They’re designed that way so, in case of an accident, they’ll blow straight up and absorb the energy,” Booker said. He noticed Atkins’ subdued expression. Grinning, he said, “Don’t sweat it. There’s no danger of a nuclear explosion, but if you screw up with the high explosives that detonate the nuclear primary, you’re going to have trouble.”
“What about radioactivity?” Atkins asked.
“Only if you puncture the shielding in one of the pits or accidentally release some of the tritium gas,” he said. Used in combination with plutonium, tritium was a booster that increased the bomb’s explosive yield.
During the short flight to Texas, Booker had given Atkins a crash course in the fundamentals of nuclear fusion. Boosting was one of the keys to getting highly explosive yields from relatively small quantities of fissile material. It involved injecting a mixture of tritium and deuterium gas directly into the pit, the weapon’s explosive core.
Booker, Atkins soon realized, was a gifted practitioner of the bombmaker’s art.
Within an hour of their arrival—their plane was met on the runway—they’d already checked into Building 16- 12 at the Pantex plant, where they received picture IDs, badges, name tags, and dosimeters to register any exposure to radiation. Armed guards went over their clothing and shoes with hand-held metal detectors.
Security was formidable. Atkins noticed there was even a guard on the roof of the building, manning an M-60 machine gun. The roads that crisscrossed the complex were lined with fourteen-foot-high fences topped with barbed wire. As at the Oak Ridge Y-12 plant, guard towers were plentiful.
Booker and Atkins were ushered into a small office, where the plant manager—his name was Carson—met them. A somber-looking man in a blue suit, he kept dabbing at his chin with a bloody handkerchief. He’d cut himself shaving as he hurried to meet them at the plant.
“You have presidential clearance to remove any weapon you need,” Carson said irritably. “I’ve got to tell you I don’t approve of this.”
Booker asked whether they’d felt the quake here in Texas.
The plant manager nodded. “We had some light damage. Nothing serious.”
Booker said. “You’re nearly a thousand miles from the epicenter.” He shook his head in wonderment. The main seismic wave energy had traveled in the opposite direction and yet they’d still felt it out here in Texas. Amazing. “We’re looking at another quake, maybe even larger,” he said. “So make me feel good. Tell me I’m going to have your full cooperation and support.”
“Whatever you need will be made available,” Carson said tersely. He asked what kind of weapon they wanted.
“One of the MK/B-61s,” Booker said. “It’s a superb warhead. Many of them are still in service. The cruise missiles use your basic MK/B-61. Excellent safing components and a superb hard case.” One of the larger weapons still in use, the bomb came in four configurations, ranging from a 500-kiloton yield up to one megaton. It was designed so that the yield and fusing could be programmed in flight.
Carson sat down at his desk and tapped a few keys on a computer terminal. “We have more than a hundred of those warheads in storage in Building 12-11.” He printed out a sheet of paper and handed it to Booker. “The manifest lists the dates of disassembly. May I ask what yield we’re talking about?”
“One megaton, maybe a little more if we have to boost it,” Booker said. “Right now we’re not sure.”
The debate on what size weapon to use was still raging in Memphis. Atkins hoped to hear soon from Guy Thompson, whose team had been crunching numbers around the clock, trying to calculate the maximum yield and where to place the weapon. They were playing a deadly balancing act. Atkins wasn’t sure that clear-cut, definitive answers existed. No matter what they did, it was going to be a huge gamble. At times he thought the only thing that came close to explaining what they were up against was Chaos Theory, the notion of the importance of randomness in the universe.
Carson drove them to one of the igloos. A truck-sized forklift rolled away the twenty-five-ton concrete barrier that blocked the entrance. Punching a code into a keypad, he unlocked a pair of steel blast doors that opened automatically. They entered a bunker that roughly resembled a Quonset hut in shape. The arched roof was fifteen feet high. A pair of tracks ran down the middle of the floor.
“The walls are made of corrugated steel two inches thick,” Carson said. “On the outside, they’re banked with six feet of dirt.”
Fascinated, Atkins watched as a tractor operated by remote control rolled down the tracks and removed one of two dozen stainless steel drums stored on a metal rack that ran the length of the wall. The drum contained the “pit” or nuclear package of an MK/B-61 weapon that had been retired five years earlier.
Carson placed a small handheld instrument that resembled a photographer’s light meter next to the steel canister. “This is a spectrograph,” he explained for Atkins’ benefit. “Each one of these bombs has its own electronic fingerprint. This tells me we’ve got the right one.”
The tractor loaded the canister on the forklift. Within minutes they were headed to Building 12-11, one of the Gravel Gerties. After Carson opened the double doors, again with a special keypad, Atkins stepped into a tunnel that intersected with a labyrinth of other long passageways.
“Where to now?” he asked Booker, who was striding ahead of him. The physicist looked completely at home.
“The X-ray cell.”
A guard had them place their right hands on a glass-surfaced scanner. The reading was automatically compared with a similar scan taken when they’d first arrived at the plant. They were ushered through a steel door into a wedge-shaped space outfitted with a turntable and CAT scanner. The weapon’s nuclear package had already been removed from the stainless steel canister and placed on the turntable.
“That’s all there is to it?” Atkins asked, staring incredulously at the cylindrical device. About four feet long, it was barely a foot and a half in diameter.
Booker grinned. “That may not look like much, but it makes a hell of a bang. Its compact size makes it perfect for an underground explosion. When I’m finished, we’ll put it back in its hard case. It’s got one of the best subassembly designs I’ve ever seen. A series of polyurethane spacers absorb shock and support all the internal components. It was designed to slam into the ground and still go off.”
Seated at a computer terminal above the turntable, Booker carefully examined the CAT-scan images of the pit. The X-rays showed diagonal slices of the weapon. For security reasons, Atkins wasn’t allowed to watch. He knew that Booker was inspecting the weapon’s nuclear components, namely the plutonium-239 in the primary and the lithium deuteride uranium in the secondary.
Booker had explained the physics. When the secondary implodes, the lithium converts to tritium, which, in turn, undergoes fusion with the deuterium to create the thermonuclear blast.
After nearly an hour hunched over the computer screen, Booker pronounced the nuclear package fit.
“Now comes the tricky part,” he said.
Atkins understood. Booker had to install the double layer of high explosives that were bonded with plastic so they could be shaped. The explosives and detonators surrounded the weapon’s pit. When this material exploded, it started the implosion process, compressing the plutonium to a supercritical mass. The amount and type of high explosives used in the weapon was a carefully guarded secret.
They took an elevator to a lower level, where Booker would work alone on the explosives in a space that reminded Atkins of an operating room—all bright lights, gleaming tile, and stainless steel. Booker put on a heavy lead apron, gloves, and a facemask to protect himself from any radioactive emissions from the pit. He also wore antistatic booties.
“I helped develop the explosive,” he said. “I wish I could tell you about it. Wonderful stuff. A mixture of PETN, C4, and some other goodies.”
Atkins knew that C4 consisted of TNT plus a plasticizer and had the consistency of putty. It was fashioned into precisely cut “lenses” and carefully fitted around the plutonium pit. The lens design, one of the great breakthroughs of the Manhattan Project, controlled the explosion, shaping the blast to flow inward and set off the required implosion. The explosives were already cut and available. But it would take Booker several hours to
