“How you doing, bro?” said Robert.
“I’ve been better and I’ve been worse.”
“Balance is good in life.”
“Ninety-two and ninety-four. What do they mean to you?”
“Even numbers.”
“Another perspective.”
“Give me some context.”
His brother sounded engaged now, instead of just curious.
“Pure science. Your area of expertise.”
Two ticks of the clock went by.
“Ninety-two is the atomic number for uranium. Ninety-four is the atomic number for plutonium.”
“That’s what I remembered too.”
“Why?”
“Hypothetical.”
“Okay.”
“What sort of uranium and plutonium would you need to build a nuke?”
“What?”
“Just answer the question.”
“What the hell are you involved in, John?”
His brother did not often call him John. To his older sibling Puller was either “bro” or sometimes “Junior”-although lately the latter term had not been used by him very much because it was a reminder of their father.
“Just give me your best answer.”
“You need lots of things. Most you can obtain. Others you can build. If you have time and some expertise it’s not that hard. What’s hard to get is the nuclear fuel for the process. There’re only two that exist.”
“Uranium and plutonium.”
“Right. And you need highly enriched uranium, U-235 or HEU, to make a nuclear bomb. To do that you need a manufacturing facility, big bucks, lots of scientists, and a number of years.”
“And plutonium?”
“Should we be talking about this? They’re monitoring the call.”
“Nobody’s listening, Bobby,” said Puller. “I made arrangements for this to be private.”
His brother didn’t say anything for a long moment.
“Then I’d say whatever you’re involved in is way beyond a hypothetical.”
“And plutonium?”
“You get plutonium-239 mostly from radiating uranium in a nuclear breeder reactor. What you’re really doing is scrubbing out plutonium-240, which is abundant in reactor-grade plutonium but which can cause a fizzle when using it as a nuclear weapon.”
“But again, tough to get.”
“Impossible to get for the man on the street. Who has a nuclear breeder reactor in their backyard?”
“But could you get it?”
“I suppose you could steal it or buy it on the black market.”
“How about in the U.S.? How do they make it?”
“The only U.S.-owned gaseous diffusion plant is in Paducah, Kentucky. But that’s used to enrich uranium for fuel in nuclear reactors, totally different process.”
“But could it be highly enriched by that process? To get it to be the fuel for a nuclear weapon?”
“Paducah is set up to enrich uranium for use in nuclear reactors, not build the fuel for bombs.”
“But could a plant like Paducah highly enrich uranium?” Puller persisted.
“Theoretically, yes.” He paused. “Where exactly is all this going?”
“How much U-235 would you need to build a bomb?”
“Depends on what type of bomb and what type of method you’re using.”
“Ballpark,” said Puller.
“With a simple bomb design and a Nagasaki yield you’d need anywhere from fifteen to fifty kilograms of HEU or six to nine kilograms of plutonium. If your weapons program is super-sophisticated and your bomb design is perfect you could get the same boom with roughly nine kilos of HEU or as little as two kilos of plutonium.”
“So Nagasaki?”
“Yield equivalent to over twenty-one thousand tons of dynamite plus the radiation fallout kicker. That’s forty-two million pounds of TNT. Mass destruction.”
“And a little more HEU or plutonium?”
“Your results go up exponentially. It’s all in your bomb design. You can use the gun method, which is not good at all, although the first A-bomb dropped on Japan used that design. That’s basically a long tube. Half your nuclear charge at one end backed by a conventional explosive and the other half of your nuke fuel at the other end. The conventional explosives are detonated, it pushes the fuel down the tube where it hits the other half of the fuel, and you have your chain reaction. It’s crude, highly inefficient, and your explosive yield is severely limited. You’d need a tube of infinite length to sustain the chain reaction. And you can only use uranium, not plutonium, because of impurity factors. That’s why the industry moved on to the implosion method.”
Puller said, “Give me the two-cent tour on the implosion method.”
“You can use either uranium or plutonium. You basically use conventional explosives, called explosive lenses, to squeeze the pit where your nuclear fuel is located into a supercritical mass. The shock wave compressing the uranium or plutonium must be perfectly spherical, or the pit material will escape through a hole and you’ll end up with what’s called a fizzle. You also need an initiator, tampers and pushers, and ideally a neutron reflector to push neutrons back in the pit. The trick is to keep the pit from blowing apart too quickly, before you reach optimal supercritical mass. The longer the fission material is allowed to react, the more atoms are split and the bigger the boom. You can triple your explosive yield without a gram more of nuclear fuel if your design is good.”
“What are some of the elements you’d need?”
“Meaning what exactly?”
“Talk to me about gold foil and tungsten carbide.”
There was silence for three beats. “Why those two specifically? Do you know that they’re present in your case?”
“Yes.”
“Jesus.”
“Talk to me, Bobby. I’m running out of time here.”
“Gold foil can be used in the initiator component. You use a small sphere with layers of beryllium and polonium separated by gold foil. That’s placed in the center of the pit and is obviously a critical part of the design.”
“And the tungsten carbide?”
“It’s three times stiffer than steel and dense as hell and therefore works very well as the neutron reflector. That is to get the neutrons back into the pit to maximize the supercritical stage. Are you telling me that… Where the hell are you?”
“In the U.S.”
“How did they get the fuel?”
“What if I told you there was a secret government facility operating in the 1960s that was closed a long time ago and a three-foot-thick dome of concrete was put over it, and the sucker was just left that way? All the workers at the plant were shipped in from outside and lived in a neighborhood right next to it. The workers were never allowed to talk about it with the local folks, and when the plant closed down they shipped all the workers off. Ring any bells? You were networked in tight with all this stuff when you were with the Air Force.”
“Three feet of concrete?”
“In a dome shape.”
“Out-of-the-way place?”
“As rural as they come. Entire population far less than one block in Brooklyn. Facility had its own fire department and I found a sheet of paper in there with the numbers 92 and 94 written on it. And I also found out that blasting for coal was not to take place within miles of the dome.”
“They’re blasting near there? Are you serious?”
“Yes.”
“That’s unbelievable. Even if you’re blasting miles away, there are bedrock fissures that can be weakened. That could be catastrophic.”
“What about this facility?”
“I don’t know. I wasn’t even alive in the 1960s.”
“But if you had to guess. Based on your experience?”
There was a long sigh. “If I were still in uniform I could never tell you this.” He paused. “I could be convicted of treason. But since I already have been convicted of treason, what the hell.” He paused again. “In the past I heard of early stage processing and enrichment plants that were built in rural America. This was post-World War II when the only thing that mattered was kicking the Soviet Union’s ass. These facilities were built to enrich uranium and also work with plutonium for use in nuclear weapons. Most if not all of them were closed down.”