The sum of all fears - Tom Clancy [191]
"Every time we've won a war we've been punished for it," CINCLANT said. "At least winning this one didn't cost us a whole lot. Don't worry, there'll be a place for you when the time comes. You're my best wing commander, Captain."
"Thank you, sir. I don't mind hearing things like that."
Painter laughed. "Neither did I."
"There is a saying in English," Golovko observed. " 'With friends like these, who has need of enemies?' What else do we know?"
"It would appear that they turned over their entire supply of plutonium." the man said. A representative of the weapons research and design institute at Sarova, south of Gorkiy, he was less a weapons engineer than a scientist who kept track of what people outside the Soviet Union were up to. "I ran the calculations myself. It is theoretically possible that they developed more of the material, but what they turned over to us slightly exceeds our own production of plutonium from plants of similar design here in the Soviet Union. I think we got it all from them."
"I have read all that. Why are you here now?"
"The original study overlooked something."
"And what might that be?" the First Deputy Chairman of the Committee for State Security asked. Tritium."
"And that is?" Golovko didn't remember. He was not an expert on nuclear materials, being more grounded in diplomatic and intelligence operations.
The man from Sarova hadn't taught basic physics in years. "Hydrogen is the simplest of materials. An atom of hydrogen contains a proton, which is positively charged, and an electron, which is negatively charged. If you add a neutron - that has no electrical charge - to the hydrogen atom, you get deuterium. Add another, and you get tritium. It has three times the atomic weight of hydrogen, because of the additional neutrons. In simple terms, neutrons are the stuff of atomic weapons. When you liberate them from their host atoms, they radiate outward, bombarding other atomic nuclei, releasing more neutrons. That causes a chain reaction, releasing vast amounts of energy. Tritium is useful because the hydrogen atom is not supposed to contain any neutrons at all, much less two of them. It is unstable, and tends to break down at a fixed rate. The half-life of tritium is 12.3 years," he explained. Thus if you insert tritium in a fission device, the additional neutrons it adds to the initial fission reaction accelerate or "boost" the fission in the plutonium or uranium reaction mass by a factor of between five and forty, allowing a far more efficient use of the heavy fission materials, like plutonium or enriched uranium. Secondly, additional amounts of tritium placed in the proper location nearby the fission device - called a "primary" in this case - begin a fusion reaction. There are other ways of doing this, of course. The chemicals of choice are lithium-deuteride and lithium-hydride, which is more stable, but tritium is still extremely useful for certain weapons applications."
"And how does one make tritium?"
"Essentially by placing large quantities of lithium-aluminum in a nuclear reactor and allowing the thermal neutron flux - that's an engineering term for the back-and-forth traffic of the particles - to irradiate and transform lithium to tritium by capture of some of the neutrons. It turns up as small, faceted bubbles inside the metal. I believe that the Germans also manufactured tritium at their Greifswald plant."
"Why? What evidence do you have?"
"We analyzed the plutonium they sent us. Plutonium has two isotopes, plutonium 239 and 240. From the relative proportions, you can determine the neutron flux in the reactor. The German sample has too little 240. Something was attenuating the neutron flux. That something was probably - almost certainly - tritium."
"You are certain of that?"
"The physics involved here are complex but straightforward. In fact you can in many cases identify the plant that produced a plutonium sample by examining the ratio of various materials.