Читаем A thousand suns полностью

‘No sir, I don’t think so. But I know they were attempting to build one. Our troops recently discovered a research laboratory in Strasbourg, and a German scientist called Heisenberg is in our hands. We know from debriefing him that the laboratory was their main research strand, and that this Heisenberg was their leading physicist on the project. At the risk of complicating this with science, I can attempt to explain how we know they can’t possibly have an atom bomb.’ Wallace raised his eyebrows, a little more relaxed speaking before them all, now that he was approaching familiar territory.

Truman pursed his lips and then nodded. ‘Continue. I’ll try my best to follow.’

‘Okay.’ Wallace took a moment to consider how to explain the concept simply. ‘Mr President, sir, you know what an atom is?’

Truman frowned. ‘Of course, young man, it’s those little ball things we’re all made of, isn’t it?’

Wallace smiled, the President was essentially right. ‘Yes, sir. Well… we know from scientific work carried out in 1939 that splitting one of these releases an immense amount of energy. We also know that some molecules — ’ Truman frowned ‘- that some substances have atoms that are easier to split than others. One such substance is called uranium 235, or U-235 as we call it for short. Now, to take this idea and turn it into a bomb, one needs to split a whole lot of atoms very quickly. The way one does this is by creating what is known as a chain reaction. When one splits the first atom it sheds energy and a couple of particles known as neutrons. These neutrons in turn smash into neighbouring atoms, split them and release more neutrons. This happens repeatedly, with every new atom that is split two more neutrons are released, and pretty quickly you have billions of neutrons splitting billions of atoms, thus releasing a lot of energy. That is a chain reaction. Are you with me so far, Mr President?’

Truman nodded. ‘So far. Keep it like you’ve just done, as non-scientific as you can.’

‘So… that is the chain reaction, sir. However, as I mentioned earlier, only one type of substance, U-235, can have its atoms easily split this way, and it is very, very rare and must be very carefully refined and purified. To give you an idea, sir, of how much it has to be refined, it would take five hundred tons of mined uranium ore to produce one ounce of uranium; of this only about one per cent is U-235 while the other ninety-nine per cent is U-238, useless to the process. So, as you can see, sir, it takes a lot of work to produce the raw material for a bomb. We have been refining uranium now for nearly a year and I believe we have only just managed enough to make our first bomb.’

‘I see,’ said Truman. ‘But then could they have produced enough of this material for a small bomb?’

‘A very good question, sir. And the answer is that there needs to be a minimum amount, mass, of the substance in one place to enable the chain reaction. This is referred to as the critical mass. Once a block of U-235 is put together that exceeds this mass, the chain reaction happens pretty much automatically.’

‘Good grief! Do we have more than this amount of uranium? Is it kept apart? Separately, I mean?’

Wallace smiled at the President’s alarm, charmingly naive, but a sensible concern.

‘I believe we have in excess of that amount, and yes, it is stored carefully, sir.’

‘So what is this amount? Is it a lot, tons?’

‘The critical mass required to produce the chain reaction is calculated as one hundred and ten ounces sir.’

‘Ounces!’

‘Yes, sir, perhaps about the weight of a saucepan full of water, and about the size of, say, a baseball.’

‘Good God, that doesn’t sound like a lot! Are you sure the Germans haven’t been able to make that amount of the stuff?’

‘We are pretty certain, sir.’

‘Very certain, sir,’ Donovan added. ‘The discovery of the laboratory in Strasbourg showed they had only managed to refine much smaller amounts. And as yet, the German scientist, Heisenberg, has not relayed news of any other nuclear research projects. As far as he is concerned, his was the only atom bomb project.’

Truman took a moment to digest the information. He directed his attention towards Wallace. ‘Well, thank you, son, what’s your name?’

‘Wallace, sir.’

‘Thank you, Wallace, for bringing me up to date. I’m surprised that I actually understood your description. Well done.’

Wallace took a step back behind Donovan, aware that his moment of glory had passed and his contribution to the conference was more than likely complete.

‘I presume that means we can rule out the possibility that the threat is one of these atom bombs, then,’ Truman said, displaying a little relief.

Donovan awkwardly corrected the President. ‘Not rule out, sir, but it seems highly unlikely.’

‘Noted, Colonel Donovan.’

Wallace looked around the men at the table. All of them seemed to some degree comforted by the information he had imparted. One of them, the Chairman of the Joint Chiefs of Staff, Admiral Leahy, stirred.