Ziff under fire

Part 21 - Thermal Diffusion

'This is one end of a thermal diffusion column,' he said, 'and there are thousands of columns containing uranium hexafluoride gas. The U-235 tends to rise to the top and is drawn off and sent to the next column. This increases the concentration of U-235 from about 0.7% to 0.9%.

Beryl swallowed some beer. 'That's nowhere near concentrated enough for a bomb.'

'You are right,' Sergei said and pointed at the map again. 'This plant is the largest industrial building in the world, four-stories tall and half a mile long. The uranium hexafluoride gas from the thermal diffusion plant is forced through filters of porous nickel to increase the concentration of U-235 to nearly 7% enrichment.'

'That's still not enough,' Beryl said.

'When do we get to make a bomb?' Dunc grumbled.

 K25 building

'I'm getting there,' Sergei said. 'In the third plant, ionized uranium hexafluoride gas molecules are accelerated to into a vacuum chamber mounted between two magnets. The magnetic field forces the gas molecules to follow a circular path dependent on their mass. The heavier U-238 flies further out than the U-235 which is collect in a trap. So, the Americans are separating the U-235 one molecule at a time. I told them to use centrifuges but the engineers don't think they can make them go fast enough.'

'Using the output from the first two plants as feedstock , we expect get the enrichment up to about 89%, the remaining 11% being U-238.'

'Now we're getting somewhere,' Beryl said.

'Gloik, Ah could celebrate with a wee dram more beer,' Dunc said.

'Sorry,' Sergei said. 'We're out of beer. How about some Bourbon?'

'Gloik. A poor substitute for Scotch, but it'll have to do.'

Sergei poured a shot of Bourbon into Dunc's dish and topped it up with some beer from his own bottle.

Sergei produced a packet of cigarettes and offered them to Kozak. Beryl said, 'I hope you're not going to smoke in here. It is a dangerous habit that makes you stink.'

Sergei put the cigarettes away.

Kozak interrupted. 'Zis is all very interesting but Murga wants us to steal a bomb or enough U-235 to build a bomb. 'Ow can we do zhis?'

Diagram of final electro-magnetic separation system.   Tuballoy was the code name for the project.

One of the 'race track' assemblies

'I think it is not possible,' Sergei said sadly. 'The atom bombs are made at Los Alamos in New Mexico and the Americans do not yet have enough U-235 to make a bomb. Every molecule we extract here is sent to Los Alamos. Don't tell anyone I said that! It's top secret. Ha, Ha . . . Maybe we wait a few more months.'

'Zat will be too late,' Kozak groaned. 'Murga will not be pleased.'

'What about plutonium?' Beryl asked.

'That is even less possible. The production reactor is at Hanford in Washington State. We make only a little here at Oak Ridge with a pile which uses heavy water as a moderator instead of graphite. We get the heavy water and the uranium from Canada.'

'I looked into stealing some of the plutonium but it is too difficult. The security is tight and the radiation very dangerous. It sets off the geiger-müller radiation counters. They go mad. Also, making a bomb is difficult because it will explode too quickly.'

'Zhen we must use plan B,' Kozak announced. 'Murga says Germany will be defeated so we must sabotage ze process and get ze plans to Russia so Joseph Stalin can build a bomb quickly.'

Sergei looked puzzled. 'So now Germany is kaput . . . finished. And am a real Russian spy? Now I work for Mother Russia?'

'Why don't we go forward to a time when the Americans have the bombs in production?' I asked. 'Then we can steal one and take it backward in time to now.'

'Paradox.' Kozak said. ''itler did not explode a bomb so we can only succeed where there is no clear history.'

'Wait a minute,' I said sarcastically. 'Why are we trying to steal a bomb if you already know it didn't happen?'

'I already said zat to Murga. 'E wants it for ze Russians.'

'So 'ow we sabotage ze process?' Kozak asked.