Ziff under fire

Part 20 - Sergei, Russian spy

'Are yeh no going to tell us what an isotope is?' Dunc asked.

'A good question. Ze nucleus of each element has a number of protons ranging from hydrogen wiz only one proton up to uranium with 92 protons. Now protons 'av' a positive electrical charge and would repel each uzzer except that neutrons keep ze protons stuck togezzer. U-235 'as 143 neutrons and U-238 'as 146.'

'You know about carbon,' Beryl interjected. 'The nucleus of a carbon atom has 6 protons and also 6, 7 or 8 neutrons which give us the isotopes carbon-12, carbon-13 and carbon-14.'

'Yes.' Kozak added. 'Ze number after ze element name or symbol is ze total number of protons and neutrons in ze nucleus.'

'So, how do you tell them apart?' I asked.

'We 'av' to measure zheir weight.'

Beryl finished his sentence. 'Because the isotopes of each element are chemically identical.'

'So, yeh're saying we have to separate the U-235 atoms from the U-238,' Dunc said, 'and then hit the U-235 atoms with neutrons to set 'em off.'

U-235 Fission

'Exactement. Except zhere is ze problem of critical mass. If we put too much pure U-235 in one place it will explode spontaneously.'

'So we must bring two sub critical masses together very quickly,' Beryl said, 'and keep them together long enough to make a very big bang.'

'If not,' Kozak added, 'we get a fizzle.'

'What about plutonium?' Beryl asked.

'A plutonium-239 nucleus is created when a U-238 nucleus absorbs a neutron. And PU-239 will fission like U-235 so it can be used to build a bomb. Also it can be separated from uranium using chemical processes.

'Okay,' I said. 'How much plutonium-239 or uranium-235 is enough for a bomb?'

'It depends on the purity and how much we can compress ze plutonium. Probably less zhan 10 kilograms (22 pound).'

'What about the H-bomb?' I asked.

'Ze first hydrogen bomb test explosion was in 1952.'

'Could you tell me about it? How does it work?'

'Basically, when two protons (hydrogen nuclei) and two neutrons are fused to make helium, some of the mass is converted into energy according to Einstein's equation, Energy = mass multiplied by the square of the velocity of light.'

Fusion using deutrium and tritium

'This is a very simplified explanation of what 'appens in the sun and most of the stars in the universe and explains why ze stars can keep pouring out enormous amounts of radiation for billions of years. So zhis is quiet different from the fission of uranium or plutonium.'

'Why does this happen in the sun?'

'To make fusion possible requires enormous pressure and temperature which 'appens when a lot of hydrogen is compressed by the sun's gravitation force. To make a fusion bomb, we need an isotope of hydrogen wiz a neutron and this exists, it is called deuterium. We can use a fission bomb trigger to create ze temperature and pressure need to fuse ze protons and neutrons togezzer. But zat is anuzzer story.'

Kozak interrupted the lecture to offer some food and suggested we all get some sleep. We finished off a box of eggs with toast and found a bed. I had to share with Kozak. Beryl slept on a couch in the living room

In the morning, I was helping Beryl toast bread on the stove when someone rapped on the front door in a distinctive rhythm.

The door opened and a large man with a broad face looked in. I looked around for Dunc but he had ducked under the table.

To my surprise the man said, with just a trace of a foreign accent, 'You are early. I expected you tomorrow.' He looked over his shoulder as he closed the door behind him. 'How did you get here?'

'We walked,' Kozak said enigmatically.

The man raised one eyebrow dramatically. 'So. We spies do not reveal our methods. Yes?'

'You must be Kozak,' he said and wrinkled his nose. 'But who is burning the toast?'

'My assistants, Ziff Dion and Beryl Rose,' Kozak told him.

'Ziff Dion and Beryl?' The man beamed at me. 'And I am Sergei, the Russian spy.'