Oppenheimer, Putin, and the South African bomb

[Nat Quinn]

After watching the film Oppenheimer last week, I could not help brooding about the atomic bomb then and now. What would have happened if the USA had made the bomb in July 1944 instead of July 1945? Would they have dropped it on Germany? In the 1980s, South Africa made six gun-type atomic bombs, like the one the US dropped on Hiroshima on 6 August 1945. Could we have also made implosion-type bombs, like the one the US dropped on Nagasaki? Above all, there is this mystery: since everyone now knows how to make an atomic bomb, why is it that, 78 years later, nobody has ever used an atomic bomb again as a weapon, neither a rogue government nor a terrorist gang? We have been extremely lucky. How long will our luck last?

First, a quiz question. Einstein’s famous equation, E = mc², says that there is an enormous amount of energy associated with all mass. C is the speed of light: 300 000 000 metres a second. The equation applies to all forms of energy, not just nuclear. A spring compressed, and therefore containing potential energy, is slightly lighter than the same spring relaxed, although the mass difference is so miniscule that no scale could ever measure it. Here is the question. The Hiroshima bomb exploded with the energy of 16 000 tons of TNT and killed about 100 000 people. How much mass in that bomb was converted into energy?

Answer: about 0.75 grams (0.03 ounces). About the weight of two peas.

Disappointed

I was disappointed in Oppenheimer, not in the acting or the photography or the accuracy but in the subject matter. The film covered the Manhattan Project, the USA project from 1942 to 1946 to design and build a bomb that would harness the nuclear force, the strongest force in nature. The term atomic bomb is technically wrong. Atomic is to do with the electrons that surround the nucleus of the atom; it is to do with the electrical force and chemistry. The nuclear bomb is the correct term for the bomb that harnesses the nuclear force, which binds together the components of the nucleus. But I’ll keep using “atomic bomb” wrongly because it sounds more dramatic. The project drew together the most extraordinarily clever and interesting group of scientists ever assembled, predominantly from eastern Europe and disproportionately Jewish. One of them, Hungarian and Jewish, is often described as the cleverest man who ever lived.

I was hoping that the film would concentrate on the enthralling technical discussions of these marvellous people and their experiments. It did nothing of the kind. The best part of the film was the assembly of the Trinity bomb and its detonation on 16 July 1945, but it was too short. Instead most of the film was about the hearings into the security risk and possibly communist leanings of Oppenheimer himself. I found these tedious, unimportant and interminable. They made the film far too long.

The boss of the Manhattan Project was an army engineering officer, General Leslie Groves, well played by Matt Damon. Groves knew nothing about nuclear science but was a wonderful manager and detector of talent. He saw immediately that Robert Oppenheimer, a brilliant nuclear scientist, would make the perfect leader of the scientific team, which he did. Oppenheimer was played by Cillian Murphy, a strangely compelling actor with starey eyes and a permanent look of sympathetic surprise. Most of the film dealt with hearings into his security risk after WW2 had ended. They were accurate, often using original transcripts; they were also exceptionally boring.

They were useful only in that they illustrated the nonsense of the anti-communist mania in the USA in the 1950s. Oppenheimer might have had some communist leanings but so what? There were a lot of clever idiots around at the time who admired communism and thought Stalin was a lovely chap. The best way to deal with them would be to be completely open about communism, discuss it freely, and show them all what evil nonsense it was, and would always be. Anyway, all the elaborate security precautions proved a waste of time. The Trinity detonation showed the success of the implosion atomic bomb. (They did not need to test the gun-type; they knew it would work.) When President Harry Truman of the USA and Winston Churchill of the UK met Joseph Stalin of the USSR at Potsdam on 17 July 1945, they told him they had developed an entirely new and much more powerful bomb. Stalin was not the slightest surprised. He obviously knew all about it already.

Chain reaction

Both atomic bombs and nuclear reactors use fissile materials to sustain a nuclear fission chain reaction. However, they do so in fundamentally different ways, so that it is physically impossible for a power reactor to explode like an atomic bomb. (Nuclear power is by far the safest form of energy we know.) Natural uranium, which is abundant, consists of 99.3% Uranium-238 and 0.7% Uranium-235. Only the 235 is fissile. While they were working on a nuclear reactor they had built, the Manhattan scientists noticed to their surprise that a “new” element had been made. They called it plutonium.

When Uranium-238 captures a neutron, it goes to Uranium-239. After two beta decays, this goes to Plutonium-239 which is also fissile.So, this could be used in a bomb. The trouble was that if it captured another neutron, it turned to Plutonium-240, which is not fissile and which is a strong neutron poison, soaking up neutrons. 240 is also subject to spontaneous fission, releasing neutrons in an uncontrolled manner. (Actually plutonium was not new at all. It is always being made everywhere, including in the room you are sitting in now, and including your own body, doing no harm whatsoever. There is uranium everywhere and neutrons everywhere, and so the reaction above happens everywhere – but in tiny amounts.)

To sustain a chain reaction you need critical mass of a fissile material: the surface area must be as small as possible to stop neutrons leaking away but the mass must be as big as possible so that there are more fissile nuclei available. In the gun-type bomb, using Uranium-235, one sub-critical mass is fired into another in a canon. This was the Hiroshima bomb and all six of the South African bombs. The gun-type would not work for plutonium because the neutrons from the 240 would cause the plutonium to splutter apart before it could explode properly. The only way for a plutonium bomb was implosion. You had to take a mass of plutonium and suddenly shrink its volume to reduce its surface area to make more neutrons available for fission. Imagine taking a steel ball the size of a large apple and shrinking it in a fraction of a second to the size of a golf ball. You had to do that with a plutonium ball. That seemed quite impossible. One man thought it was perfectly possible.

Cleverest man

John von Neumann (born Neumann János Lajos, in Hungary in 1903) is often cited as the cleverest man who ever lived. Among Einstein, Bohr, Teller and the other men of genius at Manhattan, he stood alone, the only inhabitant of a league above the rest. Edward Teller, himself a genius, said of von Neumann, ”Von Neumann would carry on a conversation with my three-year-old son, and the two of them would talk as equals, and I sometimes wondered if he used the same principle when he talked to the rest of us”. Von Neumann laid down fundamental principles that are still used in maths, physics, quantum mechanics, economics, game theory, computing and robotics. He was also expert in practical engineering, including conventional explosives. He suggested that, by surrounding the ball of plutonium with wedges of different types of chemical explosives, the different properties of the gases from the explosions could be used as lenses to concentrate the shockwaves inward in a symmetrical way so as to produce immense and even pressure on the plutonium ball. The maths were exceedingly complicated, and they had only crude mechanical calculators, but they did have the world’s greatest living mathematician. So they designed and made the Trinity bomb.

The film shows the different segments of chemical explosives being hoisted up the tower and assembled. The final result looked a bit like a giant soccer ball about two metres in diameter. It was then enclosed in steel containment and wired with electric cables with electrodes to ignite the different sections at exactly the same time. The bomb worked well. Von Neumann’s calculations were correct, even if the bomb was very big. It needed the gigantic American B29 bomber to deliver it over Japan. (It cost twice as much to design and build the B29 as it did the atomic bomb.) The bombs were dropped. The war ended.

Von Neumann does not appear at all in the film. Not does Richard Feynman. Edward Teller and President Truman are slandered. Enrico Fermi is treated fairly.

Today implosion-type nuclear weapons can be made smaller than a soccer ball, to be fired in missiles rather than dropped from gigantic four-engined bombers. The dramatic reduction in size from the Trinity bomb has several causes. Von Neumann had already invented the fundamental principle of explosive lenses, and it is much easier to follow and improve than to invent something new. Electronic computers made calculations a million times faster than the mechanical counting machines. Explosives improved.

In the 1980s South Africa made six crude gun-type bombs using enriched uranium. Each would have worked as well as the Hiroshima bomb but they were big and clumsy and could not possibly be used on a missile. The intention, it seems, was to use them in demonstration. If the big power enemies of apartheid had shown any signs of a military advance against South Africa, P W Botha could have exploded an atomic bomb in the Kalahari Desert. That would have put a different complexion on things. If Saddam Hussein had exploded an atomic bomb in the Iraqi desert in February 2003, the US invasion would not have happened. What if South Africa had developed an implosion bomb?

South Africa had all the means for doing so. She is a world expert in conventional explosives. She has skilled nuclear scientists. I think South Africa could easily have made implosion bombs small enough to fit on her missiles. If North Korea could do it, South Africa could do it better. Fortunately this never happened. In 1989, F W de Klerk scrapped the bombs altogether (probably to stop the ANC inheriting them). We became the only nation in the world to produce nuclear weapons and then denounce them.

The greatest mystery for me, and greatest worry, is why no rogue nation or terrorist gang has ever used nuclear weapons. Everyone know how to make gun-type bombs. In his thriller, The Fourth Protocol, Frederick Forsyth explains exactly how to do so. The difficult part is getting hold of a sufficient quantity of enriched uranium. But governments today can make enough, and terrorist gangs could probably steal enough. It’s never happened. I wonder why? I wish I knew the reasons so that we could work on increasing their effectiveness to reduce the chances of nuclear war in future.

Terrible war

Right now there is a terrible war raging in the Ukraine. It confuses me horribly, and I keep changing my mind about it, but I am sure of one thing: nothing that happened in the past can ever justify Putin’s atrocious invasion on 24 February 2022. I think the West behaved very badly when Mikhail Gorbachev ended communism in Russia peacefully and allowed its Soviet colonies full independence. He deserved congratulations, encouragement and help from the West; he deserved the dismantling of NATO. He got none of these things. I also know that the Ukraine had been exceedingly corrupt and did not come well out in the events in 2014. But none of this excuses the bloodbath and ruin Putin has brought to pass. However, on the subject of nuclear war, there is one reason we have to be grateful to him.

When communism ended in Russia in 1989, the country threatened to fall apart. Far from proceeding from communist tyranny to democratic bliss, Russia broke up into warring factions and chaos. Boris Yeltsin, Russian president from 1991 to 1999, had one heroic hour but otherwise was corrupt and useless, allowing more anarchy. The KGB broke up into various Mafia gangs, not interested in politics but very interested in making huge piles of money and killing rivals. Nobody was in control any more – of a country with a vast arsenal of advanced nuclear weapons. The great fear was that one of these powerful gangsters would size nuclear weaponsn and then sell them to rogue states or terrorists, or use them to blackmail rich countries, with perhaps a demonstration atomic bomb exploded in a Western city to show they were not joking. Putin ended these nightmare possibilities. He came to power in 1999 and took control over the whole country. He united it. He became the Mafia don of dons. Only he could authorise he authorise the use of nuclear weapons and it was then never in his interest to do so. Whatever crimes he might have committed, and he committed plenty, we owe him thanks for reducing the chances of nuclear war.

Might he himself now use a tactical nuclear weapon if things go badly wrong for him in the Ukraine? Although the war is dragging on and on, it seems to be the Ukraine that is faring worse, far worse, than Russia, despite reports to the contrary in the Western media. I think the Ukraine is losing badly. Even if Russia were losing, I don’t think Putin would resort to the nuclear option, but I didn’t think he’d invade last year, so my thoughts mean nothing. The best thing is to end this wretched war as soon as possible.

My feeble suggestion is that the Ukraine should vow never to join Nato, that we should cede the Crimea to Russia and hold referenda in the Donbas to see whether people there want to be part of the Ukraine or part of Russia. Even if all of the Donbas breaks away, the Ukraine will still be a big country with rich soil. This is a rather cowardly out. But sometimes cowardice saves more lives than heroism.

Meanwhile I want to see more and more nuclear power, and fewer and fewer nuclear weapons.

 

source:Oppenheimer, Putin, and the South African bomb – Daily Friend

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