The science of nuclear weapons, visualized

Visualized: How Nuclear Weapons Work

In 1945, the world’s very first nuclear weapon was detonated at the Trinity Test Site in New Mexico, USA, marking the start of the atomic age.

Since then, the global nuclear stockpile has multiplied, and when geopolitical tensions rise, the idea of ​​a nuclear apocalypse naturally raises widespread concern.

But despite their catastrophic effects, the science of how nuclear weapons work is atomically small.

The Atomic Science of Nuclear Weapons

All matter is made up of atoms, which host different combinations of three particles: protons, electrons and neutrons. Nuclear weapons work by capitalizing on the interactions of protons and neutrons to create an explosive chain reaction.

At the center of each atom is a nucleus called the nucleus, which is made up of tightly bound protons and neutrons. While the number of protons is unique to each element of the periodic table, the number of neutrons can vary. Accordingly, there are several “species” of certain elements, called isotopes.

For example, here are some uranium isotopes:

  • Uranium-238: 92 protons, 146 neutrons
  • Uranium-235: 92 protons, 143 neutrons
  • Uranium-234: 92 protons, 142 neutrons

These isotopes can be stable or unstable. Stable isotopes have a relatively static or unchanged number of neutrons. But when a chemical element contains too many neutrons, it becomes unstable or fissile.

When fissile isotopes attempt to stabilize, they release excess neutrons and energy. It is from this energy that nuclear weapons derive their explosiveness.

There are two types of nuclear weapons:

  • atomic bombs: These are based on a domino effect of multiple fission reactions to produce an explosion, using either uranium or plutonium.
  • Hydrogen bombs: These are based on a combination of fission and fusion using uranium or plutonium, using lighter elements like hydrogen isotopes.

So what exactly is the difference between fission and fusion reactions?

Separation of atoms: nuclear fission

Nuclear fission – the process used by nuclear reactors – produces large amounts of energy by breaking a heavier unstable atom into two smaller atoms, setting off a nuclear chain reaction.

When a neutron is fired into the nucleus of a fissile atom like uranium-235, the uranium atom splits into two smaller atoms called “fissile fragments” in addition to neutrons and energy. These excess neutrons can then set off a self-sustaining chain reaction by hitting the nuclei of other uranium-235 atoms, resulting in an atomic explosion.

Atomic bombs use nuclear fission, although it is important to note that a fission chain reaction requires a particular amount of a fissile material like uranium-235, known as supercritical mass.

Fusion of atoms: nuclear fusion

Hydrogen bombs use a combination of fission and fusion, with nuclear fusion amplifying a fission reaction to produce a much more powerful explosion than atomic bombs.

Fusion is essentially the opposite of fission – instead of splitting a heavier atom into smaller atoms, it works by joining two atoms together to form an unstable third atom. It is also the same process that powers the Sun.

Nuclear fusion relies primarily on isotopes of lighter elements, such as the two isotopes of hydrogen, deuterium and tritium. When subjected to intense heat and pressure, these two atoms fuse to form an extremely unstable helium isotope, which releases energy and neutrons.

The released neutrons then fuel the fission reactions of heavier atoms like uranium 235, creating an explosive chain reaction.

How atomic and hydrogen bombs compare

How powerful are hydrogen bombs and how do they compare to atomic bombs?

Bomb Type Energy produced (kilotons of TNT)
Little Boy 🇺🇸 Atomic 15kt
Fat man 🇺🇸 Atomic 21kt
Bravo Castle 🇺🇸 Hydrogen 15,000kt
Tsar Bomba 🇷🇺 Hydrogen 51,000kt

Bombs Boy and Fat man were used in the atomic bombings of Hiroshima and Nagasaki in 1945, bringing a destructive end to World War II. The scale of these bombardments was, at the time, unprecedented. But comparing them to hydrogen bombs shows just how powerful nuclear weapons have become.

Bravo Castle was the code name for the largest nuclear weapon test ever conducted by the United States, a hydrogen bomb that produced a yield of 15,000 kilotons– do it 1,000 times more powerful than Boy. Additionally, radioactive traces of the explosion, which took place in the Marshall Islands near Fiji, have been found in Australia, India, Japan, the United States and Europe.

Seven years later, the Soviet Union tested Tsar Bomba in 1961, the most powerful nuclear weapon in the world. The explosion produces 51,000 kilotons of explosive energy, with a destructive radius of about 60 km.

Given how damaging a single nuclear bomb can be, it is difficult to imagine the outcome of a real nuclear conflict without fear of total annihilation, especially with the world’s nuclear arsenal at over 13,000 warheads.

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