The Manhattan Project's Biggest Secret: Why Atom Bombs Are Almost Impossible to Make

At 5.30 a.m., dawn on July 16, 1945, near a small town called Alamogordo, New Mexico, the course of human history was changed.

The first atomic bomb was detonated that day and sealed the fate of humanity.

It took the work of many people to accomplish this engineering feat, But the principal leader of that Manhattan Project, and the man considered the father of the atomic bomb, was Robert Oppenheimer.

After witnessing its awesome power on that fateful day, Oppenheimer was so taken aback, he quoted a verse from the sacred Hindu text, the Bhagavad Gita, Now I am become death, the destroyer of worlds.

We know its awesome power, but how exactly does an atom bomb work? An atom bomb works on the principle that when you break up a nucleus of an atom, a large amount of energy is released.

Why? Because it takes a large amount of energy to keep the nucleus bound together.

When you split it apart, the energy is released.

The analogy is like a stack of bowling pins.

When you hit it with a bowling ball, all the energy that you used in stacking them is released.

You can think of the nucleus of an atom being similarly stacked together.

Physics purists may ding me for this analogy, but for the purposes of simplification, this is a good way to think of it.

Scientists chose the biggest, heaviest nucleus that is found in nature to be the best candidate for splitting.

uranium.

Uranium is unique in that one of its isotopes is the only naturally occurring element on Earth that is capable of sustaining a nuclear fission reaction.

A uranium atom has 92 protons and 146 neutrons.

Together they give an atomic mass of 238, U-238.

A very small portion of uranium, when it is mined, is in the form of an isotope U-235.

This isotope has the same 92 protons but only 142 neutrons or 3 fewer than U-238.

U-235 is highly unstable which makes it highly fissionable or splittable.

When uranium U-235 is slammed by a neutron, it becomes uranium-236.

U-236 is so unstable that it almost immediately splits into two more stable atoms, Krypton and Barium.

In the process of splitting and creating two more stable atoms, a whole bunch of energy is released along with three more neutrons.

These three neutrons fly out and slam more U-235 atoms, and thus a chain reaction occurs causing more and more U-235 to be split and ultimately causes a huge explosion.

So what's the big deal? Why don't more countries have the bomb? Well, the problem is that natural uranium contains only 0.7% of this U-235 isotope, and a whole bunch of it is needed to make even one atomic bomb.

So mined natural uranium has to be enriched to get U-235.