How exactly do you “bombard” an atom in a nuclear reaction?

Question

Say you want to make a fission reaction, how exactly do you launch a neutron toward this atom to split it? Which device do you use?

I am not sure if you launch another atom or just a neutron.

In: Physics

Answer 1

In a nuclear reactor there are lots and lots of neutrons pinging about. They’re being fired off by the radioactive decay of the fuel in all directions. To start a nuclear reactor, neutron sources are used. These are radioactive elements that undergo spontaneous fission to create neutrons, which are used to start the reactor.

Using control rods to moderate the speed of the neutrons helps them hit other uranium atoms. This splits the atom, gives off energy (which we use to make electricity) and sends off more neutrons in a random direction. Some of those neutrons go on to split more uranium atoms and the reaction continues.

There are also ‘neutron guns’ or modulated neutron initiators. This is the trigger for a fission bomb. Usually some combination of radioactive elements that create neutrons when they react. In a nuclear bomb, there is a small explosion that smashes the trigger elements together. This creates a massive burst of neutrons, which then smash into the supercritical core of the weapon, accelerating the nuclear reaction.

The trick is to get the timing right so the neutrons hit the core at the right time. Too early and the you get a low yield. Too late and the core is already falling apart and you don’t get a big explosion.