Nuclear power plant - Function

Fission plants are the current standard and consist of all nuclear plants operating. They work by having a nuclear fuel arranged in rods placed inside a reactor core. Nuclear fission works by hitting a fissionable material such as Uranium 235 with a high energy neutron (an atomic particle), this is them absorbed by a Uranium atom which makes the atom unstable. Atoms can only exist for extended periods in stable form so the Uranium atom splits apart releasing two smaller atoms which in turn release a Kripton and Barium atom and three new high energy neutrons, these neutrons then hit and are absorbed by other Uranium atoms producing a nuclear chain reaction. This fission process releases the atomic energy stored within the U235 atom which generates alot of heat. Having billions of atoms undergoing this in a nuclear reactor produces huge amounts of heat energy. This is used to generate steam which then turns a turbine producing electricity.

To control this reaction, reactors have devices called moderators and control rods and neutron inhibitors. Moderators are materials such as graphite in early reactors or water in more modern reactors that slow down the neutrons which increases the chance of a nuclear chain reaction. Control rods are neutron inhibitors, they absorb the neutrons and can slow down or stop a fission reaction, balancing this allows nuclear fission to be controlled to produce power.

Where do they get these elements from?

You get the fuel through mining. You can mine for Uranium and for Thorium. Schematically, Natural Uranium is 99.3% U238, 0.7% U235.

In HWR (Heavy Water Reactors, like CANDU) and specific moderator/coolant (the ones that are great at slowing down neutrons), you can use natural uranium, even though you often enrich it a little to get a better use of the fuel.

In LWR, you need to enrich your uranium (from 0.7% U-235 to 4% U-235 usually).


How many people work at a typical powerplant? 

Roughly 1000-1500 people work at a nuclear powerplant. It increases during reactor stoppage time, since that's when you do repairs, checks, refueling, etc.