This is the last post in our series of posts on nuclear energy. Here, I shall describe the basic principles behind the design and continued operation of a nuclear reactor. In our last post, we looked at the techniques responsible for making fissile matter release energy as quickly as possible (in a nuclear explosion). Today, we will instead look at techniques to control nuclear fission reactions and usefully harness the resultant energy. Since there are a variety of various nuclear reactor designs and fuels, I shall stick to talking about a reasonably common (although a bit aged) design known as the pressurized-water reactor using U-235 fuel.
You’ve heard it all before, we need to find a new, sustainable, clean source of energy, and fast. People are looking to wind, solar, nuclear, and biofuels. But what do these things mean, really?
Today, I will discuss solar.
The sun is the main source of energy for this entire planet. We get much of our energy from coal and oil which is made of millions-of-years-old plant and animal matter. Animals get their energy from plants, which get their energy from the sun. The wind blowing your hair in your face and turning the wind turbines? That’s from the difference in temperature in different locations (due to the sun) and the rotation of the earth. Hydroelectric power like that made at the Hoover Dam? That’s from rainwater filling up a high altitude river source. What causes rain? The evaporation of water by heat from the sun, of course. As you can see, there are few sources of energy (nuclear and geothermal being the primary exceptions) which are not directly related to energy recently emitted from the sun. The problem with all of these forms of energy is that there is a “middle man” between the sun’s energy and usable electricity. Solar cells, which have been around since the mid-1950’s, attempt to dispose of the middle man allowing us to directly harness the power of the sun.
What would it take to make the earth stop spinning? This scenario is not unheard of in B-movies and bad sci-fi shows. It isn’t uncommon to have plots involving the Earth’s core slowing down or aliens from a different galaxy stopping the Earth’s rotation. A lot of these plots have the Earth stop spinning either instantaneously or within a very short period of time. Intuitively, we know that spinning bodies have energy. The Earth is a pretty massive spinning body. How much energy would the Earth have to shed to stop rotating? How would that energy affect us worldly inhabitants?
Here, I will discuss the physics behind rotation and rotational energy. We shall use simple facts about the Earth’s rotation to calculate what would happen to it were it to stop spinning.