If left unchecked, however, a partial nuclear meltdown can worsen into a total nuclear meltdown. In fact, the Three Mile Island nuclear power plant's Unit 2 reactor continues to produce power in the shadow of its deactivated counterpart. The 1979 Three Mile Island incident falls under this categorization: The Unit 1 reactor's core melted, but the protective casing around the core remained intact. If plant personnel can restore coolant circulation at this point, the accident qualifies as a partial nuclear meltdown. The first things to melt are the fuel rods themselves. On the next page, we'll go inside a nuclear meltdown. The uranium and even radiated tools and parts will continue to generate decay heat even if plant operators shut down all induced fission reactions. The radioactive materials inside a nuclear reactor, however, are a different story. A car only generates heat while it's running and possibly for a short time after. The difference, however, is that you can turn off a vehicle and allow its engine to cool off. It's like driving an automobile: You don't want to overheat the engine, because that could damage it. So, the coolant (often water) inside the reactor's core also serves to moderate the temperature of the nuclear fuel rods. Of course, you don't want temperatures inside the nuclear reactor to rise too high, lest they damage the reactor and release harmful radiation. This means more heat to boil water into steam. In a nuclear power plant, operators artificially spur on, or induce, that fission reaction by bombarding the uranium-filled fuel rods with neutrons from prior fission reactions. See, uranium and other radioactive elements already undergo spontaneous fission at very slow rates without any human help. Fission refers to when a material's atoms steadily split in two, releasing a lot of energy and a heat we call decay heat. Now head to the next page to learn what happens inside a healthy reactor.Ī nuclear power plant operates similarly, only the heat comes from an induced fission reaction that occurs in the reactor.
Out-of-control heat, on the other hand, can cause the reactor itself to melt and contaminate the surrounding environment with dangerous radiation. Properly controlled heat inside a reactor helps generate power. In this article, we'll break down how a nuclear reactor works and how a meltdown can occur.ĭon't worry too much over complex equations, because the whole situation ultimately comes down to heat. Nuclear Regulatory Commission officially recognizes the term "nuclear meltdown," but the words continue to inspire fear. Interestingly enough, neither the IAEA nor the U.S. The International Atomic Energy Agency (IAEA) ranks nuclear events on a scale of zero to seven, ranging from a mere deviation with no safety significance (level 0) to a major accident (level 7) such as Chernobyl in which widespread health and environmental damage occurs. Which creates deserted cities and landmarks of destruction like the elephant's foot.
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