Criticality

In Nuclear ReactorNuclear ReactorIn it's most simplest form, a nuclear reactor uses Uranium and other radioactive materials and the fission from uranium to create heat, and transfer that heat into steam to create power. Nuclear reactors are one of the biggest sources of energy, although not renewable, uranium has a very high energy density resulting in massive power transmissions. There are many different types of nuclear reactors, and this term serves as a broad hub/introduction for each type. After uranium is used in reactos, criticality is an important step in producing electricity. Criticality is the point at which the chain reaction of the fissile material is self sustaining.

Inside of a reactor, UraniumUraniumUranium is a naturally occuring element - atomic number of 92 and in the actinides group. Uranium is radioactive - decaying over time and releasing energy. This is the reason why Uranium is the primary source of fuel for Nuclear Reactors. The amount of energy in a single gram of uranium is about 3.5-4.5 tons of coal; around 702 gigajoules - whilst each gram of coal has around .0293 gigajoles of energy; a staggering amount inside of uranium. Isotopes There are three natural isotopes of uranium Nuclear FuelNuclear FuelNuclear fuel is fuel used inside of the nuclear industry broadly. Specifically for Nuclear Reactors, nuclear fuel is necessary for a fissile reaction. As is the name, nuclear fuel is radioactive - it decays over time and releases excess neutrons. This makes it highly energy dense and optimal for the nuclear sector. Whenever you hear someone talking about nuclear fuel, the first thing you can think about is Uranium. Being radioactive in it of itself, after enrichment, enriched uranium is a commo is used as a source of radioactive material. This material releases neutrons, and especially when it is enriched to a higher concentration it can release more. In the presence of a moderating element, such as Light WaterLight WaterLight water, although appearing to have a fancy name, is literally just ordinary water....except it does contain a small amount of Heavy Water. The point of light water is that it can be used as a moderator --however it can only be used in certain situations, as it absorbs too many neutrons to be used with unenriched uranium (which is why light water is presumably used in Spent Fuel Pools) Light water is mainly used in BWR reactors & PWR reactors Uranium Enrichment is necessary for the usage of, these neutrons can interact with fissile material and cause nuclear reactions - these impact the uranium fuel and convert it into byproducts that may be shortlived. Control RodsControl RodsControl Rods are rods that are used to control the rate of reaction inside and within a Nuclear Reactor. They have a specific design that allows for this control. BWR reactor parameters In the GE Marathon control rod, it contains stainless steel tubes filled with boron carbide poison. This isotope contains a high cross-section for the absorption of neutrons, acting as a control rod neutron poison. These control rods are uniformly placed into a reactor core according to its design parameters. are used to moderate this reaction, alongside other systems. When enough control rods are pulled from the reactor that the reactor is able to produce neutrons at a consistent or increasing rate, and produce energy from this, it is said to be at the critical state.

SubcriticalitySubcriticalitySubcriticality in a Nuclear Reactor is the point at which the Nuclear Fuel is unable to sustain a proper fission reaction. In a general reaction, to achive Criticality you must pull Control Rods so neutrons emitted from fuel can impact other Uranium atoms and release more neutrons and heat energy. However, if the nuclear fuel has lost enough of it's fissile material, it may reach a point at which it is not able to become critical, yet still producing sufficient fission reactions - it is the poin can also occur, where the fission is not enough to sustain a fission reaction.