How is nuclear reactor started

Of the eligible nuclei for being fissioned in reactors U, Th and Pu , fertile isotopes are those with an even number of nucleons, whereas fissionable ones are those with an odd number. The most important fertile isotopes are: U, Pu and Th, and the most important fissionable isotopes are U, U, Pu and Pu The total energy released in neutron-induced nuclear fission comes from the kinetic energy of fission products.

The fission capacity of nuclei is measured through the value of the efficient section that they present for fission the greater the efficient section, the greater the possibility of fiction , which depends on the energy of neutrons that interact with these nuclei. As the energy lowers, the efficient section increases and so does the fission capacity. For this reason, fission is most likely to happen with thermal slow neutrons than with fast ones. Thus, fissionable nuclei, in spite of suffering these reactions with any neutron, will fission in a greater quantity when neutrons are thermal, whereas fertile neutrons, having high fission thresholds, will only fission with the fast ones.

Uranium is used as fuel in a nuclear reactor, being in its natural form in isotopes U and U The first one is a fissionable element, and the second one is fertile. This element goes into fission in a similar way to that of U, increasing the proportion of fissions. Thorium, an element that naturally abounds in Nature, is presented as Thorium, which — through capture reactions — produces uranium, used as a fissionable element in reactors. A number of different materials can be used to fuel a reactor, but most commonly uranium is used.

Uranium is abundant, and can be found in many places around the world, including in the oceans. Other fuels, such as plutonium and thorium, can also be used. A single pellet contains as much energy as there is in one tonne of coal. A typical reactor requires about 27 tonnes of fresh fuel each year. In contrast, a coal power station of a similar size would require more than two-and-a-half million tonnes of coal to produce as much electricity. Like any industry, the nuclear industry generates waste.

However, unlike many industries, nuclear power generates very little of it — and fully contains and manages what it does produce. The vast majority of the waste from nuclear power plants is not very radioactive and for many decades has been responsibly managed and disposed of.

The used fuel which comes out of the reactor can be managed in different ways, including recycling for energy production or direct disposal. The main job of a reactor is to house and control nuclear fission —a process where atoms split and release energy.

Reactors use uranium for nuclear fuel. The uranium is processed into small ceramic pellets and stacked together into sealed metal tubes called fuel rods. Typically more than of these rods are bundled together to form a fuel assembly. A reactor core is typically made up of a couple hundred assemblies, depending on power level. Inside the reactor vessel, the fuel rods are immersed in water which acts as both a coolant and moderator.

The moderator helps slow down the neutrons produced by fission to sustain the chain reaction. Control rods can then be inserted into the reactor core to reduce the reaction rate or withdrawn to increase it.

The heat created by fission turns the water into steam, which spins a turbine to produce carbon-free electricity. All commercial nuclear reactors in the United States are light-water reactors.