Ligado na Energia: Ciclo do combustível nuclear - INB

Do you know how uranium coming from the earth turns into fuel for energy? Let's get to know the Nuclear Fuel Cycle It all starts with mining. The ore is withdrawn from the ground and crushed.

An acid solution separating the uranium from the ore is thrown over the piles of ground rocks. It is the leaching that results in the liquid called uranium liquor. After filtration and decantation this liquid becomes a concentrate, the yellowcake, which is the natural uranium in paste form.

It is then packed and goes to another stage, the conversion that turns that concentrate into uranium hexafluoride gas. In order to generate electrical energy the uranium has to be enriched, that is, concentrated. A process that increases its strength.

This is done in several ultra-centrifuge cascades installed at INB’s uranium enrichment plant in Resende, in the State of Rio de Janeiro. Within this equipment the uranium hexafluoride gas rotates at an extremely high speed, separating the lighter atoms from the heavier atoms. This causes the uranium concentration to rise from 0.

7% - natural uranium - to up to 3. 75%. It is this enrichment that allows the uranium atom to release heat and produce energy.

A special mixture is added to this enriched uranium, still in the form of gas, to once again turn it into paste, which is filtered and baked into powder. This powder is taken to a press, and comes out in the shape of pellets, small cylinders with 1cm in height and diameter. At this stage, the pellets are brittle and need to be hardened at very high temperatures.

Once they are rectified and tested, they are ready to the next step: assembling the fuel element. To have an idea, only two pellets can produce enough energy for a house with four residents, for a month. In order for the small pellets to produce electricity, they are stacked inside rods made of a super resistant steel alloy called Zircaloy.

Each of these rods contain 335 pellets of slightly enriched uranium. A set of 236 form a metal structure that is firmly held by grids and clamps. The fuel element, which is up to 5 m high, is now complete.

This fuel will supply the reactors of the nuclear power plants. It is here, in the heart of the nuclear plants, that the uranium will produce energy. The fuel element is placed in the reactor, so the uranium atoms in the pellets start the fission process.

Protons and neutrons in the nucleus of the atom are bound by an enormous amount of energy, nuclear energy. When a neutron hits the atom the bond breaks and the nucleus splits in two, releasing heat. Each atom also releases 2 or 3 neutrons, which will divide other atoms, creating a chain reaction.

A stream of water running through the reactor absorbs the heat released during nuclear fission. This heat turns to steam, which will rotate the turbines of the plant, finally producing electric power.