00:00A small piece of uranium, about the size of a grape, can generate enough energy to power an entire neighbourhood for a year.
00:07But how is it possible that something so small holds so much power?
00:11To find out, let's visit the factories responsible for producing and processing the most dangerous metal on Earth, and explore the process.
00:20The story of enriched uranium is closely tied to the birth of nuclear energy.
00:25In 1896, French physicist Henri Beckefell discovered radioactivity when he noticed that uranium emitted rays spontaneously.
00:34This discovery inspired Marie and Pierre Curie to identify elements like radium and polonium.
00:40In 1932, James Chadwick discovered the neutron, a key particle in nuclear fission.
00:46And in 1938, Otto Hahn and Fritz Strassmann, with contributions from Lise Meitner and Otto Frisch, demonstrated that a uranium atom could split when struck by neutrons, releasing a massive amount of energy.
01:00Enriched uranium, essential for controlled fission, emerged as a technical challenge.
01:06Natural uranium contains 99.3% uranium-238, which does not easily undergo fission, and only 0.7% uranium-235, which is ideal for fission.
01:20Increasing the proportion of uranium-235, a process called enrichment, became essential for reactors and nuclear weapons.
01:28During the Manhattan Project in World War II, scientists developed pioneering methods.
01:33Gaseous diffusion used porous membranes to separate uranium hexafluoride, while electromagnetic separation diverted isotopes with magnetic fields.
01:43Both were slow and consumed enormous amounts of energy.
01:47In the 1950s, gas centrifuges revolutionized enrichment.
01:52These machines, spinning at extremely high speeds, separate isotopes by weight and are much more efficient and compact.
02:00Their development was so critical that their designs were considered state secrets.
02:05In 1951, the Experimental Breeder Reactor 1 in Idaho used enriched uranium to generate electricity, lighting four light bulbs.
02:14In 1954, the Obninsk Power Plant in the Soviet Union became the first to connect nuclear electricity to the grid, using uranium enriched to 5%.
02:24Today, enriched uranium powers reactors that produce 10% of the world's electricity.
02:30But how does uranium produce so much energy?
02:33The process begins in uranium mines, located in remote regions such as the deserts of Australia, the steppes of Kazakhstan or the rocks of Canada,
02:42which together produce 70% of the world's uranium.
02:46Uranium is found in minerals like uraninite or pitchblend, often in low concentrations, ranging from 0.1 to 2%.
02:55The mines can be open-pit, where massive excavators remove layers of earth to reach the ore, or underground, with tunnels that descend hundreds of meters.
03:04In some cases, a method called in situ leaching is used.
03:08Chemical solutions, such as sulphuric acid or carbonates, are injected into underground deposits to dissolve the uranium,
03:15which is then pumped to the surface through wells.
03:18The extracted ore is transported to nearby processing plants, where it is crushed into fine particles, about the size of coarse sand, to make it easier to extract the uranium.
03:29It is then mixed with acids or alkalis in large steel tanks, a process that separates the uranium from other minerals like iron or quartz.
03:39The result is a bright yellow powder known as yellow cake, or uranium oxide, which contains about 80% pure uranium.
03:47This material has a faint metallic smell and low radioactivity, but it still requires protective suits, masks and ventilation systems to prevent inhaling particles.
03:58One tonne of this material can generate as much energy as several million tonnes of coal.
04:04The yellow cake is sent to conversion plants, where it is turned into uranium hexafluoride, a compound that becomes gas at moderate temperatures, making it ideal for enrichment.
04:15The process starts by purifying the yellow cake to remove impurities like sulphur, magnesium or traces of other metals.
04:23This is done through chemical solutions and filtration systems made from corrosion resistant stainless steel.
04:29The purified uranium is then mixed with hydrofluoric acid and heated in sealed reactors to form uranium hexafluoride, a volatile compound that turns into gas at about 56 degrees Celsius.
04:42Uranium hexafluoride is stored in cylindrical steel containers designed to handle its corrosive nature, since it reacts with water to form toxic compounds.
04:52Conversion plants operate under strict safety standards, with advanced ventilation systems and sensors that detect leaks.
05:00At room temperature, uranium hexafluoride can form green crystals, a phenomenon that technicians call nuclear snow because of its texture and colour, though handling it requires specialised equipment.
05:12Enrichment is the most critical step, where the proportion of uranium-235 is increased up to a maximum of 5% for commercial reactors.
05:21Gas centrifuges, high-tech cylindrical machines, are the main method used.
05:26These centrifuges, made from ultra-strong materials like miraging steel or carbon composites, spin at more than 50,000 revolutions per minute in vacuum chambers to minimise friction.
05:37The gaseous uranium hexafluoride is injected into the centrifuges, where the centrifugal force separates the lighter uranium-235 from the heavier uranium-238.
05:49The enriched uranium-235 is collected in separate streams, while the depleted uranium-238 is stored for uses such as radiation shielding or counterweights.
05:59The centrifuges operate in cascades, with hundreds or even thousands of machines connected in series, each one refining the uranium a little more.
06:09These facilities are quiet, but the high speed of the centrifuges creates a faint humming sound, and even a tiny imbalance, just a few milligrams, can damage them.
06:19That's why they are monitored with seismic sensors and control systems that adjust their speed in real time.
06:26A single centrifuge can process tons of uranium hexafluoride each year, and some modern facilities, like those in Europe, have cascades that fill entire buildings, running non-stop for decades.
06:39The uranium hexafluoride gas is then converted, through controlled chemical reactions, into a fine powder called uranium oxide.
06:48This powder is pressed into small cylindrical pellets about the size of a coin.
06:53Each pellet is one centimeter in diameter, and weighs around seven grams.
06:58These pellets are baked in special furnaces at about 1,400 degrees Celsius for several hours.
07:05The result is a dense, solid material that can withstand both the heat and radiation inside a nuclear reactor without breaking down.
07:13Each pellet goes through rigorous quality control. X-rays detect microscopic cracks that could affect fission.
07:19Laser scanners measure dimensions with micrometer precision, to ensure uniformity.
07:24Spectrometers analyze the chemical composition to confirm that there are no impurities, such as traces of boron or carbon, that could interfere with the nuclear reaction.
07:34A single pellet can release as much energy as one tonne of coal.
07:38The pellets are inserted into zirconium tubes, a silvery metal that resists heat and corrosion, and allows neutrons to pass without absorbing them.
07:48This property is essential for fission. Each rod, about 4 meters long, holds around 400 pellets, stacked precisely by robots equipped with visual recognition systems.
07:59This process takes place in sealed chambers with air filtration systems that eliminate microscopic particles to avoid contamination.
08:07Once filled, the rods are sealed using laser welding, which creates a perfect airtight closure.
08:14The rods are then grouped into fuel assemblies, structures that contain dozens of rods arranged in a metal grid, made from strong alloys such as stainless steel or zircoloy.
08:24Each assembly weighs about 500 kilograms and requires more than 100,000 individual welds.
08:32Every weld is checked with ultrasound to ensure its integrity.
08:36The grid is designed with precise geometric patterns to optimize the flow of neutrons and coolant inside the reactor.
08:43Before leaving the factory, the assemblies undergo extensive testing.
08:48High precision scales verify that they contain the exact amount of uranium,
08:52with tolerances of only a few grams.
08:55Vibration tests simulate extreme reactor conditions to ensure the rods stay in place during operation.
09:01Ultrasound scans detect internal defects like micro-cracks or misaligned pellets.
09:07Chemical analyses confirm the purity of the uranium, and pressure tests check the strength of the zirconium tubes.
09:14One fuel assembly can generate enough electricity to power 100 homes for a full year, keeping lights, appliances and electronics running.
09:24At this stage, the fuel emits very little radiation, so workers can handle it with basic gloves and masks.
09:31This is a surprising contrast to the energy it will release inside the reactor.
09:36At the nuclear power plant, the assemblies are placed in the reactor core, a high-tech chamber where nuclear fission begins.
09:43A typical reactor holds 480 assemblies, each with about 12 rods, for a total of 5760 rods enough to power a small city.
09:53During fission, uranium-235 atoms split when hit by neutrons, releasing heat and more neutrons that maintain a chain reaction.
10:02The energy from a single atom is millions of times greater than what is produced by burning one atom of carbon.
10:09To keep the reaction under control, control rods made of materials like boron or cadmium are used.
10:15These rods absorb neutrons and act like brakes.
10:18The core is surrounded by reinforced concrete walls up to 2 metres thick, built to resist earthquakes, floods or even the impact of an airplane.
10:27Automated systems constantly monitor temperature, pressure and neutron activity, shutting down the reactor immediately if anything goes wrong.
10:36This guarantees an exceptional level of safety.
10:39The heat generated by fission is used to boil water, creating high-pressure steam that is channelled into a turbine hall.
10:47This hall, often the size of a stadium, contains massive turbines that spin at 1800 revolutions per minute.
10:54The turbines are connected to a generator that transforms their movement into electricity.
11:00A single reactor can produce more than 750 megawatts, enough to power half a million homes, similar to lighting up a city like Valencia or Seville.
11:10Unlike coal plants that produce smoke and ash, nuclear reactors operate with almost no carbon emissions, generating about 10% of the world's electricity.
11:19This ability to produce clean and constant power makes nuclear energy a key tool in reducing environmental impact.
11:27After about a year in the reactor, the fuel rods become depleted, having released most of their energy.
11:33However, they remain extremely hot and radioactive, requiring careful handling.
11:38The rods are removed from the core using robotic arms and transferred to cooling pools inside the nuclear plant.
11:46These pools, filled with 8 metres of pure water, serve as both a coolant and a radiation barrier.
11:52The water is kept crystal clear through advanced filtration systems and is constantly monitored by sensors that detect any change in radiation or temperature.
12:01The rods stay in the pools for at least 10 years, during which time their heat and radioactivity drop significantly.
12:09Some nuclear plants store more than 700,000 spent rods, a volume that may seem large but could fit inside a medium-sized warehouse.
12:18A fascinating phenomenon occurs in these pools.
12:21The water can emit a soft blue glow due to what is known as Cherenkov radiation, caused by charged particles moving faster than light does in water.
12:31While it looks like something from a science fiction movie, the effect is completely harmless.
12:37After spending years in the pools, the rods can be transferred to dry storage containers.
12:43These are strong structures made of steel and concrete, designed to hold the fuel safely for decades or even centuries.
12:50The containers are stored in secure areas within the plants or in special facilities,
12:55and are built to withstand extreme conditions like earthquakes or impacts.
13:00Long-term nuclear waste management is an active field of research.
13:04Scientists are studying deep underground repositories, located more than 500 metres below ground,
13:10in stable rock formations such as granite or salt, to keep the waste isolated for thousands of years.
13:17Projects like Yucca Mountain in the United States or Onkalo in Finland are designed to stay safe for at least 10,000 years.
13:24Nuclear power remains one of the most promising options for a sustainable future.
13:29Despite many myths, it now follows strict safety standards and produces very little waste compared to other industries.
13:36And since it generates steady electricity with almost no carbon emissions, it plays a vital role in fighting climate change.
13:45With ongoing investment in new technologies and safe storage solutions,
13:49Atomic Energy can continue to light up our world in a clean, safe and reliable way.
13:55And that is how enriched uranium is produced.
13:58What did you think of the process?
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