URANUS (named after the planet Uranus discovered shortly before; lat. uranium * a. uranium; n. Uran; f. uranium; i. uranio), U, is a radioactive chemical element of group III of the periodic table Mendeleev, atomic number 92, atomic mass 238.0289, belongs to the actinides. Natural uranium consists of a mixture of three isotopes: 238 U (99.282%, T 1/2 4,468.10 9 years), 235 U (0.712%, T 1/2 0.704.10 9 years), 234 U (0.006%, T 1/2 0.244.10 6 years). There are also 11 known artificial radioactive isotopes of uranium with mass numbers from 227 to 240. 238 U and 235 U are the founders of two natural decay series, as a result of which they turn into stable isotopes 206 Pb and 207 Pb, respectively.
Uranium was discovered in 1789 in the form of UO 2 by the German chemist M. G. Klaproth. Uranium metal was obtained in 1841 by the French chemist E. Peligot. For a long time, uranium had very limited use, and only with the discovery of radioactivity in 1896 did its study and use begin.
Properties of uranium
In its free state, uranium is a light gray metal; below 667.7°C it is characterized by an orthorhombic (a=0.28538 nm, b=0.58662 nm, c=0.49557 nm) crystal lattice (a-modification), in the temperature range 667.7-774°C - tetragonal (a=1.0759 nm, c=0.5656 nm; R-modification), with more high temperature- body-centered cubic lattice (a = 0.3538 nm, g-modification). Density 18700 kg/m 3, melting point 1135°C, boiling point about 3818°C, molar heat capacity 27.66 J/(mol.K), electrical resistivity 29.0.10 -4 (Ohm.m), thermal conductivity 22.5 W/(m.K), temperature coefficient of linear expansion 10.7.10 -6 K -1. The temperature of transition of uranium to the superconducting state is 0.68 K; weak paramagnetic, specific magnetic susceptibility 1.72.10 -6. The nuclei 235 U and 233 U fission spontaneously, as well as upon the capture of slow and fast neutrons, 238 U fission only upon the capture of fast (more than 1 MeV) neutrons. When slow neutrons are captured, 238 U turns into 239 Pu. The critical mass of uranium (93.5% 235U) in aqueous solutions is less than 1 kg, for an open ball it is about 50 kg; for 233 U critical mass is approximately 1/3 of the critical mass of 235 U.
Education and keeping in nature
The main consumer of uranium is nuclear energy ( nuclear reactors, nuclear power plants). In addition, uranium is used to produce nuclear weapons. All other areas of uranium use are of strictly subordinate importance.
The article talks about when the chemical element uranium was discovered and in what industries this substance is used in our time.
Uranium is a chemical element of the energy and military industries
At all times, people have tried to find highly efficient energy sources, and ideally, to create the so-called. Unfortunately, the impossibility of its existence was theoretically proven and justified back in the 19th century, but scientists still never lost hope of realizing the dream of some kind of device that would be capable of delivering large amounts of “clean” energy for a very long time.
This was partially realized with the discovery of such a substance as uranium. The chemical element with this name formed the basis for the development of nuclear reactors, which in our time provide energy to entire cities, submarines, polar ships, etc. True, their energy cannot be called “clean”, but in recent years many companies have been developing compact “atomic batteries” based on tritium for widespread sale - they have no moving parts and are safe for health.
However, in this article we will examine in detail the history of the discovery chemical element called uranium and the fission reaction of its nuclei.
Definition
Uranium is a chemical element that has atomic number 92 on the periodic table. Its atomic mass is 238.029. It is designated by the symbol U. Under normal conditions, it is a dense, heavy metal with a silvery color. If we talk about its radioactivity, then uranium itself is an element with weak radioactivity. It also does not contain completely stable isotopes. And the most stable of the existing isotopes is considered to be uranium-338.
We have figured out what this element is, and now we will look at the history of its discovery.
Story
A substance such as natural uranium oxide is known to people with ancient times, and ancient masters used it to make glaze, which was used to cover various ceramics to waterproof vessels and other products, as well as to decorate them.
An important date in the history of the discovery of this chemical element was 1789. It was then that the chemist and German by birth Martin Klaproth was able to obtain the first metallic uranium. And the new element received its name in honor of the planet discovered eight years earlier.
For almost 50 years, the uranium obtained then was considered pure metal However, in 1840, the French chemist Eugene-Melchior Peligot was able to prove that the material obtained by Klaproth, despite the suitable external signs, is not a metal at all, but uranium oxide. A little later, the same Peligo received real uranium - very heavy metal gray color. It was then that the atomic weight of such a substance as uranium was determined for the first time. The chemical element was placed in 1874 by Dmitri Mendeleev in his famous periodic table of elements, with Mendeleev doubling the atomic weight of the substance. And only 12 years later it was experimentally proven that he was not mistaken in his calculations.
Radioactivity
But the truly widespread interest in this element in scientific circles began in 1896, when Becquerel discovered the fact that uranium emits rays, which were named after the researcher - Becquerel's rays. Later, one of the most famous scientists in this field, Marie Curie, called this phenomenon radioactivity.
The next important date in the study of uranium is considered to be 1899: it was then that Rutherford discovered that the radiation of uranium is inhomogeneous and is divided into two types - alpha and beta rays. A year later, Paul Villar (Villard) discovered the third and last type of radioactive radiation known to us today - the so-called gamma rays.
Seven years later, in 1906, Rutherford, based on his theory of radioactivity, conducted the first experiments, the purpose of which was to determine the age of various minerals. These studies laid the foundation, among other things, for the formation of theory and practice
Uranium nuclear fission
But, probably, the most important discovery, thanks to which the widespread mining and enrichment of uranium for both peaceful and military purposes began, is the process of fission of uranium nuclei. This happened in 1938, the discovery was carried out by German physicists Otto Hahn and Fritz Strassmann. Later, this theory received scientific confirmation in the works of several more German physicists.
The essence of the mechanism they discovered was as follows: if you irradiate the nucleus of the uranium-235 isotope with a neutron, then, capturing a free neutron, it begins to fission. And, as we all now know, this process is accompanied by the release of a colossal amount of energy. This happens mainly due to the kinetic energy of the radiation itself and fragments of the nucleus. So now we know how uranium nuclei fission occurs.
The discovery of this mechanism and its results is the starting point for the use of uranium for both peaceful and military purposes.
If we talk about its use for military purposes, then for the first time the theory that it is possible to create conditions for such a process as the continuous fission reaction of a uranium nucleus (since enormous energy is needed to detonate a nuclear bomb) was proven by Soviet physicists Zeldovich and Khariton. But in order to create such a reaction, uranium must be enriched, since in its normal state it does not possess the necessary properties.
We have become familiar with the history of this element, now let’s figure out where it is used.
Applications and types of uranium isotopes
After the discovery of a process such as the chain fission reaction of uranium, physicists were faced with the question of where can it be used?
Currently, there are two main areas where uranium isotopes are used. These are the peaceful (or energy) industry and the military. Both the first and second use the reaction of the uranium-235 isotope, only the output power differs. Simply put, in nuclear reactor there is no need to create and maintain this process with the same power as needed to explode a nuclear bomb.
So, the main industries that use the uranium fission reaction have been listed.
But obtaining the uranium-235 isotope is extremely difficult and expensive. technological problem, and not every state can afford to build enrichment factories. For example, to obtain twenty tons of uranium fuel, in which the content of the uranium 235 isotope will be from 3-5%, it will be necessary to enrich more than 153 tons of natural, “raw” uranium.
The uranium-238 isotope is mainly used in the design of nuclear weapons to increase their power. Also, when it captures a neutron with the subsequent process of beta decay, this isotope can eventually turn into plutonium-239, a common fuel for most modern nuclear reactors.
Despite all the disadvantages of such reactors (high cost, difficulty of maintenance, risk of accident), their operation pays off very quickly, and they produce incomparably more energy than classical thermal or hydroelectric power plants.
The reaction also made it possible to create nuclear weapon mass destruction. It is distinguished by its enormous strength, relative compactness and the fact that it is capable of making large areas of land unsuitable for human habitation. True, modern atomic weapons use plutonium, not uranium.
Depleted uranium
There is also a type of uranium called depleted. It has a very low level of radioactivity, which means it is not dangerous to people. It is again used in the military sphere, for example, it is added to the armor of the American Abrams tank to give it additional strength. In addition, in almost all high-tech armies you can find various ones. In addition to their high mass, they have another very interesting property - after the destruction of a projectile, its fragments and metal dust spontaneously ignite. And by the way, such a projectile was first used during World War II. As we see, uranium is an element that has found application in a wide variety of areas of human activity.
Conclusion
According to scientists' forecasts, around 2030 all large uranium deposits will be completely depleted, after which the development of its hard-to-reach layers will begin and the price will rise. By the way, it itself is absolutely harmless to people - some miners have been working on its extraction for entire generations. Now we understand the history of the discovery of this chemical element and how the fission reaction of its nuclei is used.
By the way, it is known interesting fact- uranium compounds were used for a long time as paints for porcelain and glass (so-called until the 1950s.
The history of the use of knots goes back many millennia. According to scientists, even cave people used simple knots in their everyday life. The ancestors of complex types of knots are sailors. With the advent of sailing ships, the need arose for convenient and reliable knots to secure the mast, sails and other gear. Not only the speed of the ship, but also the life of the entire crew depended on the quality of the unit. Therefore, sea knots are very different from ordinary ones. They are not only reliable, they are easy to tie and just as easy to untie, which is not possible with regular knots.
The classification of knots came to us from England. Usually the British divide sea knots into 3 types:
- Knot – needed to increase the diameter of a rope or weave something.
- Hitch - attach a rope to various objects (masts, yards, anchors).
- Bend – connect ropes of different diameters into one.
There are about five hundred descriptions of sea knots, but only a few dozen are currently in use, as motor ships are replacing sailing ships. The ability to tie sea knots will be useful not only for yachtsmen, but also for tourists and fishermen. By gradually mastering the diagrams with pictures below, you will quickly learn how to do this.
Straight knot
Although this unit is one of the most ancient, it is not particularly reliable. Its disadvantages are frequent displacements on the rope, it is not easy to untie after heavy loads and getting wet, and with such a knot the strength of the rope decreases. Used for easy gripping on light pulls and splicing two ends of the cable. More complex knots are knitted on its basis. Despite the fact that the knot is very simple, it has its own nuances. The free ends should be on one side of the rope. If they are located on different sides, then such a knot is considered incorrect and is called not a simple one, but a thief’s one.
How to tie a straight knot:
- A regular knot is tied.
- We make a loop from one fixed end of the end rope.
- We wrap the free end around the outside of the loop and bring it inside.
- We tighten it. The result is the correct node. For greater security, another regular knot is tied on top.
Gazebo knot (Bowline)
In yachting, this unit is used more often than others. Initially, it was used to tie a gazebo - a device with which sailors climbed onto the mast of a ship. That's why it got its name. This knot has no disadvantages; it is easy to tie and untie. You can use it to tie ropes of different diameters and materials and not be afraid that it will come undone. It is most often used when mooring a ship or in cases where you need to make a loop or tie something.
How to tie a gazebo knot:
- We make a regular loop.
- We insert the free end inside the loop and braid it diagonally around the fixed end.
- We pass it back inside the loop.
- We tighten the ends of the rope. To make the knot strong, it is very important to tighten the ends tightly.
Figure eight knot
By appearance looks like the number 8, so the name speaks for itself. The knot is simple, but very important. More complex knots are knitted on its basis. The advantage of the figure eight knot is that it will never move or unravel under stress. Also, when the cable gets wet, it can be easily tied and untied. Used as a stopper at the end of the cable and as a securing knot. You can use it to make handles for a wooden bucket or secure strings on musical instruments.
How to knit a figure eight:
- We make a regular loop.
- We rotate our loop 360 degrees and thread the free end inside the loop.
- We tighten it.
How to knit a figure eight stitch:
- Fold the free end in half to make a loop.
- Make a second loop near the double end.
- Rotate the second loop 360 degrees.
- We pass the first loop inside the second.
- We tighten it.
Noose knot
This knot is a self-tightening loop. Its advantages are simplicity and speed of knitting, reliability and easy untying. Suitable for tying to objects with a flat surface.
How to knit a noose:
- Make a loop at the end of the rope.
- Make a second loop to make a bow.
- We wrap the free end of the rope 3-4 times around.
- We insert the end from the back into the second loop.
- We tighten it.
Bloody Knot
In ancient times, such knots were tied on a cat - a whip with nine or more ends. The cat was used as an instrument of torture and to maintain discipline on the ship - the blow was very painful, lacerations did not heal for a long time. This is why the knot got its bloody name.
How to tie a bloody knot:
- The free end of the rope is wrapped twice around the stationary one.
- We tighten it.
Flat knot
Used when you need to tie the ends of a rope of different diameters or from different materials. Withstands heavy loads and wetness well. But this is not the simplest knot; it is easy to tie it incorrectly. The most important nuance when knitting a flat knot is that the ends of the ropes must be parallel to each other.
How to knit a flat knot:
- Make a loop from the thick end of the rope.
- The thin end is inserted inside the thick one.
- Make two turns over the thick end.
- We tighten it.
Clove hitch
Initially, this knot was used to fasten ropes - thin ropes from which ladders for cables were made. It is one of the most reliable tightening fasteners. Its peculiarity is that greater reliability is possible only under load. Also, its reliability is affected by the surface on which it is tied. A big plus of a knotted knot is the ability to tie it with one hand. Used to fasten ropes to objects with a smooth and even surface - logs, masts. On objects with edges, the bleaching knot will not be as effective.
How to knit a bleached knot:
- The free end of the rope is wrapped around the object.
- An overlap is made.
- We thread the end into the resulting loop.
- We tighten it.
Second method (knitting with half bayonets):
- Let's make a loop. The long end of the rope is on top.
- We throw a loop over the object.
- We make a loop at the lower end of the rope and throw it on top of the object.
- We tighten it.
Anchor knot or fishing bayonet
It has been used for thousands of years to attach a rope to an anchor. This knot is also used to tie the ends of the cable to any mounting hole. It is a reliable and easy to untie knot.
How to tie an anchor knot:
- We pass the end of the rope two times through the loop of the anchor or other fastening hole.
- We throw the free end of the rope over the fixed end and pass it through the resulting loop.
- We tighten both loops.
- We make a regular knot on top for reliability.
Stopper knot
Used in cases where it is necessary to increase the diameter of the cable.
How to tie a stopper knot:
- We fold the stop rope in half.
- We attach it to the main one.
- We wrap the free end of the locking rope around the main and second ends of the locking rope 5-7 times.
- The fixed end that we wrapped is returned to the loop of the stop rope.
- Tighten both ends.
Clew knot
Such a knot used to be used to tie sheets - gear for controlling the sail. Currently, it is used for tying ropes of different diameters. Not suitable for knitting synthetic ropes as they are slippery.
How to tie a clew knot:
- We make a loop from a thick rope.
- We bring a thin rope inward, go around the loop and wind it under itself.
- We tighten it.
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