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Sergey Venezky
STORIES ON METALS

URANIUM

FUEL TWENTIETH CENTURY

In honor of the seventh planet. - Mosaic of the ancient Romans. - Card matted. - Ingenious foresight. - Becquerel waiting for the sun. - Opening in an abandoned barn. - Encyclopedia error? - Sensational message. - The idea of "boys". - Where did the lanthanum? - Case in a barbershop. - Where to get neutrons? - Useful "magnificence". - "Match"! - Events in the metro. - A drop in the ocean. - In old Chicago. - "Come here for Breakfast!". - Nervous driver. - Fermi hides a smile. - Day, became black. - The first step. - Nuclear destroys the ice. - "The package" in the Sun. - Fantastic prospects.

It is difficult to say what the name would have given the German scholar Martin Heinrich works opened in 1789 chemical element, if a few years before this is not an event has occurred which have excited all circles of society: in 1781, the English astronomer William Herschel, observing, using a homemade telescope starry sky, discovered a luminous cloud, which he at first took for a comet, but later became convinced that sees a new, hitherto unknown seventh planet of the solar system. In honor of the Greek God of the sky Herschel named it Uranium. Was under the impression this event works gave the newborn to the element name for the new planet.

After about half a century, in 1841, the French chemist eugène Melchior, Pelego were able to obtain uranium metal. Industrial world remained indifferent to heavy, comparatively soft metal, and what appeared to be uranium. Its mechanical and chemical properties have not attracted any metallurgists or engineering. Only glassmakers in Bohemia Yes Saxon masters of porcelain and faience Affairs were willingly used the oxide of the metal, to give the glass a beautiful yellow-green color or decorate dishes intricate velvet-black pattern.

"Artistic abilities" of uranium compounds was known by the ancient Romans. During the excavations conducted near Naples, managed to find glass mosaic mural amazing beauty. Archaeologists were amazed: for two millennia glass almost faded. When samples of glass were subjected to chemical analysis, it was found that there is uranium oxide, which mosaic was owes its longevity. But if the oxides and salts of uranium was engaged in "socially useful work", then the metal in its pure form, almost nobody was interested in.

Mendeleev took a new value for the atomic weight of uranium and moved it to the end of his tableEven scientists, and those were only very superficially familiar with this item. Details were scarce, and sometimes completely wrong. So, it was believed that its atomic mass is equal to approximately 120. When the D. I. Mendeleev created the Periodic system, this value is confused him all the cards: the uranium in its properties did not want to fit into the cell of the table that was reserved for the element with this atomic mass. And then the scientist, contrary to the opinion of many of his colleagues, decided to accept a new value for the atomic mass of uranium - 240 and moved the item to the end of the table. Life has confirmed the correctness of the great chemist: the atomic mass of uranium is equal to 238,03.

But the genius of D. I. Mendeleev was manifested not only in this. Back in 1872, when most scientists believed the uranium in the background of many valuable elements of a kind of ballast, the Creator of the Periodic system was able to predict it truly bright future: "Among all known chemical elements uranium is distinguished by the fact that it has the highest atomic weight... the Highest known concentration of the mass of ponderable matter... existing uranium... should result in him outstanding features...

Convinced that the study of uranium from its natural sources, will lead even to many new discoveries, I highly recommend those who are looking for items for new research, carefully engage in uranium compounds".

The prediction of the great scientist came true in less than a quarter of a century: in 1896, the French physicist Antoine Henri Becquerel, conducting experiments with salts of uranium, made a discovery, which is considered to be one of the greatest scientific discoveries ever made by man. Here's how it happened. Becquerel had long been interested in the phenomenon of phosphorescence (i.e., luminescence)inherent to certain substances. One scientist decided to use for his experiments one of the salts of uranium. On the wrapped in black paper plate he put cut from patterned metal figure, covered with a layer of uranium salt, and put it in bright sunlight, so that phosphorescence was more intense. Four hours Becquerel took the plate and saw on it a distinct silhouette metal figures. Again and again he repeated his experiments - the result was the same. And now, 24 February 1896 at the meeting of the French Academy of Sciences scientist reported that he researched phosphorescent composition of uranium in the light emits invisible rays that pass through the black opaque paper, and restore the silver salt on the plate.

Two days later, Becquerel decided to continue the experiments, but as a sin, the weather was cloudy and no sun what happened? Knowing weather, scientist hid already cooked, but not exposed to light transparencies together with samples of the salts of uranium in the drawer of your Desk, where they spent several days. Finally, on the night of 1 March, the wind cleared the Paris sky with clouds and sun rays in the morning flashed over the city. Becquerel, eagerly waiting for this, hurried to his laboratory and removed from the drawer slides to expose them to the sun. But being very pedantic experimenter, he at the last moment decided to show the slides, while the logic seemed to tell, that in the past few days with them, nothing could happen because they were in a dark box, and without light is not absorbent for use no substance. At this moment, the scientist did not know that in a few hours ordinary photographic plates price in a few francs, destined to become an invaluable scientific treasure, and day 1 March 1896 will forever go down in the history of world science.

What Becquerel saw on the developed plates, literally struck him: the black silhouettes of samples sharply and clearly marked on the photosensitive layer. Hence, the phosphorescence is not to blame. But then what are these rays emits a salt of uranium? The scientist again and again doing similar experiments with other compounds of uranium, including those who do not have the ability to phosphoresce or years lay in a dark place, and every time the plates appeared the image.

The Becquerel occurs is not yet clear thought that Uranus represents the first example of metal detecting property, like an invisible phosphorescence".

At the same time, the French chemist Henri Moissan managed to develop a way of obtaining pure uranium metal. Becquerel asked Massana little uranium powder and found that the radiation of pure uranium to a much greater extent than its compounds, and is the property of uranium remained unchanged under different conditions of the experiments, in particular when strong heating and cooling to low temperatures.

With the publication of new data Becquerel was in no hurry: he waited for Moissan will tell about his very interesting research. This obliged scientific ethics. And here November 23, 1896 at the meeting of the Academy of Sciences Moissan did a report on work to obtain pure uranium, and Becquerel spoke about a new property in this item, which was spontaneous transformation of its atoms, accompanied by release of radiant energy. This property was called radioactivity.

Secrets of the uranium nucleusOpening Becquerel marked the beginning of a new era in physics - era transformation of elements. Now the atom could not be considered as one and indivisible - before science has opened the way to the depths of this "building block" of the material world.

Of course, now that Uranus has riveted the attention of scientists. However, they were also interested in the following question: is it only the uranium inherent radioactivity? It may be that in nature there are other elements with this property?

The answer to this question could give outstanding physics wife of Pierre Curie and Marie Sklodowska-Curie. With the help of a device constructed husband, Maria Curie examined a great number of metals, minerals, and salts. The work was carried out in incredibly difficult conditions. The laboratory served as an abandoned wooden shed, which the couple found in one of the Paris courts. "It was Barack from boards with asphalt floors and glass roof, poorly protected from rain, without any attachments, is later recalled M. Curie. - There were only the old wooden tables, cast iron stove, not giving enough heat, and chalkboard, which is so loved to use Pierre. There was not a fume cupboards for experiments with harmful gases, so had to do these operations on the yard when the weather would permit, or indoors with the Windows open". In the diary of P. Curie has a record of the fact that sometimes the work was carried out at a temperature of only six degrees above zero.

Many problems were encountered with obtaining the necessary materials. Uranium ore was very expensive, and to buy on their modest means enough to her spouse Curie could not. They decided to go to the Austrian government to sell them at the low price this waste ore from which Austria was extracted uranium used in the form of salts for coloring glass and porcelain. Scientists supported the Vienna Academy of Sciences, and several tons of waste was delivered to their Paris laboratory.

Marie Curie worked with extraordinary tenacity. The study of a variety of materials confirmed the correctness of the Becquerel, who believed that the radioactivity of pure uranium, more than any of its compounds. Talked about this the results of hundreds of experiments. But Marie Curie was subjected to research new substances. And then... Surprise! Two uranium mineral halkola and resin ore Bohemia - more acted on the device than uranium. The conclusion suggests itself: they contain some unknown element, characterized by an even higher ability to radioactive decay. In honor of Poland, the homeland of M. Curie - wife called him sir.

Again, again Titanic work - and still win: open item hundreds of times superior to the radioactivity of uranium. This element scientists called radium, which in Latin means "ray".

The discovery of radium to some extent diverted the scientific community from uranium. For about forty years he was not particularly concerned about the minds of scientists and engineers seldom spoiled him with their attention. In one of the volumes of technical encyclopedia, published in 1934, stated: "Elemental uranium practical application is not". Solid edition had not sinned against the truth, but after only a few years life has made significant adjustments in view of the possibilities of uranium.

In early 1939, there were two scientific reports. The first, aimed at the French Academy of Sciences Frederic Joliot-Curie, was entitled "Experimental evidence of an explosive fission of the nuclei of uranium and thorium with neutrons". The second message by its authors were German physicists Otto Frisch and Lise Meitner - published English journal "Nature", it was called: "the Decay of uranium neutrons: a new type of nuclear reaction". There we were talking about a new, hitherto unknown phenomenon occurring with the core of the heavy element uranium.

Even a few years before uranium was really interested in "the boys" - so friendly was called the group of talented young physicists working under the direction of Enrico Fermi at the University of Rome. The passion of these scientists was the neutron physics, concealed a lot of the new and unknown.

It was found that irradiation by neutrons, as a rule, the nucleus of one element into another kernel, occupying the next cell in the Periodic system. And when irradiated by neutrons last, the 92nd element is uranium? This should form element, already standing at 93-m - element, which failed to create even nature!

Liked the idea of "the boys". Why, isn't it tempting to find out what is an artificial element, how it looks, how it behaves? So - irradiated uranium. But what happened? Uranium appeared not one radioactive element, as expected, and at least a dozen. There was some mystery in the behavior of uranium. Enrico Fermi sends a message about it in one of the scientific journals. Perhaps, he thinks, was formed 93rd element, but the exact proof of this. On the other hand, there is evidence that in irradiated uranium there are some other elements. What?

Attempt to give an answer to this question took the daughter of Maria skłodowska - Curie, Irene Joliot-Curie. She repeated the experiments of Fermi and carefully studied the chemical composition of uranium after irradiation of its neutrons. The result was more than a surprise: in the uranium appeared the element lanthanum, located approximately in the middle of the periodic table, i.e. very far from uranium.

When the same experiments were done by German scientists Otto Hahn and Friedrich Strassmann, they found uranium not only lanthanum, and barium. The mystery behind the mystery!

Hahn and Strassmann reported tests performed his friend the famous physicist Lise Meitner. Now uranium is the problem of trying to solve several outstanding scientists. And here's the first Frederic Joliot-Curie, and after a while Lisa Meitner come to the same conclusion: if you get a neutron, the nucleus of uranium as if falling apart. This explains the unexpected appearance of lanthanum and barium elements with atomic mass is approximately twice smaller than that of uranium.

American physicist Luis Alvarez, the later Nobel prize winner this news caught in one January morning in 1939 in the Barber chair. He calmly looked through the newspaper, when suddenly he caught sight of the modest title: "the uranium Atom is split into two halves". After a moment, to the surprise of the hairdresser and visitors waiting queue, strange client ran out of the hair salon, half trimmed with cloth tightly tied around the neck and fluttering in the wind. Ignoring the surprised passers-by, physicist raced in the laboratory of the University of California, where he worked to tell about the amazing news to my colleagues. Those were dumbfounded at first a very original form of waving the newspaper Alvares, but when I heard about sensational opening, immediately forgot about his unusual hairstyle.

Alvarez news about the splitting of the nucleus of the uranium found in the Barber chair

Yes, it was a true sensation in science. But Joliot-Curie installed and another important fact: the collapse of the uranium nucleus is in the nature of the explosion, in which the resulting fragments are emitted in hand with great speed. While I was able to split the nucleus, the energy of the fragments is only heated a piece of uranium. If the number of divisions is large, then this huge amount of energy.

But where to get such number of neutrons to bombard them a large number of uranium nuclei? After all, a well-known scientist neutron sources gave them many billions of times less than required. Came to help nature. Joliot-Curie discovered that when the fission of uranium from him flies a few neutrons. Once in the nuclei of adjacent atoms, they must lead to a new collapse - will begin a so-called chain reaction. And because these processes last millionths of a second, immediately highlighted the enormous energy of the inevitable explosion. It would seem that everything is clear. But the pieces of uranium has repeatedly irradiated with neutrons, and they do not explode, i.e. a chain reaction did not occur. Probably still need some conditions. What? This question Frederic Joliot-Curie to answer until he could.

And yet the answer was found. Found him in the same 1939 young Soviet scientists AB Zeldovich and SHE Chariton. In their work they found that there are two ways of development of the nuclear chain reaction. The first is to increase the size of the piece of uranium, as the irradiation of a small piece of many newly released neutrons can escape from it, not having met on his way a single kernel. With the growth of the mass of uranium, the probability of a neutron in the goal, of course, increases.

There is another way - the enrichment of the uranium isotope 235. The fact that natural uranium has two main isotopes, atomic mass equal to 238 and 235. In the core of the first of them, which accounts for hundreds of times more atoms, there are three more neutron. "Poor" neutron uranium-235 greedily swallows them is much stronger than his "wealthy" brother, which, under certain conditions, absorbs a neutron, is not divided into parts, and turns into another element. This property isotope scientists later used for artificial transuranium elements. For chain reactions indifference of uranium-238 to neutron is disastrous: the process of becoming, not having had time to gain strength. But the more uranium "greedy" to neutrons of atoms of the isotope 235, the more energetic will be the reaction.

But to begin the process, need to be the first neutron - TA "match", which should cause the "atomic fire". Of course, for this purpose you can use conventional neutron sources, which scientists had previously used in his research, is not very convenient, but possible. Isn't there a more appropriate "match"?

There. It found other Soviet scientists K. A. Petrzhak, and N. Flerov. Exploring in 1939-1940 the behavior of uranium, they came to the conclusion that its kernel is able to disintegrate spontaneously. This was confirmed by the results of the experiments carried out by them in one of the Leningrad laboratories.

The experiment was carried out in stantsii metroBut, maybe, uranium decayed not himself, but, for example, under the action of cosmic rays: because the Earth is constantly under fire. Hence, the experiments need to be repeated deep under the ground, which cannot be penetrated by these cosmic visitors. After consulting with the largest Soviet scientist tonikom I.V. Kurchatov, young researchers decided to conduct experiments on some stations of the Moscow metro. In the people's Commissariat of Railways is not met obstacles, and soon in the office of the chief of the metro station "Dinamo", which was at a depth of 50 meters , on the shoulders of scientific workers was delivered equipment, which weighed about three tons.

As always, the passing of the blue train, thousands of passengers were walking up and down the escalator, and none of them imagined that somewhere nearby is conducted experiments, the value of which can hardly be overestimated. And then, finally, obtained results similar to those observed in Leningrad. There was no doubt: the nuclei of uranium inherent spontaneous decay. To notice him, it was necessary to show outstanding experimental skills: an hour out of every 60000000000000 atoms of uranium decays only one. Truly a drop in the bucket!

K. A. Petrzhak, and N. Flerov wrote the final page in the biography of uranium, which was preceded by conducting the world's first chain reaction. It was implemented on December 2, 1942, Enrico Fermi.

In the late 30-ies Fermi, like many other eminent scientists, fleeing from the Nazi plague, was forced to emigrate to America. Here he intended to continue his most important experiments. But this required a lot of money. It was necessary to convince the American government that the experiments Fermi will allow you to get powerful weapons that can be used to combat fascism. This mission was undertaken by the world renowned scientist albert Einstein. He writes a letter to U.S. President Franklin Roosevelt, which begins with the words: "Sir! The last work of E. Fermi and L. Szilard, which I read in manuscript, allows to expect that the element uranium in the near future can be turned into a new and important source of energy...". In a letter to a scientist called on the government to start funding the study of uranium. Given the enormous authority of Einstein and the seriousness of the international situation, Roosevelt gave his consent.

At the end of 1941, the inhabitants of Chicago may have noticed in the territory of one of the stadiums in the unusual excitement that had nothing to sport the slightest relation. To the gate it and then drove cars with cargo. Numerous guard did not allow outsiders to even come close to the fence of the stadium. Here, on the tennis courts, located at the Western stand, Enrico Fermi was preparing his dangerous experiment - implementation of a controlled chain reaction of nuclear fission of uranium. Work on the construction of the world's first nuclear reactor was carried out day and night throughout the year.

It was the morning of December 2, 1942. All night the scientists did not sleep a wink, again and again checking the calculations. It's no joke to say the stadium is located in the heart of new York city, and although the calculations were convinced that the reaction in the nuclear boiler will be delayed, i.e. will not be explosive nature, to endanger the lives of hundreds of thousands of people had no right. The day started long time ago, it was time for Breakfast, but it's all forgotten about - not wanted as soon as possible to begin the assault of the atom. However, Fermi is not in a hurry: it is necessary to give the tired people entertain the desired discharge, then again everything carefully weigh and consider. Care and caution. And now, when all waited for the command to start the experiment, Fermi uttered his famous phrase, known in the history of the conquest of the atom, only two words: "Come here for Breakfast!".

Breakfast over, all again in their places - the experience begins. The scientists focused on the devices. Agonizing minutes of waiting. And, finally, the neutron counters clicked, as the guns. They seemed choked with a huge number of neutrons, not having time to read! Chain reaction has begun! This happened in 15 hours and 25 minutes on Chicago time. Atomic fire was allowed to burn for 28 minutes, and then at the command of the Fermi chain reaction was terminated.

One of the participants answered the phone and agreed encrypting the phrase has informed his superiors: "the Italian Navigator has reached the New world!" This meant that the great Italian scientist Enrico Fermi was released energy of the atomic nucleus and proved that man can control and use it on their own.

But will the will of strife. In those years, when these events took place, the chain reaction was seen primarily as a stage on the way to build an atomic bomb. It is in this direction and were continued in America the work of scientists Temnikov.

The situation in scientific circles connected with these works, was extremely tense. But it is not without its oddities.

In the autumn of 1943, it was decided to take out the German-occupied Denmark to America's largest physics Niels Bohr, to use his vast knowledge and talent. A dark night on a fishing boat, secretly guarded English submarines, scientist under the guise of a fisherman was taken to Sweden, where his plane had to travel to England, and then in the United States. All baggage Boron consisted of one bottle. This simple green bottle from under Danish beer, which he secretly from the Germans kept the precious heavy water, a physicist shore as the Apple of an eye: according to many scientists Temnikov, it is heavy water could serve as a neutron moderator in nuclear reactions. Boron is very difficult endured a tiring flight and as soon as he came to, the first thing you checked, whether a bottle of heavy water. And then, to his great chagrin, he discovered that he became a victim of his own absent-mindedness: in his hands was a bottle of the real Danish beer, and a container of heavy water remained at home in the refrigerator.

When the giant plants of oak ridge, located in Tennessee, was the first small piece of uranium-235, used for the atomic bomb, he was sent with a special courier hidden among the cantons of the state of new Mexico Los Alamos, where he created this deadly weapon. The courier, who was himself driving, not said, what is transferred in the box, but he had heard terrible stories about the mysterious "death rays"born in oak ridge. The farther he went, the more excitement gripped him. In the end, he decided, at the first suspicious sign in the behavior box, hidden behind it, to escape from the machine that is urine. Driving along the long bridge, the driver suddenly heard a loud gunshot. If ejected as per mission plan, he jumped out of the car and ran as fast as I didn't run never before in my life. But, after running a considerable distance, he stopped in exhaustion, he was convinced that the whole and unharmed, and even dared to look back. Meanwhile, his machine has already grown a long tail impatiently signalised cars. Had to go back and continue the path. But as soon as he got behind the wheel, as again there was a loud shot, and instinct again literally threw the poor guy out of the car and forced him to rush away from the ill-fated boxes. Only after the enraged COP caught up with him on the motorcycle and saw government documents, frightened the driver learned that the shots came from the neighboring polygon, where at that time felt new artillery shells.

The driver-courier who was carrying a sample of uranium-235, was not a thing frightened

Work at Los Alamos was performed in conditions of the strictest secrecy. All great scientists were here under fake names. So, Niels Bohr, for example, was known at Los Alamos as Nicholas Baker, Enrico Fermi was Henry farmer, Eugene Wigner - Eugene Wagner. Once, when Fermi and Wigner went with the territory of one of the secret factory, they were stopped by hour. Fermi showed his ID to the name of the farmer, and the Wigner couldn't find their documents. The time was the list of those who were allowed to enter the plant and leaving it. "Your name?" - he asked. Absent-minded Professor first habit muttered "Wigner", but then I caught myself and corrected himself: "Wagner". This raised suspicions at the time. Wagner was in the list, and the Wigner - no. He turned to Fermi, who already knew in person, and asked: "This man's name is Wagner?". - "His name is Wagner. It's just as true as what I Farmer", - hiding smile, solemnly assured the time Fermi, and he missed scientists.

Around mid-1945 work on the creation of the atomic bomb, which had spent two billion dollars, was completed, and on August 6, over the Japanese city of Hiroshima occurred giant fiery mushroom that killed tens of thousands of lives. This date became a black day in the history of civilization. The greatest achievement of science has generated the greatest tragedy of mankind. The scientists, before the whole world, the question arose: what next? To continue to develop nuclear weapons, to create even more terrible means of destruction of people? No! Now the enormous energy contained in the nuclei of atoms, must serve man.

The first step in this direction was made by the Soviet scientists under the leadership of academician I.V. Kurchatov. on June 27, 1954, Moscow radio broadcast the message of exceptional importance: "At the present time in the Soviet Union by the efforts of Soviet scientists and engineers successfully completed the design and construction of the first industrial plant for the atomic energy useful capacity of 5,000 kilowatts". For the first time on the wire was the current that was carrying energy, birthed in the bowels of the uranium atom. The launch of the first nuclear power plant has begun development of a new branch of technology - nuclear power. Uranium was peaceful combustible XX century.

The idea is to get rid of nuclear waste industry, sending them into space, to the Sunit took another five years, and the stocks of the Soviet shipyards came the world's first atomic icebreaker "Lenin". To make its engines at full power (44 thousand horsepower!), it was necessary to "burn" only a few dozen grams of uranium. A small piece of that nuclear fuel can replace thousands of tons of fuel oil or coal, which are forced to carry normal ships engaged, for example, the flight London - new York. And together with the stock of uranium fuel in a few tens of kilos within three years to crush the ice of the Arctic, not going to the port on the "gas station". In 1974 he started to perform their "duties" even more powerful nuclear icebreaker Arktika: the power of its engines - 75 thousand horsepower! on August 17, 1977 "Arctic", breaking the seemingly indestructible ice armour of the Central polar basin of the Arctic ocean, reached the North pole. Had been an age-old dream of many generations of sailors and polar explorers, and uranium has contributed to the solution of this problem also. The most powerful nuclear-powered icebreaker has already appeared in two "sisters" - "Siberia" and "Russia".

Every year the share of nuclear fuel in the global energy balance becomes more tangible. A few years ago in the USSR launched the first commercial nuclear power reactor on the so-called fast neutrons. An important feature of such reactors is that as a nuclear fuel they can use not scarce uranium-235, and the most common on earth isotope of this element is uranium-238. In the reactor not only releases massive amounts of energy, but also produces an artificial element polonium-239, which itself is able to share, and hence be a source of nuclear energy. "As it turns out would - wrote I.V. Kurchatov, that will burn in the furnace of the coal, and will paddle together with ash even more coal.

Advantages of nuclear fuel is undeniable. However, it is fraught with many difficulties, of which perhaps the most important is the destruction of the resulting radioactive waste. To keep them in special containers at the bottom of the seas and oceans? Bury them deep in the ground? It is unlikely therefore possible to completely solve the problem, because ultimately deadly substances remain on our planet. And don't try to send them somewhere far away on other celestial bodies? That is the idea put forward by one of the American scientists. He offered to ship waste from nuclear power plants on the "trademarks" spacecraft, following the route of the Earth - Sun. Of course, today such "make" expensive would cost to senders, but, according to some optimistic experts, after some ten years, these transport operations will be quite justified.

Nowadays, you do not need to have a rich imagination to predict uranium great future. Uranus tomorrow is a space rocket, looking deep into the Universe, and a giant underwater city, provided the energy for decades, the creation of artificial Islands and watering deserts, this penetration to the Earth's interior and climate change our planet.

Fabulous prospects open before us the uranium is one of the most amazing metal nature!

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