Plutonium (Latin Plutonium, symbol Pu) is a radioactive chemical element with atomic number 94 and atomic weight 244.064. Plutonium is an element of Group III of Dmitry Ivanovich Mendeleev’s periodic table and belongs to the actinide family. Plutonium is a heavy (density under normal conditions 19.84 g/cm³) brittle radioactive metal of a silvery-white color.
Plutonium has no stable isotopes. Of the hundred possible isotopes of plutonium, twenty-five have been synthesized. The nuclear properties of fifteen of them were studied (mass numbers 232-246). Four have found practical application. The longest-lived isotopes are 244Pu (half-life 8.26-107 years), 242Pu (half-life 3.76-105 years), 239Pu (half-life 2.41-104 years), 238Pu (half-life 87.74 years) - α-emitters and 241Pu (half-life 14 years) - β-emitter. In nature, plutonium occurs in negligible quantities in uranium ores (239Pu); it is formed from uranium under the influence of neutrons, the sources of which are reactions occurring during the interaction of α-particles with light elements (included in ores), spontaneous fission of uranium nuclei and cosmic radiation.
The ninety-fourth element was discovered by a group of American scientists - Glenn Seaborg, Kennedy, Edwin McMillan and Arthur Wahl in 1940 at Berkeley (at the University of California) when bombing a target of uranium oxide ( U3O8) by highly accelerated deuterium nuclei (deuterons) from a sixty-inch cyclotron. In May 1940, the properties of plutonium were predicted by Lewis Turner.
In December 1940, the plutonium isotope Pu-238 was discovered, with a half-life of ~90 years, followed a year later by the more important Pu-239 with a half-life of ~24,000 years.
Edwin MacMillan in 1948 proposed to name the chemical element plutonium in honor of the discovery of the new planet Pluto and by analogy with neptunium, which was named after the discovery of Neptune.
Metallic plutonium (239Pu isotope) is used in nuclear weapons and serves as nuclear fuel in power reactors operating on thermal and especially fast neutrons. The critical mass for 239Pu as metal is 5.6 kg. Among other things, the 239Pu isotope is the starting material for the production of transplutonium elements in nuclear reactors. The 238Pu isotope is used in small-sized nuclear power sources used in space research, as well as in human cardiac stimulants.
Plutonium-242 is important as a “raw material” for the relatively rapid accumulation of higher transuranium elements in nuclear reactors. δ-stabilized plutonium alloys are used in the manufacture of fuel cells, since they have better metallurgical properties compared to pure plutonium, which undergoes phase transitions when heated. Plutonium oxides are used as an energy source for space technology and find their application in fuel rods.
All plutonium compounds are poisonous, which is a consequence of α-radiation. Alpha particles pose a serious danger if their source is in the body of an infected person; they damage the surrounding tissue of the body. Gamma radiation from plutonium is not dangerous to the body. It is worth considering that different isotopes of plutonium have different toxicities, for example, typical reactor plutonium is 8-10 times more toxic than pure 239Pu, since it is dominated by 240Pu nuclides, which is a powerful source of alpha radiation. Plutonium is the most radiotoxic element of all actinides, however, it is considered far from the most dangerous element, since radium is almost a thousand times more dangerous than the most poisonous isotope of plutonium - 239Pu.
Biological properties
Plutonium is concentrated by marine organisms: the accumulation coefficient of this radioactive metal (the ratio of concentrations in the body and in the external environment) for algae is 1000-9000, for plankton - approximately 2300, for starfish - about 1000, for mollusks - up to 380, for muscles, bones , liver and stomach of fish - 5, 570, 200 and 1060, respectively. Land plants absorb plutonium mainly through the root system and accumulate it to 0.01% of their mass. In the human body, the ninety-fourth element is retained mainly in the skeleton and liver, from where it is almost not excreted (especially from the bones).
Plutonium is highly toxic, and its chemical danger (like any other heavy metal) is much weaker (from a chemical point of view, it is also poisonous like lead.) in comparison with its radioactive toxicity, which is a consequence of alpha radiation. Moreover, α-particles have a relatively low penetrating ability: for 239Pu, the range of α-particles in air is 3.7 cm, and in soft biological tissue 43 μm. Therefore, alpha particles pose a serious danger if their source is in the body of an infected person. At the same time, they damage the tissues of the body surrounding the element.
At the same time, γ-rays and neutrons, which plutonium also emits and which are able to penetrate the body from the outside, are not very dangerous, because their level is too low to cause harm to health. Plutonium belongs to a group of elements with particularly high radiotoxicity. At the same time, different isotopes of plutonium have different toxicity, for example, typical reactor plutonium is 8-10 times more toxic than pure 239Pu, since it is dominated by 240Pu nuclides, which is a powerful source of alpha radiation.
When ingested through water and food, plutonium is less toxic than substances such as caffeine, some vitamins, pseudoephedrine, and many plants and fungi. This is explained by the fact that this element is poorly absorbed by the gastrointestinal tract, even when supplied in the form of a soluble salt, this same salt is bound by the contents of the stomach and intestines. However, ingestion of 0.5 grams of finely divided or dissolved plutonium can result in death from acute digestive irradiation within days or weeks (for cyanide this value is 0.1 grams).
From an inhalation point of view, plutonium is an ordinary toxin (roughly equivalent to mercury vapor). When inhaled, plutonium is carcinogenic and can cause lung cancer. So, when inhaled, one hundred milligrams of plutonium in the form of particles of an optimal size for retention in the lungs (1-3 microns) leads to death from pulmonary edema in 1-10 days. A dose of twenty milligrams leads to death from fibrosis in about a month. Smaller doses lead to chronic carcinogenic poisoning. The danger of inhalation of plutonium into the body increases due to the fact that plutonium is prone to the formation of aerosols.
Even though it is a metal, it is quite volatile. A short stay of metal in a room significantly increases its concentration in the air. Plutonium that enters the lungs partially settles on the surface of the lungs, partially passes into the blood, and then into the lymph and bone marrow. Most (approximately 60%) ends up in bone tissue, 30% in the liver and only 10% is excreted naturally. The amount of plutonium that enters the body depends on the size of aerosol particles and solubility in the blood.
Plutonium entering the human body in one way or another is similar in properties to ferric iron, therefore, penetrating into the circulatory system, plutonium begins to concentrate in tissues containing iron: bone marrow, liver, spleen. The body perceives plutonium as iron, therefore, the transferrin protein takes plutonium instead of iron, as a result of which the transfer of oxygen in the body stops. Microphages carry plutonium to the lymph nodes. Plutonium that enters the body takes a very long time to be removed from the body - within 50 years, only 80% will be removed from the body. The half-life from the liver is 40 years. For bone tissue, the half-life of plutonium is 80-100 years; in fact, the concentration of element ninety-four in bones is constant.
Throughout World War II and after its end, scientists working in the Manhattan Project, as well as scientists of the Third Reich and other research organizations, conducted experiments using plutonium on animals and humans. Animal studies have shown that a few milligrams of plutonium per kilogram of tissue is a lethal dose. The use of plutonium in humans consisted of usually 5 mcg of plutonium being injected intramuscularly into chronically ill patients. It was eventually determined that the lethal dose to a patient was one microgram of plutonium, and that plutonium was more dangerous than radium and tended to accumulate in bones.
As is known, plutonium is an element practically absent in nature. However, about five tons of it were released into the atmosphere as a result of nuclear tests in the period 1945-1963. The total amount of plutonium released into the atmosphere due to nuclear tests before the 1980s is estimated at 10 tons. By some estimates, soil in the United States contains an average of 2 millicuries (28 mg) of plutonium per km2 of fallout, and the occurrence of plutonium in the Pacific Ocean is elevated relative to the overall distribution of nuclear materials on earth.
The latest phenomenon is associated with US nuclear testing in the Marshall Islands at the Pacific Test Site in the mid-1950s. The residence time of plutonium in surface ocean waters ranges from 6 to 21 years, however, even after this period, plutonium falls to the bottom along with biogenic particles, from which it is reduced to soluble forms as a result of microbial decomposition.
Global pollution with the ninety-fourth element is associated not only with nuclear tests, but also with accidents in production and equipment interacting with this element. So in January 1968, a US Air Force B-52 carrying four nuclear warheads crashed in Greenland. As a result of the explosion, the charges were destroyed and plutonium leaked into the ocean.
Another case of radioactive contamination of the environment as a result of an accident occurred with the Soviet spacecraft Kosmos-954 on January 24, 1978. As a result of an uncontrolled deorbit, a satellite with a nuclear power source on board fell into Canadian territory. As a result of the accident, more than a kilogram of plutonium-238 was released into the environment, spreading over an area of about 124,000 m².
The most terrible example of an emergency leak of radioactive substances into the environment is the accident at the Chernobyl nuclear power plant, which occurred on April 26, 1986. As a result of the destruction of the fourth power unit, 190 tons of radioactive substances (including plutonium isotopes) were released into the environment over an area of about 2200 km².
The release of plutonium into the environment is not only associated with man-made incidents. There are known cases of plutonium leakage, both from laboratory and factory conditions. More than twenty accidental leaks from the 235U and 239Pu laboratories are known. During 1953-1978. accidents led to a loss of 0.81 (Mayak, March 15, 1953) to 10.1 kg (Tomsk, December 13, 1978) 239Pu. Industrial incidents resulted in a total of two deaths at Los Alamos (August 21, 1945 and May 21, 1946) due to two accidents and the loss of 6.2 kg of plutonium. In the city of Sarov in 1953 and 1963. approximately 8 and 17.35 kg fell outside the nuclear reactor. One of them led to the destruction of a nuclear reactor in 1953.
When a 238Pu nucleus fissions with neutrons, 200 MeV of energy is released, which is 50 million times more than the most famous exothermic reaction: C + O2 → CO2. “Burning” in a nuclear reactor, one gram of plutonium produces 2,107 kcal - this is the energy contained in 4 tons of coal. A thimble of plutonium fuel in energy equivalent can be equivalent to forty wagons of good firewood!
The “natural isotope” of plutonium (244Pu) is believed to be the longest-lived isotope of all transuranium elements. Its half-life is 8.26∙107 years. Scientists have been trying for a long time to obtain an isotope of a transuranium element that would exist longer than 244Pu - great hopes in this regard were pinned on 247Cm. However, after its synthesis it turned out that the half-life of this element is only 14 million years.
Story
In 1934, a group of scientists led by Enrico Fermi made a statement that during scientific work at the University of Rome they had discovered a chemical element with serial number 94. At Fermi’s insistence, the element was named hesperium, the scientist was convinced that he had discovered a new element, which is now called plutonium, thus suggesting the existence of transuranium elements and becoming their theoretical discoverer. Fermi defended this hypothesis in his Nobel lecture in 1938. It was only after the discovery of nuclear fission by the German scientists Otto Frisch and Fritz Strassmann that Fermi was forced to make a note in the printed version published in Stockholm in 1939 indicating the need to reconsider “the whole problem of transuranium elements.” The fact is that the work of Frisch and Strassmann showed that the activity discovered by Fermi in his experiments was due precisely to fission, and not to the discovery of transuranium elements, as he had previously believed.
A new element, the ninety-fourth, was discovered at the end of 1940. It happened in Berkeley at the University of California. By bombarding uranium oxide (U3O8) with heavy hydrogen nuclei (deuterons), a group of American radiochemists led by Glenn T. Seaborg discovered a previously unknown alpha particle emitter with a half-life of 90 years. This emitter turned out to be the isotope of element No. 94 with a mass number of 238. Thus, on December 14, 1940, the first microgram quantities of plutonium were obtained along with an admixture of other elements and their compounds.
During an experiment conducted in 1940, it was found that during a nuclear reaction, the short-lived isotope neptunium-238 is first produced (half-life 2.117 days), and from it plutonium-238:
23392U (d,2n) → 23893Np → (β−) 23894Pu
Long and laborious chemical experiments to separate the new element from impurities lasted two months. The existence of a new chemical element was confirmed on the night of February 23–24, 1941 by G. T. Seaborg, E. M. Macmillan, J. W. Kennedy and A. C. Wall through the study of its first chemical properties - the ability to possess at least at least two oxidation states. A little later than the end of the experiments, it was established that this isotope is non-fissile, and, therefore, uninteresting for further study. Soon (March 1941), Kennedy, Seaborg, Segre and Wahl synthesized a more important isotope, plutonium-239, by irradiating uranium with highly accelerated neutrons in a cyclotron. This isotope is formed by the decay of neptunium-239, emits alpha rays and has a half-life of 24,000 years. The first pure compound of the element was obtained in 1942, and the first weight quantities of metallic plutonium were obtained in 1943.
The name of the new element 94 was proposed in 1948 by MacMillan, who, a few months before the discovery of plutonium, together with F. Eibelson, obtained the first element heavier than uranium - element No. 93, which was named neptunium in honor of the planet Neptune - the first beyond Uranus. By analogy, they decided to call element No. 94 plutonium, since the planet Pluto is second after Uranus. In turn, Seaborg proposed calling the new element “plutium,” but then realized that the name did not sound very good compared to “plutonium.” In addition, he put forward other names for the new element: ultimium, extermium, due to the erroneous judgment at that time that plutonium would become the last chemical element in the periodic table. As a result, the element was named “plutonium” in honor of the discovery of the last planet in the solar system.
Being in nature
The half-life of the longest-lived isotope of plutonium is 75 million years. The figure is very impressive, however, the age of the Galaxy is measured in billions of years. It follows from this that the primary isotopes of the ninety-fourth element, formed during the great synthesis of the elements of the Universe, had no chance of surviving to this day. And yet, this does not mean that there is no plutonium in the Earth at all. It is constantly formed in uranium ores. By capturing neutrons from cosmic radiation and neutrons produced by the spontaneous fission of 238U nuclei, some - very few - atoms of this isotope turn into 239U atoms. The nuclei of this element are very unstable, they emit electrons and thereby increase their charge, and the formation of neptunium, the first transuranium element, occurs. 239Np is also unstable, its nuclei also emit electrons, so in just 56 hours half of 239Np turns into 239Pu.
The half-life of this isotope is already very long and amounts to 24,000 years. On average, the content of 239Pu is about 400,000 times less than that of radium. Therefore, it is extremely difficult not only to mine, but even to detect “terrestrial” plutonium. Small quantities of 239Pu - parts per trillion - and decay products can be found in uranium ores, for example in the natural nuclear reactor at Oklo, Gabon (West Africa). The so-called “natural nuclear reactor” is considered to be the only one in the world in which actinides and their fission products are currently being formed in the geosphere. According to modern estimates, a self-sustaining reaction with the release of heat took place in this region several million years ago, which lasted more than half a million years.
So, we already know that in uranium ores, as a result of the capture of neutrons by uranium nuclei, neptunium (239Np) is formed, the β-decay product of which is natural plutonium-239. Thanks to special instruments - mass spectrometers - the presence of plutonium-244 (244Pu), which has the longest half-life - approximately 80 million years, was discovered in Precambrian bastnaesite (cerium ore). In nature, 244Pu is found predominantly in the form of dioxide (PuO2), which is even less soluble in water than sand (quartz). Since the relatively long-lived isotope plutonium-240 (240Pu) is in the decay chain of plutonium-244, its decay does occur, but this occurs very rarely (1 case in 10,000). Very small amounts of plutonium-238 (238Pu) are due to the very rare double beta decay of the parent isotope, uranium-238, which was found in uranium ores.
Traces of the isotopes 247Pu and 255Pu were found in dust collected after explosions of thermonuclear bombs.
Minimal amounts of plutonium could hypothetically be present in the human body, given that a huge number of nuclear tests have been conducted in one way or another related to plutonium. Plutonium accumulates mainly in the skeleton and liver, from where it is practically not excreted. In addition, element ninety-four is accumulated by marine organisms; Land plants absorb plutonium mainly through the root system.
It turns out that artificially synthesized plutonium still exists in nature, so why is it not mined, but obtained artificially? The fact is that the concentration of this element is too low. About another radioactive metal - radium they say: “a gram of production - a year of work,” and radium in nature is 400,000 times more abundant than plutonium! For this reason, it is extremely difficult not only to mine, but even to detect “terrestrial” plutonium. This was done only after the physical and chemical properties of plutonium produced in nuclear reactors were studied.
Application
The 239Pu isotope (along with U) is used as nuclear fuel in power reactors operating on thermal and fast neutrons (mainly), as well as in the manufacture of nuclear weapons.
About half a thousand nuclear power plants around the world generate approximately 370 GW of electricity (or 15% of the world's total electricity production). Plutonium-236 is used in the manufacture of atomic electric batteries, the service life of which reaches five years or more, they are used in current generators that stimulate the heart (pacemakers). 238Pu is used in small-sized nuclear power sources used in space research. Thus, plutonium-238 is the power source for the New Horizons, Galileo and Cassini probes, the Curiosity rover and other spacecraft.
Nuclear weapons use plutonium-239 because this isotope is the only suitable nuclide for use in a nuclear bomb. In addition, the more frequent use of plutonium-239 in nuclear bombs is due to the fact that plutonium occupies less volume in the sphere (where the bomb core is located), therefore, the explosive power of the bomb can be gained due to this property.
The scheme by which a nuclear explosion involving plutonium occurs lies in the design of the bomb itself, the core of which consists of a sphere filled with 239Pu. At the moment of collision with the ground, the sphere is compressed to a million atmospheres due to the design and thanks to the explosive surrounding this sphere. After the impact, the core expands in volume and density in the shortest possible time - tens of microseconds, the assembly jumps through the critical state with thermal neutrons and goes into the supercritical state with fast neutrons - a nuclear chain reaction begins with the participation of neutrons and nuclei of the element. The final explosion of a nuclear bomb releases temperatures of the order of tens of millions of degrees.
Plutonium isotopes have found their use in the synthesis of transplutonium (next to plutonium) elements. For example, at the Oak Ridge National Laboratory, with long-term neutron irradiation of 239Pu, 24496Cm, 24296Cm, 24997Bk, 25298Cf, 25399Es and 257100Fm are obtained. In the same way, americium 24195Am was first obtained in 1944. In 2010, plutonium-242 oxide bombarded with calcium-48 ions served as a source for ununquadium.
δ-Stabilized plutonium alloys are used in the manufacture of fuel rods, because they have significantly better metallurgical properties compared to pure plutonium, which undergoes phase transitions when heated and is a very brittle and unreliable material. Alloys of plutonium with other elements (intermetallic compounds) are usually obtained by direct interaction of elements in the required proportions, while arc melting is mainly used; sometimes unstable alloys are obtained by spray deposition or cooling of melts.
The main industrial alloying elements for plutonium are gallium, aluminum and iron, although plutonium is capable of forming alloys and intermediates with most metals with rare exceptions (potassium, sodium, lithium, rubidium, magnesium, calcium, strontium, barium, europium and ytterbium). Refractory metals: molybdenum, niobium, chromium, tantalum and tungsten are soluble in liquid plutonium, but almost insoluble or slightly soluble in solid plutonium. Indium, silicon, zinc and zirconium are capable of forming metastable δ-plutonium (δ"-phase) when rapidly cooled. Gallium, aluminum, americium, scandium and cerium can stabilize δ-plutonium at room temperature.
Large quantities of holmium, hafnium and thallium allow some δ-plutonium to be stored at room temperature. Neptunium is the only element that can stabilize α-plutonium at high temperatures. Titanium, hafnium and zirconium stabilize the structure of β-plutonium at room temperature when rapidly cooled. The applications of such alloys are quite diverse. For example, a plutonium-gallium alloy is used to stabilize the δ phase of plutonium, which avoids the α-δ phase transition. Plutonium-gallium-cobalt ternary alloy (PuGaCo5) is a superconducting alloy at 18.5 K. There are a number of alloys (plutonium-zirconium, plutonium-cerium and plutonium-cerium-cobalt) that are used as nuclear fuel.
Production
Industrial plutonium is produced in two ways. This is either irradiation of 238U nuclei contained in nuclear reactors, or separation by radiochemical methods (co-precipitation, extraction, ion exchange, etc.) of plutonium from uranium, transuranic elements and fission products contained in spent fuel.
In the first case, the most practical isotope 239Pu (mixed with a small admixture of 240Pu) is produced in nuclear reactors with the participation of uranium nuclei and neutrons using β-decay and with the participation of neptunium isotopes as an intermediate fission product:
23892U + 21D → 23893Np + 210n;
23893Np → 23894Pu
β-decay
In this process, a deuteron enters uranium-238, resulting in the formation of neptunium-238 and two neutrons. Neptunium-238 then spontaneously fissions, emitting beta-minus particles that form plutonium-238.
Typically, the content of 239Pu in the mixture is 90-95%, 240Pu is 1-7%, the content of other isotopes does not exceed tenths of a percent. Isotopes with long half-lives - 242Pu and 244Pu are obtained by prolonged irradiation with 239Pu neutrons. Moreover, the yield of 242Pu is several tens of percent, and 244Pu is a fraction of a percent of the 242Pu content. Small amounts of isotopically pure plutonium-238 are formed when neptunium-237 is irradiated with neutrons. Light isotopes of plutonium with mass numbers 232-237 are usually obtained in a cyclotron by irradiating uranium isotopes with α-particles.
The second method of industrial production of 239Pu uses the Purex process, based on extraction with tributyl phosphate in a light diluent. In the first cycle, Pu and U are jointly purified from fission products and then separated. In the second and third cycles, the plutonium is further purified and concentrated. The scheme of such a process is based on the difference in the properties of tetra- and hexavalent compounds of the elements being separated.
Initially, spent fuel rods are dismantled and the cladding containing spent plutonium and uranium is removed by physical and chemical means. Next, the extracted nuclear fuel is dissolved in nitric acid. After all, it is a strong oxidizing agent when dissolved, and uranium, plutonium, and impurities are oxidized. Plutonium atoms with zero valence are converted into Pu+6, and both plutonium and uranium are dissolved. From such a solution, the ninety-fourth element is reduced to the trivalent state with sulfur dioxide and then precipitated with lanthanum fluoride (LaF3).
However, in addition to plutonium, the sediment contains neptunium and rare earth elements, but the bulk (uranium) remains in solution. Next, the plutonium is again oxidized to Pu+6 and lanthanum fluoride is added again. Now the rare earth elements precipitate, and the plutonium remains in solution. Next, neptunium is oxidized to a tetravalent state with potassium bromate, since this reagent has no effect on plutonium, then during secondary precipitation with the same lanthanum fluoride, trivalent plutonium passes into a precipitate, and neptunium remains in solution. The end products of such operations are plutonium-containing compounds - PuO2 dioxide or fluorides (PuF3 or PuF4), from which metallic plutonium is obtained (by reduction with barium, calcium or lithium vapor).
Purer plutonium can be achieved by electrolytic refining of the pyrochemically produced metal, which is done in electrolysis cells at 700° C with an electrolyte of potassium, sodium and plutonium chloride using a tungsten or tantalum cathode. The plutonium obtained in this way has a purity of 99.99%.
To produce large quantities of plutonium, breeder reactors are built, so-called “breeders” (from the English verb to breed - to multiply). These reactors got their name due to their ability to produce fissile material in quantities exceeding the cost of obtaining this material. The difference between reactors of this type and others is that the neutrons in them are not slowed down (there is no moderator, for example, graphite) in order for as many of them as possible to react with 238U.
After the reaction, 239U atoms are formed, which subsequently form 239Pu. The core of such a reactor, containing PuO2 in depleted uranium dioxide (UO2), is surrounded by a shell of even more depleted uranium dioxide-238 (238UO2), in which 239Pu is formed. The combined use of 238U and 235U allows “breeders” to produce 50-60 times more energy from natural uranium than other reactors. However, these reactors have a big drawback - fuel rods must be cooled by a medium other than water, which reduces their energy. Therefore, it was decided to use liquid sodium as a coolant.
The construction of such reactors in the United States of America began after the end of World War II; the USSR and Great Britain began their construction only in the 1950s.
Physical properties
Plutonium is a very heavy (density at normal level 19.84 g/cm³) silvery metal, in a purified state very similar to nickel, but in air plutonium quickly oxidizes, fades, forming an iridescent film, first light yellow, then turning into dark purple. When severe oxidation occurs, an olive green oxide powder (PuO2) appears on the metal surface.
Plutonium is a highly electronegative and reactive metal, many times more so even than uranium. It has seven allotropic modifications (α, β, γ, δ, δ", ε and ζ), which change in a certain temperature range and at a certain pressure range. At room temperature, plutonium is in the α-form - this is the most common allotropic modification for plutonium In the alpha phase, pure plutonium is brittle and quite hard - this structure is about as hard as gray cast iron unless it is alloyed with other metals, which will give the alloy ductility and softness. In addition, in this highest density form, plutonium is the sixth densest element (Only osmium, iridium, platinum, rhenium and neptunium are heavier. Further allotropic transformations of plutonium are accompanied by abrupt changes in density. For example, when heated from 310 to 480 ° C, it does not expand, like other metals, but contracts (delta phases " and "delta prime") When melted (transition from the epsilon phase to the liquid phase), the plutonium also contracts, allowing unmelted plutonium to float.
Plutonium has a large number of unusual properties: it has the lowest thermal conductivity of all metals - at 300 K it is 6.7 W/(m K); plutonium has the lowest electrical conductivity; In its liquid phase, plutonium is the most viscous metal. The resistivity of the ninety-fourth element at room temperature is very high for a metal, and this feature will increase with decreasing temperature, which is not typical for metals. This “anomaly” can be traced up to a temperature of 100 K - below this mark the electrical resistance will decrease. However, from 20 K the resistance begins to increase again due to the radiation activity of the metal.
Plutonium has the highest electrical resistivity of all the actinides studied (so far), which is 150 μΩ cm (at 22 °C). This metal has a low melting point (640 °C) and an unusually high boiling point (3,227 °C). Closer to the melting point, liquid plutonium has a very high viscosity and surface tension compared to other metals.
Due to its radioactivity, plutonium is warm to the touch. A large piece of plutonium in a thermal shell is heated to a temperature exceeding the boiling point of water! In addition, due to its radioactivity, plutonium undergoes changes in its crystal lattice over time - a kind of annealing occurs due to self-irradiation due to temperature increases above 100 K.
The presence of a large number of allotropic modifications in plutonium makes it a difficult metal to process and roll out due to phase transitions. We already know that in the alpha form the ninety-fourth element is similar in properties to cast iron, however, it tends to change and turn into a ductile material, and form a malleable β-form at higher temperature ranges. Plutonium in the δ form is usually stable at temperatures between 310 °C and 452 °C, but can exist at room temperature if doped with low percentages of aluminum, cerium or gallium. When alloyed with these metals, plutonium can be used in welding. In general, the delta form has more pronounced characteristics of a metal - it is close to aluminum in strength and forgeability.
Chemical properties
The chemical properties of the ninety-fourth element are in many ways similar to the properties of its predecessors in the periodic table - uranium and neptunium. Plutonium is a fairly active metal; it forms compounds with oxidation states from +2 to +7. In aqueous solutions, the element exhibits the following oxidation states: Pu (III), as Pu3+ (exists in acidic aqueous solutions, has a light purple color); Pu (IV), as Pu4+ (chocolate shade); Pu (V), as PuO2+ (light solution); Pu (VI), as PuO22+ (light orange solution) and Pu(VII), as PuO53- (green solution).
Moreover, these ions (except for PuO53-) can be simultaneously in equilibrium in the solution, which is explained by the presence of 5f electrons, which are located in the localized and delocalized zone of the electron orbital. At pH 5-8, Pu(IV) dominates, which is the most stable among other valences (oxidation states). Plutonium ions of all oxidation states are prone to hydrolysis and complex formation. The ability to form such compounds increases in the Pu5+ series
Compact plutonium slowly oxidizes in air, becoming covered with an iridescent, oily film of oxide. The following plutonium oxides are known: PuO, Pu2O3, PuO2 and a phase of variable composition Pu2O3 - Pu4O7 (Berthollides). In the presence of small amounts of moisture, the rate of oxidation and corrosion increases significantly. If a metal is exposed to small amounts of moist air for long enough, plutonium dioxide (PuO2) forms on its surface. With a lack of oxygen, its dihydride (PuH2) can also form. Surprisingly, plutonium rusts much faster in an atmosphere of an inert gas (such as argon) with water vapor than in dry air or pure oxygen. In fact, this fact is easy to explain - the direct action of oxygen forms a layer of oxide on the surface of plutonium, which prevents further oxidation; the presence of moisture produces a loose mixture of oxide and hydride. By the way, thanks to this coating, the metal becomes pyrophoric, that is, it is capable of spontaneous combustion; for this reason, metallic plutonium is usually processed in an inert atmosphere of argon or nitrogen. At the same time, oxygen is a protective substance and prevents moisture from affecting the metal.
The ninety-fourth element reacts with acids, oxygen and their vapors, but not with alkalis. Plutonium is highly soluble only in very acidic media (for example, hydrochloric acid HCl), and is also soluble in hydrogen chloride, hydrogen iodide, hydrogen bromide, 72% perchloric acid, 85% orthophosphoric acid H3PO4, concentrated CCl3COOH, sulfamic acid and boiling concentrated nitric acid. Plutonium does not dissolve noticeably in alkali solutions.
When solutions containing tetravalent plutonium are exposed to alkalis, a precipitate of plutonium hydroxide Pu(OH)4 xH2O, which has basic properties, precipitates. When solutions of salts containing PuO2+ are exposed to alkalis, amphoteric hydroxide PuO2OH precipitates. It is answered by salts - plutonites, for example, Na2Pu2O6.
Plutonium salts readily hydrolyze upon contact with neutral or alkaline solutions, creating insoluble plutonium hydroxide. Concentrated solutions of plutonium are unstable due to radiolytic decomposition leading to precipitation.
Plutonium-239, the main isotope of plutonium used in nuclear explosive devices, is produced in any nuclear reactor using uranium fuel when a neutron is captured by a uranium-238 nucleus. In Russia, almost all weapons-grade plutonium was produced in special industrial reactors. A characteristic feature of industrial reactors is the relatively low degree of fuel use - the typical burnup value is 400-600 MW-day/t. This is due to the fact that with a greater burnup depth, a significant amount of the plutonium-240 isotope is formed in the fuel. The Pu-240 isotope is a fairly intense emitter of spontaneous neutrons and therefore its presence significantly deteriorates the quality of plutonium as a weapons-grade material.82 According to the classification adopted in the United States, weapons-grade plutonium is considered to be material with a Pu-240 content of less than 5.8%.
The separation of plutonium from spent fuel is carried out using radiochemical methods in special production facilities. Due to the high radioactivity of spent fuel, all reprocessing operations are carried out using remote means in “canyons” with thick concrete walls. The plutonium production process is accompanied by the formation of large volumes of radioactive and toxic waste and requires the creation of complex infrastructure for their processing and disposal.
Industrial reactors were used to produce other nuclear weapons materials, in particular tritium, used in the tritium-deuterium mixture to strengthen the primary components of thermonuclear weapons. The production of tritium for weapons purposes is usually carried out in a nuclear reactor by irradiating the nuclei of the lithium-6.83 isotope with neutrons. The produced tritium is separated from lithium targets during their processing in a vacuum furnace and is purified by chemical methods. In the early years of the development of the nuclear arsenal, reactors also produced polonium-210, which was used in the production of beryllium-polonium neutron sources necessary to initiate a chain reaction when detonating a nuclear charge. (In subsequent years, beryllium-polonium initiators were replaced by external neutron initiation systems based on electrostatic tubes.)84 Polonium was produced by irradiating bismuth targets with neutrons.
Development of reactor technology
For the production of plutonium in the USSR, mainly channel-type reactors were used, using graphite as a neutron moderator and cooled by water pumped through channels with fuel elements. Fuel - blocks of natural metal uranium in an aluminum shell - was loaded into vertical technological channels made in the graphite masonry.
actor zone. To equalize the radial distribution of power and neutron fluxes in the reactor zone of water-graphite industrial reactors, channels with highly enriched uranium fuel were located along its periphery.
In total, three generations of graphite reactors were designed in the USSR. The first generation reactor is reactor A, which was put into operation in June 1948 in Chelyabinsk-40 (later Chelyabinsk-65). The reactor designed by N.A. Dollezhal had a power of 100 MW (later it was increased to 900 MW). The reactor was cooled using a direct-flow scheme - water and coolant were taken from an external source, pumped through the reactor zone and discharged into the environment. The fuel (about 150 tons of uranium) was located in vertical channels of a 1353-ton graphite stack.85
The second generation reactor (for example, the AV-1 reactor, commissioned in 1950) was a vertical graphite stack cylinder with vertical channels for fuel and control rods. Compared to reactor A, AV-1 had more power and was safer. Like reactor A, the second generation reactors were once-through and were used exclusively for the production of weapons-grade plutonium.86
Third-generation reactors built after 1958 were designed as dual-use reactors.88 Representatives of third-generation reactors are the ADE series reactors that are still operating. Each such reactor has a power of about 2000 MW and produces approximately 0.5 tons of weapons-grade plutonium per year. The steam generated during operation is used to produce approximately 350 MW of heat and 150 MW of electricity. Unlike reactors of the first and second generations, reactors of the third generation have a double-circuit cooling system with closed circulation of water through the primary circuit, a heat exchanger, a steam generator, and a turbine for producing electricity.
| Power | up to 2000 MW |
| Power generation | 150-200 MW(e) |
| Heat production | 300-350 Gcal/h |
| Moderator | graphite |
| Coolant | water |
| Number of channels | 2832 |
| Number of fuel elements in the channel | 66-67 |
300-350 t |
75 kg |
| Fuel burn-up | 600-1000 MW-day/t |
| Fuel composition (natural uranium) | metal natural uranium |
| Fuel composition (HEU) | dispersed (8.5% U02 in aluminum matrix) |
| Rod diameter | 35 mm |
| Shell material | Aluminium alloy |
| Shell thickness | gt; 1 mm |
| Spent fuel storage | wet |
| Standard storage time | 6 months |
| Maximum permissible storage time | 18 months |
Table 3-2. Characteristics of the ADE87 reactor
Development of radiochemical technology
The development of the national school of radiochemistry began at the Radium Institute of the USSR Academy of Sciences under the leadership of Academician V. G. Khlopin. In 1946, the country's first acetate-fluoride technology for the industrial separation of plutonium and uranium from irradiated uranium fuel was proposed at RIAN. The technology was tested and tested at the experimental radiochemical installation U-5 at the NII-9 Institute and implemented at the first radiochemical plant (plant B) in Chelyabinsk-40 (later Chelyabinsk-65).
At the initial stage of operation, the chemical processing of plant B was based on the redox process of acetate precipitation of uranyl triacetate. This process took place in two stages - the first involved the purification of plutonium and uranium from fission products and the separation of plutonium from uranium during acetate deposition. At the second stage, refining (additional purification) of plutonium was carried out during its precipitation using lanthanum fluoride.
Radiochemical technology has been constantly improved to improve its safety, the completeness of recovery and purity of plutonium and uranium, and to reduce the consumption of materials and the volume of waste generated. Due to the high chemical aggressiveness of fluorine, the use of lanthanum-fluoride technology was expensive and unsafe. Therefore, when developing the second radiochemical plant (BB plant), built in Chelyabinsk-40 in the late 50s, it was decided to abandon lanthanum-fluoride technology in favor of using a double acetate deposition cycle. Acetate technology, however, was also very expensive, resulted in large volumes of solutions and waste, and required the creation of a number of auxiliary industries. Therefore, in the early 60s, the second cycle of acetate precipitation (at the plutonium refining stage) was replaced by sorption methods based on the selective absorption of plutonium by ion exchange resins. The introduction of sorption technology significantly improved the quality of the plant's products. However, the use of the new technology turned out to be unsafe and, after the explosion of a sorption column that occurred in Chelyabinsk in 1965,90 it was decided to begin work on the introduction of extraction technologies. (The first research on extraction technologies began in the late 40s.) Extraction technologies have become the basis of the currently dominant scheme for reprocessing spent reactor fuel of the Purex type and are used at all radiochemical plants in Russia. Purex is a multi-stage process based on the selective extraction of plutonium and uranium using tributyl phosphate.
Many institutes and organizations took part in the creation of radiochemical technologies. Scientific development and testing of radiochemical technologies were carried out at the Radium Institute, the All-Russian Research Institute of Inorganic Materials, and the All-Russian Research Institute of Chemical Technology.91 The main design developments and production of equipment were carried out by the Sverdlovsk Research Institute of Chemical Engineering. Design solutions were examined or developed by the All-Union Scientific Research and Design Institute of Energy Technologies (VNIPIET) located in Leningrad. The main burden of testing scientific and technical solutions and introducing technologies was borne directly by plutonium production plants.
Plutonium production complex
Industrial production of plutonium was carried out by an integrated complex of three plants: Chelyabinsk-65, Tomsk-7 and Krasnoyarsk-26.
Chelyabinsk-65 (PO Mayak)
The Chelyabinsk-65 plant, currently known as PA Mayak,92 is located in the north of the Chelyabinsk region in the city of Ozersk. Founded in 1948, the plant was the first complex in the USSR for the production of plutonium and plutonium products. Plutonium production was carried out by five uranium-graphite reactors (A, IR-AI, AV-1, AV-2 and AV-3), launched between 1948 and 1955.93 Between 1987 and 1990. all uranium-graphite reactors were shut down. They are currently used for scientific observations and are being prepared for dismantling. The reactor plant at various times included (and includes) other types of reactors used for the production of tritium and other isotopes.
Irradiated fuel from industrial reactors was processed at the radiochemical plant (plant B) that was part of the plant. The radiochemical plant began processing irradiated uranium on December 22, 1948, and the first years of its operation were extremely difficult. Lack of experience and knowledge, imperfect technology and equipment, high corrosion and radioactivity of process solutions led to a high accident rate and overexposure of personnel.94 The plant was reconstructed several times in the early 50s and continued to operate steadily until 1959. From that moment, production volumes began to decline and in the early 60s the plant was shut down. Subsequently, the radiochemical plant RT-1 was built on the site of plant B.
Reprocessing of industrial reactor fuel continued at the BB plant. Construction of the BB plant, designed to replace the first radiochemical production, began in 1954 and was completely completed in September 1959. In 1987, after two of the five reactors producing plutonium were shut down, the BB plant was stopped and the separation of weapons-grade plutonium in Chelyabinsk 65 was discontinued. Between 1987 and 1990 The irradiated fuel from industrial reactors that continued to operate was sent for reprocessing to the radiochemical plant in Tomsk-7.
Plutonium products from radiochemical plants were transferred to chemical and metallurgical plant B. Plant B was built in 1948 to produce plutonium metal and nuclear weapons parts.95 The second stage of the plant made it possible to produce weapons parts from uranium. Currently, the plant continues to work on processing fissile weapons materials and producing ammunition parts. In 1997, the plant, like the chemical and metallurgical production in Tomsk-7, began work on the enrichment of weapons-grade uranium.
In addition to the production of plutonium, the production of tritium and other special isotopes was established in Chelyabinsk-65.96 Since 1951, a 50-MW AI reactor was used for these purposes, using 2% enriched uranium as fuel. Somewhat later, tritium production was organized in heavy water reactors, the first of which was the OK-180.97 reactor (Tritium production at OK-180 began, apparently, only after 1954). On December 27, 1955, the second heavy water reactor was put into operation. OK-190. These reactors were shut down in 1965 and 1986. and they were replaced by two new installations. In 1979, the light water (water-water) reactor "Ruslan" was put into operation, and in 1986-1987 the heavy water reactor "Lyudmila" began operation.98 The "Ruslan" and "Lyudmila" reactors continue to be used for the production of tritium, isotope raw materials for the radioisotope plant (plutonium-238, cobalt-60, carbon-14, iridium-192 and others) and radiation-doped silicon.
The separation of isotopes is carried out by the RT-1 plant complex. The fuel irradiated for the purpose of producing tritium is transferred to the tritium plant, which is part of the Mayak PA, the only production enterprise in the country.
tritium and tritium assemblies for nuclear weapons." Isotope products are supplied to the radioisotope plant (in operation since 1962) for the production of alpha, gamma and beta radio sources, thermal generators based on plutonium-238 and strontium-90 and a wide range of radionuclides.100
The Mayak plant is an important part of the fuel cycle of nuclear power plant reactors and other reactor facilities. A significant part of the infrastructure of the old defense plant B became part of the RT-1 radiochemical plant, which was put into operation in 1976. The first RT-1 line was designed to process highly enriched uranium-aluminum fuel from industrial and ship reactors. In 1978, the plant began reprocessing fuel from VVER-440 reactors. Currently, three RT-1 technological lines are used for processing fuel from VVER-440 and BN-600 reactors, fuel from transport and research reactors, and HEU fuel from industrial reactors. Fuel processing is carried out according to the Purex scheme. The plant also includes facilities for acceptance and intermediate storage of spent fuel, installations for storage, processing and vitrification of radioactive waste and storage facilities for separated uranium and plutonium. The RT-1 plant is capable of annually processing 400 tons of fuel from nuclear power plant reactors and 10 tons of fuel from transport reactors (20-30 reactor zones of transport plants per year).
In addition to fuel reprocessing, the scope of activity of RT-1 includes work on radioactive waste management and experimental work on research
| Reactor | | Type | Purpose | Power MW |
| PA "Mayak" (Chelyabinsk-65) | | | |
|
| A | 1948-1987 | water-graphite, direct flow | plutonium | 100/900 |
| IR-AI | 1951-1987 | water-graphite, direct-flow | plutonium | 50/500 |
| AB-1 | 1950-1989 | water-graphite, direct flow | plutonium | 300/1200 |
| AV-2 | 1951-1990 | water-graphite, direct flow | plutonium | 300/1200 |
| AB-3 | 1952-1990 | water-graphite, direct flow | plutonium, tritium | 300/1200 |
| OK-180 | 1951-1965 | heavy-water | tritium | 100? |
| OK-1EO | 1955-1986 | heavy-water | tritium | 100? |
| Ruslan | 1979-present | water-water | tritium, isotopes | No data |
| Lyudmila | 1986-present | heavy-water | tritium, isotopes | no data |
| Siberian Chemical Plant (Tomsk-7) | | |
||
| I-1 | 1955-1990 | water-graphite, direct flow | plutonium | 600/1200 |
| EI-2 | />1956-1990 | | plutonium | 600/1200 |
| ADE-3 | 1961-1992 | water-graphite, double-circuit | plutonium | 1600/1900 |
| ADE-4 | 1964-present | water-graphite, double-circuit | plutonium | 1600/1900 |
| ADE-5 | 1965-present | water-graphite, double-circuit | plutonium | 1600/1900 |
| Mining and chemical plant (Krasnoyarsk-26) | | |
||
| HELL | 1958-1992 | water-graphite, direct flow | plutonium | 1600/1800 |
| ADE-1 | 1961-1992 | water-graphite, direct flow | plutonium | 1600/1800 |
| ADE-2 | 1964-present | water-graphite, double-circuit | plutonium | 1600/1800 |
Table 3-3. Industrial reactors built in the USSR
and pilot plants for the production of mixed uranium-plutonium oxide fuel (MOX fuel). In Chelyabinsk-65, construction began on a plant for the production of plutonium fuel for fast reactors (Workshop 300).101 Construction of the half-completed plant was frozen in 1989.
Chelyabinsk-65 is one of the main sites for storing fissile materials. The RT-1 plant stores approximately 30 tons of nuclear-grade plutonium.102 The plant also stores significant amounts of weapons-grade fissile material recovered from dismantled nuclear weapons. In the summer of 1994, construction began in Chelyabinsk-65 of a central storage facility for weapons-grade uranium and plutonium released during the dismantling of nuclear weapons. It is assumed that the first stage of the storage facility, capable of receiving 25 thousand containers with weapons-grade materials, will be put into operation in 1999; construction of the second stage will increase the storage capacity to 50 thousand containers. According to the project developed by the St. Petersburg Institute VNIPIET, the repository should provide safe storage of materials for 80-100 years.103
The plant has a wide scientific and technical base to support the work of its main production facilities, which includes a central plant laboratory, an instrument plant, a tool plant, a machine repair shop and a specialized construction department. The city has a branch of the Moscow Engineering Physics Institute, the country's leading university in the field of applied nuclear physics.
Tomsk-7 (Siberian Chemical Plant)
The Siberian Chemical Plant in Tomsk-7104 was founded in 1949 as a complex for the production of weapons-grade fissile materials and parts from them. Plutonium production in Tomsk-7 was carried out by five reactors: I-1, EI-2, ADE-3, ADE-4, and ADE-5. The I-1 reactor, put into operation on November 20, was a direct-flow reactor by design and was used exclusively for plutonium production. In September 1958 and July 1961, the EI-2 and ADE-3 reactors began operating at the plant, respectively. The ADE-4 and ADE-5 reactors were put into operation in 1965 and 1967. With the exception of I-1, all Tomsk-7 reactors had a closed heat removal circuit and were used both for plutonium production and for the production of heat and electricity.
The first three reactors at Tomsk-7 were shut down on August 21, 1990 (I-1), December 31, 1990 (EI-2), and August 14, 1992 (ADE-3). The two reactors remaining in operation have a total capacity of 3800 MW and produce 660-700 MW of heat and 300 MW of electricity. Thermal energy is used to supply heat to Seversk (Tomsk-7) and nearby Tomsk, as well as for the production needs of the Siberian Chemical Combine and the neighboring petrochemical complex.
Currently, the spent fuel from industrial reactors of the Siberian Chemical Combine is reprocessed at the radiochemical plant included in the plant, which was put into operation in 1956. Until 1983, fuel reprocessing was carried out according to the acetate scheme. After this, the plant was transferred to Purex technology.
Until recently, plutonium isolated at the radiochemical plant was supplied to the Tomsk-7 chemical and metallurgical plant for conversion into metal form, alloying, and production of ammunition parts.105 Apparently, freshly produced plutonium was mixed with plutonium from decommissioned warheads to maintain an acceptable concentration level
americium-241 in plutonium.106 Beginning in October 1994, freshly produced plutonium is converted into dioxide and sent for storage.
Another section of the chemical and metallurgical plant is working on processing highly enriched uranium and producing weapons parts from it. In 1994- Operations for converting highly enriched weapons-grade uranium into low-enrichment uranium as part of the Russian-American agreement on the sale of HEU began here. Part of the work carried out in Tomsk-7 includes the conversion of metallic uranium into the oxide form. A significant portion of uranium passes through radiochemical processing to remove chemical contaminants (alloying materials, fission product residues and transuranium elements). Purified uranium oxide powder is packaged in sealed containers and sent to Sverdlovsk-44 and Krasnoyarsk-45 for fluorination and de-enrichment. At the end of 1996, a production site for fluoridation and uranium de-enrichment also began operating in Tomsk-7.107
Krasnoyarsk-26 (Mining and Chemical Combine)
The plant in Krasnoyarsk-26108 was created in February 1950109 for the production of weapons-grade plutonium. A distinctive feature of the reactor and radiochemical plants and associated workshops, laboratories and warehouses of Krasnoyarsk-26 is their location in a multi-level tunnel system inside a mountain range, at a depth of 200-250 m underground.
The Krasnoyarsk-26 reactor plant was put into operation on August 25, 1958, and by 1964 there were three graphite reactors operating at the plant (AD, ADE-1, ADE-2). In 1964, a radiochemical plant began operating in Krasnoyarsk-26. (From 1958 to 1964, spent reactor fuel was reprocessed at the Chelyabinsk-65 and/or Tomsk-7 plants.) Plutonium dioxide, the final product of the plant, was transferred to the chemical and metallurgical plants of Chelyabinsk-65 and/or Tomsk-7 for the production of metallic plutonium and weapon parts. Since October 1994, separated plutonium in oxide form has been stored in the plant's warehouses.
Two once-through reactors of Krasnoyarsk-26 (AD and ADE-1) were shut down in 1992.11 The third reactor has a dual-circuit cooling system and is similar in design to the operating reactors of Tomsk-7. As with Tomsk-7, the reactor produces heat for the local population and cannot be shut down without building replacement capacity.
In 1972, work began on the design of the RT-2 radiochemical plant complex in Krasnoyarsk-26. In accordance with the project, the RT-2 plant must carry out radiochemical processing of fuel from VVER-1000 reactors. Construction of the first stage of the spent reactor fuel storage plant began in 1976 on an above-ground site located 4-5 km north of the underground complex. The storage facility with a capacity of 6000 tons of fuel was put into operation in December 1985 and by 1995 it was 15-20% full. Construction of the second stage of the RT-2 radiochemical plant with a capacity of 1500 tons/year also began in the late 70s. years. However, due to insufficient funding and opposition from the local environmental movement, in 1989 the construction of the plant (30% completed) was frozen. Despite the Russian government's decision to complete construction in February 1995,112 the future of the RT-2 plant remains unclear.
But as the reactor operates, the weapons-grade isotope of plutonium quickly burns up, as a result, a large number of isotopes 240 Pu, 241 Pu and 242 Pu accumulate in the reactor, formed by the successive capture of several neutrons - since the burnup depth is usually determined by economic factors. The lower the burnup depth, the fewer isotopes 240 Pu, 241 Pu and 242 Pu will contain plutonium separated from irradiated nuclear fuel, but the less plutonium is formed in the fuel.
Special production of plutonium for weapons containing almost exclusively 239 Pu is required mainly because isotopes with mass numbers 240 and 242 create a high neutron background, making it difficult to design effective nuclear weapons, in addition, 240 Pu and 241 Pu have a significantly shorter period half-life than 239 Pu, due to which the plutonium parts heat up, and additional heat removal elements have to be introduced into the design of the nuclear weapon. Additionally, the decay products of heavy isotopes spoil the crystal lattice of the metal, which can lead to a change in the shape of plutonium parts, which can lead to the failure of a nuclear explosive device.
In principle, all these difficulties can be overcome, and nuclear explosive devices made from “reactor” plutonium have been successfully tested, however, in ammunition, where compactness, light weight, reliability and durability play an important role, exclusively specially produced weapons-grade plutonium is used. The critical mass of metallic 240 Pu and 242 Pu is very large, 241 Pu is slightly larger than that of 239 Pu.
Production
Disposal
Since the late 1990s, the United States and Russia have been developing agreements to dispose of excess weapons-grade plutonium.
see also
Notes
- Critical mass // European nuclear society (English)
- AGREEMENT between the Government of the Russian Federation and the Government of the United States of America on cooperation in relation to reactors producing plutonium (as amended on March 12, 2003), prepared by Codex JSC
- In Zheleznogorsk, the country's last reactor, which had been producing weapons-grade plutonium for the last half century, was closed. (undefined) . Retrieved November 10, 2014.
- Ivan Fursov. Uranium diet: US nuclear power industry could face fuel shortage (English), RT (September 25, 2013). Retrieved December 27, 2013. "Production of military-grade plutonium has also been stopped in both the US (in 1988) and Russia (in 1994)."
- On international cooperation of Russia in the field of disposal of excess weapons-grade plutonium / Ministry of Foreign Affairs of the Russian Federation, Department for Security and Disarmament Issues of the Ministry of Foreign Affairs of the Russian Federation, 11-03-2001
- Ubeev A.V. Plutonium Disposition Agreement / Nuclear Non-Proliferation: A Concise Encyclopedia, PIR Center
- 2000 Plutonium Management and Disposition Agreement / State.gov, Office of the Spokesman, April 13, 2010 (English)
- A law has been signed to ratify the Agreement between the governments of Russia and the United States on the disposal of plutonium that is no longer necessary for defense purposes // kremlin.ru, June 7, 2011
- kremlin.ru,
| Plutonium | |
|---|---|
| Atomic number | 94 |
| Appearance of a simple substance | |
| Properties of the atom | |
| Atomic mass (molar mass) |
244.0642 a. e.m. (/mol) |
| Atomic radius | 151 pm |
| Ionization energy (first electron) |
491.9(5.10) kJ/mol (eV) |
| Electronic configuration | 5f 6 7s 2 |
| Chemical properties | |
| Covalent radius | n/a pm |
| Ion radius | (+4e) 93 (+3e) 108 pm |
| Electronegativity (according to Pauling) |
1,28 |
| Electrode potential | Pu←Pu 4+ -1.25V Pu←Pu 3+ -2.0V Pu←Pu 2+ -1.2V |
| Oxidation states | 6, 5, 4, 3 |
| Thermodynamic properties of a simple substance | |
| Density | 19.84 /cm³ |
| Molar heat capacity | 32.77 J/(mol) |
| Thermal conductivity | (6.7) W/( ·) |
| Melting temperature | 914 |
| Heat of Melting | 2.8 kJ/mol |
| Boiling temperature | 3505 |
| Heat of vaporization | 343.5 kJ/mol |
| Molar volume | 12.12 cm³/mol |
| Crystal lattice of a simple substance | |
| Lattice structure | monoclinic |
| Lattice parameters | a=6.183 b=4.822 c=10.963 β=101.8 |
| c/a ratio | — |
| Debye temperature | 162 |
Plutonium- a radioactive chemical element of the actinide group, widely used in production nuclear weapons(the so-called “weapons-grade plutonium”), and also (experimentally) as nuclear fuel for nuclear reactors for civil and research purposes. The first artificial element obtained in quantities available for weighing (1942).
The table on the right shows the main properties of α-Pu, the main allotropic modification of plutonium at room temperature and normal pressure.
History of plutonium
The plutonium isotope 238 Pu was first artificially produced on February 23, 1941 by a group of American scientists led by Glenn Seaborg by irradiating nuclei uranium deuterons. It is noteworthy that only after artificial production was plutonium discovered in nature: in negligible quantities, 239 Pu is usually found in uranium ores as a product of the radioactive transformation of uranium.
Finding plutonium in nature
In uranium ores, as a result of the capture of neutrons (for example, neutrons from cosmic radiation) by uranium nuclei, neptunium(239 Np), the β-decay product of which is natural plutonium-239. However, plutonium is formed in such microscopic quantities (0.4-15 parts Pu per 10 12 parts U) that its extraction from uranium ores is out of the question.
origin of name plutonium
In 1930, the astronomical world was excited by wonderful news: a new planet had been discovered, the existence of which had long been spoken of by Percival Lovell, an astronomer, mathematician and author of fantastic essays about life on Mars. Based on many years of movement observations Uranus And Neptune Lovell came to the conclusion that beyond Neptune in the solar system there should be another, ninth planet, forty times farther from the Sun than the Earth.
This planet, the orbital elements of which Lovell calculated back in 1915, was discovered in photographs taken on January 21, 23 and 29, 1930 by astronomer K. Tombaugh at the Flagstaff Observatory ( USA) . The planet was named Pluto. The 94th element, artificially obtained at the end of 1940 from nuclei, was named after this planet, located in the solar system beyond Neptune. atoms uranium a group of American scientists led by G. Seaborg.
Physical properties plutonium
There are 15 isotopes of plutonium - The isotopes with mass numbers from 238 to 242 are produced in the largest quantities:
238 Pu -> (half-life 86 years, alpha decay) -> 234 U,
This isotope is used almost exclusively in RTGs for space purposes, for example, on all vehicles that have flown beyond the orbit of Mars.
239 Pu -> (half-life 24,360 years, alpha decay) -> 235 U,
This isotope is most suitable for the construction of nuclear weapons and fast neutron nuclear reactors.
240 Pu -> (half-life 6580 years, alpha decay) -> 236 U, 241 Pu -> (half-life 14.0 years, beta decay) -> 241 Am, 242 Pu -> (half-life 370,000 years, alpha -decay) -> 238 U
These three isotopes do not have serious industrial significance, but are obtained as by-products when energy is produced in nuclear reactors using uranium, through the sequential capture of several neutrons by uranium-238 nuclei. Isotope 242 is most similar in nuclear properties to uranium-238. Americium-241, produced by the decay of the isotope 241, was used in smoke detectors.
Plutonium is interesting because it undergoes six phase transitions from its solidification temperature to room temperature, more than any other chemical element. With the latter, the density increases abruptly by 11%, as a result, plutonium castings crack. The alpha phase is stable at room temperature, the characteristics of which are given in the table. For application, the delta phase, which has a lower density, and a cubic body-centered lattice is more convenient. Plutonium in the delta phase is very ductile, while the alpha phase is brittle. To stabilize plutonium in the delta phase, doping with trivalent metals is used (gallium was used in the first nuclear charges).
Applications of plutonium
The first plutonium-based nuclear device was detonated on July 16, 1945 at the Alamogordo test site (test codenamed Trinity).
Biological role of plutonium
Plutonium is highly toxic; The maximum permissible concentration for 239 Pu in open water bodies and the air of working rooms is 81.4 and 3.3 * 10 −5 Bq/l, respectively. Most isotopes of plutonium have a high ionization density and a short particle path length, so its toxicity is due not so much to its chemical properties (plutonium is probably no more toxic in this regard than other heavy metals), but rather to the ionizing effect on surrounding body tissues. Plutonium belongs to a group of elements with particularly high radiotoxicity. In the body, plutonium produces large irreversible changes in the skeleton, liver, spleen, kidneys, and causes cancer. The maximum permissible content of plutonium in the body should not exceed tenths of a microgram.
Artworks related to the theme plutonium
- Plutonium was used for the De Lorean DMC-12 machine in the movie Back to the Future as fuel for a flux accumulator to travel to the future or the past.
— The charge of the atomic bomb detonated by terrorists in Denver, USA, in Tom Clancy’s “All the Fears of the World” was made from plutonium.
— Kenzaburo Oe “Notes of a Pinch Runner”
— In 2006, Beacon Pictures released the film Plutonium-239 ( "Pu-239")
Description of plutonium
Plutonium(Plutonium) is a silvery heavy chemical element, a radioactive metal with atomic number 94, which is represented in the periodic table by the symbol Pu.
This electronegative active chemical element belongs to the group of actinides with an atomic mass of 244.0642, and, like neptunium, which received its name in honor of the planet of the same name, this chemical owes its name to the planet Pluto, since the predecessors of the radioactive element in Mendeleev’s periodic table of chemical elements are and neptunium, which were also named after distant cosmic planets in our Galaxy.
Origin of plutonium
Element plutonium was first discovered in 1940 at the University of California by a group of radiologist and scientific researchers G. Seaborg, E. McMillan, Kennedy, A. Walch when bombarding a uranium target from a cyclotron with deuterons - heavy hydrogen nuclei.
In December of the same year, scientists discovered plutonium isotope– Pu-238, the half-life of which is more than 90 years, and it was found that under the influence of complex nuclear chemical reactions the isotope neptunium-238 is initially produced, after which the isotope is already formed plutonium-238.
In early 1941, scientists discovered plutonium 239 with a decay period of 25,000 years. Isotopes of plutonium can have different neutron contents in the nucleus.
A pure compound of the element was only obtained at the end of 1942. Every time radiological scientists discovered a new isotope, they always measured the half-lives of the isotopes.
At the moment, plutonium isotopes, of which there are 15 in total, differ in time duration half-life. It is with this element that great hopes and prospects are associated, but at the same time, serious fears of humanity.
Plutonium has significantly greater activity than, for example, uranium and is one of the most expensive technically important and significant substances of a chemical nature.
For example, the cost of a gram of plutonium is several times more than one gram, , or other equally valuable metals.
The production and extraction of plutonium is considered costly, and the cost of one gram of metal in our time confidently remains at around 4,000 US dollars.
How is plutonium obtained? Plutonium production
The production of the chemical element occurs in nuclear reactors, inside which uranium is split under the influence of complex chemical and technological interrelated processes.
Uranium and plutonium are the main, main components in the production of atomic (nuclear) fuel.
If it is necessary to obtain a large amount of a radioactive element, the method of irradiation of transuranic elements, which can be obtained from spent nuclear fuel and irradiation of uranium, is used. Complex chemical reactions allow the metal to be separated from uranium.
To obtain isotopes, namely plutonium-238 and weapons-grade plutonium-239, which are intermediate decay products, irradiation of neptunium-237 with neutrons is used.
A tiny fraction of plutonium-244, which is the longest-lived isotope due to its long half-life, was discovered in cerium ore, which is likely preserved from the formation of our planet Earth. This radioactive element does not occur naturally in nature.
Basic physical properties and characteristics of plutonium
Plutonium is a fairly heavy radioactive chemical element with a silvery color that only shines when purified. Nuclear mass of metal plutonium equal to 244 a. eat.
Due to its high radioactivity, this element is warm to the touch and can heat up to a temperature that exceeds the boiling temperature of water.
Plutonium, under the influence of oxygen atoms, quickly darkens and becomes covered with an iridescent thin film of initially light yellow, and then a rich or brown hue.
With strong oxidation, the formation of PuO2 powder occurs on the surface of the element. This type of chemical metal is subject to strong oxidation processes and corrosion even at low levels of humidity.
To prevent corrosion and oxidation of the metal surface, a drying facility is necessary. Photo of plutonium can be viewed below.
Plutonium is a tetravalent chemical metal; it dissolves well and quickly in hydroiodic substances and acidic environments, for example, in chloric acid.
Metal salts are quickly neutralized in environments with a neutral reaction, alkaline solutions, while forming insoluble plutonium hydroxide.
The temperature at which plutonium melts is 641 degrees Celsius, the boiling point is 3230 degrees.
Under the influence of high temperatures, unnatural changes in the density of the metal occur. In its form, plutonium has various phases and has six crystal structures.
During the transition between phases, significant changes in the volume of the element occur. The element acquires its most dense form in the sixth alpha phase (the last stage of the transition), while the only things heavier than the metal in this state are neptunium and radium.
When melted, the element undergoes strong compression, so the metal can float on the surface of water and other non-aggressive liquid media.
Despite the fact that this radioactive element belongs to the group of chemical metals, the element is quite volatile, and when it is in a closed space over a short period of time, its concentration in the air increases several times.
The main physical properties of the metal include: low degree, level of thermal conductivity of all existing and known chemical elements, low level of electrical conductivity; in the liquid state, plutonium is one of the most viscous metals.
It is worth noting that any plutonium compounds are toxic, poisonous and pose a serious danger of radiation to the human body, which occurs due to active alpha radiation, therefore all work must be performed with the utmost care and only in special suits with chemical protection.
You can read more about the properties and theories of the origin of a unique metal in the book Obruchev "Plutonia"" Author V.A. Obruchev invites readers to plunge into the amazing and unique world of the fantastic country of Plutonia, which is located deep in the bowels of the Earth.
Applications of plutonium
The industrial chemical element is usually classified into weapons-grade and reactor-grade (“energy-grade”) plutonium.
Thus, for the production of nuclear weapons, of all existing isotopes, it is permissible to use only plutonium 239, which should not contain more than 4.5% plutonium 240, since it is subject to spontaneous fission, which significantly complicates the production of military projectiles.
Plutonium-238 is used for the operation of small-sized radioisotope sources of electrical energy, for example, as an energy source for space technology.
Several decades ago, plutonium was used in medicine in pacemakers (devices for maintaining heart rhythm).
The first atomic bomb created in the world had a plutonium charge. Nuclear plutonium(Pu 239) is in demand as nuclear fuel to ensure the functioning of power reactors. This isotope also serves as a source for producing transplutonium elements in reactors.
If we compare nuclear plutonium with pure metal, the isotope has higher metallic parameters and does not have transition phases, so it is widely used in the process of obtaining fuel elements.
Oxides of the Plutonium 242 isotope are also in demand as a power source for space lethal units, equipment, and fuel rods.
Weapons-grade plutonium is an element that is presented in the form of a compact metal that contains at least 93% of the Pu239 isotope.
This type of radioactive metal is used in the production of various types of nuclear weapons.
Weapons-grade plutonium is produced in specialized industrial nuclear reactors that operate on natural or low-enriched uranium as a result of the capture of neutrons.