Formation of plutonium. Weapons-grade plutonium: application, production, disposal. Name and features

Humanity has always been in search of new sources of energy that can solve many problems. However, they are not always safe. So, in particular, those widely used today, although they are capable of producing simply a colossal amount of such necessary for everyone electrical energy, still carry a mortal danger. But, in addition to peaceful purposes, some countries on our planet have learned to use it for military purposes, especially to create nuclear warheads. This article will discuss the basis of such destructive weapons, the name of which is weapons-grade plutonium.

Brief information

This compact form of the metal contains a minimum of 93.5% of the 239Pu isotope. Weapons-grade plutonium was named so so that it could be distinguished from its “reactor counterpart.” In principle, plutonium is always formed in absolutely any nuclear reactor, which, in turn, operates on low-enriched or natural uranium, containing, for the most part, the 238U isotope.

Application in the military industry

Weapons-grade plutonium 239Pu is the basis of nuclear weapons. At the same time, the use of isotopes with mass numbers 240 and 242 is irrelevant, since they create a very high neutron background, which ultimately complicates the creation and design of highly effective nuclear ammunition. In addition, the plutonium isotopes 240Pu and 241Pu have a significantly shorter half-life compared to 239Pu, so plutonium parts become very hot. It is in this regard that engineers are forced to additionally add elements to remove excess heat into nuclear weapons. By the way, 239Pu in its pure form is warmer than the human body. It is also impossible not to take into account the fact that the products of the decay process of heavy isotopes subject the crystal lattice of the metal to harmful changes, and this quite naturally changes the configuration of plutonium parts, which, in the end, can cause a complete failure of a nuclear explosive device.

By and large, all of the above difficulties can be overcome. And in practice, tests have already been carried out more than once on the basis of “reactor” plutonium. But it should be understood that in nuclear weapons their compactness, low dead weight, durability and reliability are by no means the least important. In this regard, they use exclusively weapons-grade plutonium.

Design features of production reactors

Almost all plutonium in Russia was produced in reactors equipped with a graphite moderator. Each of the reactors is built around cylindrically assembled blocks of graphite.

When assembled, the graphite blocks have special slots between them to ensure continuous circulation of the coolant, which uses nitrogen. The assembled structure also has vertically located channels created for the passage of water cooling and fuel through them. The assembly itself is rigidly supported by a structure with openings under the channels used to discharge already irradiated fuel. Moreover, each of the channels is located in a thin-walled tube cast from a lightweight and extremely strong aluminum alloy. Most of the described channels have 70 fuel rods. Cooling water flows directly around the fuel rods, removing excess heat from them.

Increasing the power of production reactors

Initially, the first Mayak reactor operated with a thermal power of 100 MW. However, the main leader of the Soviet nuclear weapons program made a proposal, which was that the reactor should operate at a power of 170-190 MW in winter, and in summer period time - 140-150 MW. This approach allowed the reactor to produce almost 140 grams of precious plutonium per day.

In 1952, full-fledged research work was carried out in order to increase the production capacity of operating reactors using the following methods:

• By increasing the flow of water used for cooling and flowing through the cores of a nuclear plant.
• By increasing resistance to the phenomenon of corrosion that occurs near the channel liner.
• Reducing the rate of graphite oxidation.
• Increasing temperature inside fuel cells.

Eventually throughput circulating water increased significantly after the gap between the fuel and the channel walls was increased. We also managed to get rid of corrosion. For this, the most suitable aluminum alloys were selected and sodium bichromate began to be actively added, which ultimately increased the softness of the cooling water (pH became about 6.0-6.2). Graphite oxidation has ceased to occur actual problem after nitrogen was used to cool it (previously only air was used).

In the late 1950s, the innovations were fully realized in practice, reducing the highly unnecessary inflation of uranium caused by radiation, significantly reducing the heat hardening of uranium rods, improving cladding resistance, and increasing production quality control.

Production at Mayak

"Chelyabinsk-65" is one of those very secret plants where weapons-grade plutonium was created. The enterprise had several reactors, and we will take a closer look at each of them.

Reactor A

The installation was designed and created under the leadership of the legendary N. A. Dollezhal. It operated with a power of 100 MW. The reactor had 1149 vertically arranged control and fuel channels in a graphite block. The total weight of the structure was about 1050 tons. Almost all channels (except 25) were loaded with uranium, the total mass of which was 120-130 tons. 17 channels were used for control rods, and 8 for experiments. The maximum design heat release of the fuel cell was 3.45 kW. At first, the reactor produced about 100 grams of plutonium per day. The first metallic plutonium was produced on April 16, 1949.

Technological disadvantages

Almost immediately, quite serious problems were identified, which consisted of corrosion of aluminum liners and coating of fuel cells. The uranium rods also swelled and became damaged, causing cooling water to leak directly into the reactor core. After each leak, the reactor had to be stopped for up to 10 hours in order to dry the graphite with air. In January 1949, the channel liners were replaced. After this, the installation was launched on March 26, 1949.

Weapons-grade plutonium, the production of which at reactor A was accompanied by all sorts of difficulties, was produced in the period 1950-1954 with an average unit power of 180 MW. Subsequent operation of the reactor began to be accompanied by more intensive use, which quite naturally led to more frequent shutdowns (up to 165 times a month). As a result, the reactor was shut down in October 1963 and resumed operation only in the spring of 1964. It completely completed its campaign in 1987 and over the entire period of many years of operation it produced 4.6 tons of plutonium.

AB reactors

It was decided to build three AB reactors at the Chelyabinsk-65 enterprise in the fall of 1948. Their production capacity was 200-250 grams of plutonium per day. The chief designer of the project was A. Savin. Each reactor consisted of 1996 channels, 65 of which were control channels. The installations used a technical innovation - each channel was equipped with a special coolant leak detector. This move made it possible to change the liners without stopping the operation of the reactor itself.

The first year of operation of the reactors showed that they produced about 260 grams of plutonium per day. However, already from the second year of operation, the capacity was gradually increased, and already in 1963 its figure was 600 MW. After the second overhaul, the problem with the liners was completely resolved, and the power was already 1200 MW with an annual production of plutonium of 270 kilograms. These indicators remained until the reactors were completely closed.

AI-IR reactor

The Chelyabinsk enterprise used this installation from December 22, 1951 to May 25, 1987. In addition to uranium, the reactor also produced cobalt-60 and polonium-210. Initially, the facility produced tritium, but later began to produce plutonium.

Also, the plant for processing weapons-grade plutonium had in operation reactors operating on heavy water and a single light water reactor (its name was “Ruslan”).

Siberian giant

"Tomsk-7" was the name of the plant, which housed five reactors for the creation of plutonium. Each of the units used graphite to slow down the neutrons and ordinary water to ensure proper cooling.

The I-1 reactor operated with a cooling system in which water passed through once. However, the remaining four installations were equipped with closed primary circuits equipped with heat exchangers. This design made it possible to additionally generate steam, which in turn helped in the production of electricity and heating of various living spaces.

Tomsk-7 also had a reactor called EI-2, which, in turn, had a dual purpose: it produced plutonium and, due to the steam generated, generated 100 MW of electricity, as well as 200 MW of thermal energy.

Important information

According to scientists, the half-life of weapons-grade plutonium is about 24,360 years. Huge number! In this regard, the question becomes especially acute: “How to properly deal with the waste from the production of this element?” Most the best option is considered a building special enterprises for subsequent processing of weapons-grade plutonium. This is explained by the fact that in this case the element can no longer be used for military purposes and will be under human control. This is exactly how weapons-grade plutonium is disposed of in Russia, but the United States of America has taken a different route, thereby violating its international obligations.

Thus, the American government proposes to destroy highly enriched material not by industrial means, but by diluting plutonium and storing it in special containers at a depth of 500 meters. It goes without saying that in this case the material can easily be removed from the ground at any time and used again for military purposes. According to Russian President Vladimir Putin, initially the countries agreed to destroy plutonium not by this method, but to carry out disposal at industrial facilities.

The cost of weapons-grade plutonium deserves special attention. According to experts, tens of tons of this element may well cost several billion US dollars. And some experts have even estimated 500 tons of weapons-grade plutonium at as much as 8 trillion dollars. The amount is really impressive. To make it clearer how much money this is, let’s say that in the last ten years of the 20th century, Russia’s average annual GDP was $400 billion. That is, in fact, the real price of weapons-grade plutonium was equal to twenty annual GDP Russian Federation.

There are 15 known isotopes of plutonium. The most important of these is Pu-239 with a half-life of 24,360 years. The specific gravity of plutonium is 19.84 at a temperature of 25°C. The metal begins to melt at a temperature of 641°C and boils at 3232°C. Its valency is 3, 4, 5 or 6.

The metal has a silvery tint and turns yellow when exposed to oxygen. Plutonium is a chemical reactive metal and easily dissolves in concentrated hydrochloric acid, perchloric acid, and hydroiodic acid. During decay, the metal releases heat energy.

Plutonium is the second transuranic actinide discovered. In nature, this metal can be found in large quantities in uranium ores.

Plutonium is poisonous and requires careful handling. The most fissionable isotope of plutonium has been used as a nuclear weapon. In particular, it was used in a bomb that was dropped on the Japanese city of Nagasaki.

This is a radioactive poison that accumulates in the bone marrow. Several accidents, some fatal, occurred while experimenting on people to study plutonium. It is important that the plutonium does not reach critical mass. In solution, plutonium forms a critical mass faster than in the solid state.

Atomic number 94 means that all plutonium atoms are 94. In air, plutonium oxide forms on the surface of the metal. This oxide is pyrophoric, so smoldering plutonium will flicker like ash.

There are six allotropic forms of plutonium. The seventh form appears at high temperatures.

In an aqueous solution, plutonium changes color. Various shades appear on the surface of the metal as it oxidizes. The oxidation process is unstable and the color of plutonium can change suddenly.

Unlike most substances, plutonium becomes denser when melted. In the molten state, this element is more viscous than other metals.

The metal is used in radioactive isotopes in thermoelectric generators that power spacecraft. In medicine, it is used in the production of electronic cardiac stimulators.

Inhaling plutonium vapor is hazardous to health. In some cases, this can cause lung cancer. Inhaled plutonium has a metallic taste.

Dose-forming radionuclides. Part 5
Date of: 03/08/2011
Subject: Health

The main characteristics of dose-forming radionuclides are given. The main emphasis is on presenting the potential dangers of radionuclides. For safety purposes, the radiotoxic and radiobiological effects of radioisotopes on the body and the environment are considered. The foregoing makes it possible to be more conscious of the radiation hazard of dose-forming radionuclides.

11. Cesium-137

Cesium ( lat. caesium-Cs, chemical element Group I Periodic table Mendeleev, atomic number 55, atomic mass 132.9054. Named from Latin caesius- blue (opened by bright blue spectral lines). Silvery-white metal from the alkali group; fusible, soft like wax; density is 1.904 g/cm 3 and has a specification. weight 1.88 (at 15ºС), melting point - 28.4ºС. It ignites in air and reacts explosively with water. The main mineral is pollucite.

There are 34 known isotopes of cesium with mass numbers 114-148, of which only one (133 Cs) is stable, the rest are radioactive. The isotopic abundance of cesium-133 in nature is approximately 100%. 133 Cs belongs to trace elements. It is found in small quantities in almost all environmental objects. Clarke (average) nuclide content in the earth's crust is 3.7∙10 -4%, in soil - 5∙10 -5%. Cesium is a constant microelement of plant and animal organisms: in living phytomass it is contained in an amount of 6∙10 -6%, in the human body - approximately 4 g. With a uniform distribution of cesium-137 in the human body with a specific activity of 1 Bq/kg, the absorbed dose rate is according to various authors, varies from 2.14 to 3.16 µGy/year.

This silvery-white alkali metal occurs in nature as the stable isotope Cs-133. This is a rare element with an average content in the earth's crust of 3.7∙10 -4%. Ordinary, natural cesium and its compounds not radioactive. Only the artificially produced isotope 137 Cs is radioactive. The long-lived radioactive isotope of cesium 137 Cs is formed by the fission of 235 U and 239 Pu nuclei with a yield of about 7%. During radioactive decay, 137 Cs emits electrons with a maximum energy of 1173 keV and turns into the short-lived γ-emitting nuclide 137m Ba (Table 18). It has the highest chemical activity among alkali metals; it can only be stored in sealed evacuated ampoules.

Cesium metal is used in photocells and photomultipliers in the manufacture of photocathodes and as a getter in fluorescent tubes. Cesium vapor is the working fluid in MHD generators and gas lasers. Cesium compounds are used in optics and night vision devices.

The products of nuclear fission reactions contain significant amounts of decomposed cesium radionuclides, among which 137 Cs is the most dangerous. Radiochemical plants can also be a source of pollution. Cesium-137 is released into the environment mainly as a result of nuclear tests and accidents at nuclear power plants. By the beginning of 1981, the total activity of 137 Cs released into the environment reached 960 PBq. The density of pollution in the Northern and Southern Hemispheres and on average on the globe was 3.42, respectively; 0.86 and 3.14 kBq/m2, and in the territory former USSR on average - 3.4 kBq/m2.

During the accident in the Southern Urals in 1957, a thermal explosion of a radioactive waste storage facility occurred, and radionuclides with a total activity of 74 PBq, including 0.2 PBq of 137 Cs, entered the atmosphere. During a fire at the Windscale RCP in Great Britain in 1957, 12 PBq of radionuclides were released, of which 46 TBq of 137 Cs. Technological discharge of radioactive waste from the Mayak enterprise in the Southern Urals in the river. The current in 1950 was 102 PBq, including 137 Cs 12.4 PBq. Wind removal of radionuclides from the lake's floodplain. Karachay in the Southern Urals in 1967 amounted to 30 TBq. 137 Cs accounted for 0.4 TBq.

The Chernobyl accident in 1986 became a real disaster. nuclear power plant(Chernobyl Nuclear Power Plant): 1850 PBq of radionuclides were released from the destroyed reactor, with radioactive cesium accounting for 270 PBq. The spread of radionuclides has reached planetary proportions. In Ukraine, Belarus and Central region The Russian Federation received more than half of the total amount of radionuclides deposited in the CIS. There are known cases of environmental contamination as a result of careless storage of sources of radioactive cesium for medical and technological purposes.

Cesium-137 is used in gamma flaw detection, measurement technology, and for radiation sterilization food products, medical supplies and drugs, in radiotherapy for the treatment of malignant tumors. Cesium-137 is also used in the production of radioisotope current sources, where it is used in the form of cesium chloride (density 3.9 g/cm 3 , energy release about 1.27 W/cm 3 ).

Cesium-137 is used in limit level sensors for bulk solids in opaque bins. Cesium-137 has certain advantages over radioactive cobalt-60: a longer half-life and less harsh gamma radiation. In this regard, devices based on 137 Cs are more durable, and radiation protection is less cumbersome. However, these advantages become real only in the absence of 137 Cs impurity with a shorter half-life and harsher gamma radiation.

It is widely used as a source of γ-radiation. In medicine, cesium sources, along with radium sources, are used in therapeutic γ-devices and devices for interstitial and cavity gamma therapy. Since 1967, the phenomenon of transition between two hyperfine levels of the ground state of the cesium-137 atom has been used to define one of the basic units of time - seconds.

Radiocesium 137 Cs is an exclusively man-made radionuclide; its presence in the studied environment is associated with nuclear weapons testing or the use of nuclear technologies. 137 Cs is a β-γ-emitting radioisotope of cesium, one of the main components of technogenic radioactive contamination of the biosphere. Formed as a result of nuclear fission reactions. Contained in radioactive fallout, discharges, and waste from radiochemical plants. OA 137 Cs in drinking water is limited to levels of 11 Bq/dm 3 or 8 Bq/dm 3.

A geochemical feature of 137 Cs is its ability to be very firmly retained by natural sorbents. As a result, upon entering the OPS, its activity quickly decreases as it moves away from the source of pollution. Natural waters relatively quickly purify themselves due to the absorption of 137 Cs by suspensions and bottom sediments.

Cesium can accumulate in significant quantities in agricultural plants, and in particular in seeds. It comes most intensively from the aquatic environment and moves through the plant at high speed. The introduction of potassium fertilizers and liming into the soil significantly reduces the absorption of cesium by plants, and the more strongly, the higher the proportion of potassium.

The accumulation coefficient is especially high in freshwater algae and Arctic land plants (especially lichens), and in the animal world - in reindeer through the reindeer moss on which they feed. Cesium-137 mainly penetrates into living organisms through the respiratory and digestive organs. This nuclide comes mainly from food in an amount of 10 mcg/day. It is excreted from the body mainly through urine (on average 9 mcg/day). Cesium is a permanent chemical microcomponent of the body of plants and animals. The main reservoir of cesium in the body of mammals is the muscles, heart, and liver. About 80% of cesium that enters the body accumulates in the muscles, 8% in the skeleton, and the remaining 12% is distributed evenly throughout other tissues.

Cesium-137 is excreted mainly through the kidneys and intestines. The biological half-life of accumulated cesium-137 for humans is generally considered to be 70 days (according to the International Commission on Radiological Protection). During excretion, significant amounts of cesium are reabsorbed into the blood in the lower intestine. An effective means for reducing the absorption of cesium in the intestine is the sorbent ferrocyanide, which binds the nuclide into an indigestible form. In addition, to accelerate the elimination of the nuclide, natural excretory processes are stimulated and various complexing agents are used.

The development of radiation injuries in humans can be expected when absorbing a dose of approximately 2 Gy or more. Doses of 148, 170 and 740 MBq correspond to mild, moderate and severe degrees of damage, but a radiation reaction is observed even with units of MBq.

137 Cs belongs to the group of radioactive substances that are evenly distributed throughout organs and tissues; for this reason, it is classified as a medium-hazardous nuclide in terms of radiotoxicity. It has a good ability to enter the body along with potassium through the food chain.

The main source of cesium entering the human body is food products of animal origin contaminated with the nuclide. The content of radioactive cesium in a liter of cow's milk reaches 0.8-1.1% of the daily intake of the nuclide, goat and sheep - 10-20%. However, it mainly accumulates in the muscle tissue of animals: 1 kg of meat from cows, sheep, pigs and chickens contains 4.8, 20 and 26% (respectively) of the daily intake of cesium. In protein chicken eggs falls less - 1.8-2.1%. Cesium accumulates in even larger quantities in the muscle tissues of hydrobionts: the activity of 1 kg of freshwater fish can exceed the activity of 1 liter of water by more than 1000 times (in marine fish it is lower).

The main source of cesium for the Russian population is dairy and grain products (after the Chernobyl accident - dairy and meat products); in Europe and the USA, cesium comes mainly from dairy and meat products and less from grains and vegetables. The constant internal irradiation created in this way causes significantly more harm than external irradiation with this isotope.

Published methods for measuring the activity of 137 Cs by its β-emission involve radiochemical sample preparation and isolation of cesium with a high degree of purity to eliminate the interfering influence of other β-emitters. Modern methods determinations of 137 Cs are based, as a rule, on the detection of gamma radiation with an energy of 661.6 keV. They are divided into instrumental ones, the lower limit of determination (LDL) of which is 1-10 Bq/kg (or Bq/dm3), and methods with preliminary chemical enrichment (LDL up to 10 -2 Bq/kg). To concentrate 137 Cs from dilute solutions, its co-precipitation with ferrocyanides of nickel, copper, zinc, iron, cobalt, calcium, magnesium or sorbent collectors based on them is most often used.

Plutonium (plutonium) Pu is an artificial radioactive chemical element of group III of Mendeleev’s Periodic Table of Elements, atomic number 94, a transuranium element, belongs to the actinides. The first nuclide 238 Pu was discovered in 1940 by G. Th. Seaborg, E. M. McMillan, J. E. Kennedy and A. C. Val ( A.Ch.Wahl). In the spring of 1941, Seaborg and his co-workers discovered and for the first time isolated a quarter microgram of 239 Pu after the decay of 239 Np, formed by irradiation of 238 U with heavy hydrogen nuclei (deuterons). Following uranium and neptunium, the new element received its name in honor of the planet Pluto discovered in 1930. Since August 24, 2006, by decision of the International Astronomical Union, Pluto is no longer a planet solar system. In Greek mythology, Pluto (aka Hades) is the god of the kingdom of the dead.

Plutonium Pu is the most dangerous heavy metal. It has 15 radioactive isotopes with mass numbers from 232 to 246, mainly α-emitters. On Earth there are only traces of this element and only in uranium ores. The T½ values ​​of all plutonium isotopes are much less than the age of the Earth, and therefore all primary plutonium (which existed on our planet during its formation) completely decayed. However, minute amounts of 239 Pu are constantly produced by the beta decay of 239 Np, which in turn arises from the nuclear reaction of uranium with neutrons (for example, cosmic ray neutrons).

Therefore, traces of plutonium were found in uranium ores in such microscopic quantities (0.4-15 parts of Pu per 10 12 parts of U) that its extraction from uranium ores is out of the question. About 5000 kg of it was released into the atmosphere as a result of nuclear tests. By some estimates, soil in the United States contains an average of 2 milliCuries (28 mg) of plutonium per km 2 of fallout. It is a typical product of human creation; it is produced in nuclear reactors from uranium-238, which is successively converted into uranium-239, neptunium-239 and plutonium-239.

The even isotopes plutonium-238, -240, -242 are not fissile materials, but can fission under the influence of high-energy neutrons (they are fissile). They are not capable of maintaining a chain reaction (with the exception of plutonium-240). The isotopes 232 Pu - 246 Pu were obtained; 247 Pu and 255 Pu were also found among the products of thermonuclear bomb explosions. The most stable is the inaccessible 244 Pu (α-decay and spontaneous fission, T 1/2= 8.2·10 7 years, atomic mass 244.0642). When free, it is a brittle silvery-white metal. Traces of the isotopes 247 Pu and 255 Pu were found in dust collected after explosions of thermonuclear bombs.

Enormous efforts and resources were devoted to nuclear research and the creation of the nuclear industry in the USA, as later in the USSR. IN short term The nuclear and physicochemical properties of plutonium were studied (Table 19). The first plutonium-based nuclear device was detonated on July 16, 1945 at the Alamogordo test site (test codenamed Trinity). In the USSR, the first experiments to obtain 239 Pu began in 1943-1944. under the leadership of academicians I.V. Kurchatov and V.G. Khlopin. For the first time in the USSR, plutonium was isolated from neutron-irradiated uranium. In 1945 and 1949, the first radiochemical separation plant began operating in the USSR.

Note. All plutonium isotopes are weak gamma emitters. Plutonium-241 turns into americium-241 (a powerful gamma emitter)

Only two isotopes of plutonium have practical use for industrial and military purposes. Plutonium-238, produced in nuclear reactors from neptunium-237, is used to produce compact thermoelectric generators. Six million electron volts are released from the decay of one atomic nucleus of plutonium-238. In a chemical reaction, the same energy is released when several million atoms are oxidized. An electricity source containing one kilogram of plutonium-238 develops a thermal power of 560 MW. The maximum power of a chemical current source of the same mass is 5 W.

There are many emitters with similar energy characteristics, but one feature of plutonium-238 makes this isotope indispensable. Alpha decay is usually accompanied by strong gamma radiation, penetrating through large layers of matter. 238 Pu is an exception. The energy of gamma rays accompanying the decay of its nuclei is low, and it is not difficult to protect against it: the radiation is absorbed by a thin-walled container. The probability of spontaneous fission of nuclei of this isotope is also low. Therefore, it has found application not only in current sources, but also in medicine. Batteries containing plutonium-238 serve as a source of energy in special cardiac stimulators, the service life of which reaches 5 years or more.
The plutonium-beryllium alloy works as a laboratory neutron source. The Pu-238 isotope is found in a number of nuclear thermoelectric power generators on board space research vehicles. Due to its long lifetime and high thermal power, this isotope is used almost exclusively in RTGs for space purposes, for example, on all vehicles that have flown beyond the orbit of Mars.

Of all the isotopes, the most interesting is Pu-239, its half-life is 24110 years. As a fissile material, 239 Pu is widely used as nuclear fuel in nuclear reactors (the energy released during the fission of 1 G 239 Pu, equivalent to the heat released by the combustion of 4000 kg of coal), in the production of nuclear weapons (so-called “weapon-grade plutonium”) and in atomic and thermonuclear bombs, as well as for fast neutron nuclear reactors and nuclear reactors for civil and research purposes . As a source of α-radiation, plutonium, along with 210 Po, was found wide application in industry, in particular, in devices for eliminating electrostatic charges. This isotope is also used in instrumentation and control equipment.

Plutonium has many specific properties. It has the lowest thermal conductivity of all metals, the lowest electrical conductivity, with the exception of manganese. In its liquid phase it is the most viscous metal. Melting point -641°C; boiling point -3232°C; density - 19.84 (in alpha phase). It is an extremely electronegative, chemically reactive element, much more so than uranium. It quickly fades to form an iridescent film (like an iridescent oil film), initially light yellow, eventually turning dark purple. If the oxidation is quite severe, an olive green oxide powder (PuO 2) appears on its surface. Plutonium readily oxidizes and quickly corrodes even in the presence of slight moisture.

When temperature changes, plutonium undergoes the most severe and unnatural changes in density. Plutonium has six different phases (crystal structures) in solid form, more than any other element.

Compounds of plutonium with oxygen, carbon and fluorine are used in the nuclear industry (directly or as intermediate materials). Plutonium metal does not dissolve in nitric acid, but plutonium dioxide dissolves in hot concentrated nitric acid. However, in a solid mixture with uranium dioxide (for example, in spent fuel from nuclear reactors), the solubility of plutonium dioxide in nitric acid increases because the uranium dioxide dissolves in it. This feature is used in the reprocessing of nuclear fuel (Table 20).

The most important compounds of plutonium: PuF 6 (a low-boiling liquid; thermally much less stable than UF 6), solid oxide PuO 2, carbide PuC and nitride PuN, which in mixtures with corresponding uranium compounds can be used as nuclear fuel.

The most widely used radioisotope devices are ionization fire alarms or radioisotope smoke indicators. When mechanically processed, plutonium easily forms aerosols.

In nature, it is formed during the β-decay of Np-239, which, in turn, occurs during the nuclear reaction of uranium-238 with neutrons (for example, neutrons from cosmic radiation). Industrial production of Pu-239 is also based on this reaction and occurs in nuclear reactors. Plutonium-239 is the first to be formed in a nuclear reactor when uranium-238 is irradiated; the longer this process takes, the more heavier isotopes of plutonium are produced. Plutonium-239 must be chemically separated from the fission products and the remaining uranium in the spent fuel. This process is called reprocessing. Since all isotopes have the same number of protons and a different number of neutrons, their chemical properties (chemical properties depend on the number of protons in the nucleus) are identical, so it is very difficult to separate isotopes using chemical methods.

The subsequent separation of Pu-239 from uranium, neptunium and highly radioactive fission products is carried out at radiochemical plants using radiochemical methods (co-precipitation, extraction, ion exchanges, etc.). Metallic plutonium is usually obtained by reducing PuF 3, PuF 4 or PuO 2 with barium, calcium or lithium vapor.

Then its ability to fission under the influence of neutrons is used in atomic reactors, and its ability to undergo a self-sustaining chain fission reaction in the presence of a critical mass (7 kg) is used in atomic and thermonuclear bombs, where it is the main component. The critical mass of its α-modification is 5.6 kg (a ball with a diameter of 4.1 cm). 238 Pu is used in “nuclear” electric batteries that have a long service life. Plutonium isotopes serve as raw materials for the synthesis of transplutonium elements (Am, etc.).

By irradiating Pu-239 with neutrons, it is possible to obtain a mixture of isotopes, from which the Pu-241 isotope, like Pu-239, is fissile and could be used to produce energy. However, its half-life is 14.4 years, which does not allow it to be stored for a long time; moreover, when decaying, it forms non-fissile Am-241 (α-, γ-radioactive) with a half-life of 432.8 years. It turns out that approximately every 14 years the amount of Am-241 in the environment doubles. It is difficult to detect it, like other transuranium elements, with conventional γ-spectrometric equipment and very specific and expensive detection methods are required. The Pu-242 isotope is most similar in nuclear properties to uranium-238; Am-241, obtained from the decay of the Pu-241 isotope, was used in smoke detectors.

Americium-241, as well as other transuranium elements (neptunium, californium and others), is an environmentally hazardous radionuclide, being predominantly an α-emitting element that causes internal irradiation of the body.

There is more than enough plutonium accumulated on Earth. Its production is absolutely not required for both defense and energy. However, of the 13 reactors that existed in the USSR that produced weapons-grade plutonium, 3 continue to operate: two of them in the city of Seversk. The last such reactor in the United States was shut down in 1988.

The quality of plutonium is determined by the percentage of isotopes in it (except plutonium-239) (Table 21).

As of September 1998, plutonium prices set by the isotope division of Oak Ridge National Laboratory (ORNL) were as follows: $8.25/mg for plutonium-238 (97% purity); $4.65/mg for plutonium-239 (>99.99%); $5.45/mg for plutonium-240 (>95%); $14.70/mg for plutonium-241 (>93%) and $19.75/mg for plutonium-242.

This classification of plutonium by quality, developed by the US Department of Energy, is quite arbitrary. For example, a nuclear bomb can also be made from fuel and reactor plutonium, which are less suitable for military purposes than weapons-grade plutonium. Plutonium of any quality can be used to create radiological weapons (when radioactive substances are dispersed without causing a nuclear explosion).

Just 60 years ago, green plants and animals did not contain plutonium; now up to 10 tons of it are dispersed in the atmosphere. About 650 tons produced nuclear energy and over 300 tons in military production. A significant portion of all plutonium production is located in Russia.

Once in the biosphere, plutonium migrates along the earth's surface, becoming involved in biochemical cycles. Plutonium is concentrated by marine organisms: its accumulation coefficient (i.e. the ratio of concentrations in the body and in external environment) for algae is 1000-9000, for plankton (mixed) - about 2300, for mollusks - up to 380, for starfish - about 1000, 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. Since the 70s In the 20th century, the share of plutonium in radioactive contamination of the biosphere increases (irradiation of marine invertebrates due to plutonium becomes greater than due to 90 Sr and 137 Cs). The maximum permissible concentration for 239 Pu in open water bodies and the air of working rooms is 81.4 and 3.3ּ 10 -5 Bq/l, respectively.

The behavior of plutonium in the air determines the conditions for its safe storage and handling during production (Table 22). The oxidation of plutonium poses a risk to human health because plutonium dioxide, being a stable compound, is easily inhaled into the lungs. Its specific activity is 200 thousand times higher than that of uranium; moreover, the liberation of the body from the plutonium that has entered it practically does not occur throughout a person’s entire life.

The biological half-life of plutonium is 80-100 years when it is in bone tissue, its concentration there is almost constant. The half-life from the liver is 40 years. Chelated additives can speed up the elimination of plutonium.

Plutonium is called “nuclear poison”; its permissible content in the human body is estimated in nanograms. The International Commission on Radiological Protection (ICRP) has set the annual absorption limit at 280 nanograms. This means that for occupational exposure, the concentration of plutonium in the air should not exceed 7 picoCurie/m 3 . The maximum permissible concentration of Pu-239 (for professional staff) 40 nanoCuries (0.56 micrograms) and 16 nanoCuries (0.23 micrograms) for lung tissue.

Ingestion of 500 mg of plutonium as finely divided or dissolved material can result in death from acute exposure to the digestive system within days or weeks. Inhalation of 100 mg of plutonium in the form of particles of an optimal size for retention in the lungs of 1-3 microns leads to death from pulmonary edema in 1-10 days. Inhalation of a dose of 20 mg leads to death from fibrosis in about a month. For doses much lower than these values, a chronic carcinogenic effect appears.
Throughout life, an adult's risk of developing lung cancer depends on the amount of plutonium taken into the body. Ingestion of 1 microgram of plutonium poses a 1% risk of developing cancer (normal risk of cancer is 20%). Accordingly, 10 micrograms increases the risk of cancer from 20% to 30%. Exposure to 100 micrograms or more guarantees the development of lung cancer (usually within a few decades), although evidence of lung damage may take several months to appear. If it penetrates the circulatory system, it will most likely begin to concentrate in tissues containing iron: bone marrow, liver, spleen. If 1.4 micrograms are placed in the bones of an adult, the resulting immune system will deteriorate and cancer may develop within a few years.

The fact is that Pu-239 is an α-emitter, and each of its α-particles in biological tissue forms 150 thousand ion pairs along its short path, damaging cells and producing various chemical transformations. 239 Pu belongs to substances with a mixed type of distribution, since it accumulates not only in the bone skeleton, but also in the liver. It is retained very well in the bones and is practically not removed from the body due to the slowness of metabolic processes in bone tissue. For this reason, this nuclide belongs to the category of the most toxic.

Bibliography

Description of plutonium

Plutonium(Plutonium) is a silvery heavy chemical element, a radioactive metal with atomic number 94, which is designated 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 necessary, obtain large quantity radioactive element, the method of irradiation of transuranium 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 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.

To the main physical properties metal can be attributed to: 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) 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, therefore 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 production various types 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.

Plutonium (plutonium) Pu, - artificially obtained radioactive chemical element, Z=94, atomic mass 244.0642; belongs to actinides. Currently, 19 isotopes of plutonium are known. The lightest of them is 228 Ri (71/2=1.1 s), the heaviest is ^Pu (7i/ 2 =2.27 days), 8 nuclear isomers. The most stable isotope is 2A- 236, 238, 239, 240, 242 and 244: 21013, 6.29-11,2.33-10,8.51109, 3.7-12,1.48-8 and 6.66-uz Bq/g, respectively. The average energy of a-radiation of isotopes with A = 236, 238, 239, 240, 242 and 244 is 5.8, 5.5, 5.1, 5.2, 4.9 and 4.6 MeV, respectively. Light isotopes of plutonium (2 3 2 Pu, 2 34 Pu, 235 Pu, 2 3 7 Pu) undergo electron capture. 2 4 "Pi - p-emitter (Ep = 0.0052 MeV). Practically the most important is 2 39Ru (7|/ 2 =2.44-104 years, a-decay, spontaneous fission (z, my %)) is divided under the influence of slow neutrons and is used in nuclear reactors as fuel, and in atomic bombs as a charge substance.

Plutonium-236 (7i/ 2 =2.85i years), a-emitter: 5.72 MeV (30.56%) and 5.77 MeV (69.26%), daughter nuclide 2 3 2 U, specific activity 540 Ci/ G. Probability of spontaneous fission kg 6. The spontaneous fission rate of 5.8-7 divisions per 1 g/hour corresponds to a half-life for this process of 3.5-109 years.

Can be obtained by reactions:

This isotope is also formed during the decay of the a-emitter 2 4оСш (7i/ 2 =27 days) and the p-emitter 23 6m Np (7i/ 2 =22 h). 2 h 6 Ri decays in the following directions: a-decay, probability 100% and spontaneous fission (probability

Plutopium-237 (7!/ 2 =45> 2 days), daughter product 2 37Np. Can be obtained by bombarding natural uranium with helium ions with an energy of 40 MeV through nuclear reactions:

It is also formed in small quantities when uranium is irradiated with reactor neutrons. The main type of decay is electron capture

(99%, characteristic X-ray emission, daughter product ^Np), but there is a-decay to form 2 zi and weak y-emission, half-life 45.2 days. 2 z7Rts is used in systems for monitoring the chemical yield of plutonium during its isolation from samples of environmental components, as well as for studying the metabolism of plutonium in the human body

Plutonium-238, 7*1/2=87.74 years, a-emitter (energies 5.495(76%), 5.453(24%) and 5.351(0.15%) MeV, weak y-emitter (energies from 0.044 to 0.149 MeV). The activity of 1 g of this nuclide is ~633.7 GBq (specific activity 17 Ci/g); every second in the same amount of substance -1200 acts of spontaneous fission occur. The rate of spontaneous fission is 5.1-6 fissions per 1 g /hour correspond to a half-life for this process of 3.8-10 10 years. In this case, a very high thermal power develops: 567 W / kg. G D el = 3.8-10 10 years. Cross section of thermal neutron capture a = 500 barn , fission cross section under the influence of thermal neutrons is 18 barn. It has a very high specific α-radioactivity (283 times stronger than ^Pu), which makes it much more serious source of neutrons from reactions (a, n).

• 2 h 8Pu is formed as a result of the following decays:
  • (3 -decay of nuclide 2 3 8 Np:

2 h 8 Ru is formed in any nuclear reactor operating on natural or low-enriched uranium, containing mainly the 2 h 8 u isotope. In this case, the following nuclear reactions occur:

It is also formed when uranium is bombarded with helium ions with an energy of 40 MeV:

decay occurs in the following directions: a-decay in 2 34U (probability 10%, decay energy 5.593 MeV):

the energy of the emitted alpha particles is 5.450 Mei (in 2.9% of cases; and 5.499 Mei (in 70.91% of cases). The probability of spontaneous fission is 1.9-7%.

During the a-decay of 2 3 8 Pu, 5.5 MeV of energy is released. In a source of electricity containing one kilogram of 2-3 8 Ri, a thermal power of ~50 watts develops. The maximum power of a chemical current source of the same mass is 5 watts. There are many emitters with similar energy characteristics, but one feature of 2 3Ri makes this isotope irreplaceable. Usually a decay is accompanied by strong y emission. 2 z 8 Ri is an exception. The energy of y-quanta accompanying the decay of its nuclei is low. The probability of spontaneous fission of nuclei of this isotope is also low. 288 Ri is used for the manufacture of nuclear electric batteries and neutron sources, as power sources for pacemakers, for generating thermal energy in spacecraft, as part of radioisotope smoke detectors, etc.

Plutonium-239, 71/2=2.44th 4 years, a-decay 00%, total decay energy 5.867 MeV, emits a-particles with energies of 5.15 (69%), 5.453 (24%) and 5.351(0, 15%) and weak y-radiation, thermal neutron capture cross section st = 271 barn. Specific activity 2.33109 Bq/g. The rate of spontaneous division of 36 divisions/g/hour corresponds to 7” divisions = 5.5-10*5 years. 1 kg 2 39Ri is equivalent to 2.2-107 kilowatt-hours of thermal energy. The explosion of 1 kg of plutonium is equal to the explosion of 20,000 tons of TNT. The only isotope of plutonium used in atomic weapons. 2 39Pu is part of the 2P+3 family. Its decay product is 2 35U. This isotope is fissioned by thermal neutrons and is used in nuclear reactors as a fuel. 2 39Ri is obtained in jalopy paktops according to pakpiya:

Reaction cross section -455 barn. *39Pu is also formed when

bombardment of uranium with deuterons with energies above 8 MeV by nuclear reactions:

as well as when uranium is bombarded with helium ions with an energy of 40 MeV
spontaneous division, probability 1.36-10*7%.

Chemical separation of plutonium from uranium is a relatively simpler task than separation of uranium isotopes. As a result, the cost of plutonium is several times lower than the cost of 2 zzi. When a 2 39Pu nucleus is split by neutrons into two fragments of approximately equal mass, about 200 MeV of energy is released. Capable of maintaining a fission chain reaction. The relatively short half-life of 2 39Pu (compared to ^u) implies a significant release of energy during radioactive decay. 2 39Rc produces 1.92 W/kg. A well-insulated block of plutonium heats up to a temperature of over 100° in two hours and soon to the a-p transition point, which poses a problem for weapons design due to volume changes during phase transitions of plutonium. Specific activity 2 39Pu 2.28-12 Bq/g. 2 39Pu is easily fissile by thermal neutrons. The fissile isotope 239 Pu upon complete decay provides thermal energy equivalent to 25,000,000 kWh/kg. 2 39Pi has a fission cross section for slow neutrons of 748 barn, and a radiation capture cross section of 315 barn. 2 39Pu has larger scattering and absorption cross sections than uranium and a larger number of neutrons during fission (3.03 neutrons per fission event compared to 2.47 for 2 zzi), and, accordingly, a lower critical mass. Pure 2 39Pu has average value neutron emission from spontaneous fission -30 neutrons/s-kg (-10 fissions/s).-

Plutonium-240, 71/2=6564 l, a-decay, specific activity 8.51-109 Bq/g. Spontaneous fission rate 1.6-6 divisions/g/hour, Ti/2=i.2-io u l. 24°Pu has a three times smaller effective neutron capture cross section than 239 Pu and in most cases turns into 2 4*Pu.

24op and is formed during the decay of certain radionuclides:

Decay energy 5.255 MeV, a-particles with energies 5.168 (72.8%), 5.123 (27.10%) MeV;

Spontaneous division, probability 5.7-6.

In uranium fuel, the content of ^Pu increases during reactor operation. In the spent fuel of a nuclear reactor there is 70% *39Pu and 26% 2 4°Pu, which makes it difficult to manufacture atomic weapons, so weapons-grade plutonium is obtained in reactors specially designed for this by processing uranium after several tens of days of irradiation. *4°Pu is the main isotope that pollutes weapons-grade 2 39Pu. The level of its content is important because of the intensity of spontaneous fission - 415,000 fission/s-kg, 1000 neutrons/s-kg are emitted, since each fission produces 2.26 neutrons - 30,000 times more than an equal mass of 2 39Ri. The presence of just 1% of this isotope produces so many neutrons that the cannon charge circuit is inoperable - early initiation of the explosion will begin and the charge will be atomized before the bulk of the explosive explodes. The cannon scheme is possible only with a content of *39Pu, which is practically impossible to achieve. Therefore, plutonium bombs are assembled using an implosion scheme, which allows the use of plutonium that is quite heavily contaminated with the isotope IgPu. Weapons-grade plutonium contains 2 4°Pu

Due to the higher specific activity (1/4 of 2 39Pi), the thermal output is higher, 7.1 W/kg, which exacerbates the problem of overheating. The specific activity of ^Pu is 8.4109 Bq/g. The content of IgPu in weapons-grade plutonium (0.7%) and in reactor-grade plutonium (>19%). The presence of 24 °Pu in fuel for thermal reactors is undesirable, but this isotope serves as fuel in fast reactors.

Plutonium-241, G,/2=14 l, daughter product 241 Am, p- (99%, ?рmax=0.014 MeV), a (1%, two lines: 4.893 (75%) and 4.848 (25%) MeV ) and y-emitter, specific activity of ^Pu 3.92-12 Ci/g. It is obtained by strong irradiation of plutonium with neutrons, as well as in a cyclotron by the reaction 2 3 8 U(a,n) 241 Pu. This isotope is fissile by neutrons of any energy (the neutron absorption cross section of ^'Pu is 1/3 greater than that of ^Phi, the fission cross section of thermal neutrons is about 100 barn, the probability of fission upon absorption of a neutron is 73%), has a low neutron background and moderate thermal power and therefore does not directly affect the ease of use of plutonium. It decays into 241 Am, which fissions very poorly and creates a lot of heat: 10 6 W/kg. ^‘Pu has a large fission cross section for reactor neutrons (poo barn), which allows it to be used as fuel. If a weapon initially contains 241 Ri, then after a few years its reactivity decreases, and this should be taken into account to prevent a decrease in charge power and an increase in self-heating. 24 'Ru itself does not heat up much (only 3.4 W/kg) despite its very short half-life due to very weak P radiation. When a neutron is absorbed by a 24 * Pu nucleus, if it does not fission, it turns into 242 Pu. 241 Pu is the main source of ^‘As.

Plutonium-242 (^/2=373300 years),

Plutonium-243 No/2=4-956 hours), p"- (energy 0.56 MeV) and y-emitter (several lines in the range 0.09-0.16 MeV) Cross section of the reaction 242 Pu(n ,y) 243 Pu on slow neutrons 00 barn. Formed during the p-decay of "^sPu 24 zAsh, can be obtained by irradiation with neutrons 2 4 2 Pu. Due to its short half-life, it is present in irradiated reactor fuel in small quantities.

Plutonium-244 (Ti/ 2 =8.o*io 7 years), a-emitter, E a = 4.6 MeV, capable of spontaneous fission, specific activity 6.66-105 Bq/g, thermal neutron capture cross section 0=19 barn. It is not only the longest-lived isotope of plutonium, but also the longest-lived of all isotopes of transuranium elements. Specific activity 2

Even heavier isotopes of plutonium are subject to p-decay, and their lifetimes range from several days to several tenths of a second. In thermonuclear explosions, all isotopes of plutonium are formed, up to 2 57Pu. But their lifetime is tenths of a second, and many short-lived isotopes of plutonium have not yet been studied.

Plutonium is a very heavy, silvery-white metal that shines like nickel when freshly refined. Atomic mass 244.0642 amu. (g/mol), atomic radius 151 pm, ionization energy (first electron) 491.9(5.10) kJ/mol (eV), electronic configuration 5f 6 7s 2. Ion radius: (+4e) 93, (+3e) 08 pm, electronegativity (Pauling) 1.28, T P l = 639.5°, G K ip = 3235°, plutonium density 19.84 (a-phase ), the heat of evaporation of plutonium is 80.46 kcal/mol. The vapor pressure of plutonium is significantly higher than the vapor pressure of uranium (at 1540 0 300 times). Plutonium can be distilled from molten uranium. Six allotropic modifications of metallic plutonium are known. At temperatures

IN laboratory conditions Metallic plutonium can be obtained by reduction reactions of plutonium halides with lithium, calcium, barium or magnesium at 1200°:

Metallic plutonium is also obtained by reducing plutonium trifluoride in the vapor phase at 1300 0 using calcium silicide according to the reaction

or thermal decomposition of plutonium halides in a vacuum.

Plutonium has many specific properties. It has the lowest thermal conductivity of all metals, the lowest electrical conductivity, with the exception of manganese. In its liquid phase it is the most viscous metal. When temperature changes, plutonium undergoes the most severe and unnatural changes in density.

Plutonium has six different phases (crystal structures) in solid form (Table 3), more than any other element. Some transitions between phases are accompanied by dramatic changes in volume. In two of these phases - delta and delta prime - plutonium has the unique property of contracting as the temperature increases, and in the others it has an extremely high temperature coefficient of expansion. When melted, the plutonium contracts, allowing the unmelted plutonium to float. In its densest form, the a-phase, plutonium is the sixth densest element (only osmium, iridium, platinum, rhenium and neptunium are heavier). In the a-phase, pure plutonium is brittle. A large number of alloys and intermetallic compounds of plutonium with Al, Be, Co, Fe, Mg, Ni, Ag are known. The compound PuBe, 3 is a source of neutrons with an intensity of 6.7 * 107 neutrons/skg.

Rice. 5.

Due to its radioactivity, plutonium is warm to the touch. A large piece of plutonium in a thermally insulated shell is heated to a temperature exceeding the boiling point of water. Finely ground plutonium is pyromorphic and spontaneously ignites at 300 0. It reacts with halogens and hydrogen halides, forming halides, with hydrogen - hydrides, with carbon - carbide, with nitrogen it reacts at 250 0 to form nitride, and when exposed to ammonia it also forms nitrides. Reduces CO2 to CO or C, and carbide is formed. Interacts with gaseous sulfur compounds. Plutonium is easily soluble in hydrochloric, 85% phosphoric, hydroiodic, perchloric and concentrated chloroacetic acids. Dilute H2SO4 dissolves plutonium slowly, but concentrated H2S04 and HN03 passivate it and do not react with it. Alkalis have no effect on metallic plutonium. 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.

Table 3. Densities and temperature range of plutonium phases:

The main valence of plutonium is 4+. It is an electronegative, chemically reactive element (by 0.2 V), much more so than uranium. It quickly fades, forming an iridescent film, initially light yellow, eventually turning into dark purple. If the oxidation is quite rapid, an olive green oxide powder (PuO 2) appears on its surface.

Plutonium oxidizes easily and corrodes quickly even in the presence of slight moisture. It becomes rusty in an atmosphere of inert gas with water vapor much faster than in dry air or pure oxygen. When plutonium is heated in the presence of hydrogen, carbon, nitrogen, oxygen, phosphorus, arsenic, fluorine, silicon, and tellurium, it forms solid insoluble compounds with these elements.

Among the plutonium oxides, Pu 2 0 3 and Pu 0 2 are known.

Pu02 plutonium dioxide is an olive-green powder, black shiny crystals or balls from red-brown to amber-yellow. The crystal structure is of the fluorite type (Pu-* + form a face-centered cubic system, and O 2- form a tetrahedron). Density 11.46, Gpl=2400°. It is formed from almost all salts (for example, oxalate, peroxide) of plutonium when heated in air or in an atmosphere of 0 2, at temperatures of 700-1000 0, regardless of the oxidation state of plutonium in these salts. For example, it can be obtained by calcination of Pu(IV) Pu(C 2 0 4) 2 -6H 2 0 oxalate hexahydrate (formed during spent fuel reprocessing):

Pu0 2, midday at low temperatures, easily dissolves in concentrated hydrochloric and nitric acids. On the contrary, calcined Pu0 2 is difficult to dissolve and can only be brought into solution as a result of special treatment. It is insoluble in water and organic solvents. Slowly reacts with a hot mixture of concentrated HN0 3 with HF. This stable compound is used as a gravimetric form in the determination of plutonium. It is also used to prepare fuel in nuclear power.

Particularly reactive Pu0 2, but containing small amounts of oxalate, is obtained by the decomposition of Pu(C 2 0 4) 2 -6H 2 0 at 130-^-300°.

Hydride R11H3 obtained from elements at 150-5-200°.

Plutonium forms halides and oxyhalides, disilicide PuSi 2 and sesquisulfide PuSi,33^b5, which are of interest due to their low fusibility, as well as carbides of various stoichiometries: from PuS to Pu2C3. RiS - black crystals, G 11L = 1664 0. Together with UC it can be used as fuel for nuclear reactors.

Plutonium nitride, PuN - crystals of gray (to black) color with a face-centered cubic lattice of the NaCl type (0 = 0.4905 nm, z = 4, space group Ptzm; the lattice parameter increases with time under the influence of its own a-radiation); T pl.=2589° (with decomposition); density 14350 kg/m3. Has high thermal conductivity. At high temperatures (~1boo°) it is volatile (with decomposition). It is obtained by reacting plutonium with nitrogen at 6oo° or with a mixture of hydrogen and ammonia (pressure 4 kPa). Powdered plutonium PuN oxidizes in air at room temperature, completely transforming into Pu0 2 after 3 days, dense plutonium oxidizes slowly (0.3% in 30 days). It hydrolyzes slowly with cold water and quickly when heated, forming Pu0 2; easily dissolves in dilute hydrochloric and sulfuric acids to form the corresponding Pu(III) salts; According to the force of action on plutonium nitride, acids can be arranged in the series HN0 3 >HC1>H 3 P0 4 >>H 2 S04>HF. Can be used as reactor fuel.

There are several plutonium fluorides: PuF 3, PuF 4, PuF6.

Plutonium tetrafluoride PuF 4 is a pink substance or brown crystals, monoclinic system. Isomorphous with Zr, Hf, Th, U, Np and Ce tetrafluoride. Г pl = 1037 0, Г к, «1 = 1277°. It is poorly soluble in water and organic solvents, but easily dissolves in aqueous solutions in the presence of Ce(IV), Fe(III), Al(III) salts or ions that form stable complexes with fluorine ions. The pink precipitate PuF 4 -2.5H 2 0 is obtained by precipitation with hydrofluoric acid from aqueous solutions Pu(III) salts. This compound dehydrates when heated to 350 m in a current of HF.

PuF 4 is formed by the action of hydrogen fluoride on plutonium dioxide in the presence of oxygen at 550° according to the reaction:

PuF 4 can also be obtained by treating PuF 3 with fluorine at 300 0 or by heating Pu(III) or Pu(IV) salts and a flow of hydrogen fluoride. From aqueous solutions of Pu(IV), PuF 4 is precipitated with hydrofluoric acid in the form of a pink precipitate with the composition 2PuF 4 H 2 0. PuF 4 almost completely coprecipitates with LaF 3. When heated in air to 400 0 PuF 4 turns into Pu0 2.

Plutonium hexafluoride, PuFe - volatile crystals at room temperature of a yellowish-brown color (at low temperatures - colorless) of an orthorhombic structure, Gpl = 52°, T knp =b2° at atmospheric pressure, density 5060 kgm-z, heat of sublimation 12.1 kcal/mol, heat of evaporation = 7.4 kcal mol * 1, heat of fusion = 4.71 kcal/mol, very prone to corrosion and sensitive to autoradiolysis. PuFe is a low-boiling liquid, thermally much less stable and less volatile than UF6. PuFe vapor is colored like NO 2, the liquid is dark brown. Strong fluorinating agent and oxidizing agent; reacts violently with water. Extremely sensitive to moisture; c H 2 0 in daylight can react very vigorously with a flash to form Pu0 2 and PuF 4 . PuFe, condensed at -195 0 on ice, when heated, slowly hydrolyzes to Pu0 2 Fo. Compact PuFe spontaneously decomposes due to the a-radiation of plutonium.

UF6 is obtained by treating PuF 4 or Pu0 2 with fluorine at 6004-700°.

Fluorination of PuF 4 with fluorine at 7004-800° occurs very quickly and is an exothermic reaction. To avoid decomposition, the resulting PuF6 is quickly removed from the hot zone - frozen or synthesis is carried out in a fluorine flow, which quickly removes the product from the reaction volume.

PuFa can also receive by payback:

There are Pu(III), Pu(IV) and Pu(VII) nitrates: Pu(N0 3) 3, Pu(N0 3) 4 and Pu0 2 (N0 3) 2, respectively.

Plutonium nitrate, Pu(N0 3) 4 *5H 2 0 is obtained by slow (over several months) evaporation of a concentrated Pu(IV) nitrate solution at room temperature. Well soluble in HN0 3 and water (nitric acid solution is dark green, brown). Soluble in acetone, ether and tributyl phosphate. Solutions of plutonium nitrate and alkali metal nitrates in concentrated nitric acid upon evaporation release double nitrates Me 2 [Pu(N0 3)b], where Me + =Cs +, Rb +, K +, Th +, C 9 H 7 NH +, C 5 H 5 NH + , NH 4 + .

Plutonium (IV) oxalate, Pu(C 2 0 4) 2 -6H 2 0, is a sandy (sometimes yellow-green) powder. Isomorphous with U(C 2 0 4)-6H 2 0. Plutonium oxalate hexahydrate is poorly soluble in mineral acids and well in solutions of oxalates and ammonium or alkali metal carbonates with the formation of complex compounds. Precipitated with oxalic acid from nitrate (i.5*4.5M HNO.0 solutions of Pu(IV):

It dehydrates when heated in air to 0°, above 400 0 it decomposes:

In compounds, plutonium exhibits oxidation states from +2 to +7. In aqueous solutions it forms ions corresponding to oxidation states from +3 to +7. In this case, ions of all oxidation states, except Pu(VII), can be in solution simultaneously in equilibrium. Plutonium ions in solution undergo hydrolysis and easily form complex compounds. The ability to form complex compounds increases in the Pu5 + series

Pu(IV) ions are the most stable in solution. Pu(V) is disproportioned into Pu(lV) and Pu(Vl). The valence state of Pu(VI) is characteristic of strongly oxidizing aqueous solutions, and it corresponds to the plutonyl ion Pu0 2 2+. Plutonium ions with charges 3 + and 4 + exist in aqueous solutions in the absence of hydrolysis and complex formation in the form of highly hydrated cations. Pu(V) and Pu(VI) in acidic solutions are oxygen-containing cations of the M0 2 + and M0 2 2+ type.

The oxidation states of plutonium (III, IV, V and VI) correspond to the following ionic states in acidic solutions: Pu 3+, Pu4 +, Pu0 2 2+ and Pu0 5 3 Due to the "closeness of the oxidation potentials of plutonium ions to each other" in solutions they can simultaneously plutonium ions with different oxidation states exist in equilibrium. In addition, disproportionation of Pu(IV) and Pu(V) is observed:

The rate of disproportionation increases with increasing plutonium concentration and temperature.

Reese+ solutions have a blue-violet color. In its properties, Rts + is close to rare earth elements. Its hydroxide, fluoride, phosphate and oxalate are insoluble. Pu(IV) is the most stable state of plutonium in aqueous solutions. Pu(IV) is prone to complex formation with nitric, sulfuric, hydrochloric, acetic and other acids. Thus, in concentrated nitric acid, Pu(IV) forms complexes Pu(N0 3)5- and Pu(G) 3)6 2". In aqueous solutions, Pu(IV) is easily hydrolyzed. Plutonium hydroxide (green) is prone to polymerization. Insoluble fluoride, hydroxide, oxalate, iodate Pu(IV).Pu(IV) coprecipitates well with insoluble hydroxides, lanthanum fluoride, Zr, Th, Ce iodates, Zr and Bi phosphates, Th, U(IV), Bi, La oxalates. Pu(IV) form double fluorides and sulfates with Na, K, Rb, Cs and NH 4 +. Pu(obtained in about.2 M solution of HN0 3 by mixing solutions of Pu(III) and Pu(VI). From salts of Pu( VI) Of interest are sodium plutonylacetate NaPu0 2 (C 2 H 3 0 2) 3 and ammonium plutonylacetate NH 4 Pu0 2 (C 2 H 3 0 2), which are similar in structure to the corresponding compounds U, Np and At.

Formal oxidation potentials of plutonium (in V) in lM solution of HC10 4:

The stability of the complex formed with this anion for actinide ions decreases in the following order: M4 + >M0 2+ >M3 + >M0 2 2+ > M0 2+, i.e. in order of decreasing ionic potential. The ability of anions to form complexes with actinide ions decreases for singly charged anions - fluoride > nitrate > chloride > perchlorate; for doubly charged anions carbonate>oxalate>sulfate. A large number of complex ions are formed with organic substances.

Both Pu(IV) and Pu(VI) are well extracted from acidic solutions with ethyl ether, TBP, diisopropyl ketone, etc. Claw-shaped complexes, for example, with a-thenoyltrifluoroacetone, p-diketone, cupferone, are well extracted with non-polar organic solvents . Extraction of Pu(IV) complexes with a-thenoyltrifluoroacetone (TTA) makes it possible to purify plutonium from most impurities, including actinide and rare earth elements.

Aqueous solutions of plutonium ions in different states have the following colors: Pu(III), as Pcs + (blue or lavender); Pu(IV), as Pc4* (yellow-brown); Pu(VI), as Pu0 2 2+ (pink-orange). Pu(V), like Pu0 2+, is initially pink, but being unstable in solution, this ion disproportionates into Pu 4+ and Pu0 2 2+; Pu 4+ is then oxidized, moving from Pu0 2 + to Pu0 2 2+, and reduced to Pu 3+. Thus, an aqueous solution of plutonium over time becomes a mixture of Pcs + and Pu0 2 2+. Pu(VII), as Pu0 5 2 - (dark blue).

To detect plutonium, a radiometric method is used, based on measuring the a-radiation of plutonium and its energy. This method is characterized by fairly high sensitivity: it allows discover 0.0001 µg 2 39Pi. If there are other α-emitters in the analyzed sample, identification of plutonium can be performed by measuring the energy of α-particles using α-spectrometers.

A number of chemical and physicochemical methods for the qualitative determination of plutonium use the difference in the properties of the valence forms of plutonium. The Pu(III) ion in fairly concentrated aqueous solutions can be detected by its bright blue color, which differs sharply from the yellow-brown color of aqueous solutions containing Pu(IV) ions.

The light absorption spectra of solutions of plutonium salts in various oxidation states have specific and narrow absorption bands, which makes it possible to identify valence forms and detect one of them in the presence of others. The most characteristic light absorption maxima of Pu(III) lie in the region of 600 and 900 mmk, Pu(IV) - 480 and 66 mmk, Pu(V) - 569 mmk and Pu(VI) 830+835 mmk.

Although plutonium is chemically toxic, like any heavy metal, this effect is weak compared to its radiotoxicity. The toxic properties of plutonium appear as a consequence of a-radioactivity.

For 2 s 8 Pu, 2 39Pu, 24op U) 242p u> 244Pu radiation hazard group A, MZA=z,7-uz Bk; for 2 4>Pu and 2 43Pu radiation hazard group B, MZA = 3.7-104 Bq. If the radiological toxicity is 2 3 and taken as unity, the same indicator for plutonium and some other elements forms the series: 235U 1.6 - 2 39Pu 5.0 - 2 4 1 Ash 3.2 - 9"Sr 4.8 - ^Ra 3.0. It can be seen that plutonium is not the most dangerous among radionuclides.

Let's look briefly at industrial production plutonium

Plutonium isotopes are produced in powerful uranium reactors using slow neutrons using the (p, y) reaction and in breeder reactors using fast neutrons. Plutonium isotopes are also produced in power reactors. By the end of the 20th century, the world had produced a total of -1300 tons of plutonium, of which ~300 tons were for weapons use, the rest was a by-product of nuclear power plants (reactor plutonium).

What distinguishes weapons-grade plutonium from reactor-grade plutonium is not so much the degree of enrichment and chemical composition, how much isotopic composition, which depends in a complex way both on the time of irradiation of uranium with neutrons and on the storage time after irradiation. The content of the isotopes 24°Pu and 2 4‘Pu is especially important. Although an atomic bomb can be created with any content of these isotopes in plutonium, nevertheless, the presence of 2 4 «p u in 239r determines the quality of the weapon, because the neutron background and such phenomena as the growth of critical mass and thermal output depend on it. The neutron background affects the explosive device by limiting the total mass of plutonium and the need to achieve high implosion speeds. Therefore, bombs of the old designs required a low content of 2 4or and. But “high” design projects use plutonium of any purity. Therefore, the term “weapon-grade plutonium” has no military meaning; this is an economic parameter: a “high” bomb design is significantly more expensive than a “low” one.

As the share of 24op U) increases, the cost of plutonium falls and the critical mass increases. The 7% 24°Pu content makes the overall cost of plutonium minimal. Average composition of weapons-grade plutonium: 93.4% 239 Ri, 6.o%

24°Pu and 0.6% 241 Pu. The thermal power of such plutonium is 2.2 W/kg, the level of spontaneous fission is 27100 fissions/s. This level allows 4 kg of plutonium to be used in a weapon with a very low probability of pre-detonation in a good implosion system. After 20 years, most of the 24, Pu will turn into ^'At, significantly increasing the heat release - up to 2.8 W/kg. Since 241 Pu is highly fissile, but 241 At is not, this will lead to a decrease in the reactivity margin of plutonium. Neutron radiation from 5 kg of weapons-grade plutonium of 300,000 neutrons/s creates a radiation level of 0.003 rad/hour at a distance of 1 m. The background is reduced by a reflector and explosive, surrounding him, for the 10th time. However, prolonged contact of maintenance personnel with a nuclear explosive device during its maintenance can result in a radiation dose equal to the annual limit.

Due to the small difference in masses 2 - "* 9 Pu and 24 ° Pu, these isotopes are not separated industrial methods enrichment. Although they can be separated using an electromagnetic separator. It is easier, however, to obtain purer 2 zeRi by reducing the time spent in the *z*i reactor. There is no reason to reduce the content of 24 °Pi to less than 6%, since this concentration does not interfere with the creation of effective triggers for thermonuclear charges.

In addition to weapons-grade plutonium, there is also reactor-grade plutonium. Plutonium from spent nuclear fuel consists of many isotopes. The composition depends on the type of reactor and operating mode. Typical values ​​for a light water reactor: 2 × 8 Pu - 2%, 239Pu - 61%, 24 °Pll - 24%, 24iPu - 10%, 242 Pll - 3%. It is difficult to make a bomb from such plutonium (virtually impossible for terrorists), but in countries with developed technology, reactor plutonium can be used to produce nuclear charges.

Table 4. Characteristics of plutonium types.

The isotopic composition of plutonium accumulated in the reactor depends on the degree of fuel burnup. Of the five main isotopes formed, two are with odd Z- 2 39Pi and 24,Pi are fissionable, i.e. capable of fission under the influence of thermal neutrons, and can be used as reactor fuel. In the case of using plutonium as reactor fuel, the amount of accumulated 2 39 Ri and 241 Ri is important. If plutonium recovered from spent fuel is reused in fast neutron reactors, its isotopic composition gradually becomes less suitable for weapons use. After several fuel cycles, the accumulation of 2 × 8 Pu, #2 4″ Pu and ^ 2 Pu makes it unsuitable for this purpose. Mixing in such material is a convenient method to "denature" the plutonium, ensuring that fissile materials do not proliferate.

Both weapons-grade and reactor-grade plutonium contain some amount of ^Pu. ^'Pu decays into 24 'Am by emission of a p-particle. Since the daughter 241 At has a significantly longer half-life (432 l) than the parent 241 Pu (14.4 l), its amount in the charge (or in the NFC waste) increases as ^'Pu decays. y-Radiation generated in as a result of the decay of 241 Am, much stronger than that of 241 Pu, therefore, it also increases over time. The concentration of ®4phi and the period of its storage directly correlate with the level of y-radiation resulting from an increase in the content of 24 'As. Plutonium cannot be stored for a long time - Once it has been used, it must be used, otherwise it will have to be subjected to time-consuming and expensive recycling again.

Table 5. Some characteristics of weapons-grade and reactor-grade plutonium

The most practically important isotope 2 39Pu is produced in nuclear reactors during long-term neutron irradiation of natural or enriched uranium:

Unfortunately, other nuclear reactions are also taking place, leading to the emergence of other isotopes of plutonium: 2 - 38 Pu, a4or u, 24 Phi and 242 Pu, the separation of which from 2 39Rc, although solvable, is a very difficult task:

When uranium is irradiated by reactor neutrons, both light and heavy isotopes of plutonium are formed. Let us first consider the formation of plutonium isotopes with a mass less than 239.

A small portion of the neutrons emitted during fission have energy sufficient to excite the reaction 2 3 8 U(n,2n) 2 3?u. 237 U is a p-emitter and with T’,/ 2 =6.8 days it turns into long-lived 2 37Np. This isotope in a graphite reactor on natural uranium is formed in an amount of 0.1% of the total amount of simultaneously formed 2 39Pu. The capture of slow neutrons by 2 3?Np leads to the formation of 2 3 8 Np. The cross section of this reaction is 170 barn. The chain of reactions looks like:

Since two neutrons are involved here, the yield is proportional to the square of the radiation dose and the ratio of the amounts of 238 Pu to 2 39Pu is proportional to the ratio of 2 39Pu to 238 U. The proportionality is not strictly observed due to the lag in the formation of 23?Np associated with the 6.8 day period half-life of ^U. A less important source of the formation of 238 Pu in 2 39Pu is the decay of 242 St, formed in uranium reactors. 238 Pu is also formed by the reactions:

Since this is a third-order neutron reaction, the ratio of the amount of 2 3 8 Pu formed in this way to 2 39 Pu is proportional to the square of the ratio * 3 8 Pu to 2 3 8 U. However, this chain of reactions becomes relatively more significant when working with uranium enriched in ^u.

The concentration of 2 × 8 Pu in a sample containing 5.6% 24 °Pu is 0.0115%. This value makes a fairly significant contribution to the total a-activity of the drugs, since ^Pu Ti/2= 86.4 l.

The presence of 2 6 Pu in plutonium produced in the reactor is associated with a number of reactions:

The yield of 2 3 6 Pu during the irradiation of uranium is ~ω-9-io" 8%.

From the point of view of the accumulation of plutonium in uranium, the main transformations are associated with the formation of the isotope 2 39Pu. But other side reactions are also important, since they determine the yield and purity of the target product. The relative content of the heavy isotopes 240 Pu, ^Phi, 242 Pu, as well as 23Pu, 2 37Np and ^"Ash depends on the dose of neutron irradiation of uranium (the residence time of uranium in the reactor). The cross sections for neutron capture by plutonium isotopes are large enough to cause successive reactions (n, y) even at low concentrations of 2 39Pu in uranium.

Table 6. Isotopic composition of plutonium isolated from irradiated it thrones of natural uranium. _

The 241 Pu formed during the irradiation of uranium with neutrons turns into 241 As, which is discharged during the chemical-technological processing of uranium blocks (241 At, however, gradually accumulates again in purified plutonium). For example, the a-activity of metallic plutonium, containing 7.5% 24 °Pu, increases by 2% after a year (due to the formation of 24, At). 24, Pu has a large fission cross section for reactor neutrons, amounting to - poo barn, which is important when using plutonium as reactor fuel.

If uranium or plutonium is subjected to strong neutron irradiation, the synthesis of minor actinides begins:

Formed from 2 4*Pu, 2 4*Am in turn reacts with neutrons, forming 2 3 8 Pu and 2 4 2 Pu:

This process opens up the possibility of obtaining plutonium preparations with relatively low y-radiation.

Rice. 6. Change in the ratio of plutonium isotopes during long-term irradiation of 2 39Pu with a neutron flux of 3*10*4 n/cm 2 s.

Thus, the long-lived isotopes of plutonium - ^Pu and 2 44Pu are formed during long-term (about a hundred days or more) irradiation with 2 39Pu neutrons. In this case, the yield of 2 4 2 Pu reaches several tens of percent, while the amount of 2 44 Pu formed is a fraction of a percent of ^Pu. At the same time, Am, Cm and other transplutonium, as well as fragmentation elements are obtained.

In the production of plutonium, uranium (in the form of metal) is irradiated in an industrial reactor (thermal or fast), the advantages of which are high neutron density, low temperature, and the possibility of irradiation for a time much shorter than the reactor campaign.

The main problem that arose during the production of weapons-grade plutonium in a reactor was choosing the optimal time for irradiation of uranium. The fact is that the isotope 238, which makes up the bulk of natural uranium, captures neutrons, forming 239Pu, while 2333 supports the fission chain reaction. Since the formation of heavy isotopes of plutonium requires additional neutron capture, the amount of such isotopes in uranium grows more slowly than the amount of 2 39Pu. Uranium irradiated in a reactor a short time, contains a small amount of 2 39Pu, but it is purer than with long exposures, since harmful heavy isotopes did not have time to accumulate. However, 2 39Рц itself is subject to fission and with an increase in its concentration in the reactor, the rate of its transmutation increases. Therefore, uranium must be removed from the reactor several weeks after the start of irradiation.

Rice. 7- Accumulation of plutonium isotopes in the reactor: l - ^Pu; 2 - 240 Pu (at short times, weapons-grade plutonium is formed, and at long times, reactor-grade plutonium is formed, i.e., unsuitable for weapons use).

The overall irradiation rate of a fuel cell is expressed in megawatt days/ton. Weapons-grade plutonium is produced from elements with a small amount of MW-day/t and produces fewer by-product isotopes. Fuel cells in modern pressurized water reactors reach levels of 33,000 MW-day/t. Typical exposure in a breeder reactor is 100 MW-day/t. During the Manhattan Project, natural uranium fuel received only 100 MW-day/t, so it produced a very high quality 239 Ri (total 1 % 2 4°Pll).

home » How to earn » Formation of plutonium. Weapons-grade plutonium: application, production, disposal. Name and features