What weapons-grade plutonium looks like. What is plutonium. Half-lives of some isotopes of plutonium
Weapon-grade plutonium- This is plutonium in the form of a compact metal containing at least 93.5% of the 239Pu isotope. Designed to create nuclear weapons.
1.Name and features
It is called "armory" to distinguish it from "reactor". Plutonium is formed in any nuclear reactor fueled by natural or low-enriched uranium, containing mainly the isotope 238U, by capturing excess neutrons. But as the reactor operates, the weapon-grade plutonium isotope quickly burns out, and as a result, a large amount of 240Pu, 241Pu, and 242Pu isotopes accumulates in the reactor, which are formed during sequential captures of several neutrons - since the burnup is usually determined by economic factors. The lower the burnup, the fewer isotopes 240Pu, 241Pu and 242Pu, the plutonium separated from the irradiated nuclear fuel will contain, but the less plutonium is formed in the fuel.
Special production of plutonium for weapons containing almost exclusively 239Pu is required mainly because isotopes with mass numbers 240 and 242 create a high neutron background, which makes it difficult to design effective nuclear weapons, in addition, 240Pu and 241Pu have significantly shorter half-lives than 239Pu, which causes the plutonium parts to heat up, and heat removal elements have to be added to the design of a nuclear weapon. Even pure 239Pu is warmer than the human body. In addition, the decay products of heavy isotopes damage the crystal lattice of the metal, which can lead to a change in the shape of plutonium parts, which is fraught with the failure of a nuclear explosive device.
In principle, all these difficulties are surmountable, and nuclear explosive devices 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 240Pu and 242Pu is very high, 241Pu is somewhat larger than that of 239Pu.
2.Production
In the USSR, the production of weapons-grade plutonium was carried out first at the Mayak Combine in Ozersk (formerly Chelyabinsk-40, Chelyabinsk-65), then at the Siberian Chemical Combine in Seversk (formerly Tomsk-7), later the Krasnoyarsk Mining was put into operation. -chemical plant in Zheleznogorsk (also known as Sotsgorod and Krasnoyarsk-26). The production of weapons-grade plutonium in Russia was discontinued in 1994. In 1999, the reactors in Ozersk and Seversk were shut down, in 2010 the last reactor in Zheleznogorsk was shut down.
In the United States, weapons-grade plutonium was produced in several locations, such as the Hanford Complex in Washington state. The production was closed in 1988.
3. Synthesis of new elements
The transformation of some atoms into others occurs during the interaction of atomic or subatomic particles. Of these, only neutrons are available in large quantities. A gigawatt nuclear reactor produces about 3.75 kg (or 4 * 1030) neutrons per year.
4.Production of plutonium
Plutonium atoms are formed as a result of a chain of atomic reactions that begin with the capture of a neutron by an atom of uranium-238:
U238 + n -\u003e U239 -\u003e Np239 -\u003e Pu239
or, more precisely:
0n1 + 92U238 -\u003e 92U239 -\u003e -1e0 + 93Np239 -\u003e -1e0 + 94Pu239
With continued irradiation, some atoms of plutonium-239 are able, in turn, to capture a neutron and turn into a heavier isotope plutonium-240:
Pu239 + n -\u003e Pu240
To obtain plutonium in sufficient quantities, the strongest neutron fluxes are needed. These are just created in nuclear reactors. In principle, any reactor is a source of neutrons, but for industrial production plutonium is naturally used specially designed for this.
The world's first commercial plutonium production reactor is the B-reactor at Hanford. It started working on September 26, 1944, power - 250 MW, productivity - 6 kg of plutonium per month. It contained about 200 tons of uranium metal, 1200 tons of graphite and was cooled with water at a rate of 5 cubic meters / min.
Loading panel of the Hanford reactor with uranium cassettes:
Scheme of his work. In the reactor for irradiation of uranium-238, neutrons are created as a result of a stationary chain reaction of uranium-235 fission. On average, 2.5 neutrons are produced per U-235 fission. To maintain the reaction and simultaneously produce plutonium, it is necessary that, on average, one or two neutrons would be absorbed by U-238, and one would cause the next atom of U-235 to fission.
The neutrons produced by the fission of uranium have very high speeds. Uranium atoms are arranged in such a way that the capture of fast neutrons by nuclei of both U-238 and U-235 is unlikely. Therefore, fast neutrons, having experienced several collisions with surrounding atoms, gradually slow down. At the same time, the U-238 nuclei absorb such neutrons (intermediate speeds) so strongly that there is nothing left for the fission of U-235 and the maintenance of a chain reaction (U-235 is fissioned from slow, thermal neutrons).
This is fought by a moderator surrounding the blocks with uranium by some light substance. In it, neutrons are decelerated without absorption, experiencing elastic collisions, in each of which a small part of the energy is lost. Water and carbon are good moderators. Thus, neutrons slowed down to thermal speeds travel through the reactor until they cause fission of U-235 (U-238 absorbs them very weakly). With a certain configuration of the moderator and uranium rods, conditions will be created for the absorption of neutrons and U-238 and U-235.
The isotopic composition of the resulting plutonium depends on the duration of the uranium rods in the reactor. A significant accumulation of Pu-240 occurs as a result of prolonged irradiation of the uranium cassette. With a short residence time of uranium in the reactor, Pu-239 is obtained with an insignificant Pu-240 content.
Pu-240 is harmful to weapons production for the following reasons:
1. It is less fissile material than Pu-239, so slightly more plutonium is required to make weapons.
2. The second, much more important reason. The level of spontaneous fission in Pu-240 is much higher, which creates a strong neutron background.
In the earliest years of the development of atomic weapons, neutron emission (strong neutron background) was a problem on the way to a reliable and effective charge due to its premature detonation. Strong fluxes of neutrons made it difficult or impossible to compress a bomb nucleus, containing several kilograms of plutonium, into a supercritical state - before that it was destroyed by the strongest, but still not the maximum possible energy yield. The arrival of mixed nuclei - containing highly enriched U-235 and plutonium (in the late 1940s) - overcame this difficulty when it became possible to use relatively small amounts of plutonium in most uranium nuclei. The next generation of charges, fusion amplification devices (in the mid-1950s) completely eliminated this difficulty, guaranteeing high energy release, even with low-power fission initial charges.
Plutonium produced in special reactors contains a relatively small percentage of Pu-240 (<7%), плутоний "оружейного качества"; в реакторах АЭС отработанное ядерное топливо имеет концентрацию Pu-240 более 20%, плутоний "реакторного качества".
In special-purpose reactors, uranium remains for a relatively short period of time, during which not all of the U-235 burns out and not all of the U-238 goes into plutonium, but a smaller amount of Pu-240 is formed.
There are two reasons for producing low Pu-240 plutonium:
Economic: the only reason for the existence of special plutonium reactors. Decaying plutonium by fission, or converting it into the less fissile Pu-240, decreases recoil and increases production costs (up to the point where its price balances with the cost of processing irradiated fuel with low plutonium concentration).
Complexity of handling: While neutron emission is not such a major problem for weapon designers, it can create difficulties in manufacturing and handling such a charge. Neutrons make an additional contribution to the professional irradiation of those who assemble or maintain weapons (neutrons themselves do not have an ionizing effect, but they create protons capable of doing so). In fact, charges that involve direct contact with humans, such as the Davy Crocket, may therefore require ultrapure plutonium with low neutron emissions.
The direct casting and processing of plutonium is done manually in sealed chambers with gloves for the operator. Like these:
This implies very little protection for humans from neutron-emitting plutonium. Therefore, plutonium with a high Pu-240 content is processed only by manipulators, or the time of each worker's work with it is strictly limited.
For all these reasons (radioactivity, the worst properties of Pu-240), it is explained why reactor-grade plutonium is not used for the manufacture of weapons - it is cheaper to produce weapons-grade plutonium in special. reactors. Although from the reactor, too, most likely, it is possible to make a nuclear explosive device.
Plutonium ring
This ring is made of electrolytically purified plutonium metal (purity over 99.96%). Typical of rings prepared at Los Alamos and sent to Rocky Flats to make weapons, prior to the recent suspension of production. The ring weighs 5.3 kg, sufficient for the manufacture of a modern strategic charge, with a diameter of approximately 11 cm. The ring shape is important for ensuring critical safety.
Casting of plutonium-gallium alloy recovered from the weapon core:
Plutonium during the Manhattan Project
Historically, the first 520 milligrams of plutonium metal produced by Ted Magel and Nick Dallas at Los Alamos on March 23, 1944:
Press for hot pressing of plutonium-gallium alloy in the form of hemispheres. This press was used at Los Alamos to make plutonium cores for the charges detonated at Nagasaki and Operation Trinity.
Products cast on it:
Additional Plutonium Side Isotopes
The capture of a neutron, which is not accompanied by an act of fission, creates new isotopes of plutonium: Pu-240, Pu-241 and Pu-242. The latter two accumulate in insignificant quantities.
Pu239 + n -\u003e Pu240
Pu240 + n -\u003e Pu241
Pu241 + n -\u003e Pu242
A side chain of reactions is also possible:
U238 + n -\u003e U237 + 2n
U237 -\u003e (6.75 days, beta decay) -\u003e Np237
Np237 + n -\u003e Np238
Np238 -\u003e (2.1 days, beta decay) -\u003e Pu238
The overall measure of the irradiance (depletion) of a fuel cell can be expressed in megawatt-days / tonne (MW-day / tonne). Plutonium armory quality is obtained from elements with a small amount of MW-day / t, it produces less side isotopes. Fuel cells in modern pressurized water reactors reach 33,000 MWd / t. Typical exposition in a weapons-grade breeder (with expanded breeding of nuclear fuel) reactor 1000 MW-day / t. Plutonium in Hanford graphite-moderated reactors is irradiated up to 600 MW-day / t; in Savannah, a heavy water reactor produces plutonium of the same quality at 1000 MW-day / t (possibly due to the fact that some of the neutrons are spent on the formation of tritium) ... During the Manhattan Project, natural uranium fuel received only 100 MW-day / t, thus producing very high quality plutonium-239 (only 0.9-1% Pu-240, other isotopes in even smaller quantities).
Similar information.
At the summit on nuclear security, Dmitry Medvedev announced the closure of the last reactor in Russia to produce weapons-grade plutonium.
Military observer Sergei Ptichkin comments:
On the fifteenth of April in the “closed” city of Zheleznogorsk, Krasnoyarsk Territory, a truly significant event took place: the reactor was shut down. In the USSR, plutonium for the manufacture of warheads was produced in different time in different quantities at different enterprises nuclear industry... However, its mass production began at the AD and ADE reactors in Zheleznogorsk. Here, in the granite mountains, a unique underground plant was built for the production of many components of nuclear weapons and military spacecraft. The total length of the tunnels cut in the rocks exceeds two hundred kilometers. There are no similar Cyclopean structures anywhere in the world.
Plutonium is a separate and very bright page in the history of the nuclear arms race in the 20th century. It does not exist in its pure form in nature. They first received it in 1940 in the United States, where work was already underway on the atomic project. Over time, it turned out that Pu-239 is ideal for creating a compact and very powerful nuclear weapon, which is why they began to call it weapons-grade. Its critical mass is significantly less than that of the main nuclear explosive U-235. Initially, plutonium was used as the main detonator for simple atomic and then complex thermonuclear warheads. With the development of high technology, Pu-239 began to be used as a "clean" explosive. Especially in small-caliber ammunition, where, with a minimum volume, it was necessary to obtain the maximum explosive effect. Plutonium charges began to be used in multiple strategic missile warheads, in artillery shells, torpedoes and sabotage mines.
Plutonium could be considered an ideal filling for all types of nuclear weapons, if not for a number of essential features of this substance, obtained only artificially. The production of weapons-grade plutonium itself is very difficult and expensive. Therefore, only the USA and the USSR could afford to produce it in the required quantities. In addition to its technological complexity, its production is extremely dangerous and requires adherence to truly unprecedented protection measures. Pu-239 is one of the most chemically toxic elements.
Being chemically extremely active, Pu-239 is unstable, it begins to oxidize very quickly, to enter into reactions with its surroundings. The creators of atomic and hydrogen bombs did everything possible and, probably, impossible to exclude even the slightest possibility of oxidation and loss of combat properties for Pu-239, but anything can happen over the decades. It cannot be ruled out that plutonium, the basis of modern nuclear weapons, does not maintain its calculated critical mass over decades of storage in arsenals. Computer calculations show that both the United States and Russia are all right with nuclear weapons. But this is a virtual simulation, and full-scale nuclear tests have not been carried out for a long time, and what is the real state of the warheads assembled in the seventies and eighties of the twentieth century, it is still impossible to say unequivocally.
The most powerful reactor for the production of weapons-grade plutonium in Zheleznogorsk - ADE-2 - has been in continuous operation for almost half a century. In addition to producing Pu-239, the reactor produced heat and electricity for the city of nuclear scientists and rocket scientists. Since 1995, the production of weapons-grade plutonium has ceased in Zheleznogorsk, although this fact has never been particularly advertised. ADE-2 has been operating for fifteen years as an ordinary nuclear power plant - it produced heat and electricity. On April 15, the peaceful operation of the reactor was completely stopped. Previously, all space production was removed from the giant underground enterprise.
Now Russia, in accordance with international agreements, has to begin the process of destroying the accumulated weapons-grade plutonium. The United States has already promised to allocate $ 400 million to our country for these purposes. To date, according to open sources, about 300 tons of weapons-grade plutonium have been produced in the world. This amount is sufficient for guaranteed and repeated destruction of life on Earth. So further production of Pu-239 is completely pointless. If, of course, we assume that the creators of nuclear weapons have found a way to ensure the stability of weapons-grade plutonium for an infinitely long time.
The question, which remains aside from the weapons ones, is what will happen to the giant underground industrial complex? Billions of "golden rubles" were invested in its creation, and it is still necessary to dispose of the further fate of the unique and very expensive underground structure in a state-like manner.
Especially for the Century
Plutonium-239, the main plutonium isotope used in nuclear explosive devices, is produced in any uranium-fueled nuclear reactor by capturing a neutron 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 a relatively low degree of fuel utilization - the characteristic value of the burnup is 400-600 MWd / t. This is due to the fact that a significant amount of plutonium-240 isotope is formed in the fuel at a greater burnup depth. The Ri-240 isotope is a fairly intense emitter of spontaneous neutrons and therefore its presence significantly degrades the quality of plutonium as a weapon material.82 According to the US classification, weapons-grade plutonium is considered to be material with a Pu-240 content of less than 5.8%.
Plutonium is separated from spent fuel by radiochemical methods at special production facilities. Due to the high radioactivity of spent fuel, all reprocessing operations are carried out remotely in thick concrete “canyons.” The plutonium production process generates large volumes of radioactive and toxic waste and requires a complex infrastructure for their processing and disposal.
Industrial reactors were used to develop other nuclear weapons materials, in particular tritium, which is 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 under neutron irradiation of the nuclei of the isotope of lithium-6.83. The produced tritium is released from lithium targets when they are processed in a vacuum furnace and purified by chemical methods. In the early years of the development of the nuclear arsenal, the reactors also produced polonium-210, which was used in the production of beryllium-polonium neutron sources necessary to initiate a chain reaction when a nuclear charge is detonated. (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.
Reactor technology development
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 cells. The fuel - blocks of natural uranium metal in an aluminum shell - was loaded into vertical technological channels made in the graphite masonry.
actor zone. To level 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 according to a once-through scheme - water - the coolant was taken from an external source, pumped through the reactor zone and discharged into environment... Fuel (about 150 tons of uranium) was placed 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 cylinder of graphite stack with vertical channels for fuel and control rods. Compared to reactor A, AV-1 had a higher power and was safer. Like reactor A, the second generation reactors were direct-flow and were used exclusively for the production of weapons-grade plutonium.86
The reactors of the third generation, built after 1958, were designed as dual-use reactors.88 Representatives of the third generation reactors are the reactors of the ADE series that are still in operation. Each such reactor has a capacity of about 2000 MW and produces about 0.5 tons of weapons-grade plutonium per year. The steam generated during operation is used to generate approximately 350 MW of heat and 150 MW of electricity. Unlike reactors of the first and second generations, the reactors of the third generation have a two-circuit cooling system with closed circulation of water along the primary circuit, a heat exchanger, a steam generator, and a turbine for generating electricity.
| Power | up to 2000 MW |
| Power generation | 150-200 MW (e) |
| Heat production | 300-350 Gcal / h |
| Moderator | graphite |
| Heat carrier | water |
| Number of channels | 2832 |
| The number of fuel cells in the channel | 66-67 |
300-350 t |
75 kg |
| Fuel burnup | 600-1000 MW-d / t |
| Fuel composition (natural uranium) | natural uranium metal |
| Fuel composition (HEU) | dispersed (8.5% U02 in an aluminum matrix) |
| Bar diameter | 35 mm |
| Sheath material | aluminium alloy |
| Shell thickness | gt; 1 mm |
| Spent fuel storage | wet |
| Standard storage time | 6 months |
| Maximum allowed storage time | 18 months |
Tab. 3-2. Characteristics of the ADE87 reactor
Development of radiochemical technology
The development of the domestic school of radiochemistry began at the Radium Institute of the USSR Academy of Sciences under the leadership of Academician V.G. Khlopin. In 1946 at RIAN, the country's first acetate-fluoride technology for industrial separation of plutonium and uranium from irradiated uranium fuel was proposed. The technology was tested and tested at the U-5 experimental radiochemical plant at the NII-9 Institute and introduced at the first radiochemical plant (plant B) in Chelyabinsk-40 (later Chelyabinsk-65).
At the initial stage of operation, the chemical redistribution of plant B was based on the redox process of acetate precipitation of uranyl triacetate. This process took place in two stages - the first was the purification of plutonium and uranium from fission products and the separation of plutonium from uranium in the course of acetate deposition. At the second stage, plutonium was refined (purified) by precipitation with lanthanum fluoride.
Radiochemical technology has been constantly improved to improve its safety, the completeness of extraction 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 (plant BB), built in Chelyabinsk-40 in the late 50s, it was decided to abandon the lanthanum-fluoride technology in favor of using a double cycle of acetate precipitation. Acetate technology, however, was also very expensive, led to large volumes of solutions and waste, and required the creation of a number of auxiliary production... Therefore, in the early 1960s, the second cycle of acetate precipitation (at the stage of plutonium refining) was replaced by sorption methods based on the selective absorption of plutonium by ion-exchange resins. The introduction of sorption technology has significantly improved the quality of the plant's products. However, using new technology It turned out to be unsafe and, after the explosion of the sorption column in Chelyabinsk in 1965, 90 it was decided to start work on the introduction of extraction technologies. (The first research on extraction technologies began in the late 1940s.) 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. Research and development of radiochemical technologies were carried out at the Radium Institute, All-Russian Research Institute of Inorganic Materials, All-Russian Research Institute of Chemical Technology. 91 Basic design developments and the production of equipment was carried out by the Sverdlovsk Research Institute of Chemical Engineering. Design solutions were examined or developed by the All-Union Scientific Research and Development Center located in Leningrad. design institute energy technologies (VNIPIET). The main burden of verifying scientific and technical solutions and introducing technologies was borne directly by the plutonium production plants.
Plutonium Production Complex
Industrial plutonium production was carried out by an integrated complex of three plants: Chelyabinsk-65, Tomsk-7 and Krasnoyarsk-26.
Chelyabinsk-65 (PA "Mayak")
Combine Chelyabinsk-65, now 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 was produced 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 being used for scientific observation and are being prepared for dismantling. The reactor plant at different times included (and still is) reactors of other types, used for the production of tritium and other isotopes.
The irradiated fuel of industrial reactors was processed at the radiochemical plant (plant B), which was part of the plant. The radiochemical plant began reprocessing irradiated uranium on December 22, 1948, and the first years of its operation were extremely difficult. Lack of experience and knowledge, imperfection of technologies and equipment, high corrosiveness and radioactivity of technological solutions caused high accidents and overexposure of personnel.94 The plant was repeatedly reconstructed 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, a radiochemical plant RT-1 was built on the site of plant B.
The reprocessing of industrial reactor fuel was continued at the BB plant. The construction of the BB plant, which was designed to replace the first radiochemical production, began in 1954 and was fully 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 has been discontinued. Between 1987 and 1990 Irradiated fuel from industrial reactors that were still in operation was sent for reprocessing to a radiochemical plant in Tomsk-7.
Plutonium products from radiochemical plants were transferred to chemical metallurgical plant B. Plant B was built in 1948 for the production of metallic plutonium and parts for nuclear weapons.95 The second phase of the plant made it possible to make weapons parts from uranium. Currently, the plant continues to work on the processing of fissile weapons materials and the production of ammunition parts. In 1997, the plant, like the chemical and metallurgical production in Tomsk-7, got involved in the work on the enrichment of weapons-grade uranium.
In addition to plutonium production, the production of tritium and other special isotopes was launched at Chelyabinsk-65.96 Since 1951, a 50-MW AI reactor has been used for this purpose, using uranium with a 2% enrichment as fuel. Somewhat later, the production of tritium 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 Ruslan light-water (water-moderated) reactor was put into operation, and in 1986-1987, the Lyudmila heavy-water reactor began operation. isotopic raw materials for a radioisotope plant (plutonium-238, cobalt-60, carbon-14, iridium-192 and others) and radiation-doped silicon.
Isotope isolation is carried out by the complex of the RT-1 plant. The fuel irradiated for the purpose of tritium production is transferred to the tritium plant, which is part of the Mayak PA - the only enterprise in the country for the production of
tritium and tritium units 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 Combine is an important link in the fuel cycle of nuclear power plants and other reactor facilities. A significant part of the infrastructure of the old defense plant B became part of the radiochemical plant RT-1, which was put into operation in 1976. The first line RT-1 was designed to process highly enriched uranium-aluminum fuel from industrial and marine reactors. In 1978, the plant began reprocessing fuel from VVER-440 reactors. At present, three RT-1 technological lines are used for reprocessing 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 the reception and intermediate storage of spent fuel, facilities for storage, processing and vitrification of radioactive waste, and storage facilities for separated uranium and plutonium. The RT-1 plant is capable of annually reprocessing 400 tons of nuclear power plant fuel and 10 tons of transport reactor fuel (20-30 reactor zones of transport installations per year).
In addition to fuel reprocessing, RT-1's scope of activity includes work on radioactive waste management and experimental work on research
| Reactor | | A type | Appointment | Power Mw |
| PA "Mayak" (Chelyabinsk-65) | | | |
|
| AND | 1948-1987 | water-graphite, direct flow | plutonium | 100/900 |
| IR-AI | 1951-1987 | water-grafit, direct-flow | plutonium | 50/500 |
| AB-1 | 1950-1989 | water-graphite, direct flow | plutonium | 300/1200 |
| AB-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 | There is no data |
| Ludmila | 1986-present | heavy water | tritium isotopes | there is 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 Combine (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 |
Tab. 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 (Shop 300) .101 Construction of the half-completed plant was frozen in 1989.
Chelyabinsk-65 is one of the main sites for the storage of fissile materials. The RT-1 plant stores approximately 30 tonnes of energy plutonium.102 The plant also stores a significant amount of weapons-grade fissile materials recovered from liquidated nuclear weapons. In the summer of 1994, the construction of a central storage facility for weapons-grade uranium and plutonium released during the dismantling of nuclear weapons began in Chelyabinsk-65. It is assumed that the first stage of the storage facility, capable of receiving 25 thousand containers with weapons materials, will be put into operation in 1999; construction of the second stage will increase the storage capacity up to 50 thousand containers. According to the project developed by the St. Petersburg Institute VNIPIET, the repository must ensure safe storage of materials for 80-100 years.103
The plant has a wide scientific and technical base to support the work of the main industries, which includes a central plant laboratory, an instrument plant, an instrument 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 Combine)
The Siberian Chemical Combine 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, which was put into operation on November 20, was a once-through 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 system and were used both for the production of plutonium and for the production of heat and electricity.
The first three reactors in 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 generate 660-700 MW of heat and 300 MW of electricity. Thermal energy used for heat supply to Seversk (Tomsk-7) and nearby Tomsk, as well as for the production needs of the Siberian Chemical Combine and the neighboring petrochemical complex.
At present, the spent fuel of industrial reactors of the Siberian Chemical Combine is reprocessed at the radiochemical plant, which is part of the plant, which was commissioned in 1956. Until 1983, the reprocessing of fuel was carried out according to the acetate scheme. After that, the plant was transferred to Purex technology.
Until recently, plutonium separated at the radiochemical plant was supplied to the chemical and metallurgical plant of Tomsk-7 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 mined plutonium has been converted into dioxide and sent to storage.
Another section of the chemical and metallurgical plant is working on the processing of highly enriched uranium and the production of weapon parts from it. In 1994- Operations of converting highly enriched weapons-grade uranium into low-enriched uranium were launched here as part of the Russian-American agreement on the sale of HEU. The part of the work carried out in Tomsk-7 includes the conversion of metallic uranium into the oxide form. A significant part of uranium goes through the redistribution of radiochemical processing to remove chemical pollutants (alloying materials, residues of fission products and transuranium elements). Purified uranium oxide powder is packed into sealed containers and sent to Sverdlovsk-44 and Krasnoyarsk-45 for fluorination and enrichment. At the end of 1996, a production site for fluorination and uranium enrichment began operating in Tomsk-7.107
Krasnoyarsk-26 (Mining and Chemical Combine)
The plant in Krasnoyarsk-26108 was established in February 1950109 for the production of weapons-grade plutonium. Distinctive feature reactor and radiochemical plants and associated workshops, laboratories and storage facilities Krasnoyarsk-26 is their placement in a multilevel system of tunnels inside the 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 three graphite reactors were operating at the plant (AD, ADE-1, ADE-2). In 1964 a radiochemical plant began operating in Krasnoyarsk-26. (From 1958 to 1964, the spent fuel of the reactors was reprocessed at the plants of Chelyabinsk-65 and / or Tomsk-7.) 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, the separated plutonium in the form of oxide has been stored at the plant's warehouses.
Two direct-flow reactors in Krasnoyarsk-26 (AD and ADE-1) were shut down in 1992.11 The third reactor has a two-loop cooling system and is similar in design to the operating reactors of Tomsk-7. As in the case of Tomsk-7, the reactor produces heat for the local population and cannot be shut down without the construction of replacement facilities.
In 1972, work began on the design of the complex of the radiochemical plant RT-2 in Krasnoyarsk-26. In accordance with the project, the RT-2 plant is to carry out radiochemical reprocessing of fuel from VVER-1000 reactors. Construction of the first stage of the spent reactor fuel storage plant began in 1976 on the ground site located 4-5 km north of the underground complex. The storage facility with a capacity of 6,000 tons of fuel was put into operation in December 1985 and by 1995 it was filled by 15-20%. Construction of the second stage of RT-2, a radiochemical plant with a capacity of 1,500 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 (built at 30%) was frozen. Despite the decision of the Russian government to complete the construction in February 1995, 112 the future of the RT-2 plant is unclear.
Name and features
It is called "armory" to distinguish it from "reactor". Plutonium is formed in any nuclear reactor fueled by natural or low-enriched uranium, containing mainly the isotope 238 U, by capturing excess neutrons. But it usually contains more isotopes 240 Pu, 241 Pu, and 242 Pu, which are produced by sequential captures of several neutrons - since the burnup is usually determined by economic factors. The lower the burnup, the fewer isotopes heavier 239 will contain plutonium separated from irradiated nuclear fuel, but the less plutonium in the fuel is formed.
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, which makes 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 are heated, and heat removal elements have to be additionally introduced into the design of a nuclear weapon. Even pure 239 Pu is warmer than the human body. In addition, 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 is fraught with the failure of a nuclear explosive device.
In principle, all these difficulties are surmountable, and nuclear explosive devices made of "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 more than that of 239 Pu.
In the USSR, the production of weapons-grade plutonium was carried out first at the Mayak Combine (near the Kyshtym station, Chelyabinsk Region), then at the Siberian Chemical Combine in Seversk (formerly Tomsk-7), later the Krasnoyarsk Mining and Chemical Combine in the city of Krasnoyarsk was put into operation. Zheleznogorsk (also known as Sotsgorod and Krasnoyarsk-26).
In the United States, weapons-grade plutonium was produced at several locations, such as the Hanford Complex in Washington state.
see also
Notes
Links
- Reactor-Grade and Weapons-Grade Plutonium in Nuclear Explosives, Canadian Coalition for Nuclear Responsibility
- Nuclear weapons and power-reactor plutonium, Amory B. Lovins, February 28, 1980, Nature, Vol. 283, No. 5750, pp. 817-823
- Garwin Richard L. The Nuclear Fuel Cycle: Does Reprocessing Make Sense? // Nuclear energy / B. van der Zwaan. - World Scientific, 1999. - P. 144. - ISBN 978-981-02-4011-0
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See what "Weapon-grade plutonium" is in other dictionaries:
Nuclide table General information Name, symbol Plutonium 240, 240Pu Neutrons 146 Protons 94 Nuclide properties Atomic mass 240.0538135 (20) ... Wikipedia
Nuclide table General information Name, symbol Plutonium 239, 239Pu Neutrons 145 Protons 94 Nuclide properties Atomic mass 239.0521634 (20) ... Wikipedia
94 Neptunium ← Plutonium → Americium Sm Pu ... Wikipedia
I; m. Chemical element (Pu), a radioactive silvery white metal related to actinides (obtained artificially; used in nuclear power as a raw material for nuclear fuel). Armory item (used in nuclear ... ... encyclopedic Dictionary
plutonium - I; m. see also. plutonium Chemical element (Pu), a radioactive silvery white metal related to actinides (obtained artificially; used in nuclear power as a raw material for obtaining nuclear fuel) Weapon-grade plutonium. ... ... Dictionary of many expressions
Plutonium (Pu) Atomic number 94 Appearance of a simple substance Properties of an atom Atomic mass ( molar mass) 244.0642 a. e. m. (g / mol) ... Wikipedia
Purpose of the reactor Weapon Technical parameters Coolant Water Fuel Unenriched uranium metal Development Project 1946 1948 ... Wikipedia
Radioactive waste (RW) waste containing radioactive chemical elements and of no practical value. These are often products of nuclear processes such as nuclear fission. Most of the radioactive waste is made up of the so-called "inactive ... ... Wikipedia
Plutonium (Latin Plutonium, denoted by the symbol Pu) is a radioactive chemical element with atomic number 94 and atomic weight 244.064. Plutonium is an element of the III group of the periodic system of Dmitry Ivanovich Mendeleev, belongs to the actinide family. Plutonium is a heavy (density under normal conditions 19.84 g / cm³) brittle radioactive metal of silvery-white color.
Plutonium has no stable isotopes. Of a hundred possible isotopes of plutonium, twenty-five have been synthesized. Fifteen of them studied nuclear properties (mass numbers 232-246). Four have found practical applications. The longest-lived isotopes - 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. Plutonium is naturally found in trace amounts in uranium ores (239Pu); it is formed from uranium under the action of neutrons, the sources of which are the reactions occurring during the interaction of α-particles with light elements (which are part of the ores), the 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) during the bombardment of a uranium oxide target ( U3O8) by highly accelerated deuterium nuclei (deuterons) from a sixty-inch cyclotron. In May 1940, the properties of plutonium were predicted by Louis Turner.
In December 1940, the plutonium isotope Pu-238 was discovered, with a half-life of ~ 90 years, a year later, 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 (isotope 239Pu) is used in nuclear weapons and serves as the nuclear fuel for power reactors operating on thermal and especially fast neutrons. The critical mass for 239Pu in the form of 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 stimulators of human cardiac activity.
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 harmful to the body. It is worth considering that different plutonium isotopes 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. 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 external environment) for algae is 1000-9000, for plankton - about 2300, for starfish - about 1000, for mollusks - up to 380, for muscles, bones, liver and stomach of fish - 5, 570, 200 and 1060, respectively. Terrestrial plants assimilate plutonium mainly through the root system and accumulate it up 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 hazard (like any other heavy metal) is much less pronounced (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 power: for 239Pu, the range of α-particles in air is 3.7 cm, and in soft biological tissue, 43 microns. Therefore, α-particles pose a serious danger if their source is in the body of an infected person. At the same time, they damage the body tissues surrounding the element.
At the same time, γ-rays and neutrons, which plutonium also emits and which are able to penetrate into 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 the element is taken with water and food, plutonium is less toxic than substances such as caffeine, some vitamins, pseudoephedrine and many plants and fungi. This is due to the fact that this element is poorly absorbed by the gastrointestinal tract, even when supplied in the form of a soluble salt, this very salt is bound by the contents of the stomach and intestines. However, the absorption of 0.5 gram of plutonium in a finely divided or dissolved state can lead to death from acute irradiation of the digestive system in a few days or weeks (for cyanide this value is 0.1 gram).
From the point of view of inhalation, plutonium is an ordinary toxin (roughly corresponds to mercury vapor). When inhaled, plutonium is carcinogenic and can cause lung cancer. So when inhaling one hundred milligrams of plutonium in the form of particles of the optimal size for keeping 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 penetration of plutonium into the body is increased due to the fact that plutonium is prone to the formation of aerosols.
Despite being a metal, it is quite volatile. A short stay of metal in a room significantly increases its concentration in the air. Once in the lungs, plutonium partially settles on the surface of the lungs, partially passes into the blood, and then into the lymph and bone marrow substance. Most (about 60%) goes to bone tissue, 30% to the liver and only 10% is excreted naturally. The amount of plutonium ingested depends on the size of the aerosol particles and the 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 pull plutonium through the lymph nodes. Once in the body, plutonium is removed from it for a very long time - over the course of 50 years, only 80% will be excreted 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 the ninety-fourth element in the bones is constant.
During and after World War II, scientists at the Manhattan Project, as well as scientists from the Third Reich and other research organizations, experimented with 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 was that chronically ill patients were usually injected intramuscularly with 5 μg of plutonium. As a result, it was found that the lethal dose for a patient is equal to one microgram of plutonium, and that plutonium is more dangerous than radium and is prone to accumulation in bones.
As you know, plutonium is an element practically absent in nature. However, about five tons of it was 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 prior to the 1980s is estimated at 10 tons. According to some estimates, the soil in the United States of America contains on average 2 millicurie (28 mg) plutonium per km2 of fallout, and the presence of plutonium in the Pacific Ocean is increased compared to the general proliferation of nuclear materials on earth.
The latter phenomenon is associated with the conduct of US nuclear tests on the territory of the Marshall Islands in the Pacific Range in the mid-1950s. The residence time of plutonium in the surface waters of the ocean is from 6 to 21 years, however, even after this period, plutonium falls to the bottom together with biogenic particles, from which it is reduced to soluble forms as a result of microbial decomposition.
World pollution with the ninety-fourth element is associated not only with nuclear tests, but also with accidents in industries and equipment interacting with this element. So in January 1968, the US Air Force B-52, carrying four nuclear charges, crashed in Greenland. As a result of the explosion, the charges were destroyed and plutonium spilled into the ocean.
Another case of radioactive contamination of the environment as a result of the accident occurred with the Soviet spacecraft "Kosmos-954" on January 24, 1978. As a result of an uncontrolled de-orbit, a satellite with a nuclear power source on board fell into the territory of Canada. As a result of the accident, more than a kilogram of plutonium-238 was released into the environment, spreading over an area of \u200b\u200babout 124,000 m².
The most terrible example of an accidental 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 \u200b\u200babout 2200 km².
The release of plutonium into the environment is associated not only with man-made accidents. There are known cases of plutonium leakage from both laboratory and factory conditions. There are more than twenty known leakage accidents from the 235U and 239Pu laboratories. During 1953-1978. accidents led to the loss from 0.81 (Mayak, March 15, 1953) to 10.1 kg (Tomsk, December 13, 1978) 239Pu. Accidents at industrial plants resulted in the total death of two people in the city of Los Alamos (August 21, 1945 and May 21, 1946) due to two accidents and losses 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 is fissioned by neutrons, energy is released in the amount of 200 MeV, which is 50 million times more than in the case of the most famous exothermic reaction: C + O2 → CO2. "Burning" in a nuclear reactor, one gram of plutonium gives 2 107 kcal - this is the energy contained in 4 tons of coal. A thimble of plutonium fuel in the energy equivalent can be equated to forty wagons of good firewood!
It is believed that the "natural isotope" of plutonium (244Pu) is 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.
History
In 1934, a group of scientists led by Enrico Fermi made a statement that during scientific works at the University of Rome, they discovered a chemical element with atomic number 94. At the insistence of Fermi, the element was called the Hesperium, the scientist was convinced that he had discovered a new element, which is now called plutonium, thus making the assumption about the existence of transuranium elements and becoming their theoretical discoverer. Fermi defended this hypothesis in his Nobel lecture in 1938. Only after the discovery of nuclear fission by German scientists Otto Frisch and Fritz Strassmann, Fermi was forced to make a note in the printed version, published in Stockholm in 1939, indicating the need to revise "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 transuranic elements, as he previously believed.
The new ninety-fourth element was opened at the end of 1940. It happened at Berkeley at the University of California. When uranium oxide (U3O8) was bombarded with heavy hydrogen nuclei (deuterons), a group of American radiochemists led by Glenn T. Seaborg discovered a previously unknown emitter of alpha particles with a half-life of 90 years. This emitter turned out to be an isotope of element 94 with a mass number of 238. Thus, on December 14, 1940, the first microgram quantities of plutonium were obtained together with an admixture of other elements and their compounds.
In the course of an experiment carried out in 1940, it was found that during a nuclear reaction carried out, a short-lived isotope neptunium-238 (half-life of 2.117 days) is first obtained, and from it already 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. K. Wall thanks to the study of its first chemical properties - the ability to have at least at least two oxidation states. A little later than the end of the experiments, it was found that this isotope is non-fissile, and therefore uninteresting for further study. Soon (March 1941) Kennedy, Seaborg, Segre and Val synthesized a more important isotope, plutonium-239, by irradiating uranium with neutrons strongly accelerated 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 94 element was proposed in 1948 by Macmillan, who a few months before the discovery of plutonium, together with F. Abelson, received the first element heavier than uranium - element 93, which was named neptunium in honor of the planet Neptune - the first behind Uranus. By analogy, it was decided to call element No. 94 plutonium, since the planet Pluto is the second after Uranus. In turn, Seaborg proposed to call the new element "plutium", but then realized that the name does not sound very much 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. Eventually, the element was named "plutonium" after the discovery of the last planet in the solar system.
Being in nature
The longest-lived plutonium isotope has a half-life of 75 million years. The figure is quite 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 to survive to this day. And yet, this does not mean that there is no plutonium at all in the Earth. It is constantly formed in uranium ores. Capturing neutrons from cosmic radiation and neutrons formed during the spontaneous (spontaneous) fission of 238U nuclei, some - very few - atoms of this isotope are converted into 239U atoms. The nuclei of this element are very unstable, they emit electrons and thereby increase their charge, 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 quite long at 24,000 years. On average, the 239Pu content is about 400,000 times less than that of radium. Therefore, it is extremely difficult not only to extract - even to detect "terrestrial" plutonium. Small amounts of 239Pu - a trillionth - and fission products can be found in uranium ores, for example, in a natural nuclear reactor in Oklo, Gabon, West Africa. The so-called "natural nuclear reactor" is considered the only one in the world in which actinides and their fission products are currently being formed in the geosphere. By current estimates in this region several million years ago there was a self-sustaining reaction with the release of heat, which lasted more than half a million years.
So, we already know that neptunium (239Np) is formed in uranium ores as a result of the capture of neutrons by uranium nuclei, the product of β-decay of which is natural plutonium-239. Thanks to special instruments - mass spectrometers, the presence of plutonium-244 (244Pu), which has the longest half-life - about 80 million years, was detected in Precambrian bastnesite (in cerium ore). In nature, 244Pu is found mainly 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 plutonium-244 decay chain, its decay takes place, but this happens very rarely (1 case in 10,000). Very small amounts of plutonium-238 (238Pu) are attributed to the very rare double beta decay of the parent isotope, uranium-238, which has been found in uranium ores.
Traces of isotopes 247Pu and 255Pu were found in the dust collected after the explosions of thermonuclear bombs.
The minimum amount of plutonium can hypothetically be found in the human body, given that a huge number of nuclear tests have been carried out 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, the ninety-fourth element is accumulated by marine organisms; terrestrial plants assimilate plutonium mainly through the root system.
It turns out that artificially synthesized plutonium still exists in nature, so why is it not mined, but produced 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 than plutonium! For this reason, it is extremely difficult not only to extract - even to detect - "terrestrial" plutonium. It was possible to do this only after the physical and chemical properties plutonium obtained in nuclear reactors.
Application
The isotope 239Pu (along with U) is used as a nuclear fuel for 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 about 370 GW of electricity (or 15% of the total electricity production in the world). 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 work of the heart (pacemakers). 238Pu is used in small-sized nuclear power sources used in space research. Thus, plutonium-238 is a power source for New Horizons, Galileo and Cassini probes, the Curiosity rover and other spacecraft.
Plutonium-239 is used in nuclear weapons, as 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 a smaller volume in the sphere (where the bomb core is located), therefore, one can gain in the explosive power of the bomb due to this property.
The scheme according to which a nuclear explosion with the participation of plutonium occurs is in the construction of the bomb itself, the core of which consists of a sphere filled with 239Pu. At the moment of collision with the earth, the sphere is compressed to a million atmospheres due to the structure and due to the explosive substance surrounding this sphere. After the impact, the nucleus expands in volume and density in the shortest time - ten microseconds, the assembly jumps through the critical state on thermal neutrons and goes into a supercritical state on fast neutrons - a nuclear chain reaction begins with the participation of neutrons and element nuclei. In the final explosion of a nuclear bomb, a temperature of the order of tens of millions of degrees is released.
Plutonium isotopes have found their application in the synthesis of transplutonium (after plutonium) elements. For example, at the Oak Ridge National Laboratory, 24496Cm, 24296Cm, 24997Bk, 25298Cf, 25399Es and 257100Fm are obtained under long-term neutron irradiation of 239Pu. In the same way, americium 24195Am was first obtained in 1944. In 2010, plutonium-242 oxide bombarded with calcium-48 ions was the source of ununquadium.
δ-Stabilized plutonium alloys are used in the manufacture of fuel rods, because they have significantly better metallurgical properties in comparison with pure plutonium, which undergoes phase transitions when heated and is a very fragile and unreliable material. Alloys of plutonium with other elements (intermetallic compounds) are usually obtained by direct interaction of elements in the required ratios, 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 intermediate compounds 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) upon rapid cooling. Gallium, aluminum, americium, scandium and cerium can stabilize δ-plutonium at room temperature.
Large amounts 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 β-plutonium structure at room temperature with sharp cooling. The use of such alloys is quite diverse. For example, a plutonium-gallium alloy is used to stabilize the δ-phase of plutonium, which avoids the α-δ phase transition. The plutonium-gallium-cobalt ternary alloy (PuGaCo5) is a superconducting alloy at a temperature of 18.5 K. There are a number of alloys (plutonium-zirconium, plutonium-cerium and plutonium-cerium-cobalt) that are used as nuclear fuel.
Production
Commercial plutonium is produced in two ways. This is either irradiation of 238U nuclei contained in nuclear reactors, or radiochemical separation (coprecipitation, extraction, ion exchange, etc.) of plutonium from uranium, transuranium elements and fission products contained in spent fuel.
In the first case, the most practical isotope 239Pu (in a mixture with a small admixture of 240Pu) is obtained 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. Next, neptunium-238 fissions spontaneously, emitting beta minus particles that form plutonium-238.
Usually the content of 239Pu in a mixture is 90-95%, 240Pu-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 fractions of a percent of the content of 242Pu. Small amounts of isotopically pure plutonium-238 are produced by neutron irradiation of neptunium-237. Light plutonium isotopes with mass numbers 232-237 are usually obtained on a cyclotron by irradiating uranium isotopes with α-particles.
The second method of industrial production of 239Pu uses a 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, plutonium is subjected to further purification and concentration. The scheme of such a process is based on the difference in the properties of tetra- and hexavalent compounds of the separated elements.
Initially, the spent fuel rods are dismantled and the cladding containing the spent plutonium and uranium is removed by physical and chemical methods. Next, the recovered nuclear fuel is dissolved in nitric acid. After all, it is a strong oxidizing agent when dissolved, and uranium and plutonium, and impurities are oxidized. Plutonium atoms with zero valence are converted into Pu + 6, dissolution of both plutonium and uranium occurs. 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 precipitate contains neptunium and rare earth elements, but the bulk (uranium) remains in solution. Then plutonium is again oxidized to Pu + 6 and lanthanum fluoride is added again. Now the rare earth elements are deposited, and the plutonium remains in solution. Further, neptunium is oxidized to a tetravalent state with potassium bromate, since this reagent does not act on plutonium, then during the 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 (by reduction with barium, calcium or lithium vapor) metal plutonium is obtained.
The production of purer plutonium can be achieved by electrolytic refining of a pyrochemically produced metal, which is produced in electrolysis cells at a temperature of 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 obtain large quantities of plutonium, breeder reactors are built, the so-called "breeders" (from the English verb to breed - to multiply). These reactors got their name due to their ability to obtain fissile material in an amount exceeding the cost of this material to obtain. The difference between reactors of this type from the rest is that the neutrons in them are not slowed down (there is no moderator, for example, graphite) in order for them to react as much as possible with 238U.
After the reaction, 239U atoms are formed, which later 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-238 dioxide (238UO2), in which 239Pu is formed. The combined use of 238U and 235U allows bridders to produce 50-60 times more energy from natural uranium than other reactors. However, these reactors have a big drawback - the fuel rods must be cooled by an environment 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 to build them only in the 1950s.
Physical properties
Plutonium is a very heavy (standard density 19.84 g / cm³) silvery metal, in a purified state it is very similar to nickel, but in air plutonium quickly oxidizes, dims, forming an iridescent film, first light yellow, then turning into dark purple. With strong oxidation, an olive-green oxide powder (PuO2) appears on the metal surface.
Plutonium is a highly electronegative and reactive metal, many times greater than even uranium. It has seven allotropic modifications (α, β, γ, δ, δ ", ε and ζ), which vary 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 fragile and very hard - this structure is about the same hard as gray cast ironif it is not alloyed with other metals that will give the alloy plasticity and softness. In addition, in this most dense form, plutonium is the sixth densest element (only osmium, iridium, platinum, rhenium and neptunium are heavier than it). Further allotropic transformations of plutonium are accompanied by abrupt changes in density. So, for example, when heated from 310 to 480 ° C, it does not expand, like other metals, but contracts (phases "delta" and "delta-prime"). Upon melting (transition from the epsilon phase to the liquid phase), the plutonium also compresses, allowing the 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 specific resistance 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. Such an "anomaly" can be traced up to a temperature of 100 K - below this mark, the electrical resistance will decrease. However, from a mark of 20 K, the resistance starts to increase again due to the radiation activity of the metal.
Plutonium has the highest electrical resistivity of all the studied actinides (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 its 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 thermo-jacket is heated to a temperature exceeding the boiling point of water! In addition, due to its radioactivity, plutonium undergoes changes in its crystal lattice - there is a kind of annealing due to self-irradiation due to an increase in temperature above 100 K.
The large number of allotropic modifications in plutonium makes it a difficult metal to handle 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, but it tends to change and turn into a plastic material, and form 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 a low percentage of aluminum, cerium or gallium. Alloyed with these metals, plutonium can be used in welding. In general, the delta shape has more pronounced characteristics of the metal - in terms of strength and forging ability it is close to aluminum.
Chemical properties
The chemical properties of the ninety-fourth element are very similar to those 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 in solution simultaneously in equilibrium, 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 the other valences (oxidation states). Plutonium ions of all oxidation states are prone to hydrolysis and complexation. The ability to form such compounds increases in the series Pu5 +
Compact plutonium slowly oxidizes in air, becoming covered with a rainbow oily oxide film. The following plutonium oxides are known: PuO, Pu2O3, PuO2 and the phase of variable composition Pu2O3 - Pu4O7 (berthollides). In the presence of a small amount of moisture, the rate of oxidation and corrosion increases significantly. If a metal is exposed to small amounts of humid air for a long time, plutonium dioxide (PuO2) is formed on its surface. With a lack of oxygen, its dihydride (PuH2) can also form. Surprisingly, plutonium rusts in an atmosphere of inert gas (such as argon) with water vapor much faster than in dry air or pure oxygen. In fact, this fact is easy to explain - the direct action of oxygen forms an oxide layer on the plutonium surface, which prevents further oxidation, the presence of moisture produces a loose mixture of oxide and hydride. By the way, thanks to just such a coating, the metal becomes pyrophoric, that is, it is capable of spontaneous combustion, for this reason, plutonium metal 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 readily soluble only in very acidic media (for example, hydrochloric acid HCl), and also dissolves in hydrogen chloride, hydrogen iodide, hydrogen bromide, 72% perchloric acid, 85% phosphoric acid H3PO4, concentrated CCl3COOH, sulfamic acid and concentrated boiling acid. Plutonium does not noticeably dissolve in alkali solutions.
When alkalis are exposed to solutions containing tetravalent plutonium, a precipitate of plutonium hydroxide Pu (OH) 4 xH2O, which has basic properties, precipitates. Under the action of alkalis on solutions of salts containing PuO2 +, amphoteric hydroxide PuO2OH precipitates. Salts correspond to it - plutonites, for example, Na2Pu2O6.
Plutonium salts are readily hydrolyzed upon contact with neutral or alkaline solutions, creating insoluble plutonium hydroxide. Concentrated plutonium solutions are unstable due to radiolytic decomposition leading to precipitation.