The density of plutonium is 239. Entertaining nuclear physics (13 photos)

This metal is called precious, but not for its beauty, but for its irreplaceability. In the periodic table of Mendeleev, this element occupies cell number 94. It is with it that scientists pin their greatest hopes, and it is plutonium that they call the most dangerous metal for humanity.

Plutonium: description

By appearance it is a silvery-white metal. It is radioactive and can be represented in the form of 15 isotopes with different half-lives, for example:

• Pu-238 – about 90 years
• Pu-239 – about 24 thousand years
• Pu-240 – 6580 years
• Pu-241 – 14 years
• Pu-242 – 370 thousand years
• Pu-244 – about 80 million years

This metal cannot be extracted from ore, since it is a product of the radioactive transformation of uranium.

How is plutonium obtained?

The production of plutonium requires the fission of uranium, which can only be done in nuclear reactors. If we talk about the presence of the element Pu in earth's crust, then for 4 million tons of uranium ore there will be only 1 gram of pure plutonium. And this gram is formed by the natural capture of neutrons by uranium nuclei. Thus, in order to obtain this nuclear fuel (usually the isotope 239-Pu) in an amount of several kilograms, it is necessary to carry out a complex technological process in a nuclear reactor.

Properties of plutonium

The radioactive metal plutonium has the following physical properties:

• density 19.8 g/cm 3
• melting point – 641°C
• boiling point – 3232°C
• thermal conductivity (at 300 K) – 6.74 W/(m K)

Plutonium is radioactive, which is why it is warm to the touch. Moreover, this metal is characterized by the lowest thermal and electrical conductivity. Liquid plutonium is the most viscous of all existing metals.

The slightest change in the temperature of plutonium leads to an instant change in the density of the substance. In general, the mass of plutonium is constantly changing, since the nuclei of this metal are in a state of constant fission into smaller nuclei and neutrons. The critical mass of plutonium is the name given to the minimum mass of a fissile substance at which fission (a nuclear chain reaction) remains possible. For example, the critical mass of weapons-grade plutonium is 11 kg (for comparison, the critical mass of highly enriched uranium is 52 kg).

Uranium and plutonium are the main nuclear fuels. To obtain plutonium in large quantities, two technologies are used:

• uranium irradiation
• irradiation of transuranium elements obtained from spent fuel

Both methods involve the separation of plutonium and uranium as a result of a chemical reaction.

To obtain pure plutonium-238, neutron irradiation of neptunium-237 is used. The same isotope is involved in the creation of weapons-grade plutonium-239; in particular, it is an intermediate decay product. $1 million is the price for 1 kg of plutonium-238.

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 small 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 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 operate spaceships. 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.

The integrated fast reactor (IFR) is not just a new type of reactor, it is a new fuel cycle. Integral fast reactor is a fast neutron reactor without a moderator. It only has an active zone and no blanket.
IBR uses metal fuel− an alloy of uranium and plutonium.
Its fuel cycle uses fuel reduction directly in the reactor itself using pyroprocessing. In IBR pyroprocessing, almost pure uranium is collected on a solid cathode, and a mixture of plutonium, americium, neptunium, curium, uranium and some fission products is collected in a liquid cadmium cathode floating in the electrolyte salt. The remaining fission products are collected in the electrolyte salt and in the cadmium layer.
The integrated fast reactor is cooled with liquid sodium or lead. The production of metal fuel is simpler and cheaper than ceramic fuel. Metallic fuel makes the pyroprocess a natural choice. Metallic fuel has better thermal conductivity and heat capacity than oxide fuel. The fuel is an alloy of uranium and plutonium.
The initial loading into an integrated fast reactor should contain more isotopes fissile under the influence of thermal neutrons ( > 20%) than in a thermal neutron reactor. This could be highly enriched uranium or plutonium, decommissioned nuclear weapons, etc. During operation, the reactor converts materials (fertile) that are non-fissile under the influence of thermal neutrons into fissile ones. Fertile materials in a fast reactor can be depleted uranium (mostly U-238), natural uranium, thorium, or uranium processed from irradiated fuel from a conventional water reactor.
The fuel is contained in a steel casing with liquid sodium located between the fuel and the casing. The free space above the fuel allows helium and radioactive xenon to freely collect without significantly increasing the pressure inside the fuel element and allows the fuel to expand without damaging the reactor cladding.
The advantage of lead over sodium is its chemical inertness, especially in relation to water or air. On the other hand, lead is much more viscous, making it difficult to pump. In addition, it contains neutron-activated isotopes, which are practically absent in sodium.
The cooling circuits are designed in such a way that they allow heat transfer by convection. So if there is a loss of power to the pumps or an unexpected shutdown of the reactor, the heat around the core will be sufficient to circulate the coolant.
In IBR, fissile isotopes are not separated from plutonium isotopes, as well as from fission products, and therefore the use of such a process for the production of weapons is practically impossible. In addition, plutonium is not removed from the reactor, which makes its unauthorized use unrealistic. After the actinides (uranium, plutonium and minor actinides) are processed, the waste remaining is fission products Sm-151 with a half-life of 90 l or long-lived ones like Tc-99 with a half-life of 211,000 l or more.
IBR wastes either have short half-lives or very long ones, meaning they are weakly radioactive. The total amount of IBR waste is 1/20 of the reprocessed fuel (which is usually considered waste) of thermal neutron reactors of the same power. 70% of fission products are either stable or have half-lives of about a year. Technetium-99 and iodine-129, of which 6% in fission products have very long periods half-lives, but can be transmuted in the reactor into isotopes with short half-lives (15.46 s and 12.36 h) by absorption of neutrons in the reactor. Zirconium-93 (5% in waste) can be recycled into fuel cladding where radioactivity is not a concern. The remaining components of the waste are less radioactive than natural uranium.
The IDB uses a fuel cycle that is two orders of magnitude more efficient in terms of fuel use compared to traditional cycles in slow neutron reactors, preventing the proliferation of nuclear weapons, minimizing high-level waste, and, moreover, using some waste as fuel.
In an IBR, the fuel and cladding are designed so that as the temperature increases and they expand, more and more neutrons leave the core, reducing the intensity of the chain reaction. That is, a negative reactivity coefficient works. In IBR, this effect is so strong that it can stop the chain reaction without operator intervention

Pyroprocessing ‒ high temperature method electrolytic reprocessing of spent nuclear fuel. Compared to the hydrometallurgical method(for example PUREX) , pyroprocessing is used directly at the reactor. Solvents are molten salts (for example, LiCl + KCl or LiF + CaF 2) and molten metals (for example, cadmium, bismuth, magnesium), rather than water and organic compounds.In pyroprocessing, the extraction of uranium, as well as plutonium and minor actinides, occurs simultaneously and they can be immediately used as fuel. The volume of waste is smaller and contains mainly fission products. Pyro Processing is used in IBRs and molten salt reactors.

How much does 1 cube of plutonium weigh, the weight of 1 m3 of plutonium. The number of kilograms in 1 cubic meter, the number of tons in 1 cubic meter, kg in 1 m3. Bulk density of plutonium specific gravity.

What do we want to learn today? How much does 1 cube of plutonium weigh, the weight of 1 m3 of plutonium? No problem, you can find out the number of kilograms or the number of tons at once, the mass (weight of one cubic meter, weight of one cube, weight of one cubic meter, weight of 1 m3) is indicated in Table 1. If anyone is interested, you can skim the small text below and read some explanations. How is the amount of substance, material, liquid or gas we need measured? Except for those cases when it is possible to reduce the calculation of the required quantity to the counting of goods, products, elements in pieces (piece counting), it is easiest for us to determine the required quantity based on volume and weight (mass). In everyday life, the most common unit of volume measurement for us is 1 liter. However, the number of liters suitable for household calculations is not always an appropriate way to determine the volume for business activities. In addition, liters in our country have not become a generally accepted “production” and trading unit for measuring volume. One cubic meter, or in its abbreviated version - one cube, turned out to be a fairly convenient and popular unit of volume for practical use. We are accustomed to measuring almost all substances, liquids, materials and even gases in cubic meters. It's really convenient. After all, their costs, prices, rates, consumption rates, tariffs, supply contracts are almost always tied to cubic meters (cubes), and much less often to liters. No less important for practical activities is knowledge of not only the volume, but also the weight (mass) of the substance occupying this volume: in this case we are talking about how much 1 cubic meter weighs (1 cubic meter, 1 cubic meter, 1 m3). Knowing mass and volume gives us a fairly complete idea of ​​quantity. Site visitors, when asking how much 1 cube weighs, often indicate specific units of mass in which they would like to know the answer to the question. As we noticed, most often they want to know the weight of 1 cube (1 cubic meter, 1 cubic meter, 1 m3) in kilograms (kg) or tons (t). Essentially, you need kg/m3 or t/m3. These are closely related units that define quantity. In principle, a fairly simple independent conversion of weight (mass) from tons to kilograms and vice versa is possible: from kilograms to tons. However, as practice has shown, for most site visitors a more convenient option would be find out immediately how many kilograms 1 cubic (1 m3) of plutonium weighs or how many tons 1 cubic (1 m3) of plutonium weighs, without converting kilograms into tons or vice versa - the number of tons into kilograms per cubic meter (one cubic meter, one cubic meter, one m3). Therefore, in Table 1 we indicated how much 1 cubic meter (1 cubic meter, 1 cubic meter) weighs in kilograms (kg) and tons (t). Choose the table column that you need yourself. By the way, when we ask how much 1 cubic meter (1 m3) weighs, we mean the number of kilograms or the number of tons. However, from a physical point of view, we are interested in density or specific gravity. The mass of a unit volume or the amount of substance contained in a unit volume is bulk density or specific gravity. In this case bulk density and specific gravity of plutonium. Density and specific gravity in physics are usually measured not in kg/m3 or tons/m3, but in grams per cubic centimeter: g/cm3. Therefore, in Table 1, specific gravity and density (synonyms) are indicated in grams per cubic centimeter (g/cm3)

The plutonium isotope 238 Pu was first artificially obtained on February 23, 1941 by a group of American scientists led by G. Seaborg by irradiating uranium nuclei with deuterons. Only then was plutonium discovered in nature: 239 Pu is usually found in negligible quantities in uranium ores as a product of the radioactive transformation of uranium. Plutonium is the first artificial element obtained in quantities available for weighing (1942) and the first whose production began on an industrial scale.
The element's name continues the astronomical theme: it is named after Pluto, the second planet after Uranus.

Being in nature, receiving:

In uranium ores, as a result of the capture of neutrons (for example, neutrons from cosmic radiation) by uranium nuclei, neptunium (239 Np) is formed, the product b- the decay of which is natural plutonium-239. However, plutonium is formed in such microscopic quantities (0.4-15 parts Pu per 10 12 parts U) that its extraction from uranium ores is out of the question.
Plutonium is produced in nuclear reactors. In powerful neutron streams, the same reaction occurs as in uranium ores, but the rate of formation and accumulation of plutonium in the reactor is much higher - a billion billion times. For the reaction of converting ballast uranium-238 into energy-grade plutonium-239, optimal (within acceptable) conditions are created.
Plutonium-244 also accumulated in a nuclear reactor. Isotope of element No. 95 - americium, 243 Am captured a neutron and turned into americium-244; americium-244 transformed into curium, but in one out of 10 thousand cases a transition occurred into plutonium-244. A plutonium-244 preparation weighing only a few millionths of a gram was isolated from a mixture of americium and curium. But they were enough to determine the half-life of this interesting isotope - 75 million years. Later it was refined and turned out to be equal to 82.8 million years. In 1971, traces of this isotope were found in the rare earth mineral bastnäsite. 244 Pu is the longest-lived of all isotopes of transuranium elements.

Physical properties:

Silvery-white metal, has 6 allotropic modifications. Melting point 637°C, boiling point - 3235°C. Density: 19.82 g/cm3.

Chemical properties:

Plutonium is capable of reacting with oxygen to form oxide(IV), which, like all the first seven actinides, has a weak basic character.
Pu + O 2 = PuO 2
Reacts with dilute sulfuric, hydrochloric, perchloric acids.
Pu + 2HCl(p) = PuCl 2 + H 2 ; Pu + 2H 2 SO 4 = Pu(SO 4) 2 + 2H 2
Does not react with nitric and concentrated sulfuric acids. The valency of plutonium varies from three to seven. Chemically, the most stable (and therefore the most common and most studied) compounds are tetravalent plutonium. Separation of loved ones chemical properties actinides - uranium, neptunium and plutonium - may be based on the difference in the properties of their tetra- and hexavalent compounds.

The most important connections:

Plutonium(IV) oxide, PuO 2 , has a weak basic character.
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Application:

Plutonium was widely used in the production of nuclear weapons (so-called “weapons-grade plutonium”). The first plutonium-based nuclear device was detonated on July 16, 1945 at the Alamogordo test site (test codenamed Trinity).
It is used (experimentally) as nuclear fuel for nuclear reactors for civil and research purposes.
Plutonium-242 is important as a “raw material” for the relatively rapid accumulation of higher transuranium elements in nuclear reactors. If plutonium-239 is irradiated in a conventional reactor, then it will take about 20 years to accumulate microgram amounts of, for example, California-251 from grams of plutonium. Plutonium-242 is not fissile by thermal neutrons, and even in large quantities it can be irradiated in intense neutron fluxes. Therefore, in reactors, all elements from californium to einsteinium are “made” from this isotope and accumulated in weight quantities.

Kovalenko O.A.
HF Tyumen State University

Sources:
"Harmful chemical substances: Radioactive substances"Reference book L. 1990 p. 197
Rabinovich V.A., Khavin Z.Ya. "A short chemical reference book" L.: Chemistry, 1977 p. 90, 306-307.
I.N. Beckman. Plutonium. (textbook, 2009)