The element polonium was named after. Why was polonium needed? Physical and chemical properties

Chemistry

Element N° 84 - polonium - is the first element inscribed in the periodic table after the discovery of radioactivity. It is also the first (in order of atomic numbers) and the lightest of the elements that do not have stable isotopes. It is also one of the first radioactive elements used in space research.

At the same time, element No. 84 is perhaps one of the least known, least popular radioactive elements. At first it remained in the shadows, overshadowed by the glory of radium. Later, it was not advertised too much, like almost all materials from atomic and space research.

The story of the discovery of element No. 84 is quite well known. It was discovered by Pierre Curie and Maria Sklodowska-Curie. In the laboratory journal of the Curies, the symbol "Rho" (inscribed in Pierre's hand) first appears on July 13, 1898.

A few years after the death of Pierre Curie, his wife and co-author of his two most striking discoveries wrote the book “Pierre Curie.” Thanks to this book, we will learn first-hand the history of the discovery of polonium and radium, and get acquainted with the features and principles of work of two outstanding scientists. Here is an excerpt from this book: “...The ore we chose was pitchblende, uranium ore, which in its pure form is approximately four times more active than uranium oxide... The method we used is a new method of chemical analysis based on radioactivity. It consists of separating by the usual means of chemical analysis and measuring, under appropriate conditions, the radioactivity of all isolated products. In this way, you can get an idea of ​​the chemical properties of the desired radioactive element; the latter concentrates in those fractions whose radioactivity becomes greater and greater as the separation continues. We were soon able to determine that the radioactivity was concentrated predominantly in two different chemical fractions, and we concluded that at least two new radioelements were present in the resin blend: polonium and radium. We reported the existence of the element polonium in July 1898 and radium in December of the same year...”

In Latin Polonia means Poland.

"Polonium" is not the first "geographical" name for an element. By that time, germanium, ruthenium, gallium, and scandium had already been discovered. Nevertheless, this name is special; it can be considered as a name-protest: independent Polish state did not exist at that time. Poland was fragmented, divided between the Austrian, German and Russian empires...

In the famous book “Marie Curie”, written by the youngest daughter of the Curies, Eva, the following conclusion was made:

“The choice of this name shows that Marie, having become a French physicist, did not renounce her homeland. This is also evidenced by the fact that before the note “On a new radioactive substance in the composition of uraninite” appeared in the “Reports of the Academy of Sciences,” Marie sent the manuscript to her homeland, to Joseph Bogussky, the head of that laboratory of the Museum of Industry and agriculture, where her first scientific experiments began. The message was published in Swiatlo, a monthly illustrated review, almost simultaneously with its publication in Paris."
In the Polish People's Republic, the memory of Marie Skłodowska-Curie is sacred.

The house in which she was born has been restored, and the Warsaw Radium Institute is named after her.

Why radium and not polonium?

In fact, why did radium, and not polonium, bring the Curie couple worldwide fame? After all, the first element they discovered was element No. 84. After a year of work, they had no doubt that two new elements were present in uranium tar. But these elements made themselves known only by radioactivity, and in order to convince everyone, and above all chemists, that discoveries had really occurred, it was necessary to isolate these activities and obtain new elements, at least in the form of individual compounds.

All radioactive elements and isotopes, as is known, are now united into families: when decaying, the nucleus of a radioactive atom turns into the atomic nucleus of another, daughter element. All elements of radioactive families are in a certain balance with each other. It has been measured that in uranium ores the equilibrium ratio of uranium to polonium is 1.9-1010, and 0.2 mg of polonium is in equilibrium with a gram of radium. This means that in uranium minerals there is almost 4 million times less radium than uranium, and polonium is another 5 thousand times less.

The Curies, of course, did not know these exact figures. Nevertheless, realizing what a titanic work lay ahead to isolate new elements, they made the only right decision. In the book about Pierre Curie we have already quoted, it is said: “The results obtained after a year of work clearly showed that radium is easier to isolate than polonium; therefore efforts were concentrated on radium.”

Artificial polonium

The question here is quite appropriate: if polonium is truly an ultra-rare and ultra-hard-to-find element, then what does it cost to mine polonium in our time? We do not have exact figures, but today element No. 84 is no less accessible than radium. It is really difficult to obtain it from ore, but there is another way - nuclear fusion.

Today, polonium is produced in two ways, with bismuth-209 being the starting material in both cases. In nuclear reactors, it is irradiated with neutron fluxes, and then, through a relatively simple chain of nuclear transformations, the most important isotope of element No. 84 today is formed - polonium-210:

209 83 Bi + 1 1 p -γ→ 210 83 Bi -β→ 210 84 Po.
And if the same isotope of bismuth is placed in another important nuclear fusion machine - a cyclotron and there it is bombarded with streams of protons, then according to the reaction

209 83 Bi + 1 0 n -γ→ 209 84 Po + 1 0 n.

the longest-lived isotope of element N° 84 is formed.

The first reaction is more important: polonium-210 is a much more interesting isotope for technology than polonium-209. (About the reasons below.) In addition, the second reaction simultaneously with polonium produces lead-209 - one of the most difficult impurities to remove from polonium.

In general, purifying polonium and separating it from a mixture with other metals is not a particularly difficult task for modern technology. There are different methods for isolating polonium, in particular electrochemical, when metallic polonium is isolated on a platinum or gold cathode and then separated by sublimation.

Polonium is a low-melting and relatively low-boiling metal; its melting and boiling points are 254 and 962°C, respectively.

Basics of Chemistry

It is quite obvious that the current advanced methods for producing and isolating polonium became possible only after a thorough study of this rare radioactive metal. And its connections, of course. The foundations of polonium chemistry were laid by its discoverers. In one of the laboratory notebooks of the Curie spouses there is an entry made in 1898: “After the first treatment of resin blende with sulfuric acid, polonium is not completely precipitated and can be partially extracted by washing with dilute SO 4 H 2 (here and below the chemical indexing of the original is preserved). In contrast, two treatments of the resin blende residue and one treatment of the German [ore] residue with carbonates give carbonates, and SO 4 H 2 completely precipitates the active substance from the carbonate dissolved in acetic acid.”

Later, much more was learned about this element. We learned, in particular, that elemental polonium, a silvery-white metal, exists in two allotropic modifications. The crystals of one of them - low-temperature - have a cubic lattice, and the other - high-temperature - have a rhombic lattice.

The phase transition from one form to another occurs at 36°C, but at room temperature polonium is in a high-temperature form. It is heated by its own radioactive radiation. In appearance, polonium is similar to any ordinary metal. In terms of fusibility - like lead and bismuth. According to electrochemical properties - for noble metals. According to the optical and x-ray spectra - only to himself. And in terms of behavior in solutions, it is similar to all other radioactive elements: thanks to ionizing radiation in solutions containing polonium, ozone and hydrogen peroxide are constantly formed and decomposed.

In terms of chemical properties, polonium is a direct analogue of sulfur, selenium and tellurium. It exhibits valencies of 2-, 2+, 4+ and 6+, which is natural for an element of this group. Numerous polonium compounds are known and quite well studied, ranging from the simple oxide PoO 2, soluble in water, to complex complex compounds. The latter should not be surprising. The tendency to complex formation is the lot of most heavy metals, and polonium is one of them. By the way, its density - 9.4 g/cm 3 - is slightly less than that of lead.

A very important study of the properties of polonium for radiochemistry in general was carried out in 1925-1928. at the Leningrad Radium Institute. It was fundamentally important to find out whether radioactive elements found in solutions in vanishingly small quantities could form their own colloidal compounds. The answer to this question - the answer is positive - was given in the work "On the question of the colloidal properties of polonium." Its author was I.E. An old man, later a famous radiochemist, corresponding member of the USSR Academy of Sciences.

Polonium on Earth and in space

To people far from radiochemistry and nuclear physics, the following statement will seem strange: today polonium is a much more important element than radium. The historical merits of the latter are indisputable, but this is the past. Polonium is the element of today and tomorrow. First of all, this applies to the isotope polonium-210.

In total, 27 isotopes of polonium are known with mass numbers from 192 to 218. This is one of the most polyisotopic, so to speak, elements. The half-life of the longest-lived isotope is polonium-209-102 years. Therefore, naturally, in earth's crust There is only radiogenic polonium, and there is extremely little of it there - 2-10 * 14%. Several isotopes of polonium found in nature have proper names and symbols defining the place of these isotopes in the radioactive series. Thus, polonium-210 is also called radium F (RaF), 211 Po - AcC, 2I2 Po - ThC, 214 Po - RaC, 215 Po - AcA, 216 Po - ThA and 218 Po - RaA.

Each of these names has its own history, they are all associated with the “parent” isotopes of one or another atomic variety of polonium, so it would be more correct to call them not “names”, but “patronymics”. With the advent of the modern isotope designation system, the listed old names gradually almost fell out of use.

The most important isotope, polonium-210, is a pure alpha emitter. The particles emitted by it are decelerated in the metal and, traveling through it only a few micrometers, waste their energy. Nuclear energy, by the way. But energy neither appears nor disappears. The energy from polonium's alpha particles is converted into heat, which can be used for, say, heating, and which isn't that difficult to convert into electricity.

This energy is already used both on Earth and in space. The 210 Po isotope is used in power plants of some artificial satellites. In particular, he flew beyond the Earth on the Soviet satellites Kosmos-84 and Kosmos-90.

Pure alpha emitters, and polonium-210 in the first place, have several obvious advantages over other radiation sources. Firstly, the alpha particle is quite massive and carries a lot of energy. Secondly, such emitters practically do not require special protection measures: the penetrating ability and path length of alpha particles are minimal. There are third, and fourth, and fifth, but these two advantages are the main ones.

In principle, plutonium-238, polonium-210, strontium-90, cerium-144 and curium-244 are acceptable energy sources for operation on space stations. But polonium-210 has an important advantage over other competing isotopes - the highest specific power, 1210 W/cm 3 . It releases so much thermal energy that the heat can melt the sample. To prevent this from happening, polonium is placed in a lead matrix. The resulting alloy of polonium and lead has a melting point of about 600°C - much higher than either of the constituent metals. The power, however, decreases, but it remains quite large - about 150 W/cm 3 .

W. Corliss and D. Harvey, authors of the book “Energy Sources from Radioactive Isotopes,” write: “As recent research shows, 210 Po can be used in manned spacecraft.” They mention the availability of this isotope as another advantage of polonium-210. The same book says that bismuth and polonium obtained from it are easily separated by ion exchange. So the polonium space service is apparently just beginning.

And it's a good start. The radioactive isotope polonium-210 served as fuel for the “stove” installed on Lunokhod 2. The nights on the Moon are very long and cold. For 14.5 Earth days, the lunar rover was at a temperature below - 130°C. But all this time the instrument container had to maintain a temperature acceptable for complex scientific equipment.

The polonium heat source was placed outside the instrument container. Polonium radiated heat continuously; but only when the temperature in the instrument compartment dropped below the required limit did the coolant gas, heated by polonium, begin to flow into the container. The rest of the time, excess heat was dissipated into outer space. The nuclear stove of Lunokhod-2 was distinguished by complete autonomy and absolute reliability. There are, however, limitations to polonium-210. Its relatively short half-life - only 138 days - places a natural limit on the service life of radioisotope sources containing polonium.

Similar devices are used on Earth. In addition to them, polonium-beryllium and polonium-boron neutron sources are important. These are sealed metal ampoules containing a polonium-210-coated ceramic pellet of boron carbide or beryllium carbide. The flow of neutrons from the nucleus of a boron or beryllium atom generates alpha particles emitted by polonium.

Such neutron sources are lightweight and portable, relatively safe to operate, and very reliable. A brass ampoule with a diameter of 2 cm and a height of 4 cm - a Soviet polonium-beryllium neutron source - produces up to 90 million neutrons every second.

Among the other earthly affairs of element No. 84, perhaps mention should be made of its use in standard electrode alloys. These alloys are needed for spark plugs in internal combustion engines. The alpha particles emitted by Polonium-210 lower the voltage required to produce a spark and therefore make it easier to start the engine.

Safety precautions

Special care must be taken when working with polonium. Perhaps this is one of the most dangerous radioelements. Its activity is so great that, although it emits only alpha particles, you cannot handle it; the result will be radiation damage to the skin and, possibly, the entire body: polonium penetrates quite easily through the skin. Element No. 84 is also dangerous at a distance exceeding the path length of alpha particles. It can quickly become an aerosol and contaminate the air. Therefore, they work with polonium only in sealed boxes, and the fact that it is not difficult to protect yourself from polonium radiation is extremely favorable for everyone who deals with this element.

The attentive reader has probably already noticed that in this article, wherever the practical use of polonium is discussed, only one isotope appears - with a mass number of 210. Indeed, other isotopes of element No. 84, including the longest-lived of them - polonium- 209 are currently used only for research purposes, to study and clarify the nuclear physical characteristics of these isotopes. These isotopes have not yet found practical application.

True, many scientists believe that polonium-208, also a pure alpha emitter, is also promising for space energy sources. Its half-life is significantly longer than that of polonium-210 - 2.9 years. But so far this isotope is almost unavailable. The future will tell how long it will take him to only wear promising ones.

In London, the Litvinenko murder case brought the topic of using polonium for poisoning back to the front pages of the media. We are talking about this chemical element with Doctor of Chemical Sciences, Head of the Laboratory of the Radioisotope Complex of the Institute of Nuclear Research of the Russian Academy of Sciences Boris Zhuikov. Interviewed Natalia Demina.

In 2006-2007, you repeatedly made comments about polonium poisoning on Ekho Moskvy, NTV and other Russian and foreign media. After all, many at first did not understand what had happened. It was argued that this substance was illogical to use, and in general the very fact of polonium poisoning was questioned?

Yes, that was the point of view. For example, Lev Fedorov, Doctor of Chemical Sciences, President of the Union for Chemical Safety, said on Ekho Moskvy: “How can you poison with polonium-210? This is something I can’t imagine... Now, if I were thinking about how to poison a person, then the last thing I would say is polonium... Naturally, the person who would carry it across the borders would have to carry it in a lead container.”.

A participant in the discussion that took place on the television program “Sunday Evening with Vladimir Solovyov” on December 3, 2006, in which I participated, Maxim Shingarkin, an artilleryman by training, argued that Litvinenko was not poisoned, but that he himself inhaled polonium while working in a secret laboratory on the territory of UK. ( subsequently M. Shingarkin became an adviser to the chairman of the Federation Council Committee on Science and Education, a consultant to the Commission under the President of the Russian Federation for modernization and technical development of the Russian economy, and now he is a deputy State Duma, Andrei Lugovoi's comrade-in-arms in the LDPR faction - "Polit.ru").

It is difficult to understand: the people who said this are simply not at all versed in this area or are biased. Already in my first comment on this topic, I said that polonium-210 is a fairly suitable substance for poisoning, and the most likely method of poisoning is oral administration: throw a capsule with a soluble shell into tea or coffee, because it is sufficiently absorbed through the stomach . And literally the next day they reported that they had found a teapot contaminated with polonium, from which Litvinenko drank tea. Can you imagine my situation? ( Laughs).

Have you had any experience working with polonium?

Yes, many years ago, when I worked as a researcher at the Joint Institute for Nuclear Research in Dubna, I dealt with polonium-210 and other polonium isotopes in trace quantities. In general, I worked with radioactive isotopes of almost all elements. This was the direction - we were looking for new, undiscovered elements in a complex mixture of products of various nuclear reactions and in natural samples. Currently, my main focus is on radioactive isotopes for nuclear medicine, isotopes that are introduced into the human body for the diagnosis and treatment of various diseases.

Do you know people who are now involved in polonium?

Yes, but due to the nature of their service they are unlikely to agree to give you a frank interview; they have their own rules.

Well, that's understandable. After all, what relates to polonium is probably secret?

No, the properties of polonium themselves, its behavior, production methods and applications have long been no secret; everything has been published. There are also a number of publications on the effects of polonium on animals. A specialist can understand and correctly interpret what applies to a given case.

How expensive is polonium to produce?

Talk about the high cost of polonium-210 is a myth. I know the price it's selling for, but I probably shouldn't reveal it. In any case, it is very small. Of course, the manufacturers of a specific drug - a source of radioactive radiation that is convenient for use - can ask for a decent amount, but this, as they say, is a “cheat”. Polonium itself is cheap. In addition, the source used, although it was obviously made by professionals, was made poorly, made by bad professionals.

Where can one draw such a conclusion?

Due to its properties, polonium easily diffuses through organic shells and generally spreads easily. In such cases, the source is made with a multilayer coating. The people who made the sample either didn’t know this, were lazy, or hoped that the presence of polonium would not surface at all. So the performers left a fair legacy.

If polonium is so inconvenient to use, why was it used?

On the contrary, in principle, polonium-210 is a very convenient substance for poisoning, specifically for hidden poisoning, and not for provocation. Initially, it is very difficult to detect unless special analyzes are done (alpha spectrometry). And no one was going to do special tests, since this substance had not previously been used for poisoning - at least it was not discovered. Polonium-210 differs from other radioactive isotopes in that it emits almost exclusively alpha particles with an energy of 5.3 MeV, which are absorbed even by a sheet of paper. Gamma radiation, which is usually detected using Geiger counters, is extremely weak, making up only one hundred thousandth part. Accordingly, introducing it into England is not a problem, lead containers are not needed for such quantities, and it is safe to carry out various operations with a sufficiently sealed capsule.

There were opinions that polonium was used for provocation. In my opinion, such talk is absolute nonsense. There was no provocation, there was an attempt at a secret murder. For provocation, it would be advisable to use any other radionuclide, for example, americium-241 - it would be easier to detect, it is more accessible (used everywhere in smoke detectors).

How then was this polonium discovered?

Yes, they found it, but they might not have discovered it. This interesting story, I followed the developments on the Internet. The symptoms observed in Litvinenko were consistent with radiation injury. However, nothing was detected with a conventional counter that registers gamma radiation. A very weak gamma-ray line with an energy of 803 keV was noticed only as a result of long-term measurements using a good gamma spectrometer. At first, this radiation was erroneously attributed to radioactive thallium (thallium-206), which is produced by the decay of alpha-active bismuth-210m.

But then this version was recognized as erroneous, since this isotope of bismuth has too long a half-life, and they began to consider the possibility of the presence of other alpha emitters. After this, the urine was analyzed for the presence of alpha-active radionuclides and polonium was found, and in huge quantities. The assumption that British scientists were “tipped off” about polonium-210 by some provocateurs seems extremely unlikely to me. Everything was done consistently and quite logically.

Why didn't they use ordinary chemical poison?

All groups of chemical poisons are known; they would be easier to detect. Even when “disappearing” poisons are used, some traces of their use remain.

Was polonium unknown?

Unknown as a poison. Of course, there were cases, very few, of poisoning at work. But in production they get poisoned by anything.

But now...

Now you don’t have to worry and don’t have to carry the alpha counter with you. No one will use polonium for this purpose anymore. I'm sure of it. The story became too popular, and even I was asked to check something... Another thing is old cases that occurred even before Litvinenko’s poisoning, for example, the mysterious death of Yuri Shchekochikhin, the attempted poisoning of Anna Politkovskaya...

But after all these years, is there really anything left? After all, the half-life of polonium-210 is 138 days?

Yes, this means that over 10 years its quantity decreases by 100 million times. Polonium-210 will remain, but in very small quantities. It is estimated that at least 1-3 billion becquerels (decays per second) were injected into Litvinenko for the second time. This is very high activity, even too high activity: as a result, a person can die within a few days. But polonium-210 produced at the reactor must contain a small admixture of another, long-lived isotope - polonium-209 (half-life 102 years).

At first it is very difficult to detect it due to the background of the 210. But after the breakup, then you should try. It is possible, of course, to produce polonium-210 without the 209 impurity, but it will be really very expensive and difficult. It is unlikely that these people who manufactured the drug would do such things. Although, who knows?

There were opinions that Yasser Arafat was poisoned with polonium. What did the research show?

A detailed study by Swiss scientists (the report has been published) showed that there are no compelling reasons to talk about poisoning in this case, although the authors themselves initially drew a different conclusion from their results. The report provides quite convincing data that some excess polonium (which indeed existed) was most likely of natural origin - apparently the result of the decay of radon-222, which is abundant in the dungeons where Arafat often stayed. An autopsy revealed a corresponding amount of another radon decay product - lead-210. But polonium-209 was not detected. Thus, Arafat received a dose of polonium-210 that was many orders of magnitude smaller than Litvinenko, and this could not have been the cause of death.

At public hearings, information was heard that Litvinenko was killed the second or third time. Apparently, the killers wanted to hedge their bets?

Yes, this fact has long been known and published in the scientific literature. It is reliably established by the distribution of polonium in Litvinenko’s body. Moreover, the first dose administered was much less. Litvinenko would have died later anyway, and then, probably, nothing would have been discovered at all. But apparently the customers couldn’t wait...

Tell me, if as a result of such detailed studies it was possible to determine the nature of the introduction of polonium into Litvinenko, then it would probably be possible to determine the role of the British suspects A. Lugovoy and D. Kovtun?

Of course, of course. They were studied, as far as I know, at the Medical Biophysical Center named after. A.I. Burnazyan. It was reported that Lugovoi was found to have polonium, but detailed results that would help shed light on the man's role are unknown. But they didn’t go to the UK.

Was there a danger of defeat for the performers and defeat for those around them? Information appeared in the British media that Lugovoi even brought his son to the last meeting and let him shake Litvinenko’s hand...

There was some danger, given that the performers apparently were not properly instructed. But still, this is not at all as dangerous as taking polonium orally, and does not pose a danger to life. Lugovoi himself said that someone had dirty him. But whether he was dirty or whether he did something himself - that could be seen. And the fact that they followed him and deliberately left traces is simply stupid, it is unrealistic to organize it so that it would not be discovered.

In your opinion, is everything that the lawyer of the Litvinenko family and the British investigative authorities said true?

At least as far as the behavior of polonium is concerned, there are no contradictions. The only thing that is wrong is that its use created a great threat to others. Small amounts of polonium that could contaminate people in contact with Litvinenko can be detected, but they are practically harmless to health. As a result, just 52 people received an increased dose, but not enough to significantly increase their risk of getting sick in the future, the Health Protection Agency said. The real danger would be if someone finished their tea for Litvinenko. And what is also wrong is that polonium-210 is very expensive unless it is of ultra-high purity. I have already said this above. It is simply not widely available, and its distribution is fairly well controlled by government agencies.

Do you see any inconsistencies in what the British investigators are saying?

There are no discrepancies that cannot be explained based on the physical and chemical properties of polonium. On the contrary, as soon as opponents begin to put forward some objections, these objections are completely inconsistent with scientific data.

Thanks for the interview.

Polonium-210 has a very clear association with radiation. And this is not in vain, since he is extremely dangerous.

History of discovery

Its existence was predicted back in 1889 by Mendeleev, when he created his famous periodic table. In practice, this element, number 84, was obtained nine years later through the efforts of the Curies, who were studying the phenomenon of radiation. tried to find out the reason for the strong radiation emanating from some minerals, and therefore began working with several rock samples, processing them in all ways available to her, dividing them into fractions and discarding what was unnecessary. As a result, she obtained a new substance, which became an analogue of bismuth and the third discovered radioactive element after uranium and thorium.

Despite the successful results of the experiment, Maria was in no hurry to talk about her find. carried out by a colleague of the Curies, also did not give reason to talk about the discovery of a new element. Nevertheless, in a report at a meeting of the Paris Academy of Sciences in July 1898, the couple reported the alleged receipt of a substance exhibiting the properties of a metal and proposed calling it polonium in honor of Poland, Mary’s homeland. This was the first and only case in history when an element that had not yet been reliably identified was already given a name. Well, the first sample appeared only in 1910.

Physical and chemical properties

Polonium is a relatively soft, silvery-white metal. It is so radioactive that it glows in the dark and constantly heats up. Moreover, its melting point is slightly higher than that of tin - only 254 degrees Celsius. Metal oxidizes very quickly in air. At low temperatures it forms a monatomic simple cubic crystal lattice.

In terms of its chemical properties, polonium is very close to its analogue, tellurium. In addition, the nature of its compounds is greatly influenced by high levels of radiation. So reactions involving polonium can be quite spectacular and interesting, although quite dangerous from the point of view of health benefits.

Isotopes

Total science on at the moment 27 (according to other sources - 33) forms of polonium are known. None of them are stable, and all of them are radioactive. The heaviest of the isotopes (with order numbers from 210 to 218) are found in small quantities in nature, the rest can only be obtained artificially.

Radioactive polonium-210 is the longest-lived of natural forms. It is found in small quantities in radium-uranium ores and is formed through a chain of reactions starting with U-238 and lasting approximately 4.5 billion years in terms of half-life.

Receipt

1 ton contains the isotope polonium-210 in an amount equal to approximately 100 micrograms. They can be isolated by processing industrial waste, but to obtain a more or less significant volume of the element it would be necessary to process huge amount material. Much simpler and effective ways is the synthesis of natural bismuth using neutron irradiation in nuclear reactors.

The result, after some more procedures, is polonium-210. Isotopes 208 and 209 can also be obtained by irradiating bismuth or lead with accelerated beams of alpha particles, protons or deuterons.

Radioactivity

Polonium-210, like other isotopes, is an alpha emitter. The heavier group also emits gamma rays. Despite the fact that the 210 isotope is a source of only alpha particles, it is quite dangerous; it should not be handled or even approached at close range, since when it warms up, it turns into an aerosol state. It is also extremely dangerous if polonium is ingested through breathing or food. That is why work with this substance takes place in special sealed boxes. It is curious that this element was discovered in tobacco leaves about half a century ago. The decay period of polonium-210 is quite long compared to other isotopes, and therefore it can accumulate in the plant and subsequently harm the health of the smoker even more. However, any attempts to extract this substance from tobacco were unsuccessful.

Danger

Since polonium-210 emits only alpha particles, you should not be afraid of working with it if you take certain precautions. The travel length of these waves rarely exceeds ten centimeters, and in addition, they usually cannot penetrate the skin.

However, once inside the body, they cause great harm to it. When it enters the bloodstream, it quickly spreads throughout all tissues - within a few minutes its presence can be noticed in all organs. It is primarily present in the kidneys and liver, but in general it is distributed fairly evenly, which may explain its high overall damaging effect.

The toxicity of polonium is so great that even small doses cause chronic radiation sickness and death after 6-11 months. The main routes of elimination from the body are through the kidneys and gastrointestinal tract. There is a dependence on the method of entry. The half-life ranges from 30 to 50 days.

Accidental polonium poisoning is completely impossible. To obtain a sufficient amount of the substance, it is necessary to have access to a nuclear reactor and deliberately place the isotope on the victim. The difficulty of diagnosis also lies in the fact that only a few cases are known throughout history. The first victim is considered to be the daughter of the discoverers of polonium, Irene Joliot-Curie, who during research broke a capsule with the substance in the laboratory and died 10 years later. Two more cases occur in the 21st century. The first of them is the sensational case of Litvinenko, who died in 2006, and the second is the death of Yasser Arafat, in whose belongings traces of a radioactive isotope were found. However, the final diagnosis was never confirmed.

Decay

One of the longest-lived isotopes, along with 208 and 209, is polonium-210. (that is, the time during which the number of radioactive particles is halved) for the first two is 2.9 and 102 years, respectively, and for the latter 138 days and 9 hours. As for other isotopes, their lifetime is calculated mainly in minutes and hours.

The combination of various properties of polonium-210 makes it the most convenient of the range for use in various fields life. Being in a special metal shell, it can no longer harm health, but is able to give its energy for the benefit of humanity. So, what is polonium-210 used for today?

Modern Application

According to some reports, about 95% of polonium production is concentrated in Russia, with approximately 100 grams of the substance synthesized per year, and almost all of it is exported to the United States.

There are several areas in which polonium-210 is used. First of all, these are spacecraft. With its compact size, it is indispensable as an excellent source of energy and heat. Although its effectiveness is halved approximately every 5 months, heavier isotopes are much more expensive to produce.

In addition, polonium is absolutely indispensable in nuclear physics. It is widely used in studying the effects of alpha radiation on other substances.

Finally, another area of ​​application is the production of static electricity removal devices for both industry and home use. It’s amazing how such a dangerous element can become almost a kitchen utensil, being enclosed in a reliable shell.

Contents of the article

POLONIUM– radioactive chemical element Group VI of the periodic table, an analogue of tellurium. Atomic number 84. Has no stable isotopes. There are 27 known radioactive isotopes of polonium with mass numbers from 192 to 218, of which seven (with mass numbers from 210 to 218) occur in nature in very small quantities as members of the radioactive series of uranium, thorium and actinium; the remaining isotopes are obtained artificially. The longest-lived isotopes of polonium are artificially produced 209 Po ( t 1/2 = 102 years) and 208 Rho ( t 1/2 = 2.9 years), as well as 210 Po contained in radium-uranium ores ( t 1/2 = 138.4 days). The content of 210 Po in the earth's crust is only 2·10–14%; 1 ton of natural uranium contains 0.34 g of radium and a fraction of a milligram of polonium-210. The shortest-lived known isotope of polonium is 213 Po ( t 1/2 = 3·10 –7 s). The lightest isotopes of polonium are pure alpha emitters, while the heavier ones simultaneously emit alpha and gamma rays. Some isotopes decay by electron capture, and the heaviest ones also exhibit very weak beta activity ( cm. RADIOACTIVITY). Different isotopes of polonium have historical names adopted back in the early 20th century, when they were obtained as a result of a chain of decays from the “parent element”: RaF (210 Po), AcC" (211 Po), ThC" (212 Po), RaC" (214 Po), AcA (215 Po), ThA (216 Po), RaA (218 Po).

Discovery of polonium.

The existence of an element with serial number 84 was predicted by D.I. Mendeleev in 1889 - he called it dvitellurium (in Sanskrit - “second” tellurium) and assumed that its atomic mass would be close to 212. Of course, Mendeleev could not foresee that this the element will be unstable. Polonium is the first radioactive element, discovered in 1898 by the Curies in search of the source of strong radioactivity in certain minerals ( cm. RADIUM). When it turned out that uranium resin ore radiated more strongly than pure uranium, Marie Curie decided to chemically isolate a new radioactive chemical element from this compound. Before this, only two weakly radioactive chemical elements were known - uranium and thorium. Curie began with the traditional qualitative chemical analysis of the mineral according to the standard scheme, which was proposed by the German analytical chemist K.R. Fresenius (1818–1897) back in 1841 and according to which many generations of students for almost a century and a half determined cations using the so-called “hydrogen sulfide method” " At the beginning she had about 100 g of the mineral; then American geologists gave Pierre Curie another 500 g. Carrying out a systematic analysis, M. Curie each time tested individual fractions (precipitates and solutions) for radioactivity using a sensitive electrometer invented by her husband. Inactive fractions were discarded, active ones were analyzed further. She was helped by one of the leaders of the chemical workshop at the School of Physics and Industrial Chemistry, Gustav Bemon.

First of all, Curie dissolved the mineral in nitric acid, evaporated the solution to dryness, dissolved the residue in water and passed a stream of hydrogen sulfide through the solution. In this case, a precipitate of metal sulfides formed; in accordance with the Fresenius method, this sediment could contain insoluble sulfides of lead, bismuth, copper, arsenic, antimony and a number of other metals. The precipitate was radioactive, even though uranium and thorium remained in solution. She treated the black precipitate with ammonium sulfide to separate arsenic and antimony - under these conditions they form soluble thiosalts, for example, (NH 4) 3 AsS 4 and (NH 4) 3 SbS 3. The solution showed no radioactivity and was discarded. Lead, bismuth and copper sulfides remained in the sediment.

Curie dissolved the part of the precipitate that was not dissolved in ammonium sulfide in nitric acid and added it to the solution sulfuric acid and evaporated it on a burner flame until thick white SO 3 vapors appeared. Under these conditions, volatile nitric acid is completely removed, and metal nitrates are converted into sulfates. After cooling the mixture and adding cold water the sediment contained insoluble lead sulfate PbSO 4 - there was no activity in it. She threw away the precipitate and added a strong ammonia solution to the filtered solution. At the same time, a precipitate fell again, this time white; it contained a mixture of basic bismuth sulfate (BiO) 2 SO 4 and bismuth hydroxide Bi(OH) 3. Complex copper ammonia SO 4 of a bright blue color remained in the solution. The white precipitate, unlike the solution, turned out to be highly radioactive. Since the lead and copper had already been separated, the white precipitate contained bismuth and an admixture of the new element.

Curie again converted the white precipitate into dark brown Bi 2 S 3 sulfide, dried it and heated it in an evacuated ampoule. The bismuth sulfide did not change (it is resistant to heat and melts only at 685 ° C), however, some vapors were released from the sediment, which settled in the form of a black film on the cold part of the ampoule. The film was radioactive and apparently contained a new chemical element - an analogue of bismuth in the periodic table. It was polonium - the first discovered radioactive element after uranium and thorium, inscribed in the periodic table (in the same 1898, radium was discovered, as well as a group of noble gases - neon, krypton and xenon). As it turned out later, polonium easily sublimes when heated - its volatility is approximately the same as that of zinc.

The Curies were in no hurry to call the black coating on the glass a new element. Radioactivity alone was not enough. Curie's colleague and friend, the French chemist Eugene Anatole Demarsay (1852–1903), a specialist in the field of spectral analysis (he discovered europium in 1901), examined the emission spectrum of the black coating and did not find any new lines in it that could indicate the presence of a new element. Spectral analysis is one of the most sensitive methods, allowing the detection of many substances in microscopic quantities invisible to the eye. However, in an article published on July 18, 1898, the Curies wrote: “We think that the substance we isolated from uranium tar contains an as yet unknown metal, which is an analogue of bismuth in its analytical properties. If the existence of a new metal is confirmed, we propose to call it polonium, after the homeland of one of us” (Polonia in Latin - Poland). This the only case, when a new chemical element that has not yet been identified has already received a name. However, it was not possible to obtain weight quantities of polonium - there was too little of it in the uranium ore (later polonium was obtained artificially). And it was not this element that glorified the Curies, but radium

Properties of polonium.

Already tellurium partially exhibits metallic properties, while polonium is a soft silvery-white metal. Due to strong radioactivity, it glows in the dark and gets very hot, so continuous heat removal is needed. The melting point of polonium is 254 ° C (slightly higher than that of tin), the boiling point is 962 ° C, therefore, even with slight heating, polonium sublimes. The density of polonium is almost the same as that of copper - 9.4 g/cm 3 . In chemical research, only polonium-210 is used; longer-lived isotopes are practically not used due to the difficulty of obtaining them with the same chemical properties.

The chemical properties of metallic polonium are close to the properties of its closest analogue, tellurium; it exhibits oxidation states of –2, +2, +4, +6. In air, polonium slowly oxidizes (quickly when heated to 250 ° C) with the formation of red dioxide PoO 2 (when cooled, it becomes yellow as a result of rearrangement of the crystal lattice). Hydrogen sulfide from solutions of polonium salts precipitates black sulfide PoS.

The strong radioactivity of polonium affects the properties of its compounds. Thus, in dilute hydrochloric acid, polonium slowly dissolves to form pink solutions (the color of Po 2+ ions): Po + 2HCl ® PoCl 2 + H 2, however, under the influence of its own radiation, the dichloride turns into yellow PoCl 4. Dilute nitric acid passivates polonium, while concentrated nitric acid quickly dissolves it. Polonium is related to non-metals of group VI by the reaction with hydrogen with the formation of the volatile hydride PoH 2 (mp -35° C, bp +35° C, easily decomposes), reaction with metals (when heated) with the formation of solid black polonides colors (Na 2 Po, MgPo, CaPo, ZnPo, HgPo, PtPo, etc.) and reaction with molten alkalis to form polonides: 3Po + 6NaOH ® 2Na 2 Po + Na 2 PoO 3 + H 2 O. Polonium reacts with chlorine at heating with the formation of bright yellow crystals of PoCl 4, with bromine red crystals of PoBr 4 are obtained, with iodine, already at 40 ° C, polonium reacts with the formation of black volatile iodide PoI 4. White polonium tetrafluoride PoF 4 is also known. When heated, tetrahalides decompose to form more stable dihalides, for example, PoCl 4 ® PoCl 2 + Cl 2 . In solutions, polonium exists in the form of cations Po 2+, Po 4+, anions PoO 3 2–, PoO 4 2–, as well as various complex ions, for example, PoCl 6 2–.

Obtaining polonium.

Polonium-210 is synthesized by irradiating natural bismuth (it contains only 208 Bi) with neutrons in nuclear reactors (the beta-active isotope of bismuth-210 is intermediately formed): 208 Bi + n ® 210 Bi ® 210 Po + e. When bismuth is irradiated by accelerated protons, polonium-208 is formed, it is separated from bismuth by sublimation in a vacuum - as M. Curie did. In our country, the method for isolating polonium was developed by Zinaida Vasilievna Ershova (1905–1995). In 1937, she was sent to Paris to the Radium Institute in the laboratory of M. Curie (led at that time by Irène Joliot-Curie). As a result of this business trip, her colleagues began to call her “Russian Madame Curie.” Under the scientific leadership of Z.V. Ershova, a permanent, environmentally friendly production of polonium was created in the country, which made it possible to implement the domestic program for launching lunar rovers, in which polonium was used as a heat source.

Long-lived isotopes of polonium have not yet received significant practical use due to the complexity of their synthesis. To obtain them, you can use the nuclear reactions 207 Pb + 4 He ® 208 Po + 3n, 208 Bi + 1 H ® 208 Po + 2n, 208 Bi + 2 D ® 208 Po + 3n, 208 Bi + 2 D ® 208 Po + 2n , where 4 He are alpha particles, 1 H are accelerated protons, 2 D are accelerated deuterons (deuterium nuclei).

Use of polonium.

Polonium-210 emits alpha rays with an energy of 5.3 MeV, which are decelerated in solid matter, traveling only thousandths of a millimeter and giving up their energy. Its lifetime makes it possible to use polonium as an energy source in nuclear batteries of spaceships: to obtain a power of 1 kW, only 7.5 g of polonium is enough. In this respect, it is superior to other compact "nuclear" energy sources. Such an energy source worked, for example, on Lunokhod 2, heating the equipment during the long lunar night. Of course, the power of polonium energy sources decreases over time - by half every 4.5 months, but longer-lived isotopes of polonium are too expensive. Polonium can also be conveniently used to study the effects of alpha radiation on various substances. As an alpha emitter, polonium mixed with beryllium is used to make compact neutron sources: 9 Be + 4 He ® 12 C + n. Boron can be used instead of beryllium in such sources. It was reported that in 2004, inspectors from the International Atomic Energy Agency (IAEA) discovered a polonium production program in Iran. This led to the suspicion that it could be used in a beryllium source to "trigger" with neutrons a nuclear chain reaction in uranium, leading to a nuclear explosion.

Polonium, when ingested, can be considered one of the most toxic substances: for 210 Po, the maximum permissible content in the air is only 40 billionths of a microgram per 1 m 3 of air, i.e. Polonium is 4 trillion times more toxic than hydrocyanic acid. The damage is caused by alpha particles (and to a lesser extent also gamma rays) emitted by polonium, which destroy tissue and cause malignant tumors. Polonium atoms can form in human lungs as a result of the decay of radon gas in them. In addition, polonium metal can easily form tiny aerosol particles. Therefore, all work with polonium is carried out remotely in sealed boxes.

Ilya Leenson

The scientific aspects of the Litvinenko case were analyzed for TRV-Nauka by Dr. chem. sciences, head Laboratory of the Radioisotope Complex of the Institute of Nuclear Research of the Russian Academy of Sciences

Passions all around mysterious death Alexandra Litvinenko's scandals continue unabated. Finally, public hearings on his case began in London. And relatively recently, interest in this topic was fueled by the assumption that Palestinian leader Yasser Arafat was killed in a similar way. Thanks to this, the general public learned at least something about radioactive isotopes and their possible applications, however, in a very one-sided way.

At one time, I had to comment on this case in many Russian and foreign publications, radio and television programs. But the mass media is not the most suitable platform for discussing the scientific aspects of this interesting problem: the issue is too politicized. People put forward the most fantastic versions, without bothering themselves with any evidence at all. At the same time, there are a number of scientific publications that discuss various, primarily medical, aspects. This question was also raised at a number of scientific conferences on the production and use of isotopes, in which I took part.

Here I will briefly outline the following aspect: the production and properties of polonium-210, which may be associated with the poisoning of A. Litvinenko. A number of Russian "experts" expressed surprise as to why this particular substance was used, and many were unclear as to how it was used. In particular, Lev Fedorov, Dr. chem. Sciences, President of the Union for Chemical Safety, said on Ekho Moskvy: “How can you poison with polonium-210? I can’t imagine this... If I were thinking about how to poison a person, then the last thing I would say is polonium... Naturally, the person who would carry it across the borders would have to carry it in a lead container ».

A number of other experts tried to justify their conclusions based on general considerations. Thus, the famous banker Alexander Lebedev, himself a former KGB employee, stated in our public discussion with him on the NTV channel (“Sunday Evening with Vladimir Solovyov,” December 3, 2006): “I assure you that today there is not the slightest possibility of allowing our special services to do such things... Because this will certainly be followed by criminal punishment.”

Let's put aside the political aspects, who benefited or did not benefit from this. Let's figure out why polonium was used?

Obtaining polonium-210

The main method for producing polonium-210 is irradiating bismuth with slow neutrons in a nuclear reactor (see Fig. 1). Polonium must then be chemically isolated from the irradiated bismuth. This can be done by sublimation (since polonium has relatively high volatility at elevated temperatures), electrochemical or other methods. Polonium-210 produced in this way is very cheap. Talk about its high cost is not true. Another thing is its availability.

There is also a third stage in the technology, this is the preparation of the radiation source for final use. Sources can be of different types. In this particular case, the polonium must be placed in a capsule, preferably with a multi-layer shell (to avoid polonium penetration). To poison, you must either open this capsule so that the contents get into the drink, or, which is much more convenient, make a miniature ampoule with a soluble shell; this is not difficult.

For the first time, pure polonium in the Soviet Union was obtained at NII-9 (now the A. A. Bochvar High-Tech Research Institute of Inorganic Materials), which was a leader in the study of this element. The work was carried out under the guidance of our outstanding scientist Zinaida Vasilievna Ershova.

Is it possible to determine the origin of polonium using a technical method? Theoretically this is possible, but practically it is very difficult. Each nuclear reactor (in a specific irradiation channel) is characterized by its own neutron spectrum. The presence of fast neutrons leads to the formation, along with polonium-210 (half-life - 138.4 days), of small amounts of polonium-209 (half-life - 102 years, alpha particle energy - 4.9 MeV) by nuclear reaction (n, 2n) from accumulated polonium-210, as well as even smaller quantities of polonium-208 (2.9 years).

Thus, using such a “nuclear clock” it is, in principle, possible to determine the place and date of polonium production. However, this is not easy to do, and in certain cases it is impossible. This depends on how much polonium was found and where: what is important is the ratio between the stable lead-206 formed from polonium-210 and the background lead, the content of which in the natural mixture of isotopes is 24.1%. A special mass separator will be required to separate polonium isotopes (or a long exposure time for the decay of polonium-210), as well as calibration samples of polonium from the reactor, prepared in the same irradiation mode.

Russian polonium is produced at the All-Russian Research Institute of Experimental Physics in Sarov. Bismuth irradiation at the reactor is apparently carried out in another place - P/O Mayak in the city of Ozyorsk, Chelyabinsk region. The method for producing polonium-210 is not secret, so it can be produced in any other reactors where there is a special channel for irradiating targets in order to obtain isotopes. Such reactors are located in several countries around the world. Energy reactors, as a rule, are not suitable for this, although some of them have a channel for irradiating targets. It has been reported that more than 95% of polonium-210 is produced in Russia.

There are also other methods for producing polonium, but they are now practically not used, since they are much less productive and more expensive. One of these methods, used by Marie Curie, is chemical separation from uranium ores (polonium-210 is contained in the decay chain of uranium-238). Actually, polonium was discovered in 1898. Polonium-210 can also be obtained in charged particle accelerators using the nuclear reactions 208 Pb(A, 2n) or 209 Bi(d, n). At the same time, not just any accelerator is suitable for producing polonium-210. This requires an alpha particle or deuteron accelerator. There are not many such accelerators in the world. They exist in both Russia and Great Britain. However, as far as I know, in Britain the Amersham accelerator has not been configured for alpha particles for a long time and is constantly working exclusively on the production of medical isotopes for diagnostics. In a number of places I visited abroad, colleagues told me that their installations were inspected to see if they were producing polonium.

At one time, Techsnabexport JSC sold polonium-210 to the UK (to Reviss). But this was five years before the sad events, and, as my colleagues told me, the company was checked very carefully after that. Products containing polonium are not officially supplied to the UK from the USA and Russia. Polonium-210 was previously obtained at the Oak Ridge National Laboratory (USA), but now it is not produced in significant quantities there, but, on the contrary, a certain amount is obtained from Russia.

The operation of both reactors and accelerators is strictly controlled. If someone does decide to produce polonium illegally, with the existing control system this can easily be discovered.

Nuclear physical properties

As already mentioned, the half-life of polonium is 138.4 days. This means that every 138 days its activity decreases by 2 times, and in two years - by about 40 times. This half-life is very convenient for using a radionuclide as a poison.

Polonium-210, when decaying, emits alpha particles with an energy of 5.3 MeV, which have a short range in solids. For example, aluminum foil tens of microns thick completely absorbs such alpha particles. The gamma radiation that could be detected by Geiger counters is extremely weak: gamma rays with an energy of 803 keV are emitted with a decay yield of only 0.001%. Polonium-210 has the lowest gamma constant of all common alpha-active radionuclides. Thus, for americium-241 (widely used, for example, in smoke detectors) the gamma constant is 0.12, and for Po it is 5·10 –5 R×cm 2 /h×mCi (where R is a roentgen, mCi is a millicurie ). In this case, the dose coefficient and, therefore, radiotoxicity are quite comparable.

Thus, even without a protective shell, it is extremely difficult to detect a sufficient amount of polonium-210 for poisoning remotely using a conventional counter, since the radiation level is comparable to the natural background (see Fig. 2). Thus, polonium-210 is very convenient for secret transportation, and there is no need to even use lead containers. However, during transportation, special care must be taken to avoid depressurization of the container (see below).

Polonium-210 is not at all advisable to use for provocations, since it can only be detected using special equipment, which is not used in ordinary cases.

The 803 keV gamma line can only be detected through long-term measurements using a good gamma spectrometer, and the semiconductor detector must be located very close to the source. There is evidence that this is how increased radioactivity was initially found in Litvinenko, but at first the radiation was mistakenly attributed to radioactive thallium (thallium-206), which is obtained from the decay of bismuth-210m (see diagram in Fig. 1).

This was reported on the Internet even before polonium was identified. But then this version was recognized as erroneous, since this isotope of bismuth has too long a half-life, and they began to consider the possibility of the presence of other alpha emitters. After this, the urine was analyzed for the presence of alpha-active radionuclides and polonium was found, and in huge quantities. The assumption that British experts were “tipped off” about polonium-210 by certain provocateurs seems to me to have been taken out of thin air. British scientists did everything consistently and quite logically.

On the surface, alpha activity of polonium-210 can be detected using an alpha counter, which is usually used only for special purposes and not for routine testing for radioactive contamination. However, to determine that the radiation relates specifically to polonium-210, more complex equipment, usually stationary, is required - an alpha spectrometer. Activity on the order of 1 Bq (disintegrations per second) at the surface can be easily detected. If alpha activity is detected, then sample preparation is carried out (for example, using chemical isolation) and a line in the alpha spectrum of 5.3 MeV is detected on an alpha spectrometer, characterizing this particular alpha-active radionuclide.

Chemical properties

Polonium can exist in different chemical forms, but in this case it is most likely to be found in the form of soluble compounds (for example, nitrates, chlorides, sulfates), while a significant part of the solution can also be in colloidal form. It is important that from neutral and slightly acidic solutions, polonium is largely sorbed on various surfaces, in particular on metal and glass (maximum sorption is at pH ~ 5). It is difficult to wash it completely using conventional methods. It is therefore not at all surprising that a teapot and cup from which polonium was consumed were discovered.

Polonium itself, in microquantities, begins to sublimate only at temperatures of about 300°C. But he can go to environment also together with the vapor of the water in which it is contained, and in the process with the recoil nuclei.

Polonium diffuses quite easily in plastic and other organic substances; sources based on it are made with a multilayer coating. And if the ampoule was depressurized, then even the smallest traces of it can be detected using an alpha counter.

Polonium is a polyvalent element, prone to forming various complexes, and can form different chemical forms. In this regard, some of it spreads quite easily in the natural environment. It is therefore understandable that traces of polonium have spread and can be used to trace the source of polonium contamination.

Biological exposure and radiation safety

Biological studies of the effects of polonium on animals were carried out in our country mainly in the 60s at the Institute of Biophysics in the laboratory of Professor Yu. I. Moskalev, there are several publications.

It has long been known that polonium-210 is one of the most dangerous radionuclides. The levels of damage to humans by polonium-210 are shown in the table (data from experiments with animals were recalculated to the mass of a person).

The absorption of this substance through gastrointestinal tract estimated from 5 to 20%. Through the lungs - it is more effective, but such administration is extremely inconvenient for hidden poisoning, since this can greatly contaminate others and performers. Only about 2% per day is absorbed through the skin, and this use of polonium for poisoning is also ineffective.

Polonium is distributed in all organs of the body, but, of course, not quite evenly. And it is excreted from the body with any biological substances: feces, urine, then... The half-life, according to various sources, is from 50 to 100 days. One industrial accident was reported in our country that resulted in the death of a person 13 days after being exposed to 530 MBq (14 mCi) of polonium.

According to indirect data (based on the impact), the amount of polonium introduced into Litvinenko could be (0.2–4) × 10 9 Bq (becquerels), that is, disintegrations per second, by mass it is 1–25 μg, an almost invisible amount .

If polonium was contained in a cup of tea, for example ~10 9 Bq per 100 g, then up to 0.01–0.10 ml could accidentally fall on people sitting nearby as drops or aerosols, that is, up to 10 5 –10 6 Bk. This does not pose a serious danger to human life, although it exceeds permissible pollution standards. Such an amount can be easily detected, and activity of the order of 1 Bq is also detected.

In the Litvinenko story, according to the Health Protection Agency, the following happened:

• 120 people were likely exposed to polonium but received a dose below 6 mSv (millisieverts), which poses no health risk;
• 17 people received a dose greater than 6 mSv, but not significant enough to cause any illness in the near future; the increase in the risk of disease in the distant future is likely very small. The largest dose, which was nevertheless not life-threatening, was naturally received by Alexander Litvinenko’s wife Marina, with whom he had the most contact.

The permissible dose for professionals working with radioactivity in Russia is 20 mSv/year. The annual doses received by people from natural background radiation are 1–10 mSv/year, and in some places on Earth much higher, and mortality is not increased there. Only exposure to an effective dose of more than 200 mSv over the course of a year is considered potentially dangerous. Thus, claims that the use of polonium created a greater threat to others is an exaggeration.

The press raised the question of whether polonium-210 had been used as a poisonous substance before and whether this could be established. In particular, the poisons with which they may have poisoned Yu. Shchekochikhin and tried to poison A. Politkovskaya remained unknown. If polonium-210 was present in these cases, it had decayed over time to below background levels. However, exhumation may reveal polonium-209, which could have been present as an impurity (see above).

The hypothesis that Yasser Arafat was poisoned with polonium-210 was practically not confirmed. Some excess polonium-210 can be explained by natural causes - inhalation of radon-222 during the long stay of the Palestinian leader in the bunker. Polonium-210 is a decay product of radon. A corresponding amount of lead-210, which is also a product of the decay of radon, was found in Arafat's body.

Application

Until now, polonium-210 has been used for the following purposes.

1. To create autonomous sources of energy generated as a result of alpha decay. The Soviet Lunokhod and some of the Cosmos satellites were equipped with such devices.

2. As a source of neutrons, in particular, for the initiators of a nuclear explosion in atomic bombs. Neutrons are produced when beryllium is irradiated with alpha particles and initiate nuclear explosion, when the mass of uranium-235 or plutonium-239 becomes critical. Such sources were also used for neutron activation analysis of natural samples and materials.

3. As a source of alpha particles in the form of applicators for the treatment of certain skin diseases. Nowadays it is practically not used for such purposes, since there are much more suitable radionuclides.

4. As an air ionizer in antistatic devices, for example Staticmaster, manufactured by Calumet in the USA. These materials are not exported to the UK, and to extract the polonium-210 needed for poisoning, many of these devices would have to be processed, which requires a radiochemical laboratory.

Findings relating to Litvinenko's death

Conclusions of a technical nature that may be significant for solving a crime can be divided into two groups: quite definite and those that are very probable, but for an unambiguous statement an investigation is required not only in the UK, but also in Russia.

Quite definite

1. Polonium-210 is a poisonous substance for covert use. Its main difference from other radioactive substances is the difficulty of initial detection. Accordingly, it is pointless to use it for provocation; there are much more accessible and suitable radionuclides for this.

2. Polonium-210 is a substance that is convenient to covertly transport in quantities sufficient to cause poisoning. It is also easy to secretly introduce it into a person’s drink. Other methods of administration (for example, airborne spray or dermal administration) are less effective, unreliable, complex and very dangerous for the poisoner.

3. Accidental contamination of polonium-210 through negligence is almost impossible, since such a degree of contamination requires a huge amount that can only exist in places of mass production of polonium in a factory, and this can be easily determined by the distribution of polonium on the human body.

4. None of the statements made publicly by the UK investigative authorities contain any technical contradictions.

Very probable, but requires confirmation

1. It is most likely that polonium-210 was produced in Russia. It could have been brought to the UK from Russia or the US, where the substance is officially supplied. Other sources are not excluded in principle, but it would be almost impossible to hide such production. Polonium-210 has not been produced in the UK for a long time.

2. Removal from antistatic devices in the USA requires a special radiochemical laboratory, which is extremely difficult to hide under the current control system in the USA. In other countries, such antistatic devices are practically not used.

3. Establishing the origin of polonium through analysis is possible only under certain circumstances (sufficient quantities and concentration, absence of background lead, sufficient exposure before analysis, availability of a special mass separator and samples for comparison). Under favorable conditions, it is also possible to establish in which production cycle it was obtained.

4. The substance was not stolen. This is extremely difficult to organize with the existing control system. Previously, several facts of missing polonium were recorded, but all of them were disclosed, since revealing them does not pose a big problem.