Polonium. Properties of polonium. Use of polonium. Polonium: the history of the discovery of the element The chemical element polonium, the origin of the name

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 surrounding the mysterious death of Alexander Litvinenko do not subside. 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 at 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 technically? 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) according to the 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 - 5·10 –5 R×cm 2 /h×mCi (where R is a roentgen, mCi is a millicurie ). In this case, the dose coefficient and, consequently, 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 it can also pass into the environment together with the vapor of the water in which it is contained, and in the process with 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 the gastrointestinal tract is estimated from 5 to 20%. Through the lungs - it is more effective, but such an 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 initiators of a nuclear explosion in atomic bombs. Neutrons are produced when beryllium is irradiated with alpha particles and initiate a nuclear explosion when the mass of uranium-235 or plutonium-239 reaches critical mass. 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.

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 even put my mind to…. Now, if I were thinking about how to poison a person, 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 Great Britain. ( 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 the modernization and technical development of the Russian economy, and now he is a deputy of the State Duma, Andrei Lugovoy’s comrade-in-arms in the LDPR faction - "Polit.ru").

It is difficult to understand: the people who said this - they simply do not understand this area at all 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 it is clear. 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?

Polonium, due to its properties, 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 is an 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 am sure about that. 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 in 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(lat. Polonium), Po, a radioactive chemical element of group VI of the periodic system of Mendeleev, atomic number 84. Polonium is the first element discovered for its radioactive properties by P. Curie and M. Sklodowska-Curie in 1898. Named in honor of Poland (lat. Polonia) - the birthplace of M. Skłodowska-Curie. There are 25 known radioactive isotopes of Polonium with mass numbers from 194 to 218. The longest-lived is the artificially produced α-radioactive 209 Po (half-life T ½ = 103 years). There are 7 isotopes of Polonium found in nature with mass numbers 210-212, 214-216 and 218 as members of the radioactive series of uranium, actinouranium and thorium. The most stable of them is α-radioactive 210 Po (T ½ = 138 days). Milligram amounts of 210 Po can be isolated not only from natural objects, but also synthesized artificially through the nuclear reaction of neutrons with bismuth. Almost all information about Polonium was obtained using 210 Po.

Polonium is a rare element; its content in the earth's crust is about 2·10 -15%. In its free form, Polonium is a soft silvery-white metal; density 9.3 g/cm 3, melting point 254 °C, boiling point 1162 °C. The configuration of the outer electron shell of the atom is 6s 2 6p 4. In terms of chemical properties, Polonium is closest to tellurium. In compounds (like Te) it exhibits oxidation states -2, +2, +4 and +6. The oxides PoO, PoO 2 and PoO 3 are known. When Zn acts on a hydrochloric acid solution of Polonium, the volatile hydride PoH 2 is formed. In Polonium solutions there are PoO 4 2- PoO 3 2-, Po 4+ and Po 2+ ions.

Polonium hydroxide is known - PoO(OH) 2.

Easily hydrolyzed Polonium tetrahalides and sulfates of various compositions were synthesized in weight quantities. Using the carrier method (using the analogue of Polonium - tellurium), organopolonium compounds were synthesized in which the Po - carbon bond is carried out [obtained, for example, Polonium diphenyl (C 6 H 5) 2 Po, Polonium diphenyl dichloride (C 6 H 3) 2 PoCl 2, etc. etc.]. Polonium is extremely toxic and therefore work with it is carried out in special boxes.

The 210 Po isotope is used in neutron sources. The energy of 210 Po α particles can be converted into electrical energy. Electric “atomic” batteries with 210 Po, which have a long service life, were used, in particular, on the Kosmos-84 and Kosmos-89 satellites.

Polonium-210 (210 Po) is a common component of naturally occurring radioactive fallout. It enters plants from the soil through the roots or from the atmosphere as a result of deposition on above-ground organs. In small quantities (10 -4 pcurie/g) 210 Po is found in sea water; can accumulate by marine organisms (in the seaweed Porphyra umbilicalis its accumulation coefficient is ~ 1000). 210 Po enters the body of animals and humans with food. The approximate content of 210 Po in sea fish is 20-100 pcuries/kg, meat - 2-3 pcuries/kg, bread - 1 pcuries/kg, cereals - 2 pcuries/kg, tea - 500-600 pcuries/kg. In the body of animals and humans (specific concentration is about 4-10 -5 pCuries/g of raw tissue), Polonium is distributed relatively evenly throughout individual organs. The biological effect of 210 Po is due to α-radiation. Experiments on animals have shown the high toxicity of this radionuclide in high concentrations. Thus, concentrations of 210 Po above 0.0003 µCurie/g live weight reduced the life expectancy of white rats, changed the composition of peripheral blood, and caused cirrhosis of the liver; in the long term, the animals developed tumors of the kidneys, large intestines, testes and a number of other organs. The biological effect of low concentrations of 210 Po has not been sufficiently studied.

Radioactive element of group VI of the periodic system of Mendeleev. Polonium was discovered in 1898 by Marie Sklodowska-Curie and Pierre Curie. The name was given in honor of Poland.
M. Curie found that some samples of uranium resin ore are more radioactive than uranium itself. Therefore, this ore must have contained substances more radioactive than uranium. These substances (elements) were isolated. First polonium and then radium.
The longest-lived of the natural isotopes is 210 Po. The half-life of 210 Po is 138.376 days, i.e. During this time, the initial amount of 210 Po is halved. After this time, half of the 210 Po nuclei turn into nuclei of the stable lead isotope 206 Pb. The transformation of 210 Po into 206 Pb occurs as a result of α decay

210 Po → 206 Pb + α.

Those. In addition to lead nuclei (206 Pb), the decay of 210 Po also produces helium nuclei 4 He, which are usually called α (alpha) particles. Moreover, 210 Po is an almost pure α-emitter. Alpha decay, if it occurs not to the ground state or not only to the ground state of the final nucleus, is accompanied by gamma radiation. In the overwhelming majority of cases, 210 Po decays into the ground state of 206 Pb with the emission of alpha particles with an energy of 5.3 MeV, and only a tiny fraction (0.00122%) of 210 Po nuclei decays into the excited (803 keV) state of 206 Pb, which decays with the emission of gamma-ray particles. quanta The gamma radiation accompanying such alpha decay can be detected only in a precision experiment.
The 210Po isotope is not only the longest-lived among natural ones, i.e. existing on Earth, and not artificially obtained, isotopes of polonium, but also the most common. It is constantly formed due to a chain of isotope decays that begins with 238 U and ends with 206 Pb.

238 U → 234 Th → 234 Pa → 234 U → 230 Th → 228 Ra → 222 Rn → 218 Po → 214 Pb → 214 Bi → 214 Po → 210 Pb → 210 Bi → 21 0 Po → 206 Pb.

Half-life (T 1/2) of 238 U is 4.5 billion years. In the natural uranium mixture, 238 U is more than 99%. For the number of nuclei (N) isotopes of uranium (238 U) and polonium (210 Po) in a natural mixture and their half-lives (T 1/2), the following relation is true:

N(238 U)/N(210 Po) = T 1/2 (238 U)/T 1/2 (210 Po).

Similar relationships are valid for all isotopes in a chain of successive decays, since they are in the so-called secular equilibrium , when the number of decays per unit time is the same for all isotopes. As many isotope nuclei are formed as a result of previous decay per unit time, the same number of them decay. Thus, 1 ton of uranium ore contains only about 100 micrograms of polonium. Basically it is 210 Po. All other natural isotopes of polonium are even smaller (and by many). Polonium can be isolated from uranium ores during the processing of uranium production waste. However, in order to obtain a noticeable amount of polonium, an incredible amount of such waste would have to be processed. 210 Po is produced in nuclear reactors by irradiating bismuth with neutrons as a result of the reaction

209 Bi(n,γ ) 210 Bi.

210 Bi undergoes beta decay and turns into 210 Po. The half-life of 210 Bi is 5.013 days.
In addition to 210 Po, two more artificially radioactive isotopes of polonium have relatively long half-lives - 208 Po (T 1/2 = 2.898 g) and 209 Po (T 1/2 = 102 g). These isotopes can be produced by bombarding lead or bismuth targets with cyclotron-accelerated beams of alpha particles, protons or deuterons. 209 Po can be purchased from Oak Ridge National Laboratory with permission from the U.S. Atomic Energy Commission (A.E.C.) for approximately $3,200 per µCi (microcurie)*. In such a source there will be 6 · 10 -8 g 209 Po. All other polonium isotopes have half-lives from 8.8 days (206 Po) to fractions of a microsecond ( ).

Different types of ionizing radiation (α,β,γ) have markedly different penetrating abilities. Alpha particles from radioactive isotopes flying through matter easily pick up electrons and turn into helium atoms. So, in order to turn into helium, it is enough for alpha particles of 210 Po to fly less than 4 cm in air, less than 50 microns in biological tissue, and less than 30 microns in aluminum. Thus, alpha radiation from radioactive sources cannot be detected by conventional dosimeters that use Geiger counters. Alpha particles of such energies will not pass through the meter body, even if its surface is smeared with an alpha radioactive isotope. It is enough to place a pure α-emitter in a sealed package with walls no thicker than a sheet of paper (the main thing is that the radioactive drug does not “spill out” from it); more sensitive devices, such as, for example, semiconductor or scintillation detectors, will not be able to detect its radiation . The latter can help detect alpha radiation if they are in close proximity to an “open” source of radioactive contamination.

In Fig. 2 shows the characteristics of the scintillation pollution detector LB 124 SCINT, manufactured by BERTHOLD TECHNOLOGIES GmbH & Co.
Radioactive sources of 210 Po are used in both scientific research and technology. During work on the Manhattan Project, the polonium-beryllium neutron source was intended to be used as a fuse for an atomic bomb. Neutrons in such a source are obtained as a result of the interaction of alpha particles from the decay of 210 Po with beryllium, the reaction 9 Be(α,n). However, this decision was later abandoned. The specific energy release of polonium is high - 140 Watt/g. A capsule containing 0.5 g of polonium is heated to 500 o C. This property is used to create thermoelectric sources based on it, which are, in particular, used in spacecraft. Polonium is also used in static electricity removal devices. Some devices of this kind may contain polonium with an activity of up to 500 µCi (about 0.1 microgram). This amount is theoretically enough to kill 5,000 people. However, this polonium is securely packaged, and extracting it for malicious purposes requires sophisticated technology and in-depth knowledge. As a rule, the activity of the sources offered on the market is low. So you can purchase a 210 Po source with an activity of 0.1 µCi (microcuries) for $69. A source with such activity emits 3,700 particles per second. The mass of 210 Po in such a source is about 2 · 10 -11
Alpha radiation from radioactive sources cannot penetrate the skin. However, alpha-emitting nuclides pose a great danger when entering the body through the respiratory and digestive organs, open wounds and burn surfaces, and not only due to ionizing radiation, but also simply as toxic substances. The maximum permissible dose load on the body when 210 Po is ingested is only 0.03 µCi (6.8 - 10 -12 g). With the same weight 210 Po is approximately 2.5. 10 11 times more toxic than hydrocyanic acid. Once in the human body, polonium spreads through the bloodstream throughout the tissues. Polonium is excreted from the body mainly through feces and urine. Most of it is excreted in the first few days. In 50 days, about half of the polonium that enters the body is eliminated. The presence of polonium in people infected with it is identified by the weak gamma radiation of the secretions. Ingestion of one hundred thousandth of a milligram of polonium into the human body is fatal in 50% of cases. Polonium is a very volatile metal; in air, in 45 hours, 50% of it evaporates at a temperature of 55 o C.

* Units of activity - 1 Ci (Curie) = 3.7. 10 10 decays per second, 1 Ci = 10 3 mCi = 10 6 μCi. 1 Bq = 1 decay per second.

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 grounds 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

In total, science currently knows 27 (according to other sources - 33) forms of polonium. 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 polonium-210 isotope 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 a huge amount of material. A much simpler and more effective method 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 to ingest polonium 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, there is no need to be afraid of working with it if certain precautions are taken. 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 areas of 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.