Why are the particles emitted radioactive? What to read in Quantum about the atom and nucleus

Are you familiar with the atom and the atomic nucleus? // Quantum. - 1993. - No. 9. - P. 48-49.

By special agreement with the editorial board and editors of the journal "Kvant"

These initial particles... are incomparably harder than
all sorts of things solid, composed of them, is so much harder,
that they never wear out or break into pieces.
I. Newton

Backscattering...impossible to obtain...except that
the bulk of the mass of an atom is concentrated in small core. It was then that I
the idea of ​​an atom with a tiny heavy center carrying a charge arose.
E. Rutherford

It is probably fair to believe that the idea of ​​the atomic structure of matter arose from man’s long-standing desire to somehow order the world around him. The search for eternal and unchanging matter, the elements of which all bodies are composed, began in ancient times, continued for centuries, and does not stop today. There is still no definitive answer, but what discoveries have been discovered along the way! Complex structure an atom, the nucleus of which, in turn, turned out to be composite, and from such particles that by themselves, outside the nucleus, are not capable of existing for a long time. Radioactivity, interconvertibility of particles, chain and thermonuclear reactions...

Some last decades were marked by a stream of discoveries that radically changed scientists' views on the structure of matter and raised a lot of new problems. Fundamentally transformed physical experiment, the implementation of which often requires the efforts of hundreds and thousands of people. Turned out to be unusually diverse practical applications methods of atomic and nuclear physics.

The small mosaic of today’s “Kaleidoscope” only outlines the contours huge world, hidden in smallest particles matter.

Questions and tasks

1. How many quanta of different energies can a hydrogen atom emit if its electron is in the third energy level?
2. How in electron shell does the atom tend to minimize potential energy?
3. Is there a connection between the frequency of an electron's revolution around the nucleus of a hydrogen atom and the frequency of its radiation?
4. By bombarding boron atoms \(_(5)^(11)B\) with fast protons, in a cloud chamber we obtained three almost identical tracks of particles directed in different sides. What particles are these?
5. Why not all types of radioactivity are accompanied by changes chemical properties substances?
6. In what cases can the activity of a radioactive drug be considered constant?
7. What is longer - three half-lives or two average lifetimes of nuclei of the same radioactive element?
8. Alpha particles emitted radioactive substance, can only have discrete values energy. What conclusion can be drawn from this? possible values energy of the atomic nucleus?
9. Why are alpha particles emitted radioactive drugs, can't call nuclear reactions V heavy elements?
10. Why during alpha decay identical kernels the energies of alpha particles are the same, and during the beta decay of identical nuclei the energies beta particles different?
11. The figure shows a photograph taken in a cloud chamber at the moment of the splitting of a nitrogen nucleus by a neutron with the release of an alpha particle. What do the thin and thick tracks visible in the photograph belong to?
12. If nucleons are able to attract each other, then why haven’t all the nuclei yet merged into one giant nucleus?
13. Why are substances occupying places in the middle and end of the periodic table not used as neutron moderators?
14. The rest mass of an atomic nucleus is always less than the sum of the rest masses of the nucleons from which it was formed. Is it possible on this basis to assume that the law of conservation of mass is violated during the formation of a nucleus?

Microexperience

Heat, for example on a gas burner, an iron nail to the “white point”. Will you be able to heat up a piece of glass in the same way?

It's interesting that...

Thales of Miletus, ancestor ancient philosophy and science, raised all the diversity of phenomena and things to a single element - water. Anaximenes, a representative of the same Milesian school, considered air to be the origin of everything, from the condensation and rarefaction of which all things arise. A contemporary of Thales, Heraclitus of Ephesus, preferred fire, which is also the soul and mind.

The planetary model of the atom, named after Rutherford's experiments, was theoretically developed back in 1901 French physicist Perrin, famous experimental study Brownian motion. Perrin’s article was called: “Nuclear-planetary structure of the atom.”

Back in 1815, Edinburgh physician William Prout hypothesized that all chemical elements consist of hydrogen atoms. And in 1911, Rutherford could not resist the assumption that atomic nuclei consist of alpha particles.

Rutherford believed that the magnitude of the nuclear charge is proportional to the atomic weight of the element. The correct idea about the proportionality of the charge to the number of the element in periodic table put forward by the Dutch amateur physicist Van der Broek. Rutherford was skeptical about this: “...an amusing speculation that does not have sufficient substantiation.”

If Enrico Fermi had been able to fully explain the results of his experiments on artificial radioactivity caused by neutrons, then the whole world would have learned already in 1934 about the possibility of creating an atomic bomb. At that time, Rutherford was still alive, who categorically denied the use of nuclear reactions for practical purposes.

Nuclear physics methods are successfully used in forensic science, making it possible to study substances weighing less than 10–10 grams, for example, to identify people by tiny remnants of their hair.

For internal heating of the Lunokhod during its many months of operation on the surface of the Moon, a thermal unit was installed on it, consisting of sealed ampoules with radioactive substances.

The natural radioactivity of men and women is different - due to the different content of the radioactive isotope potassium-40 in their bodies.

What to read in Quantum about the atom and nucleus

(publications of recent years)

1. “Droplet model of the nucleus” - 1986, No. 5, p. 23;
2. “Atomic physics in problems” - 1986, No. 12, p. 43;
3. “Nuclear Spectra” - 1987, No. 3, p. 42;
4. “Super-elongated nuclei” - 1988, No. 11-12, p. 32;
5. “Alpha particles and Rutherford’s experiments” - 1989, No. 3, p. 49;
6. “Neutrons are looking for a killer” - 1989, No. 5, p. 44;
7. “Beyond the Table” - 1991, No. 1, p. 38;
8. “Missing “elements” - 1991, No. 5, p. 43;
9. “Physics against scammers” - 1991, No. 8, p. 7;
10. “Neutron and nuclear energy” - 1992, No. 8, p. 2.

Answers

1. When a photon is emitted by an excited atom potential energy atom decreases.
2. Alpha particles: \(_(5)^(11)B + _(1)^(1)p = 3_(2)^(4)He\)
3. The chemical properties of a substance are determined by the charge of the nucleus. But with gamma radiation, for example, the charge of the nucleus does not change.
4. When the observation time is short compared to the half-life of the drug.
5. Three half-lives.
6. The nuclear energy can only take discrete values.
7. The energy of the particle is not enough to overcome the repulsive force of the nucleus of a heavy element.
8. During beta decays, in addition to electrons, neutrinos are also emitted, carrying away part of the energy, and this energy can vary within very wide limits.
9. Particles with large charge leave a track of greater thickness. In our case, the thin trace is formed by an alpha particle, and the thick trace is formed by the nucleus of the boron obtained in the reaction.
10. Already the first transuranium elements act Coulomb forces repulsion of protons leads to instability of nuclei.
11. When a neutron collides with an atom, the more energy is transferred to the latter, the smaller its mass.
12. No you can not. The missing mass is carried away by γ-quanta emitted during the formation of the nucleus.

Microexperience

In metals valence electrons easily go into an excited state, absorbing thermal energy, and just as easily return to normal, giving off energy in the form of light. In glass, all electrons are tightly bound to the nuclei of atoms and to with great difficulty change their energy state. To obtain a noticeable glow in glass, a much higher temperature is needed.

Material prepared by A. Leonovich

The device in which the controlled chain reaction nuclear fission is called a nuclear reactor. Uranium and plutonium (produced artificially) are used as fissile substances (nuclear fuel). radioactive element With serial number ).

Nuclear reactors are used to generate energy, to produce artificial radioactive isotopes (including transuranium elements, i.e. elements with ) B as sources of powerful neutron beams. Let's look at these applications.

1. Obtaining energy. Fission fragments are decelerated in uranium over a very short path (less than ). Because of this, almost all the energy released in the reactor is released as heat in the uranium mass. This heat can be used, for example, to heat and evaporate the liquid washing the uranium, and then, through a turbine or other heat engine, convert it into mechanical and then into electrical energy(Fig. 409). First in the world nuclear power plant, based on this principle, was implemented in the Soviet Union in 1954. (Fig. 410). A drawing of the reactor of this power plant is shown in Fig. 411. The main part The reactor consists of “fuel” elements with uranium placed in a graphite moderator. The “fuel” elements are two thin-walled stainless steel tubes inserted into one another. Uranium is hermetically sealed into the cavity between the tubes, and the internal cavity forms a channel for the flow of water, which takes away the heat released in the uranium during operation of the reactor. Hermetically sealed uranium is necessary due to its chemical instability, as well as to prevent the leakage of harmful radioactive gases formed as fission products. To facilitate the development of a chain reaction, “fuel” elements are made of uranium artificially enriched with an easily fissile isotope (the enriched uranium used contains ) versus 0.7% in natural uranium).

Rice. 409. Schematic diagram nuclear power plant. The uranium rods of the reactor are washed by a coolant (gas, hollow or molten metal). which takes away the heat generated in the rods and transfers it to water in a heat exchanger, forming steam. Steam, as in a conventional power plant, drives a steam turbine and an electric generator connected to it. In another embodiment, which is also used, steam is generated directly in the reactor, and there is no heat exchanger

Rice. 410. General form nuclear power plant (1954): 1 - reactor. 2 - a crane for replacing “burnt-out” uranium rods, 3, 4 - a pump with an electric motor that circulates water through the reactor, 5 - a heat exchanger, 6 - a reactor control room (control panel), 7 - a panel with instruments signaling the occurrence of unacceptable radioactivity in various areas of the station

The operation of a uranium reactor is accompanied by intense radioactivity. To protect people from radioactive radiation and from neutrons, which in large doses are also harmful to health, the reactor is surrounded by thick-walled protection made of concrete and other materials (Fig. 411, 412).

Rice. 411. Reactor of the first Soviet nuclear power plant: 1 - graphite masonry of the reactor, enclosed in a hermetic steel shell; the dashed lines outline the reactor core in which the uranium is located; the rest of the graphite serves as a neutron reflector; 2 - top plate (cast iron), 3 - one of 128 working channels in which uranium rods are placed and cooling water flows (pressure 100 atm); 4 - channel for moving the control rod containing a neutron absorber (boron); control rods serve to regulate the power of the reactor and stop the reaction; 5 - ionization chamber for measuring the intensity of the reaction in the reactor, 6 - water protection that retains neutrons, 7,8 - inlet and outlet of water from the reactor, 9 - upper protective cover (cast iron), 10 - concrete protection (mainly from -radiation)

Rice. 412. Top part reactor without lid. The motors for moving the control rods are visible. Below are tubes for supplying water to the working channels

As a source of energy, a nuclear reactor is remarkable for its low fuel consumption. Division 1g in terms of heat generation is equivalent to burning several tons coal. This makes the use of reactors particularly promising in locations remote from coal and oil deposits, as well as in transport - on ships, submarines, airplanes. A number of large nuclear thermal power plants were built in the USSR, several icebreakers were built with nuclear engines, there are nuclear submarines.

Nuclear power has great value for the future. It is estimated that at the current rate of growth in global energy consumption, humanity may face an acute shortage of coal and oil within 50 years. The use of uranium saves the situation, since the energy reserve in earth's resources uranium is 10-20 times higher than the energy reserve in deposits of fossil organic fuels. The problem of energy sources will get final decision when will a managed thermonuclear reaction(see §228).

2. Transuranic elements. When uranium is irradiated with neutrons, the isotope turns into. The latter is unstable; experiencing -decay, it forms an isotope of element 93 - neptunium (). In turn, it undergoes -decay and in a short time (half-life 2.35 days) turns into the isotope of element 94 - plutonium (). Plutonium-239 is also unstable, but decays very slowly (half-life 24,000 years). Therefore, it can accumulate in large quantities. Like uranium-235, plutonium-239 is a good "nuclear fuel" suitable for the device nuclear reactors, and atomic bombs. To produce plutonium, reactors made from natural uranium with a moderator are used. In these reactors, a significant proportion of neutrons are absorbed into uranium-238, eventually forming plutonium. Plutonium accumulated in uranium can be isolated by chemical methods. Another artificial nuclear fuel is an isotope of uranium with a half-life of 162,000 years, which is not found in natural uranium, and is formed, similarly to plutonium, as a result of neutron irradiation of thorium. In this way, difficult-to-fissile substances - and thorium - can be processed into valuable nuclear fuel. This possibility is very significant, since there is many times more thorium on Earth than . Neptunium and plutonium are representatives of the transuranic elements located in the periodic table behind uranium.

Following plutonium, a number of transuranium elements were obtained up to element 107. In nature transuranic elements not detected: they are all radioactive and short-lived compared to the geological age of the Earth.

3. Obtaining radioactive substances. In an operating reactor there are intense fluxes of neutrons generated during the fission reaction. By irradiating substances with neutrons inside a reactor, various artificially radioactive isotopes are obtained (cf. reaction (222.1)). Another source of radioactivity in the reactor is uranium fission fragments, most of which are unstable.

Artificially radioactive elements find many applications in science and technology. Substances emitting β-radiation are used instead of the more expensive radium to illuminate thick metal objects, to treat cancer, etc. The property of large doses of β-radiation to kill living cells of a microorganism is used in food preservation. Radioactive radiation is beginning to be used in the chemical industry, as it promotes the occurrence of many important chemical reactions. Particularly interesting is the so-called tagged atom method. This method takes advantage of the fact that chemical and many physical properties radioactive isotope indistinguishable from stable isotopes of the same element. At the same time, a radioactive isotope can be easily identified by its radiation (using, for example, a gas-discharge counter). By adding a radioactive isotope to the element under study and subsequently capturing its radiation, we can trace the path of this element in the body, in a chemical reaction, during metal smelting, etc.

Meaning nuclear energy. Few years have passed since the discovery of a method for using nuclear energy in terrestrial conditions. This discovery has already yielded its first fruits. Undoubtedly further development methods for obtaining and using nuclear energy will create new unprecedented opportunities for science, technology, and industry. The scale of these opportunities is difficult to fully imagine at this stage. The liberation of nuclear energy means a colossal expansion of man's power over nature, provided, however, that nuclear energy is used for peaceful purposes. Soviet Union, possessing atomic and hydrogen bombs, struggles to use atomic energy only for peaceful purposes, for the prohibition of atomic and hydrogen weapons and other means mass destruction of people.

Let us also note that the creation of nuclear reactors is one of the most significant fruits of the science of internal structure substances. The radiation of invisible, intangible atoms and atomic nuclei led to completely tangible and visible practical result- release and use of nuclear energy hidden in uranium. This success most convincingly proves that our scientific ideas about the atom and the atomic nucleus are true, that is, they basically correctly reflect the objective reality of nature.

36. Hiss symbolically the following nuclear reactions: a) the collision of two deuterons with each other, as a result of which two particles are formed, the lighter of which is a proton; b) the same, but a lighter particle - a neutron (symbol, mass equal to one, charge equal to zero); c) the collision of a proton with a lithium isotope nucleus with a mass of 7 with the formation of two -particles; d) the collision of a deuteron with an aluminum nucleus resulting in the formation of a new nucleus and a proton.

37. Why cannot particles emitted by radioactive drugs cause nuclear reactions in heavy elements, although they cause them in the lungs?

38. Nitrogen was irradiated for 1 hour with a beam of particles accelerated in a cyclotron. Find the amount formed if the current in the beam is equal and if the nuclear reaction (218.1) is caused by one particle out of every 100,000 particles in the beam.

39. Write down the following nuclear reactions: a) splitting of a deuteron by a quantum into a proton and a neutron; b) capture of a neutron by a proton with emission of a quantum; c) splitting of a nucleus by an -quantum with the formation of two -particles: d) capture of a neutron by the nucleus of a nitrogen isotope with a mass of 14 with the emission of a proton; e) collision of a beryllium nucleus with a deuteron with the emission of a neutron.

40. Bun fast neutrons crosses an iron plate of thickness . Find the fraction of neutrons that collide with an iron nucleus if the radius of the latter is . Note. The required value is equal to the fraction of the surface of the plate covered by nuclei.

41. Applying to elastic impact balls laws of conservation of energy and momentum, calculate the fraction of energy that a neutron loses during a head-on collision with a resting nucleus of mass A amu. Calculate the maximum energy loss of a neutron upon collision with a proton, a carbon nucleus, and a lead nucleus.

42. When colliding with a proton, a neutron loses one or another share of its energy depending on the nature of the collision (head-on, side). On average, as a result of one collision with a proton at rest, the energy of a neutron is reduced by half. Find average energy neutron after collisions with protons.

43. Find the average number of collisions with protons required to reduce the neutron energy from to (see Exercise 42).

44. Three identical silver plates were irradiated with neutrons under the same conditions, but the duration of irradiation was different: , , . Measurements of activity with a half-life of 2.3 minutes showed that the activity of the second plate is several times greater than the activity of the first, and the activity of the third plate is equal to the activity of the second. Explain this result.

45. In a cloud chamber, partitioned by a solid plate, a trace of a particle crossing the plate was noticed (Fig. 413). In which direction is the particle moving? What is the sign of its charge if the magnetic field lines are directed towards us.

Rice. 413. For exercise 45. The trace of a charged particle in a cloud chamber. The particle crossed plate P. The camera was placed in a magnetic field, the lines of which were directed towards us.

46. Why do radioactive substances produced by bombarding stable nuclei with particles experience electronic decay if initial reaction protons are released, and positron decay if neutrons are released in the initial reaction?

47. Determine the minimum energy of -quanta required for the splitting of beryllium and carbon nuclei by reactions

For the masses of particles participating in the reactions, see the table on p. 560.

48. The nucleus, emitting a particle with energy, turns into a nucleus. Determine the mass of an atom if the mass of the atom is 238.1249 amu. The mass of the atom is given on p. 560.

49. The best accuracy with which the mass of an atom or molecule can be measured is one millionth of an amu. (0.000001 amu). Is it possible under these conditions to use Einstein's law to calculate the energy release when chemical reactions based on the measured values ​​of the masses of the particles participating in the reaction (the energy release during chemical reactions does not exceed )?

50. What particles - positrons or electrons - will emit fission fragments if one of them is ? (Natural barium consists of isotopes with masses from 130 to 138 amu, natural krypton consists of isotopes with masses from 78 to 86 amu)

51. Find the power of the reactor in which 1 g is divided per day. Full selection energy during fission of one nucleus is taken equal to .

52. Kinetic energy fission fragments is ; fission neutron energy - ; energy - radiation - .

Approximately what proportion of the energy released in a reactor consisting of a moderator and thin rods of uranium is released in the uranium and what in the moderator?

53. In which case is the critical mass of uranium in a reactor smaller: when the reactor is bordered by air or when it is surrounded by a dense substance that weakly absorbs neutrons?

54. Of the secondary neutrons emitted during the fission of uranium in a reactor, one part dies without causing new fissions (flies outside the reactor or is captured by the nuclei of the reactor materials), the other part causes new fissions of uranium nuclei. The number of new fissions produced by secondary neutrons emitted during the fission of one uranium nucleus is called the reactor multiplication factor (). The multiplication factor shows how many times the number of fissions increases during the lifetime of one generation of neutrons. to Tue.

57. Gasoline is pumped through the pipeline, followed by oil. Suggest a way to determine the moment when the gasoline-oil interface passes through a given section of the pipeline. Do not take a sample from the pipeline

In an individual task, six tasks are performed, the numbers of which are determined in accordance with the sequence of letters in the student’s last name according to Table 4.1.

Table 4.1 - Task options

The first task is selected according to the first letter of the surname, the second - according to the second letter, etc. For example, student's last name Chimkovsky. In this case, task No. 4 is selected first, No. 19 is second, No. 23 is third, No. 31 is fourth, No. 45 is fifth, No. 53 is sixth.

If the student's last name consists of less than six letters, then the missing number is supplemented by reusing it.

By doing individual assignment the following conditions must be met:

The numbers of the tasks to be performed must correspond to the conditions for their selection and must be indicated on the first sheet;

Completing assignments involves the use of recommended literature, but it is also possible to use other specialized literature at your disposal;

The pages of the individual assignment must be numbered, and appropriate explanations must be made along the calculations and answers.

Complete the nuclear reactions:

2. Which nucleus is formed as a result of: alpha decay of an isotope of uranium; electron beta decay of hydrogen isotope

3. Which nucleus is formed as a result of: alpha decay of a nitrogen isotope; positron beta decay of a copper isotope?

5. Write the reactions of alpha decay of uranium and lead beta decay

6. Complete the nuclear reactions:

7. When a copper isotope is irradiated with protons, the reaction can proceed in several ways: with the release of one neutron; with the release of two neutrons; with the release of a proton and a neutron. The nuclei of which elements are formed in each case? Write down the decomposition reactions.

8. Radioactive manganese obtained in two ways. The first way is to irradiate the iron isotope with deuterons, the second is to irradiate the iron isotope neutrons. Write nuclear reactions.

9. When iron is bombarded with neutrons, a beta-radioactive isotope of manganese is formed with atomic mass 56. Write the reaction for producing artificially radioactive manganese and the reaction of the subsequent beta decay that occurs with it.

10. When bombarded with boron isotope formed by alpha particles

nitrogen isotope What particle is released? Nitrogen isotope

is radioactive, producing positron decay with neutrino radiation. Write reactions.

11. How many atoms of polonium decay out of 10 6 atoms per day if its half-life is 138 days?

12. Half-life of the strontium isotope is 51 days. How many isotope nuclei will decay in 102 days if the initial number of radioactive nuclei is 10 9?

13. How much radioactive nuclei isotope mass m=10 -4 kg will remain in the sample after 7 days?

14. Water weakens neutron radiation best (4 times better than concrete and 3 times better than lead). The thickness of the half-attenuation layer of neutron radiation for water is 3 cm. How many times will a 30 cm thick layer of water attenuate neutron radiation?

15. Gamma radiation is best absorbed by lead (in 1,5 times better than steel armor and 22 times better than water). The thickness of the half-attenuation layer of gamma radiation for lead is 2 cm. How thick is a layer of lead needed to attenuate gamma radiation by 128 times?

16. Weight of the drug equal to 65 mg. Determine its activity.

17. What part of the iodine initially deposited as a result of the Chernobyl accident decayed in the first two months after the accident?

18. Calculate the thickness of the water layer at which the intensity of gamma rays will decrease by 4 times. Take the linear attenuation coefficient for water equal to 0.047 cm -1.

19. Of every million atoms of a certain radioactive isotope, 200 atoms decay every second. Determine the half-life of the isotope.

20. The activity of a radioactive element decreased by 4 times in 8 days. Find the half-life of the element.

21. To detect leaks in pipelines buried deep in the ground, radioactive substances are added to the transported liquid. How to use a Geiger counter to determine the location of a leak?

22.Why are neutrons more effective projectiles in bombarding nuclei than the charged particles emitted by radioactive elements?

23. Is there a limit to the power of nuclear and thermonuclear explosions? Explain your answer.

24. What is the difference between the fission processes of uranium nuclei in a reactor and an atomic bomb?

25. What explains that the Geiger counter registers the occurrence of ionized particles even when there is no radioactive drug nearby?

26.Why are radioactive drugs stored in thick-walled lead containers?

27.Where is the longer path of an alpha particle: at the surface of the Earth or in the upper layers of the atmosphere?

28.What fraction of radioactive nuclei decays in a time equal to half the half-life?

29. Do the local number, mass and atomic number of an element change when a gamma quantum is emitted by the nucleus?

30. Why are alpha particles emitted by radioactive drugs unable to cause nuclear reactions in heavy elements, although they cause them in the lungs?

31. On a spectrometer with an average determination error of 20%, when determining the volumetric activity of milk with a sample volume of 500 ml, 500 pulses were recorded per 100 s of measurement. Determine the volumetric activity of milk and its compliance RDU-99 standards.

32. The equivalent dose of external gamma radiation received by a person from living in a certain locality is 0.1 rem/year. Determine the exposure dose rate caused by gamma radiation from radionuclides in the soil. The relative time of a person’s stay in an open area is taken to be 0.3.

33. Using the values ​​of the exposure dose rate caused by gamma radiation from radionuclides in the soil, 60 μR/h, and the relative time of a person’s stay in an open area of ​​0.25, determine the equivalent dose of external irradiation of a person per year.

34. The equivalent dose rate at the personnel workplace is 5x10 -9 Sv/s. During the year, work is carried out 1600 hours. Is special protection required for personnel?

35. According to radiation safety standards (NRB-2000), the maximum permissible radiation dose for personnel is 50 mSv/year. During the year a person works 1700 hours. Calculate the maximum permissible equivalent dose rate (in Sv/s) at the workplace.

36 During an X-ray examination of the chest, the average equivalent doses of radiation to the patient’s organs and tissues are presented in the table given in problem 49. Determine the effective equivalent dose received by the patient during this type of examination.

37 The human body received 3x10 -13 kg of isotope at one time, of which a tenth passed into the thyroid gland. The mass of the thyroid gland is 25 g, the absorbed energy per decay is 0.25 MeV/disintegration, the half-life is 5.25 days. Determine the equivalent dose of radiation to the thyroid gland over the next 8 days.

38 The human body received 3x10 -15 kg of isotope at one time
of which a tenth part passed into the thyroid gland. The mass of the thyroid gland is 20 g, the absorbed energy per decay is 0.25 MeV/disintegration, the half-life is 29 years. Determine the equivalent dose of radiation to the thyroid gland over the next 15 days.

39 The equivalent dose rate in the workplace is 10 -10 Sv/s. A person works 6 hours a day. Is it necessary to create special protection?

40 The average absorbed dose of radiation by an employee working with an X-ray unit is 7 µGy/h. Is it dangerous for an employee to work for 200 days a year, 6 hours a day, if the maximum permissible radiation dose is 50 mGy/year?

41 The dose rate of gamma radiation from radioactive isotopes in the accident zone at a nuclear power plant is 20 rad/h. How many hours can a person work in this zone if the permissible radiation dose in an emergency situation is 25 rad?

42 The activity of the cesium preparation is 15 Cu. Determine its mass.

43 What part of the initial amount of strontium that fell as a result of the Chernobyl disaster has decayed over the past time (25 years), if its half-life is 29.1 years?

44 Calculate the thickness of the half-attenuation layer of gamma radiation for water, if linear coefficient attenuation is 0.047 cm -1 .

45 When determining the radionuclide that contaminated the surrounding area, a conventional personal pulse counter was used. Initially, its average reading was 390 pulses/min, and after 10 days - 201 pulses/min. Calculate the half-life of the radionuclide and determine it.

46 On a gamma radiometer with a registration efficiency of 20%, when measuring the volumetric activity of milk with a volume of 357 ml, 650 pulses were recorded within 100 s. What is the volumetric activity of milk? Is it suitable for consumption?

47 The exposure dose rate due to gamma radiation from radionuclides in the soil in a certain populated area is 60 µR/h. Find the equivalent dose of external gamma radiation received by a resident of this settlement during the year during his stay outside the home, taking relative time human presence in open areas equal to 0.2.

48 The human body received a one-time dose of 5x10 -13 kg of radionuclide iodine-131. Determine the equivalent dose to the human thyroid gland over 10 days. The mass of the thyroid gland is assumed to be 25 g, the absorbed energy per decay is 0.19 MeV/disintegration, the half-life is 8.04 days. Assume that 0.35 of the total amount of iodine-131 entering the body passes into the thyroid gland.

49 The table below shows the average equivalent doses of radiation to the patient’s organs and tissues during an X-ray examination chest. Determine the effective equivalent dose received by the patient during the examination.

50 Is special protection required if the equivalent dose rate at the personnel workplace from a source of ionizing radiation is Sv/s? The radiation dose is distributed evenly throughout the year. During the year, work is carried out 2800 hours.

51 Natural radionuclides of terrestrial origin. Human exposure to potassium-40 and radon.

52 Artificial sources of ionizing radiation. Radiation background.

53 Radiosensitivity of human organs and systems, their response to radiation.

54 Internal and external radiation, methods of protection against it. The ability of flora and fauna to resist radiation.

55 Features of vertical and horizontal migration of radionuclides.

56 Ways to reduce the content of radioactive substances in food products of animal origin

57 Methods for reducing the content of radioactive substances in food products of plant origin.

58 Decontamination of territory, objects, equipment, food.

59 Natural and accelerated removal of radionuclides from the body. Biological half-life.

60 Sanitary and hygienic measures when living and conducting homestead agricultural production in conditions of radioactive contamination of the territory.