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LVIVNATIONALMEDICALUNIVERSITY
BY DANYLO HALYTSKYY
Department of medicine of extraordinary situations
FAILURES ON RADIOACTIVELY-DANGEROUS OBJECTS AND THEIR MEDICALLY-SANITARY CONSEQUENCES
Methodical recommendations for self-study of students
of medical and stomatological faculties to practical and seminar lessons
on educational subject “Medicine of extraordinary situations”
Lviv – 2011
Methodical recommendations prepared: Chaplyk V.V., Pylypiv Ya.I., Humenyuk V.V., and Oliynyk P.V.
Translation:Humenyuk V.V.
Methodical recommendations are developed for self-study of students of medical and stomatologic faculties to practical and seminar lessons on educational subject “Medicine of extraordinary situations” on theme:Failures on radioactively-dangerous objects and their medically-sanitary consequences. As a result of study of theme students must know reasons and medically-sanitaryconsequences of failures on radioactively-dangerousobjects. To be acquainted with the methods of estimation of radiation situation in the cell of extraordinary situation, with the devices of radiation search, facilities of collective, individual and medical defence.
Methodical recommendations are recommended by a methodical commission of department of medicine of extraordinary situations of LNMU by Danylo Halytskyy for the printing.
Document № 105 from 26 august 2011.
A sequence of study of theme and methodical recommendations for independent preparation to practical lessons
I. Educational aim:
To learn the reasons and medically-sanitary consequences of failures on radioactively-dangerous objects. To familiarize with the methods of estimation of radiation situation in the cell of extraordinary situation, with the devices of radiation search, facilities of collective, individual and medical defence
II. Educational-having a special purpose task:
1. To know possible reasons of origin of extraordinary situations on radioactively-dangerous objects.
2. To know medically-tactical description of extraordinary situations on radioactively dangerous objects.
3.To familiarize with the methods of estimation of radiation situation in the cell of extraordinary situation, with the devices of radiation search, facilities of collective, individual and medical defence
III. Time of lesson: 2 academic hours;
IV. Place of the lesson: educational class of department
V. Educational questions and timing:
1. Reasons of origin of extraordinary situations are on radioactively-dangerous objects.
2. Medically-tactical description of extraordinary situations on radioactively-dangerous objects.
VI. METHODICAL POINTING ON INDEPENDENT PREPARATION
During independent preparation to practical lessons students must use base material of methodical recommendations, the compendium of lectures on this topic, by educational material of the indicated literature.
As a result of independent preparation students must know reasons and medically-sanitary consequences of failures on radioactively-dangerous objects. To familiarize with the methods of estimation of radiation situation in the cell of extraordinary situation, with the devices of radiation control, facilities of collective, individual and medical defense and to be ready to give an answer for the control questions of employment.
TASK FOR SELF-STUDY
- Check your base knowledge in accordance with an educational purpose and educational tasks and if necessary – correct them.
- A questions for self-control of base knowledge:
1. Principles of work of the atomic electric stations and basic types of nuclear reactors.
2. Units of ionizing radiations.
3. Types of failures on radioactively-dangerous objects.
4. Principal reasons of origin of radiation failures.
5. Influence of ionizing radiation on the organism of man.
6. Measures on liquidation of consequences of radiation failure.
7. An estimation of radiation situation in the cell of extraordinary situation.
8. Devices of radiation control and doze-metric control.
BASE EDUCATIONAL MATERIAL
Failures on radioactively-dangerous objects, their medically-sanitary consequences.
1. Principles of work of the atomic electric stations and basic types of nuclear reactors
The production of electric power on the atomic electric stations (АЕS) is based on development of the guided nuclear reaction, as a result of what a plenty of energy, which has the kernel of atom, is excreteds.
Basis of AES are nuclear reactors. During the guided nuclear reaction in reactors are selected a warm, what heats a water and converts it into a pair. Pair under high pressure makes in motion a turbine and electricity generator.
For work of AES a nuclear fuel is needed – U235. Natural-uranium, from which are got a nuclear fuel, contains U235 (0,714%), U238 (99,28%) and U234 (0,006%). Natural uranium is enriched to 3,5-4,5% of presence in it of U235. Uranium is formed in fuel pills with diameter 7-8 mm and weight about 14 gr. Pills take place in fuel bars (tvels), which are hermtizely closed tubes. Tvels are grouped in warm-freeing elements. For carry of chain reaction on permanent level there is the special regulation equipment as mobile bars from matters, which take neutrons well (Cadmium, carbide of the Bor, and others like that). In the case of introduction of such bars to the depth of active area of reactor a chain reaction is slowed, at a taking off — accelerated. By regulation bars it is possible to support work of reactor at desired level.
Nuclear reactors are the generators of enormous amount of artificial radionuclides, which after the origin are divided into the products of nuclear division (PND), products of the directed activity (PDA) and isotopes of transuranium elements (ITE).
The products of nuclear division arise up in the process of breaking up of kernels of uranium or plutonium under the action of neutrons. To them belong about 200 radio-nuclides of 35 chemical elements, which are in the table of D.I.Mendelyeyev – from zinc (sequence number 30) to gadolinium (sequence number 64). PND is, as a rule, beta- and gamma-ionising. Periods of their half-decay are from a few seconds to tens of years. The products of the directed activity (PDA) appear at the irradiation of elements of construction of active area and of warm-transmitters, which circulates through it, by neutrons. To PDA belong about 400 radionuclides, which, as well as PND, are mainly, beta- and gamma-ionizing with half-periods from seconds to tens and thousands of years. The isotopes of transuraniums arise up at the irradiation of uranium-238 by slow-neutron. About 60 of radionuclides, which in majority are alpha-ionizing with large half-periods, belong to ITE. Thus, during work of nuclear reactor about 700 different radionuclides appears in it. A scientific committee on the action of atomic radiation of United Nations considers, that a main value in the irradiation of people 20 radioisotopes of 14 chemical elements have only. They are tritium, carbon-14, magnesium-54, iron-55, krypton-85, strontium-89, strontium-90, zirconium-95, ruthenium-103, ruthenium-106, iodine-131, caesium-134, caesium-137, barium-140, cerium-141, cerium-144, plutonium-238, plutonium-239, plutonium-241, americium-241. From this list it is possible to select 8 radiouclides, deposit each of which into an effective equivalent dose exceeds 1%. Hydrogen-3, carbon-14, caesium-137, strontium-90, zirconium-95, ruthenium-103, iodine-131, cerium-144 belong to them.
Distinguish several types of nuclear reactors:
Reactors water-graphite canal-type with graphite-decelerator, that is cooled down by water, which at the same time is as thermo-transmitter. Such reactors are set on Chernobyl’ AES (three), 13 — on other AES on territory of former Soviet Union (Ignalinsk, Kursk, Smolensk).
Water-boiling reactors. In this system an ordinary water is as thermo-transmitter such as decelerator. In the reactor corps this water is boiling. A steam gathers with pressure under the dome of reactor, and go through a pipeline on a turbine, which twists electric generator. The lack of this type of reactor is possibility of get of radioactive matters together with a steam on a turbine.
Water-compressed reactor (water-watering). In the active area of reactor water is under high pressure, what eliminates its boiling. Warm of the heated water is passed on other thermo-exchange contour, which holds the water under relatively low pressure (steam-generator). Water in this contour is boiled, growing into a steam, what lead the turbine in motion – and it twists electric generator. In these reactors water is as decelerator and as thermo-transmitter. Such reactors are in Ukraine on Zaporizhzhya (six), Rivne (three), Khmel’nytskyy (one) and South-Ukrainian (three) AES.
Reactor on fast neutrons. U238 is used in these reactors, which fissions during the capture of rapid neutrons. Therefore in reactors with fast neutron a decelerator of neutrons is absent. A reactor cools down by liquid Natrium, and taken off heat is used for production of electric power as in ordinary way. In a result of reaction, which is in the reactor, there is formed a plutonium. It can be used as a nuclear fuel in ordinary nuclear reactors. In this connection from the same amount of world mining of uranium in the case of the use of reactors on fast neutrons it is possible to get energy in 100 times more by comparison to ordinary reactors. However used plutonium, which appears in these reactions, can be used for the production of nuclear weapon, that is why subsequent development of these reactors is slowed in connection with aspiration of the world countries to limit the nuclear proliferation.
2. Units of ionizing radiations
As a result of radioactive decay there are several types of ionizing radiation. Depending on the type of co-operating with matters, ionizing radiations are divided on two groups.
Radiations of the first group, which consist of the charged particles: alpha- and beta-particles, electrons, protons. They predetermine ionization of matters, running directly into atoms and giving greater part of the energy to them.
The second group is made by radiations, which do not have electric charges — neutrons, gamma- and x-ray (roentgen) radiation. They pass their energy to the matter, first to the electrons and positively charged kernels of atoms during pushing with them, and already then the excited electrons and kernels of atoms lead to ionization of other atoms.
For the estimation of intensity of ionization is used a term «linear closeness of ionization» (LCI), under which is understand the amount of pairs of ions, that appears on 1 unit of way (1 cm) after track of motion of particle. But influence of ionizing radiation activity on the living organism depends also from ability of particle to penetrate inside of living tissues (penetrating possibility).
Most strong ionizing possibility is owned by alpha-particles. On 1 cm of way such particle is able to form 30 000 pairs of ions. But hereupon alpha-particles quickly lose the energy and that is why their penetrating possibility is too low: in living tissues — to 50 micrometers, in air — several centimeters. Therefore the radionuclides of alpha-irradiation are dangerous only in case, if they get inside of organism of man.
The Beta-particles are the particles of intra-nuclear origin, which have the same small mass and negative charge, as an orbital electron. LCI of beta-particles equals to 100—300 pairs of ions. Because of giving of plenty of energy during a collision with the atoms of matter, the way of run of beta-particles decreases a lot. In living tissues it is measured by centimeters, and in air — by meters (for example, strontium-90). The beta-particles in the case of external irradiation can make the burns of skin, but, as well as alpha-particles, more dangerous in the case of getting into the organism.
Neutrons have high enough ionizing possibility (LCI – 3000), their run in air is measured by kilometers, and penetrating possibility in tissues — by meters. The main sources of neutrons are atomic reactors, thermonuclear and neutron weapon.
Gamma-radiation — it is an electromagnetic, quite «hard» radiation (of large energy). LCI of gamma-quants — 2-3 pairs of ions. In connection with small ionizing ability gamma-quants have a small linear loss of energy, and from here — large penetrating possibility, which is calculated by kilometers.
As sources of alpha-, beta- and gamma-radiations there are kernels of atoms of so-called naturally radio-active elements, which are located at the end of periodic table of Mendeleyev (after a number 83).
Due to rule of radioactive-decay for separate radio-active element, which is in the certain power condition, for one unit of time there is always disintegrated the same part of active atoms, regardless of their amount, chemical state, temperature, pressure and other factors. In this connection there is a concept of «half-period» (T1/2) – time, during which the half of radio-active atoms are disintegrated. There are distinguished short-existing isotopes, T1/2 of which is seconds, minutes, hours, days. For example, polonium-218 — 3,05 min, lead-214 — 26,8 min, radon-222 — 3,8 days and others like that; and long-existing isotopes – T1/2 is from several months to milliards of years (lead-210 — 22,3 years, uranium-234 — 245 000 years, uranium-238 — 4,47 milliards of years and others like that).
In the case of receipt of radio-active nuclides inside of organism of man, except of physical disintegration (Tph) there is needed to take into account diminishing of activity due to biological processes (Tb), which is determined as the biological period of half-excretion, that is time, during which the half of radionuclides get out from an organism. A biological period of half-excretion can be different depending on organ, tissue, age, state of organism, ration of feed and other factors.
The amount of disintegrations of radio-active atoms in a radio-active matter during 1 sec is named its activity. Unit of measuring of activity in the international system of units of SI there is a Becquerel (Bq), which means one disintegration for 1 sec. Off-system unit — curie (Ci) — is 37 billion of Bq. Relative activity is used for determining the amount (concentrations) in unit of mass, volume or plane, depending on environment, in which the measuring was conducted. For example, in vegetables, meat — Bq/kg; in milk, air — Bq/l, on earth surface — Bq/m2, Ci/km2.
Conventional unit: 1 curie = 37 billion disintegrations per second.
SI unit: 1 becquerel = 1 disintegration per second
Conversions: 1 curie (Ci) = 37 gigabecquerel (GBq); 1 gigabecquerel (GBq) = 27 millicurie (mCi)
Damages, which arose up in the living organism because of irradiation will be than greater, than more its energy passes to tissues. Energy of any type of radiation, already passed or which can be passed to unit of mass of matter during co-operating of radiation with this matter, is named the dose of irradiation.
Under exposure a given material has an ability to absorb radiation. This differs with certain materials (think lead versus water) and some will absorb more or less as radiation passes through. Amount of energy of radiation, which is taken by unit of mass of the radiation-exposed body (by tissues), named adsorbed dose. Conventional units: a dose of 1 rad means the absorption of 100 ergs of radiation energy per gram of absorbing material. SI units: a dose of 1 gray means the absorption of 1 joule of radiation energy per kilogram of absorbing material. Conversion: 1 Gy = 100 rad; 1 rad = 0.01 Gy. So, in the SI-system it is measured in greys (Gy).
But this size doesn’t take into account an ionizing possibility of different ionizing radiations (for example, on condition of identical adsorbed dose of alpha-radiation is more dangerous, than beta- or gamma-radiation). If to take into account this fact, then adsorbed dose must be multiplied on a coefficient, which shows possibility of this type of radiation to damage tissues of organism of man (so-called radiation measuring factor, or coefficient of quality). An alpha-radiation is considered more dangerous (in twenty times), than other types of radiations. After multiplying of adsorbed dose on the coefficient of quality, there can be got an equivalent dose. In the SI-system it is measured in units, which are named Sieverts (Sv). The Quality Factor (Q) depends on the type of radiation:
- X-ray, Gamma ray, or beta radiation: Q = 1
- alpha particles: Q = 20
- neutrons of unknown energy: Q = from 5 to 20 (most are 10)
Conventional units: dose equivalent (rems) is the product of dose (rads) and Q
SI units: dose equivalent (sieverts) is the product of dose (grays) and Q
Conversion: 1 Sievert (Sv) = 100 rem; 1 rem = 0.01 Sievert (Sv)
The striking action of ionizing radiation depends not only on energy and high-quality features of radiation, but also from the sensitiveness of different organs and tissues. Therefore doses of irradiation of organs and tissues it is necessary to take into account with different coefficients (tissue measuring factor, or coefficient of radiation risk). If to multiply an equivalent dose on the proper coefficients and to do a result on all organs and tissues, then we’ll get an effective dose, which shows the final effect of irradiation for organism, it is also measured in Sieverts.
There are distinguished also the exposure dose of gamma- or x-ray radiation, which is determined by the ionization action of radiation in an air. Exposure is a quantity, that expresses the radiation delivered to a point at a certain distance. In the SI-system for unit of exposure dose is used a coulomb/kg (C/kg). As an out-system unit of exposure dose is used a roentgen (R). Conversion: 1 roentgen (R) = 258 microcoulomb/kg (µC/kg); 1 millicoulomb/kg mC/kg = 3876 milliroentgen (mR)
For quantitative description of external radiation a concept «power of dose» is used — that is dose, which is correlated with time units — seconds or hour. For example, if power of doze of gamma-radiation on the surface is 10 R/hour, then after 1 hour of stay on territory of this locality a man will get a dose of irradiation 10 R, after 2 hours — 20 R, etc.
Table 1.Sizes and units of ionizing radiations
№ п/п / Name of units / Units / Correlation between units of measuringIn the SI-system / Outsystem unit
1 / Accepted dose / Gy; mGy; μGy / rad; mrad; μrad / 1 Gy=1 J/kg; 1 Gy=100 rad
1mGy=10-3Гр; 1mrad=10-3 rad
1 μGy = 10-6Gy
2 / Exposure dose of photon radiation / (Kl/kg) / R; mR; μР / 1 R=2,58 x 10-4colomb/kg
(1 Cl/kg=3886 R)
3 / Equivalent dose / Sv; mSv; μSv / ber; mber; μber / 1 Sv=100ber 1 mSv=0,1 ber
(1 ber =10 mSv)
4 / Effective dose / Sv; mSv; μSv / ber; mber; μber / 1 Sv=100ber 1 mSv =0,1 ber
(1 ber =10 mSv)
5 / Power equivalent of x-ray radioactivity / а) for air of 8,73 mJ/kg 87,3 erg/g
b) in living tissue of 93 erg/g / а) for air 1 R=8,73 mJ/kg or 1 R=0,873 rad; 1 R=8,73 x 103 Gy=0,873 rad
Dexp(Р)=0,873 x Dads (rad)
б) in living tissues 1 R=0,93 rad
6 / Power of accepted dose / Gy/sec; Gy/g; mGy/sec / rad/sec; mrad/sec; μrad/ sec / 1 Gy/g=100 rad/sec
7 / Power of display dose of radiation / (A/kg) / R/s; R/g; mR/g; μR/g / 1 A/kg=1Cll/(kg x с)
8 / Power of equivalent dose / Sv/sec; mSv/sec / Ber/s; ber/g; mber/sec / 1 Sv/s=100ber/s
9 / Energy of radiation / J / еВ / 1 еВ=1.6 x 10-19Дж
10 / Activity of radionuclide / Bq / Ci / 1 Bq=1 decay/sec
1 Ci=3.7 x 1010Bq
11 / Superficial activity, level of contamination / Bq/km2; Bq/m2 / Ci/km2; Ci/m2
12 / By volume activity (concentration) of source / Bq/m3 / Ci/m3
13 / Specific (weight) activity of source / Bq/kg / Ci/kg
3.Types of failures on radioactively-dangerous objects.
A radiation failure is a failure, related to the extras of radio-active products and (or) going of ionizing radiations beyond the level, which is foreseen by a project, in amounts, which exceed the set limits of safety of exploitation of object and that resulted (or could lead) to the irradiation of people.