URANIUM

From Big Medical Encyclopedia

URANIUM (U) — radioactive chemical element III of group of a periodic system of elements of D. I. Mendeleyev. Treats family of actinoids (see). Sequence number 92, at. weight (weight) 238,07. At. — metal of silver-white color, density

is 19,05 g/cm3, g°pl 1130 °. It is open in 1789 by the German chemist Klaprot (M. N. for Klaproth) and Uranium is called in honor of the planet.

At. it is eurysynusic in the nature, it is found in the connected state in various ores (uranite, carnotite, autunite, etc.), in carbonic and oil deposits, in sea water, etc. Average content At. in crust makes 2,5-10 ~ 4% (on weight). Being radioelement, At. substantially influences the level of a natural radioactive background (see background radiation); At. — the main power raw materials for receiving nuclear fuel. In nature meets in the form of isotopes: 238U (99,285%), 234U (0,005%) and 235U (0,71%). In the uranium ores which are a source of industrial receiving uranium also other elements of an uranium row meet (226Ra, 222Rn, 210ro, etc.).

Chemically At. has high activity, enters interaction with numerous organic and inorganic compounds; with fluorine forms fluorides of tetravalent and hexavalent uranium (UF4 and UF6), with oxygen forms dioxide (U02), trioxide (U03), mixed oxide (U308) and peroxide (U04-2H20).

The main isotope 238U is an ancestor of a decay series; half-life — 4,49-109 years; 1 mg natural At. lets out about 25,4a-particles in 1 sec. that makes 6,8 - Yu-10 of curie/mg (25,16 Bq/mg). In the course of disintegration 238U several radioelements are formed; an end product of disintegration is the stable isotope of lead (206R).

Isotopes U. have nek-ry specific properties: 238U

it is capable to take neutrons with formation of transuranic elements (ssh. Actinoids), 235U under the influence of neutrons it is split with release of enormous amount of energy. Uranium minerals contain a number of radioelements of an uranium row (radium, polonium, radon, lead, etc.). In natural ores U. is in an equilibrium state with products of the disintegration.

At. treats bio-elements and is a part of bodies and tissues of animals and the person. Natural contents At. in a skeleton — apprx. 59, in kidneys — apprx. 7 mkg. Uranium and its connections come to an organism through a respiratory organs, went. - kish. path and skin. Daily receipt with food and liquids makes apprx. 1,9 mkg.

Extent of absorption At. in an organism at various ways of receipt depends on solubility of connections U. Soluble compounds At. (uranyl nitrate, fluoric dropped, uranium trioxide, uranium pentachloride, ammonium and sodium uranium salts) get through skin in significant amounts. Almost insoluble compounds of uranium (U02, U04, U308) are practically not soaked up through skin.

Depending on the size of absorption (D) at inhalation receipt all compounds of uranium divide into a number of inhalation classes — D, N. Such compounds of uranium as UF6, U02F2 and U02 (N03) 2 which are quickly soaked up by pulmonary fabric are referred to a class D. Less soluble compounds — U03 UF4 and UCI4 are referred to a class N, and almost insoluble U02 and U308 — to a class. For substances of classes D and H size / x is accepted equal 0,05; for connections of a class G size / x makes 0,002.

The main bodies of deposition At. kidneys, a liver and bones are. To Avtoradiograficheski it is shown that At. it is preferential postponed on superficial structures of a bone from where easily gets to blood and repeatedly very slowly distributed on all volume of a mineral part of a bone. Redistribution At. on all volume of a bone can proceed within several months after introduction. For this reason it is accepted that isotopes

of uranium 229U, 230U, 231U, 237U, 239U and 240U are distributed evenly on the surface of a bone, and isotopes

of uranium 232U, 233U, 234U, 235U, 236U and 238U are distributed on all volume of a mineral part of a bone.

Adjournment At. in various parts of a skeleton unequally; its greatest numbers are postponed in a backbone, the smallest — in bones of a skull. In kidneys At. it is distributed unevenly, its most part is postponed in a bast layer; in later terms after receipt At. concentrates in distal tubules and balls of kidneys.

Allocation At. from an organism irrespective of a way of receipt prois-hodtst with a stake and urine; the most part is allocated with urine in the first 24 hours; removal with a stake is insignificant and does not exceed 1 — 3% of total quantity At., brought out of an organism.

Wedge, picture of defeat by soluble and almost insoluble compounds U. has a certain similarity. Distinguish several periods during uranium intoxication. The eclipse period proceeds from several hours to several days, is characterized by the general slackness, a loss of appetite. Emergence of the main symptoms happens on 5 — the 7th days, an outcome of intoxication — on 15 — the 30th days. The remote effects of defeats — from several months to several years. In nek-ry cases the main symptoms appear on

3 — the 4th days.

In experiments on animals at inhalation receipt At. the initial phenomena of pneumonia, in the next days — symptoms of damage of kidneys were noted. On 10 —

the 13th days — muscular weakness, at nek-ry animals — paralysis of muscles of extremities. The expressed changes in blood developed: acceleration of ROE, a leukocytosis (to 20 thousand in 1 mkl), shift of a blood count to the left, a lymphopenia, a monocytosis, reduction of quantity of eosinophils.

At acute intoxication kidneys most suffer. The disease proceeds as toxic nephrite, in hard cases is followed by an uraemic state. The combined damage of a liver and kidneys is observed, carbohydrate, protein, fatty and water exchange Is broken. In blood nonprotein nitrogen and an urea nitrogen increases. Functional and organic lesions of c are noted. N

of the village of Hron. uranium intoxication develops as a result of repeated long impact of various connections U. In blood there is a decrease in concentration of hemoglobin, number of erythrocytes, leukocytes, reticulocytes, thrombocytes. In urine periodically note the raised sugar content, a squirrel. Function of a liver, cardiovascular system, closed glands is broken. Disturbances of a nervous system are shown in the form of an asthenic syndrome, vegetative dysfunction.

In the remote terms after defeat at long uranium intoxication at animals disturbances of sexual function and reproductive ability are noted; after inhalation 235U, having considerably bigger radioactivity, than 238U, in the remote terms there were malignant new growths in lungs (see. Beam damages). At the person acute poisoning with uranium fluoride is followed by damage of airways and kidneys; patients complain of suffocation, pains behind a breast. At the same time cyanosis, cough, a fluid lungs, allocation of a green-gray phlegm, sometimes with blood are observed.

For acceleration of removal At. from an organism recommend natriydi-calcium salt dietilentria-

minpentametilfosfonovy to - you (Na Sa2 DTPF, pentafatsin) and calcium - disodium salt dietilendiamino-izopropildifosfonovy to - you (CaNa2 EDDIF, fosfitsin). In case of inhalation defeat — inhalation of an aerosol of 5% of solution of a pentafatsin or fosfitsin, inside Diacarbum (Fonuritum) of 0,25 g during the first hours after intoxication as the specific means preventing damage of kidneys; in hard cases a hemodialysis.

Occupational health during the work with uranium. On uranium mines in addition to such harmful factors as miner dust, explosive gases, noise, vibration, perhaps adverse effect of radionuclides of family U — Wa, coming to air in the form of aerosols, and also radioactive gas — radon (Vp) and its affiliated products (see Radon). Their ratio with Vp, close to equilibrium, causes the greatest radiation of upper respiratory tracts and lungs. High content of Vp and its affiliated products in air complicates a current of a silicosis (ShM.), causes hron. bronchitis; cancer of a lung, according to various researchers, can arise in 11 — 25 years after the beginning of work.

Processing of uranium ores and receiving salts U. production is connected with the same radiation factors, as At. During the heating and melting metal At. levels of beta radiation owing to redistribution of decomposition products U increase. (234Th and 234ra), their accumulation in scale on crucibles. In production of the fuel elements (fuel elements) from At., enriched with isotope 235U, the major harmful factor are alpha-active aerosols.

Accumulation enriched At. in lungs is defined by measurement of gamma radiation of isotope 235U by means of special counters (see Ra-dioizotopny diagnostic units).

URATURIA 77


Receipt through a respiratory organs of soluble compounds At. shall not exceed 2,5 mg in 1 days, and through digestive organs — 150 mg in 1 days. During the work with uraniferous mineral connections of unknown solubility the marginal receipt (MR) through a respiratory organs and the admissible concentration (AC) for personnel in air of production rooms (on total alpha activity of radionuclides of an uranium row) equal respectively 0,025 mkkyura (9,25 * • 102 Bq) in 1 year and 1-10 "14 curies/l (3,7 - 10-4 Bq/l) are accepted. Admissible concentration in air 235U — 6-10-14 of curie/l (22,2 * 10-4 Bq/l).

For prevention on mines hold the removing dust events, active airing. During the processing of ores, receiving salts U. mechanization of handling works, implementation of automatic transfer lines of processing, remote observation and process control, the mechanical ventilation providing at 5 — 7-fold air exchange considerable shift of balance between Rn and its affiliated products are necessary moistening of a r'uda before processing. Work with enriched At. it is necessary to carry out in tight boxes at exhaustion within 10 — 20 mm w.g. with use of individual protection equipment of a respiratory organs and integuments. Regularly radiation control shall be exercised (see).

Bibliography: Andreyeva O. S., Oh

dyin V. I. and Kornilov A. N. Natural and enriched uranium, Radiation and hygienic aspects, M., 1979, bibliogr.; Borisov V. P., etc. Acute management at acute radiative effects, M., 1976; B y-

hovsky A. V. Hygienic questions by underground mining of uranium ores, M., 1963, bibliogr.; Questions of occupational health on uranium mines and the enrichment enterprises, under the editorship of G. M. Parkhomenko, etc., M., 1971; Galibin G. P. and Novikov Yu. V. Toksikologiya of industrial compounds of uranium, M., 1976; Zhuravlev V. F. Toxicology of radioactive materials, M., 1982; Uranium and beryllium, the Problem of removal from an organism, under the editorship of V. S. Bala-bukhi, page 59, M., 1976; Pharmacology and toxicology of uranium connections, the lane with English, t. 2, M., 1951.

V. F. Zhuravlev; G. M. Parkhomenko (gigabyte.).

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