ZIRCONIUM

From Big Medical Encyclopedia

ZIRCONIUM r and d and about and to t and in - N y y (Zirconium, Zr) — chemical element IV of group of a periodic system of D. I. Mendeleyev. Sequence number 40, atomic weight (weight) 91,22. Content in crust makes 2-10-2% on weight. In the nature it meets preferential in the form of minerals — zircon, a baddelit. and also tsirkonosilikata.

C. — silvery white metal with characteristic gloss, in a chemically pure type only of kovka is also plastic, its density of 6,506 g/cm3 at 20 °, / °pl 1852 °, * °kip 4377 °; allocated from connections C. represents the gray spongy mass or black-gray powder. It is resistant against corrosion in chemically aggressive environments, in connections chetyrekhvalenten, shows also valency + 3 and +2 in connections with halogens.

C. finds application in metallurgy, the vacuum equipment as constructional material in nuclear power, at production of tritium targets, ceramics, refractory materials, etc. Stable C. is a part of tissues of animals and plants, contains in soft tissues of a body of the person apprx. 0,4 g. In fiziol. the relation it is almost inert element.

Natural C. has 5 stable isotopes with mass numbers 90 (51,5%), 91(11,2%), 92 (17,1%), 94 (17,4%) and 96 (2,8%). Also 17 radioisotopes and 4 nuclear isomers (see the Isomerism, an isomerism Athol Nykh of kernels) C are known. with mass numbers from 81 to 102. Most of them are ultra - and short-lived (with second, minute and hour half-lives), one (93Zr) very long-living (T1/2 = 1,5 * 106 years) and two with half-lives over two months — 88Zr (T1/2 = 83,4 days) and 95Zr (T1/2 = 64,02 days).

From radioisotopes C. the greatest value has 95Zr, being one of the main components of cleavage products of uranium and other heavy elements, is a part of radioactive fallout (see). Receive 95Zr allocation from fragmental products, and also radiation of C. neutrons in the nuclear reactor (see Reactors nuclear). 95Zr it is used in scientific research and at technological control as tracer.

95Zr comes to a human body through respiratory system, and also with food; it is postponed generally in a skeleton (30 — 40%), it is less in a liver, kidneys, a spleen, limf, nodes and gonads, it is brought out of an organism of hl. in the way with a stake and partially with urine. An effective elimination half-life 95Zr from an organism of 56 days.

According to standards of radiation safety (NRB-76), this radionuclide on radio toxicity concerns to group B, that is its open drugs with activity to 10 mkkyura (370 kBq) can be in a workplace without the permission of a sanepidsluzhba.

Admissible concentration 95Zr in water of open reservoirs of 6,2-10-8 curies! l (~ 2,3 kBq/l), in air of workrooms 3,2 «10-11 curies! l (~ 1,2 Bq/l), in free

air 1,1 * 10-12 curies! l (4,07-10 "2 Bq/l).

Prevention of beam damages (see) during the work with radioisotopes C. it is provided with observance of requirements of radiation safety (see), use of the protective equipment (see. Radiological protective processing equipment, Antiactinic protection).

See also Isotopes.

Bibliography: L e in and V. I N. Receiving radioisotopes, M., 1972; Standards of radiation safety of NRB-76, M., 1978; X about l N about in Yu. V. and d river. Characteristics of radiations of the radioactive nuclides applied in the national economy, M., 1980; Person, Medicobiological data, International commission on radiological protection, Publication No. 23, M., 1977, V. V. Bochkaryov.

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