ANTIACTINIC PROTECTION — a complex of the methods and means aimed at providing safe working conditions of personnel and life of the population in the conditions of possible impact of ionizing radiation. Item z. it is carried out by decrease in levels of radiation to the regulated dose limits by means of spiders, use of remote devices and the most rational technology based on mechanization and automation of separate operations and processes and also by means of a number of pharmaceuticals.
Methods and P.'s means z. depend on kind of work, conditions of use of radioactive materials and sources of ionizing radiation (see); they provide protection against external and internal radiation.
During the work with the closed sources of ionizing radiation i.e. when hit of radionuclides to the environment is excluded, the personnel can undergo only external radiation. Such radioactive sources use, as a rule, in gamma and therapeutic devices and as applicators, in a gamma defektoskopicheskikh installations, devices of technological control, etc. X-ray apparatus and particle accelerators are also sources of external radiation. At external radiation of people is affected by ionizing radiation only during that time term when it is near a source of radiation.
During the work with open radioactive sources, e.g. at radio isotope diagnosis, processing of radioactive waste, experimental works, etc., hit of radioactive materials to the environment is possible. At the same time they can contaminate the equipment, air of production rooms, clothes and hands working and also the free air, the soil, reservoirs. As a result, except external, also internal radiation owing to hit of radioactive materials in an organism is possible. In this case the person can be affected by ionizing radiation during that time term until radioactive materials are removed from an organism as a result fiziol, exchange processes and radioactive decay.
Protection against external radiation
Protection against external radiation is carried out by creation of stationary or mobile spiders which reduce the level of radiation to the regulated limits (see. Marginal dose of radiation ). Protective walls, overlappings of a floor and a ceiling, a door and doorways, glory-holes, etc. belong to stationary spiders. Mobile protection devices — various type of a screen and screens, tubes and diaphragms x-ray, gamma and therapeutic, gamma defektoskopicheskikh and other installations limiting a bunch of beams, containers for transportation and storage of radioactive materials, etc. (see. Radiological protective processing equipment ). Use of these or those types of protection devices and ways of protection depends on purpose of sources of radiation and conditions of their operation. During the calculation of thickness of protection devices first of all it is necessary to consider spectral structure of ionizing radiation, power of its source, and also distance, on Krom there are service personnel, and time of stay in the field of influence of radiation.
Because run of the alpha particles which are let out by radioactive materials are very small, there is no need for special protection against external radiation by alpha particles since for this purpose it is enough to be at distance of 9 — 10 cm from radioactive drug. Clothes and rubber gloves completely protect from external radiation by alpha particles.
For protection against external radiation carry out by beta particles of manipulation with radioactive materials behind special screens (screens) or with use of special protective cases. At the same time thickness of protecting screens shall be more maximum run of beta particles. Store beta and active radionuclides in the vessels or containers having also corresponding thickness of walls. As protection materials use usually plexiglass, aluminum or glass.
For protection from x-ray and gamma radiations use various protection materials at which choice they consider their properties, and also requirements to dimensions and weight. E.g., for the protection cover gamma and therapeutic or gamma defektoskopicheskikh installations where an essential role is played by the weight (weight), the most favorable protection material are such substances which best of all weaken gamma radiation, i.e. substances with a big density and big atomic number. Most often for this purpose use lead, sometimes uranium. In this case thickness of protection is less, than during the use of other material and consequently, there is less than the weight of protection cover. During creation of stationary protection, i.e. protection of the room, in Krom works with sources x-ray are conducted or gamma radiations, providing safe stay of people in the neighboring rooms, usually use concrete. During the works with x-ray and the gamma radiation of small energy (less than 300 — 400 kev) at which an essential role in weakening of radiation is played by photo-electric absorption, add substance with big atomic number to concrete, in particular barite that allows to reduce thickness of protection.
The system of protection of particle accelerators, x-ray and gamma-ray irradiation plants of different function (therapeutic, diagnostic) is based approximately on the same principle and consists of local protection (for protection of the patient against excessive radiation) and stationary protection (for prevention of radiation of personnel).
Local protection is provided with the protection cover, in Krom the source of ionizing radiation (a X-ray tube, a target of the accelerator, a radioactive source) is located. In this casing there is a window for release of a bunch of beams only in the necessary direction; the diaphragms limiting and creating the field of radiation (see); the tube protecting from the scattered radiation arising at edges of an output window and in a diaphragm. In installations where a source of radiation are radionuclides, the protection cover shall provide also decrease in level of ionizing radiation to the regulated limits at the switched-off installation (when the source of radiation is in the provision of storage) to provide access to the room where installation for carrying out there necessary adjustment and repair work is placed. During the finding of a source of radiation in the provision of storage the protection cover shall provide such weakening of gamma radiation that at distance 1 from installation the admissible dosage rate (ADR) for personnel, equal 3 mrem/hour was not exceeded (3·10 2 mzv / hour).
Stationary spiders include protective walls and overlappings, protective doors in the room, in Krom there is an installation, or a labyrinth entrance and a glory-hole. Thickness of protection is calculated proceeding from activity of a source of ionizing radiation or the maximum tension on a X-ray tube and distances to jobs of personnel and a rabotna of the k which are in the neighboring rooms.
At P.'s design z. rooms in which place particle accelerators x-ray and gamma-ray irradiation plants, it is necessary to consider the possible directions of release of a bunch of beams and in these directions to project protection against direct radiation, and in the others — to provide protection against scattered radiation. Also consider purpose of the neighboring rooms, time of stay in them of personnel and belonging of personnel to this or that category. At the same time protection shall be projected with the degree of safety equal 2. The design capacity of an equivalent dose behind protection (NPR) is calculated by a formula:
The NPR = 500 traffic regulations/t of mrem/hour,
where traffic regulations — a marginal dose for the corresponding category of persons; it is equal 5 rem a year (50 mzv in a year) for personnel (category A) and 0,5 rem a year (5 mzv in a year) for persons of category B, to a cut the workers who are directly not servicing installations, but being in the neighboring rooms belong; t — time of stay in this room.
In certain cases working conditions with sources of gamma radiation can be such when it is impossible to create stationary protection (at a recharge of installations, extraction of radioactive drug from a container, graduation of the device of gamma-radiography with an open source, etc.). At the same time means that activity of a source of radiation is small (10 — 30 mg-ekv of radium). To secure personnel against radiation, use so-called protection in distance and time. It is known that for sources of the small linear sizes the dose of radiation decreases in inverse proportion to a square of distance from it. Besides, such operations should be performed only for that time term, during to-rogo the dose received by working will not exceed admissible. This work is conducted under radiation control (see). At the same time indoors there should not be strangers, and the zone where the dose exceeds marginal for operating time, shall be protected.
If the gamma equivalent of a source is less than 0,1 mg-ekv of radium, there is no need to provide spiders. During the use of installations outside which dosage rate of radiation in a workroom and at storage of a source does not exceed 0,3 mrem/hour (3 μSv/hour) special requirements to rooms and placement of installations are not shown.
Calculation of protection against neutrons is made on the corresponding formulas and nomograms. As protection materials in this case use substances with small atomic number because at each collision with a kernel the neutron loses that the most part of the energy, than nuclear mass is closer to the mass of a neutron. For protection against neutrons usually use water, polyethylene. Having spent the energy in the course of interaction with substance of protection, the bystry neutron turns in thermal which is taken atomic nuclei, and at the same time the gamma quantum is let out. Sources of neutrons are nuclear reactors, particle accelerators, radium - beryllium drugs. In all these sources, in addition to neutrons, there are powerful flows of gamma radiation which are formed in the reactor in the course of division, and also due to disintegration of cleavage products. On particle accelerators and in radium - beryllium drugs gamma radiation arises at various nuclear reactions. Therefore at design of protection against neutrons always provide also protection against gamma radiation.
One of important actions of P. z. during the work with radioactive materials in open form the corresponding design and finishing of rooms is, at a cut distribution of radioactive materials to other rooms is most complicated. For this purpose works with radioactive materials focus in one part of the building and reduce to a minimum passes through these rooms. Finishing and the equipment of rooms shall provide their easy deactivation (see). Besides, a number of requirements to system of ventilation, the organization of jobs and the technological modes, is imposed on use of individual protection equipment, observance of measures of personal hygiene to system of collecting and removal of radioactive waste (see), etc. that allows to exclude a possibility of hit of radioactive materials in an organism and by that to provide safe working conditions. These requirements depend on the nature of the carried-out works with these or those radionuclides, their activity, and also group of radio toxicity, to a cut these radionuclides belong.
At a possibility of the choice of radioactive materials for work it is necessary to use substances with the smallest radio toxicity. Besides, work needs to be organized so that the amount of radioactive material in a workplace was minimum necessary for this operation. The number of such operations as oversleeping of powders, sublimation, etc. which are connected with loss of radioactive material is also recommended to reduce whenever possible.
During the work with radioactive materials when emergence in radioactive aerosols is possible, the service personnel are surely supplied with respirators for protection of a respiratory organs against radioactive materials. At very high levels of pollution of the air environment, edge it is possible during the performance of repair work or recovery from the accident, the personnel are supplied with the isolating pneumosuits with forced feed of air.
Biological antiactinic protection
Biological antiactinic protection — a way of increase in radiation resistance by means of the pharmaceuticals increasing the general body resistance. Unlike radioprotectors (see) they have protective action in that case when are entered repeatedly for several days or weeks before radiation. Such pharmaceuticals or their complexes have protective action at acute (single), (extended), fractioned and chronic exposure prolonged (see). They promote increase in efficiency of schemes of complex therapy of the radial illness which arose owing to external or internal radiation. These drugs have the big width of therapeutic action, for them there are no contraindications, and they can be used in any conditions.
Drugs from group of adaptogens (liquid extracts and tinctures of an eleuterokokk prickly, a ginseng, a magnolia vine Chinese, a lagokhilusa), vitamins, hormones, coenzymes, vitamin and amino-acid complexes, some microelements and antibiotics, especially in combination with vitamin and amino-acid complexes, biostimulators are among the most effective.
Action of means of biological P. z. is nonspecific. It is shown only against the background of influence of the extreme factors causing tension vital fiziol, systems of an organism. The mechanism of action of adaptogens at radiation injury is connected with the fact that they toniziruyushche act on c. N of page also stimulate system of a hemopoiesis. Increase in radiation resistance by means of vitamins, hormones and coenzymes is carried out in various ways. E.g., repeated administration of citrin with ascorbic to - that increases stability of walls of blood vessels, reduces manifestations of a hemorrhagic syndrome; glucocorticoids promote increase in release of adrenergic substances adrenal glands that leads to increase in radiation resistance of an organism.
Pharmakokhimichesky antiactinic protection
Pharmakokhimichesky antiactinic protection — a way of protection against ionizing radiation by means of introduction to an organism shortly before the beginning of beam influence of chemical (medicinal) drugs of a synthetic, animal or plant origin or their complexes weakening the damaging action on an organism of ionizing radiation. The term «pharmakokhimichesky antiactinic protection» is conditional since means (radioprotectors) which, being entered before radiation, could prevent completely emergence in an organism of the changes causing a radial illness are not known. Pharmakokhimichesky P.'s means z. increase radiation resistance or reduce sensitivity of an organism to the striking action of ionizing radiation. They can be used in medical practice for the purpose of weakening of radiation injury of radio sensitive fabrics at radiation therapy of malignant tumors, at repair work in laboratories and at the enterprises applying ionizing radiation and radioisotopes, atomic reactors and particle accelerators (at accidents), at space flights in case of a complication of a radiation situation at chromospheric solar flashes.
Pharmakokhimichesky antiactinic means belong to various classes of chemical connections. And perspective aminothiols, indolylalkylamines, arylalkylamines and other biogenic amines (a histamine, acetylcholine), and also polysaccharides are the most effective (see. Radioprotectors ). Radio protective properties of aminothiols are shown to the same extent at the cellular, subcellular levels and at radiation of all organism. Biogenic amines have antiactinic effect in an organism at preservation them pharmakol. activities are also characterized by the expressed identity of a pharmacodynamics. It formed the basis for the combined use of aminothiols and indolylalkylamines for the purpose of decrease in their toxicity and increase in radio protective activity (radio protective compoundings). At a combination an indole silt alkyl of amines, napr, Mexaminum, with aminothiols, napr, Cystaminum, tsistafosy, without addition and with addition of stimulators of c. the N of page — Phenaminum, vitamins — Wb and tranquilizers — aminazine (multicomponent compoundings) a radio protective effect remains under various conditions of radiation, including at influence of protons of high energy and gamma and neutron radiation.
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