Antiradiation protection

  • Chemical antiradiation protection
  • Antiradiation protection - protection of the person from the action of radiation in excess of permissible levels. The term antiradiation protection refers to ionizing radiation (see ionizing Radiation). There are physical and chemical (biological) methods and means antiradiation protection.
    Radioprotective physical protection - the use of special devices and ways to protect the body from the effects of external ionizing radiation or the penetration of radioactive substances in the body. Is used in x-ray rooms, radiology, departments and laboratories of a various profile. There are stationary and mobile protective device. To mobile protective devices are widely used in radiological practice screens and screens. Stationary are protective walls, Windows, doors and other, providing protection from radiation sources are more reliable than mobile devices. The thickness and the choice of protective material for stationary protection are determined by the type of radiation and its energy. Protection from γ or x-rays provide using materials with high specific gravity (brick, concrete, lead, tungsten, or lead glass). With the increase of the energy of radiation share protective material or thickness shall be increased. The quality of protection is expressed lead equivalent (which is determined by the thickness of lead in millimeters)that reduce the emission of this type in the same degree as protective material used. Protection of neutron radiation (see) or proton radiation (see) carry out the materials, having composed of hydrogen (for example, water, paraffin, organic glass). When working with sources of ionizing radiations must physical radioprotective measures of protection be combined also with the correct organization of labor. Organizational radioprotective measures include: 1) mandatory pre-theoretical and practical training on safety; 2) the system of dosimetric and radiometric control of radiation exposure and contamination jobs; 3) medical monitoring the state of health of the personnel as new recruits, and annually in terms of follow up; 4) rational arrangement of working places of the personnel in conditions of the least exposure.
    In radiotherapy departments (see Radiology Department, X-ray room) the presence of personnel in the treatment, where the irradiation of the patient, shall be prohibited. Control devices for radiation therapy produced from the next room. In x-ray rooms and radiomonitoring personnel must use mobile protective devices (aprons and gloves made of lead rubber, lead screens and other). One way antiradiation protection is to protect the distance, i.e., providing the maximum possible removal of the personnel in the process of radiation sources. The effectiveness of antiradiation protection (physical) recently with automatic devices for remote use of radioactive drugs has increased (for example, radioactive drugs in the treatment of cervical cancer is introduced from neighboring premises after the preliminary preparation of the patient). When transferring radioactive drugs (see), you should use the transport container (see Containers radioisotope) on a long handle. An important way antiradiation protection is protection of the time, so is the performance of business processes within a short period of time. Speed run workflows with radioactive drugs is determined by preliminary training of personnel, precise planning and determination. Criteria that assess the quality of antiradiation protection, are the indicators values of dose rate in the workplace and the value of dose rate of employees (see Dosimetry).

    Antiradiation protection is a set of special measures and tools designed to protect the body from radiation exposure in terms of research and production activity.
    There are physical and chemical (biological) methods and means antiradiation protection.
    Physical antiradiation protection. Task physical antiradiation protection as a branch of nuclear engineering is the development of technical facilities and activities, providing safe conditions: 1) staff directly serving the nuclear power devices, and other installation - sources of ionizing radiation, 2) persons working in neighboring areas as well as the surrounding population.
    Solving problems of radiation protection is based on using data of nuclear physics, radiobiology and dosimetry of ionizing radiation.
    The danger to the service personnel or other persons in contact with sources of ionizing radiation may be twofold.
    First, it irradiation of the whole body or its separate parts sources located outside the body (external radiation). The sources of external exposure, as a rule, are closed (nuclear reactors, accelerators, irradiators, x-ray machines and others). Obviously, external irradiation is only in those cases when a person is near a radiation source, and stop when you launch it from this zone. Second, the exposure created by the so-called open sources, which are formed in case of contamination by radioactive substances to air, water, food and surfaces of different items and earth.
    The presence of such sources may lead to the ingress of radioactive substances in the human body and its continuous irradiation as long as the radioactive substance will not in any way derived from an organism or will not break up.
    Protection against external irradiation is achieved by construction of special protective screens (protective fencing), passing through which radiation decreases to safe levels. The choice of material for the screen and the determination of its thickness are difficult engineering task. It is solved taking into account the type and the spectral composition of radiation, activity sources, their locations and sizes, and adopted permissible levels of radiation.
    The most dangerous in the case of external irradiation threads ' -quanta and neutrons - uncharged particles, relatively weakly interacting with matter and, consequently, with the highest penetration ability. The contribution of unscattered radiation dose for the protection of often small at thick protection; the main contribution to the total dose of radiation contributes who have experienced multiple scattering. The contribution of scattered radiation is produced using the so-called factor of accumulation, the value of which varies from one to several tens depending on the thickness of the layer of substance, energy radiation and nuclear material number.
    The main processes of interaction of x-ray and the V-radiation with matter, leading to the weakening of the beam that are the photoelectric effect, Compton effect and the formation of pairs (see Gamma rays, X-rays). The photoelectric effect is predominant in the region of low energies ' -rays and especially significant for heavy substances. Therefore for protection from x-ray and the V-radiation with low energy as a protective material is convenient to use the lead.
    When energy x-ray and the V-radiation over a hundred Kev dominant process is the Compton effect, the probability of which is directly proportional to the electron density of matter, and since it is for all substances nearly equal for protection against radiation in this field of energy approximately equal success you can use any materials with the same thickness in g/cm2. However, because it is cheap is most often used concrete, water or cast iron or combinations of layers of this material.
    The formation of vapor becomes apparent only when the energy of the radiation above a few MeV and in the selection of protective material is not crucial.
    For approximate calculation of the thickness of protection frequently use the layers half of abating. Layer half of weakening d is the thickness of the material, which reduces the intensity of radiation in 2 times.
    The number of layers half weakening n needed to provide a given multiplicity of weakening It, you can determine the ratio K = 2n. In table. 1 and 2 show some approximate thickness of layers half weakening for x and V-radiation depending on energy (taking into account scattering of radiation protection).
    The type of the reaction of interaction of neutrons with matter also depends on energy of neutrons and properties of substances. Qualitatively the process of absorption of neutrons in the protection can be divided into two stages: 1) the slowing down of neutrons of high-energy elastic and inelastic scattering on nuclei absorber; 2) the capture of neutrons lost energy as a result of slowing. To slow neutrons is the use of substances with a high content of hydrogen and other light elements - water, concrete, graphite, etc. If the neutron energy above 1 MeV, they added a substance with great at. weight (mass), which enhance the effects of inelastic scattering. The greatest ability to capture thermal neutrons have boron, cadmium, lithium, etc. However, some of these substances, such as cadmium, in the capture of thermal neutrons emits a secondary hard ' -radiation, from which it is necessary to provide additional protection. Sometimes it in the form of individual layers of the relatively heavier substances introduced into the basic protection or use concrete of different grades with the aggregates of iron or cast iron.
    The protection from external flows of b-radiation, alpha-particles and protons is not difficult, as the ranges of them in solid and liquid substances, are very small. In legkobetonnyh materials mileage of electrons in the energy dependence is determined by the formula:
    R = 0,54E-0.15 g/cm2,
    where E is the energy in MeV. This formula can be used to determine the thickness of the protective screen. alpha-Particles that is significantly more weight and twice larger than the electron charge, with the energy of several MeV not penetrate even through a sheet of heavy paper or cardboard.
    For protecting people from internal exposure requires the adoption of measures that exclude the possibility of getting the body of radioactive substances in quantities exceeding the limits. The latter are directly connected with the so-called maximum allowable concentrations (see) radioactive substances in air, water and on surfaces of floors, walls and equipment in industrial premises. They are defined by calculation on the basis of medical and biological research with the use of experimental animals, as well as long-term observations over people, which had in its production activity contact with radioactive substances. To these concentrations are not exceeded, industrial premises will be equipped with system of forced ventilation, liquid wastes before destruction diluted and working surfaces are periodically cleaned special decontamination means. Considerable importance is also correct planning of enterprises that use or processing of radioactive substances, regulated by the sanitary rules.