Modern approaches and technics

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As with any energy system, nuclear power plants will allocate to the environment of harmful substances, including
including - radioactive. Discharges are of two types - liquid and gaseous.
Dumping of radioactive substances (reset) (Radioactive effluents) - Controlled flow
radionuclides in water from liquid wastes of nuclear installations (eg power plant).
Allowable emissions (radioactive substances) (Permissible releases) - fixed for nuclear
installation (for example, nuclear power plant), the value of radionuclide activity, removed the calendar
year into the air through the ventilation system.

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As with any energy system, nuclear power plants will allocate to the environment of harmful substances, including
including - radioactive. Discharges are of two types - liquid and gaseous.
Dumping of radioactive substances (reset) (Radioactive effluents) - Controlled flow
radionuclides in water from liquid wastes of nuclear installations (eg power plant).
Allowable emissions (radioactive substances) (Permissible releases) - fixed for nuclear
installation (for example, nuclear power plant), the value of radionuclide activity, removed the calendar
year into the air through the ventilation system.
Permissible discharge (radioaktivnyh Substances) (Permissible radioactive effluents) - set for
nuclear facility (eg, nuclear power plant), the value of radionuclide activity originating in
the environment with sewage.
Retention of radioactive (Radioactive material retention) - methods, tools and systems for
prevent the transfer or dissemination of harmful amounts of radioactive material
beyond established boundaries, even in the event of an accident.
In the normal operation of the NPP, the emissions are not great because nuclear power plants
equipped with effective treatment systems discharges of radionuclides and other hazardous
substances. These systems keep all inappropriate in terms of environmental components and
allow them to go beyond production lines.
Retention of radioactive (Radioactive material retention) - methods, tools and systems for
prevent the transfer or dissemination of harmful amounts of radioactive material
beyond established boundaries, even in the event of an accident.
The main potential source of
pollution of the biosphere and the exposure of people living near nuclear power plants are
Aerosol waste generated during operation of the plant. Although Aerosol
station emissions do not lead to a significant contamination of the environment, remain relevant
work towards further reduction. In the future, should not only prevent
exposure of the population living near nuclear power plants, but increasing population dose.
The problem of great importance - the provision of safeguards against accidental pollution of the
environment. Its solution will greatly ease the task of placing nuclear facilities near
major cities.
There are two fundamentally different directions in the works to reduce pollution
Environment: active and passive.
With regard to nuclear power an active way is to prevent
release of radioactive products into the environment as a result of improved
flowsheets and equipment in the creation of a closed process,
precluding the release of these products into the environment in perfecting and improving the
fuel cells; to deliver high performance purification systems.
Passive method is based on the effect of diffusion of impurities
radioactive substances.
2. Radioactive substances in the atmosphere
Any operating nuclear power plant has a powerful impact on the environment in three
ways: gaseous (including radioactive) emissions, emissions
large amount of heat and the inevitable spread around the plant of a number of
liquid radioactive waste.
Radioactive substances - radionuclides into the atmosphere as a result of
nuclear facility (eg, nuclear power plant.
Dumping of radioactive substances (reset) - controlled intake of radionuclidesinto the water with
liquid wastes of nuclear installations (eg power plant).
In the normal operation of a nuclear facility, the release of radionuclides into the environment
environment must not exceed certain limits established by the legislation.
Allowable emissions (radioactive substances) - set for a nuclear facility (eg,
NPP), the value of radionuclide activity, removed the calendar year inatmospheric
air through the ventilation system.
Permissible discharge (radioaktivnyh substances) - set for a nuclear facility (eg,
NPP), the value of radionuclide activity coming into the environment with waste
waters.
In terms of radioactive contamination of the environment is operating normallyNPP
paramount interest of Aerosol emissions, as the least controlled
after they occur.
In the process of nuclear power plants generate liquid, gaseous, aerosol and solid
radioactive waste. On the road of radioactive waste into the environment
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provide a variety of protective barriers. These include, inter alia include: the fuelmatrix
cladding, primary coolant circuit, sealed the premises of the reactor
installation of the gas circuit, the circuit cleaning fluids and all other circuits and
equipment with radioactive environments, the protective shell (to limit emissions
emergency). In addition, for all reactors is limited to the number of admissible
leaking fuel rods in the core. As a result, radioactive waste outside the plant
come in quantities not exceeding permissible levels.
3. Gas cleaning plant RADIOACTIVE WASTE
3.1 Methods of processing of gas mixtures
At present, sufficiently well developed scientifically and technologically
of such methods of separating gas mixtures, as adsorption, absorption, cryogenic
distillation, membrane methods, etc. For the separation of aerosols from the pure gases used
filtration. To get rid of radioactive substances used method of exposure, at
which the gas mixture is kept in a container until the complete collapse
short-lived radionuclides. Not only used techniques of isolation and separation, but
conversion methods (eg, post-combustion of hydrogen (protium as well as tritium) to convert them
Explosion-proof and easily removable water.)
Industrial gas cleaning methods can be reduced to three groups: 1) by solid
absorbents or catalysts - the "dry method" of cleaning; 2) with liquid absorbents
(Absorbent) - cleaning fluid, and 3) cleaning without the use of absorbents and catalysts. K
first group includes methods based on adsorption, chemical interaction with
solid sinks and on the catalytic conversion of impurities into harmless or easily
deleted connections. Dry cleaning methods are usually performed with a fixed bed of sorbent,
absorber or a catalyst, which periodically must undergo regeneration or
replacement. Recently, such processes are carried out also in the "boiling" or moving
layer, which allows continuous updating of cleaning materials. Liquid means
based on the absorption of the extracted component liquid absorbent (solvent).The third
group treatment methods based on the condensation of impurities on diffusion processes
(Thermal diffusion, the separation through a porous membrane).
Depending on the desired degree of gas purification distinguish coarse, medium and fine
cleaning. However, the quantitative standards that meet this classification, change in
Depending on the requirements of technology. The required degree of gas purification is often achieved in
several stages with different conditions or even the way of the process.
3.1.1 Exposure
A characteristic feature of nuclear energy and military nuclear fuel cycle is
presence in the processes of radioactive substances. Purification of dischargesfrom certain
of them involves exposure to the natural decay of radioactive impurities (for the time
comparable to the ten periods of the decay of a radionuclide). Subjected to directexposure
exhaust gas in the bayou or a gas tank, or after preparation: Compression
combustion separation, as well as in adsorption columns.
3.1.2 Filtering
Contained in industrial gases, particles are extremely varied in their
composition, state of aggregation and dispersion. Purification of gases from the suspended particles
(Aerosols) is achieved by mechanical and electrical sredstvami.Zdes we consider only the method of filtration.
At nuclear power plants to remove aerosols (small diameter particles and liquid droplets) from the
ventilation air filters used tonkovolokonnye.
Filtering - the separation of suspensions or aerosols through filters - porous walls
(Metal, asbestos, glass, etc.), liquid or gas is leaking, but the delay
solids.
Filtering - the movement of fluid through a porous medium, such as water seepage through
ground base of the dam. In industry, often referred to as filtration filtration.
Aerosols - dispersed systems consisting of small solid or liquid particles suspended in the gas
medium (usually air). Aerosols, particulate phase which consists of droplets of liquid, called
mists, and in case of a solid dispersed phase - fumes, dust, referred to as coarse. Dimensions
particles in aerosols vary within very wide limits - from a few millimeters up to 10-7 cm
3.1.3 Cryogenic Distillation
In the method of cryogenic distillation, a mixture of gases by deep cooling is transferred to
liquid, which is distilled, that is, distillation into fractions. After which the temperature
improve and transform the liquid into gas.
Absorption - the volumetric absorption of gases or vapors, liquid (absorbent) to form a solution. In
industry carried out in the absorber (the former name - scrubbers), which havedeveloped
contact surface with the absorbent absorbing material.
Sorption - the absorption of gases, vapors and solutes by solids and liquids.
Distinguished: 1) adsorption - absorption of a solid surface or absorption at the interface
liquid-liquid or liquid-gas (vapor), 2) absorption - fluid volume absorption or
solid, 3) chemisorption - absorption with the formation of chemical compounds, and 4) capillary
condensation, which is manifested in the formation of liquid phase in the pores and capillaries of the absorber.
3.1.5 Adsorption
Adsorption - the absorption of gases, vapors and liquids the surface layer of the solid (adsorbent) or
fluid.
Adsorption is the concentration of the substance (adsorbate adsorbtiva) of
volume of the phases at the interface between them, such as gas or solution on the surface
solid (adsorbent) or a liquid. Adsorption occurs under the influence of molecular forces
adsorbent surface and leads to a decrease in surface free energy. physical
adsorption results of the dispersion or electrostatic forces. At the same molecule
adsorbate retain their individuality. If the adsorption is accompanied by chemical
reaction of the absorbed matter with adsorbent, it is called chemisorption

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