CC BY
1
УДК 544
Garipov I.T.
Junior Researcher, INP AS RUz Tashkent, Uzbekistan Khaydarov R.R.
Candidate of Phys.-Math Sci., Head of Laboratory, INP AS RUz
Tashkent, Uzbekistan Gapurova O.U.
Candidate of Chemical Sciences, Junior Researcher, INP AS RUz
Tashkent, Uzbekistan
NOVEL METHOD TO REDUCE INDOOR RADON LEVEL
Annotation
Our recent radon indoor prevention research results were presented, emphasizing the need for radon gas mitigation in homes to reduce environmental risks. A new nanostructured composite has been developed to seal entry points and reduce radon exposure indoors. This composite, containing silicon nanoparticles, polyethylhydrosiloxane, alkyltriethoxysilane solution in isopropanol, and a tin-based catalyst, also reduces exposure to VOCs and various gases by filling fine pores in materials like concrete. Gas permeability is significantly decreased, with consumption dependent on material porosity.
Keywords:
radon, nanocomposite, polyethylhydrosiloxane, VOC.
Radon, a colorless, odorless, and tasteless radioactive gas produced by natural uranium and radium decay in rocks and soils, poses a significant health risk by damaging DNA and increasing the likelihood of lung cancer. Designated a human carcinogen by the International Agency for Research on Cancer in 1988, radon is a major source of ionizing radiation for the general population, particularly indoors where it can accumulate in confined spaces like homes. This poses a serious health threat, especially in the Central Asian region, where radon seeps into structures from the surrounding soil and construction materials. The aim of this study was to develop a method using special chemicals to reduce radon gas levels in buildings and underground spaces by filling microcrevices and pores in concrete and other materials to prevent gas and water molecule diffusion. These chemicals must meet specific criteria for cost-effectiveness, high efficiency in reducing gas permeability, and adaptability to various temperature and humidity conditions.
The following organic compounds have been tested: polyethylhydrosiloxane (PEHS) and its aqueous emulsion, mixture of PEHS and benzene in the ratio 1:1, 25% solution of alkyltriethoxysilane (ATES) in isopropanol (25%ATES), mixture of PEHS and 25% solution of ATES in isopropanol. Sn-, Ti-, and Cu- organic compounds were tested as the catalysts. Tested samples of concrete, cement and gypsum had the height and the diameter of 1520 mm and 30 mm, respectively. The samples in a vertical position were treated by chemicals by means of spray.
The device for examination of gas permeability of concrete samples has been constructed. The device consists of compressor 1, receiver 2 with manometer 3, gates 4,5, holder 6 of concrete samples 7, flow meter of air 8 and vessel with gas 9 (Fig.1). The gate 5 adjusted the value of the gas pressure. In all experiments the pressure of gases in the receiver was chosen to be 110 kPa. The air, Ar and 222Rn with concentration of 100 pCu/L in air were used as the gases.
The coefficient of gas permeability K was determined by the following formula
К = AV d / S At Ap (1)
where At is the time of passing the gas through the sample, AV is the volume of gas passed through the
sample, Ap is a pressure drop of gas in the sample, S is an area of the sample, d is a thickness of the sample. In these experiments we have measured relations R between the coefficients of gas permeability for chemically non- treated samples K0 and treated samples K:
R = K0/K (2)
. Concentration of 222Rn in air was determined by radon measurement detector. It consists of electronic unit and scintillation cell. The electronic unit contains power supply, amplifier, discriminator, timer, counter, and indicator. The scintillation cell contains the zinc sulfide scintillator, photomultiplier, preamplifier, high voltage power supply and chamber with a volume of 200 mL over the scintillator. This chamber is intended to fill with gas to be analyzed. Air is either pumped or diffuses into the scintillation cell. Scintillation count is processed by electronics, and radon concentrations for predetermined intervals are stored in the memory of the device.
9
Figure 1 - Compressor 1, receiver 2 with manometer 3, gates 4,5, holder 6 of building samples 7,
flow meter of air 8, vessel with gas 9.
In the system ATES - isopropanol a retherification of following type takes place: AlkSi(OEt)s + (3-n)ROH ^ AlkSi(OEt)n(OR)s-n + (3-n)EtOH
where n = 0-2, R is C3H7. AlkSi(OR)s, AlkSi(OEt)(OR)2, AlkSi(OEth(OR) are the products of the retherification.
Products of this reaction are easily hydrolyzed even by air moisture
AlkSi(OR)3 + 3H2O ^ AlkSi(OH)3 + 3ROH
with formation of intermediate compounds AlkSi(OR)2OH, AlkSi(OR)(OH)2. When PEHS is introduced in the hydrolyzed solution, polymeric networks of linear, cyclical and ramified structures with different properties are formed.
Hydrolysis of PEHS in early stages also takes place. Then the products of hydrolysis interact with ATES. Besides the reaction with Ca(OH)2 takes plays and as the result the polymer is fixed strongly on the treated concrete.
The depth of penetration of the organic compound without catalysts is about 10-14 cm. But polymerization time is large (about 2-3 days) and consumption of the compound is significant (about 1-2 L/m2). The use of catalysts reduces duration of the polymerization process down to 1-3 hours. In this case the depth of penetration of chemicals into building materials is about 5-6 mm and as the result consumption of the organic compounds decreases. The treated materials have hydrophobic properties, relation R does not depend on humidity of the surface of materials.
Dependence of the relation R against the number of layers is given in Table 1. The best type of catalyst is the Sn-organic compound. The relation R for concrete increases slowly after the first layers and it increases very fast after the 4th and 5th layer. It is explained by high porosity of concrete. In case of cement and gypsum R increases fast after the 2nd layer. Total consumption of chemicals is about 0.4 L/m2 for concrete (but depends on type of concrete), 0.3-0.4 L/m2 and 0.2-0.3 L/m2 for cement and gypsum, respectively. There is no a big difference
between air, Ar and radon values of permeability.
The test results of these investigations demonstrate the efficacy of the described method of chemical treatment of walls, floor, ceiling, roof, etc. The method allows reducing the coefficient of gas (air, Ar and 222Rn) permeability 200 - 400 times. Consumption of the chemicals is 0.2 L/m2 for gypsum and 0.3-0.4 L/m2 for concrete and cement and depends on porosity of the materials. This method can be used for prevention of seeping radon through the constructive materials.
Table 1
Dependence of R vs. the number of layers
Gas Building Type of organic Number of layers Total consumption
material compound 2 3 4 6 of chemicals, L/m2
catalyst
Concrete Sn- 2.1 3.5 110 420 0.402
Ti- 2.0 3.1 80 320 0.560
Cu- 1.2 2.4 45 100 0.610
Air
Cement Sn- 2.5 47 120 >500 0.360
Ti- 2.3 34 98 390 0.410
Cu- 1.8 12 59 160 0.520
Gypsum Sn- 2.8 90 410 >500 0.270
Ti- 2.6 49 380 440 0.330
Cu- 2.2 35 280 360 0.410
Concrete Sn- 2.0 3.4 105 400 0.400
Ar Cement Sn- 2.3 45 115 >500 0.350
Gypsum Sn- 2.7 86 400 >500 0.260
Concrete Sn- 2.1 3.5 110 430 0.400
222Rn in air Cement Sn- 2.4 46 120 >500 0.340
Gypsum Sn- 2.7 88 420 >500 0.260
©Garipov I.T., Khaydarov R.R., Gapurova O.U., 2024
УДК 612.821
Гучук В. В.
к.т.н., ст.н.с. Институт проблем управления РАН г. Москва, РФ
ТЕХНОЛОГИЧЕСКИЕ АСПЕКТЫ ФОРМАЛИЗАЦИИ ПРОЦЕДУРЫ КОРРЕКТИРОВКИ ЭКСПЕРТНОЙ КЛАСТЕРИЗАЦИИ ОБЪЕКТОВ
Аннотация
Рассматривается принципиальная возможность формализации процедуры корректировки экспертных оценок объектов, основанной на простейших предположениях о свойствах этих объектов. Анализируется применимость конкретных понятий теории нечетких множеств.
Ключевые слова
Нечеткие множества, экспертные оценки, кластеризация, объективизация, динамические множества.
