Method for Using Measurements of the Contamination of Bottom Deposits to Estimate the Source of Radioactive Substances Flowing into a River

A method of estimating the strength of a stationary source of radioactive substances entering a river is proposed. The method is based on statistically reliable measurements of the concentration of radionuclides in bottom deposits. The stationary model of the transport of a radioactive impurity in a two-dimensionally uniform flow is used to determine a relation between the concentration of radionuclides in bottom deposits and the strength of the source. The model is based on the two-dimensional equation for turbulent diffusion and takes account of the interaction of radioactive substances between the water mass (solution, suspension) and bottom deposits. The source of ⁶⁰Co entering the Don River with contaminated underground waters as a result of an incident, which occurred in 1985, in a storage site for liquid wastes from the Novovoronezh nuclear power plant is examined as an example. The average yearly inflow of the radionuclide is estimated to be ∼1·10¹⁰ Bq/yr, which is several times less than the estimates made by experts. __________ Translated from Atomnaya Energiya, Vol. 99, No. 3, pp. 221–228, September, 2005.     

Setting standards for the safe level of radioactive contamination of water and bottom sediments in bodies of water

In this paper, we propose standards which can be used to simply and reliably monitor the content of technogenic radioactive substances in rivers and other bodies of water. We introduce the concept of “maximum safe concentration” and “reference monitored concentration” of radionuclides in water, and also the “maximum concentration of radionuclides in bottom sediments.” To determine the maximum safe concentration of radionuclides in water, we have used the basic public health principle established in NRB-96: to not exceed the limit of an effective dose of 1 mSv/y for external and internal radiation exposure for a critical population group, considering overall water use. To define the degree of radioactive contamination of the bottom of bodies of water, we propose using the maximum concentration of radionuclides in bottom sediments: a concentration less than that for which the bottom sediments may be classified in the category of “low activity solid radioactive wastes” according to OSP-72/87. We offer a calculation scheme and numerical values for the proposed standards for some radionuclides most frequently encountered in practice and examples of their use. State Institute of Applied Ecology NPO Taifun. Translated from Atomnaya énergiya, Vol. 86, No. 5, pp. 398–407, May, 1999. Original article submitted December 30, 1998.     

Use of a Two-Dimensional Stationary Radionuclide Migration Model for Predicting the 137Cs Content in the Enisei River System

A mathematical model of the transport of radioactive impurity in a two-dimensional uniform flow is examined. This model is used to predict and reconstruct the levels of radioactive contamination of water, bottom deposits, and flood plain soils of the Enisei on a 250 km long section of the river below the discharges from the Krasnoyarsk Mining and Chemical Combine. The model is based on the two-dimensional turbulent diffusion equation and takes account of the interaction of radioactive substances between the water mass (solution, suspension) and bottom deposits. The input parameters of the model are determined from in situ investigations performed on the Enisei in the period of 1990 to 2000. The Maple V R4 symbolic mathematics program package is used for the calculations.The model is verified on the basis of measurement results obtained in expedition studies of the Enisei River in 1991 (the period when the direct-flow reactors were in operation) and 1998, 2000. Comparing the computed and measured ¹³⁷Cs concentrations in the water in the top layer of the bottom deposits showed good agreement. The model is also used to estimate the contamination of flood plain soil during a flood period. Measurements obtained in model experiments with soil samples, which were performed over several years on the Berezovyi Island, are used to check the calculations.The application of the model for solving the inverse problem makes it possible to estimate from the known concentration of individual radionuclides in the flood plain soil the intensity of the discharges that produced the radioactive contamination during a flood period. The 1996 flood is examined as an example.     

The development of technology and equipment for extracting actinides from radioactive waste reservoirs

Methods of reprocessing the radioactive silt from reservoirs in order to minimize the volume of waste and to fix the radionuclides are investigated. It is shown that it is possible to compact the suspensions into a granulated product, the volume of which is 15–20 times less than the volume of the silt. The process can be realized using different methods of compressing the silt. Preliminary fixing of the radioactive hydroxide suspensions in the form of granulated hydroxides and oxides ensures safe storage of the waste. When analzing methods of dealing with reservoirs it is best to organize silt reprocessing on the spot reliable consolidation and burial. State Scientific Center of the Russian Federation-VNIINM im. A. A. Bochvara. Translated from Atomnaya énergiya, Vol. 86, No. 6, pp. 453–457, June, 1999.     

Radioecological consequences of a radiation accident in a nuclear-powered submarine in Chazhma cove

Conclusions The results of field observations and numerous radioecological inspections show that the submarine accident in Chazhma Cove in 1985 had no measurable radiation effect on Vladivostok and its beaches or the town of Shkotovo-22. The residual long-lived radioactive contamination of the site and bottom deposits in the region of Chazhma Cove is strictly localized and will not lead to serious radioecological consequences. Studies of the radioecological consequences of the accident will have to be continued in the future, including in order to determine more accurately the boundaries of the radioactive deposits in the sea water and the rates at which the radioactive deposits spread over the bottom of the bay and the inlet. Institute of Nuclear Reactors, Russian Scientific Center "Kurchatovskii institut." Naval Fleet, Vladivostok. Translated from Atomnaya énergiya, Vol. 76, No. 2, pp. 158–160, February, 1994.     

Special features of 60Co migration in a water-bearing layer

The consequences of an incident, involving a leak of liquid radioactive wastes into ground water, at the Novovoronezh nuclear power plant in 1985 are examined. The ⁶⁰Co distribution in a water-bearing layer is formed with the migration of a cobalt ion which is not sorbed and which with time transforms into a cation which is sorbed. The characteristic transformation time is several years. The parameters describing these processes for the conditions of a nuclear power plant and used for calculating ⁶⁰Co migration to the Don are presented. The processes resulting in the transformation of cobalt ions in bottom deposits and wells are also investigated. __________ Translated from Atomnaya énergiya,Vol. 100, No. 6, pp. 465–470, June, 2006.     

Response function of the convection-dispersion equations describing radionuclide migration in a finite medium

Analytical expressions are derived for the response functions for the set of n coupled convection-dispersion equations in 1-D with constant coefficients. The equations are solved for a finite medium, and for an n-member radioactive decay chain with radionuclide-specific retardation factors. An exponential transformation and the Laplace transformation are applied to this set of partial differential equations to obtain a general set of transformed solutions. These are then inverted by two procedures to produce complementary forms of the response functions. One form converges quickly for small values of dimensionless time while the other converges quickly for large values. These response functions are used to model radionuclide transport in an underground nuclear waste disposal vault.     

Handling of the Bottom Residues of a Nuclear Power Plant

The following technological operations are suggested for reprocessing bottom residues from nuclear power plants: separation of radionuclides using oxidation, filtration, and selective absorption, solidification and long-term storage of secondary radioactive wastes (cement compound from filtration stage and spent sorbent in filters); concentration and obtaining dry salts from bottom residues from which radionuclides have been removed. Laboratory and stand tests have been performed, showing that radionuclides can be removed from the bottom residues of nuclear power plants to a level below the ASA_sat according to NRB-96. This treatment decreases the volume of radioactive wastes by approximately a factor of 100. The dried purified bottom residues, which are commercial danger class III wastes, are shipped to storage sites used for industrial wastes. Calculations of the material flows are performed and the site arrangement of the wastes is given for the bottom residues from the Kursk nuclear power plant. 1 figure, 2 tables, 12 references.     

Radioactive contamination of bukhtas and bays on the Kola Peninsula and Novaya Zemlya and in the Far East

The characteristics of the radioactive contamination of bukhtas and bays are determined: the nonuniformity of the radionuclide distribution in the water and bottom deposits, the rate of accumulation of sediments, the distribution ratio, and the turbulent diffusion coefficient. A characteristic feature is the strong nonuniformity of the radionuclide distribution in bottom sediments. A mathematical model is proposed for radionuclide transport and water of bukhtas taking account of flow, turbulent diffusion, and settling of suspensions. Possible explanations are proposed for the characteristics of the radionuclide distribution in bukhtas. The reason for weak turbulent diffusion in bukhtas is examined. __________ Translated from Atomnaya énergiya, Vol. 103, No. 10, pp. 263–268, October, 2007.     

Use of radioactive catalysts for dehydrating alcohols

The authors show that catalytic processes can be influenced by radioactive radiation. The addition of radioactive material to a catalyst greatly changes the velocity and apparent activation energy of the process, and sometimes changes the direction of a heterogeneouscatalytic reaction. It is shown that radioactive radiations produce qualitative changes in the catalyst and have a marked effect on the adsorbed layer of molecules on the catalyst surface which become polarized, the degree of polarization depending on the structure of the reacting molecule.Translated from Atomnaya Énergiya, Vol. 21, No. 4, pp. 277–281, October, 1966.     

Response functions of the convection-dispersion equations describing radionuclide migration in a semi-infinite medium

Analytic expressions are derived for the response functions for the set of n coupled convection-dispersion equations in 1-D and with constant coefficients, for an n-member radioactive decay chain. The one-sided Laplace transform is applied to this set of partial differential equations, and eigen vectors and eigen values of the resulting system of equations are used to obtain general expressions for the Laplace transforms of the response functions. These are then inverted to produce analytic expressions for the response functions. These are used to solve problems with arbitrary time-varying boundary condition using convolutions. Laplace transforms of systems having similar characteristics can be written readily using results presented in this paper.     

~(125)I聚氨酯覆膜食道支架制备方法研究

以多异氰酸酯作为交联剂,采用放射性核素~(125)Ⅰ,制备出了表面覆有聚氨酯薄膜的放射性支架。对聚氨酯覆膜方法进行了研究,考察了影响膜厚度的因素,制得的支架膜厚度为7.9μm。考察了交联剂的浓度、交联方法、固化温度等影响因素,确定最佳的交联条件和方法。生理盐水浸泡30 d后,交联后的聚氨酯薄膜比未交联的聚氨酯薄膜放射性释放率显著降低,30 d放射性核素释放率为2.13%。考察了放射性膜与支架的结合力,实验中带薄膜的支架经过伸缩3次后,表面无裂纹产生,表明薄膜具有良好的结合力,放射性核素在支架表面均匀分布,已经初步达到支架的使用要求。     

Development of a unified technological process for cementing solid radwastes

The results of research on cementing finely dispersed, mixed, closely packed, and coarsely fragmented solid radioactive wastes by mixing, flow-through, and impregnation to create a unified complex of technological processes are presented. A new method of impregnation which consists of feeding under pressure through a probe into the bottom of a container with solid wastes a cement solution with a high penetrating power is shown. The drawbacks of flow-through are eliminated, the integrity of the pouring is guaranteed, and the quality is monitored by determining the degree of impregnation and density of the cement solution which has passed through the layer of solid wastes. This method of cementing can be used for all solid wastes considered and the equipment and cement compositions are basic for the works cementing solid radioactive wastes.     

Long term stability of iron for more than 1500 years indicated by archaeological samples from the Yamato 6th tumulus

One of the candidate materials for overpack in the Japanese engineered barrier system for high-level radioactive waste (HLW) is iron and therefore its long-term stability for at least 1000 years is very important for safety analysis of the repository system. Therefore, several of the iron artifacts excavated from the Yamato 6th tumulus (ancient tomb) in Nara prefecture were analyzed using X-ray computed tomography (CT) to determine corrosion depth. The samples analyzed, both of two large and 11 smaller iron artifacts are called ‘Tetsutei’. The thickness of each rust layer was measured from a cross-section image of the sample and the difference in material density between rust and iron was shown by the image density by the X-ray CT. In the case of pitting corrosion in the sample, the depth of the pits was measured directly and estimated as total corrosion depth with general corrosion layer. The corrosion depths are 0.5–2.1 mm. These data indicate conservative predictions for the extrapolations based on experimental studies. Such corrosion data from archaeological samples are useful in analogue studies of high-level radioactive waste disposal as evidence of long-term stability of a waste container.     

137Cs and 90Sr in bodies of surface water in Bryansk oblast in 1987–2002

The dynamics of the radioactive contamination with ¹³⁷Cs and ⁹⁰Sr of the Besed’ and Iput’ rivers in 1987–2004 and the nondraining Lake Svyatoe on the Besed’ River and the slowly draining Lake Kozhanovskoe in 1992–2002 is prsented. Data on the contamination of the components and shorelines of reservoirs are presented. It is shown that the radioactive contamination of these rivers is decreasing; the present level of contamination is much lower than the intervention level. The radionuclide content in the nondraining and slowly draining lakes remains high. Specifically, the ¹³⁷Cs concentration in the waters of Lake Svyatoe on the Besed’ River is at the intervention level, and the ¹³⁷Cs concentration in the fish in Lake Kozhanovskoe is ten times higher than the established norms. __________ Translated from Atomnaya énergiya, Vol. 100, No. 1, pp. 68–74, January, 2005.     

Simulation of the Radioactive Contamination of a Bukhta after a Radiation Accident

A mathematical model is developed for transport of radionuclides in the system consisting of water–hot particles in bottom deposits–particles of bottom deposits. This model is used to study the consequences of the radiation accident in bukhta Chazhma in 1985. The escape of ⁶⁰Co into the bukhta water from bottom deposits is estimated. Although the fraction of ⁶⁰Co escaping is small (about 10^–5), estimates show that its concentration in water can reach hundreds Bq/m³. The time dependence of the ⁶⁰Co concentration in the upper layer of bottom deposits is estimated.     

Radiation consequences of a hypothetical failure of a dam at the coolant reservoir of the chernobyl nuclear power plant

Mathematical simulation is used to estimate the possible radiation consequences of an accidental failure of the protective dam of the coolant reservoir at the Chernobyl nuclear power plant. The dynamics of the emptying of the reservoir and the escape of radionuclides is calculated. The additional contamination of bottom deposits in the Dnepr River, which can be caused by the accidental escape of radioactive substances from the coolant reservoir, is estimated. The additional dose load to the public is estimated taking account of the food chains. A single-step mathematical model, taking account of the contamination of the water and the bottom deposits, is constructed to study the fish food chain. It is established that for an accidental failure of the protective dam of the coolant reservoir of the nuclear power plant the dose to the public will not exceed 2.5·10⁻³ Sv in the first year after the failure. Therefore, the destruction of the protective dam of the coolant reservoir of the Chernobyl nuclear power plant, if it occurs, will not be a radiation accident, 2. figures, 1 table, 9 references. Translated from Atomnaya énergiya, Vol. 88, No. 4, pp. 303–307, April, 2000.     

Fundamental burn-up mode in a pebble-bed type reactor

This paper deals with a pebble-bed type reactor, in which the fuel is loaded from one side (top) and discharged from the other side (bottom). A boundary value problem of a single group diffusion equation coupled with simplified burn-up equations is studied, where the natural radioactive decay processes are neglected in the burn-up modelling. An asymptotic burning wave solution is found analytically in the one-dimensional case, which is called as fundamental burn-up mode. Among this solution family there are two particular cases, namely, a classic fundamental solution with a zero burn-up and a partial solitary burn-up wave solution with a highest burn-up. An example of Th–U conversion is considered and the solutions are presented in order to show the mechanism of the burning wave.     

A mathematical model for hydrothermal convection around a radioactive waste depository in hard rock

A mathematical model of thermally induced water movement in the vicinity of a hard rock depository for radioactive waste is presented and discussed. For the low permeability rocks envisaged for geological disposal the equations describing heat and mass transfer become uncoupled and linear. Analytic solutions to these linearized equations are derived for an idealized spherical model of a depository in a uniformly permeable rock mass. As the hydrogeological conditions to be expected at a disposal site are uncertain, examples of flow paths are presented for a range of different permeabilities, porosities, boundary conditions and regional cross-flows.     

Longitudinal Transport of Harmful Impurities by River Flow

A mathematical model of the longitudinal transport of radioactive impurities by a uniform river flow, taking account of the vertical migration in river bottom deposits, is described. A specific example is examined. The calculation is performed by solving the appropriate boundary value problem numerically on a personal computer. The comparison of the computational results and the results of natural observations showed that the migration of the contamination in bottom deposits can be decisive for the propagation of radioactive impurities in a river channel. 3 figures, 5 references.