Experimental study of the characteristics of the flow in the first rows of tube banks

This paper presents the experimental study of the flow instabilities in the first rows of tube banks. The study is performed using hot wire anemometry technique in an aerodynamic channel as well as flow visualizations in a water channel. In the wind channel three tube banks with square arrangement and pitch to diameter ratios P/D = 1.26, 1.4 and 1.6 were studied. The Reynolds number range for the velocities measurements, computed with the tube diameter and the flow velocity in the narrow gap between tubes was 7 × 10⁴–8 × 10⁴. Continuous and discrete wavelets were applied to decompose the velocity results, thus allowing the analysis of phenomena in time–frequency domain. Visualizations in a water channel complemented the analysis of the hot wire results. For this purpose, dye was injected in the flow in the water channel with a tube bank with P/D = 1.26. The range of the Reynolds number of the experiments was 3 × 10⁴–4 × 10⁴. The main results show the presence of instabilities, generated after the second row of the tube bank, which propagates to the interior of the bank. In the resulting flow, the three orthogonal components are equally significant. The three-dimensional behavior of the flow is responsible for a mass redistribution inside the bank that leads to velocity values not expected for the studied geometry, according to the known literature. The resulting flow process can be interpreted as a secondary flow which is characteristic of tube banks.     

On the origin of the LEIS signal in TOF- and in ESA-LEIS

The ion fraction analysis of ⁴He⁺ ions backscattered from various faces of copper single crystals is performed by using time-of-flight (TOF) and electrostatic analyzer (ESA) low-energy ion scattering (LEIS) techniques. When an experiment that integrates over 2π azimuth (typical ESA-LEIS setup) is used, the yield of ions backscattered from the Cu(1 1 0) surface may be given by projectiles penetrated much deeper than just one or two monolayers. The threshold energy for reionization processes for ⁴He⁺ and Cu found earlier by TOF-LEIS is experimentally confirmed by ESA-LEIS.     

Distribution of the volume activity of man-made radionuclides in the surface waters and depth waters of the Baltic Sea in the fall of 1989

Vil'nyus University of Technology. Sevastopol' Higher Naval Engineering College. Translated from Atomnaya Énergiya, Vol. 72, No. 4, pp. 397–400, April, 1992.     

Distribution Coefficient in the Sorption of Radionuclides onto Ando Soil in the Presence of Humic Acid

Influence of humic acid (HA) on the sorption of ⁶⁰Co, ⁸⁵Sr and ²⁴¹Am onto Ando soil was examined with respect to HA of various molecular sizes. Distribution coefficient (K _d) in the sorption of ⁶⁰Co on this type of soil was only slightly affected by the presence of HA. The K _d of ⁸⁵Sr as the HA concentration increased. The K _d of ²⁴¹Am decreased as the HA concentration increased and the K _d of HA showed a similar trend. In the solution, ²⁴¹Am selectively formed stable compounds with an HA ranging from 30,000 to 100,000 in molecular weight (MW), whereas ⁶⁰Co and ⁸⁵Sr Preferentially but weakly interacted with HA fractions smaller than 100,000MW. These results suggest that the K _d in the case of ⁶⁰Co and ⁸⁵Sr is mainly controlled by sorption of both cationic species and humic compounds, while the K _d of ²⁴¹Am is controlled by the sorption of HA.     

Progress in the thermodynamic modelling of the O-U binary system

The fuel of civil nuclear plants, UO₂, melts at 3120 K. During an hypothetical severe accident, urania, submitted to high temperatures and various oxygen potentials, presents a wide non-stoichiometry range: the melting temperature of UO_2±x, related to oxygen potential, decreases in all cases. In this scenario, urania could react with other materials, firstly zircaloy, and the melting temperature of (U, Zr)O_2±x still decreases. That is why the critical assessment of the O-U binary system including the non-stoichiometry range of urania, is a major step to a correct thermodynamic modelling of multicomponent systems for nuclear safety. The very numerous experimental information has been compiled and analysed. The associate model was used for the liquid phase, and a sublattice model for UO_2±x; U₄O_9−y, U₃O₈ and UO₃ were treated as stoichiometric. Phase diagram and thermodynamic properties have been calculated from the optimised Gibbs energy parameters. The calculated consistency with the experimental ones is quite satisfactory.     

Kinetics of the leaching of90Sr from fuel particles in soil in the near zone of the chernobyl nuclear power plant

A method is presented for calculating the fraction of⁹⁰Sr included in fuel particles in soil. Data concerning the change in forms of the occurrence of⁹⁰Sr in different soils in the 30-km zone, at different distances from the Chernobyl nuclear power plant, were used to obtain the kinetic characteristics of its leaching: the first-order rate constant and the normalized rate of solution. Depending on the direction and distance from the nuclear power plant, the first-order leaching rate constant varies from 3·10⁻⁵ to 2·10⁻³ days⁻¹ and the normalized rate of solution of the fuel matrix varies from 1·10⁻⁵ to 6.1·10⁻⁴. It was not found possible to clearly identify the influence of the distance from the nuclear power plant on the leaching rate in the northern and western sectors. In contrast, in the southerly and south-easterly directions a clear tendency was observed for the leaching rate to increase with increasing distance from the nuclear power plant. Taifun Scientific Production Enterprise. Translated from Atomnaya énergiya, Vol. 86, No. 2, pp. 129–134, February, 1999.     

Tectonic Factor in the Formation of the Radon Fields in the Atmosphere of the Tashkent Subway

Using the standard radiometers -GUARD PQ2000M and gamma-TRACER (Germany) and semiconductor spectrometers RATON (Uzbekistan), the radon fields were investigated in underground service enclosures and on the platforms of the Tashkent subway stations located on territories with different geotectonic characteristics. It is shown that the tectonic factor influences the formation of radon fields in the air in the subway station. 4 figures, 1 table, 7 references.     

The use of the Pn-approximation in the description of the distribution of neutrons in an absorbing rod

The system of nonlinear differential equations describing the distribution of neutrons in an absorbing rod in the P_n approximation is transformed into a system of integral equations more convenient for investigation. A method of solution based on the use of successive approximations is proposed.     

Prediction of the change in the average yearly concentration of radionuclides in the cooling pond at the chernobyl nuclear power plant

All-Russia Scientific-Research Institute of Nuclear Power Plants, Chernobyl Nuclear Power Plant. Translated from Atomnaya énergiya, Vol. 79, No. 3, pp. 211–214, September, 1995.     

Criticality theory for a reactor in the case of fluctuations in the fuel density

Conclusions In Fig. 2 we show graphs of the dependence of the additional reactivity that arises as a result of fluctuations of the fuel density. As follows from Fig. 2, the increase in the reactivity for sufficiently large reactors and for (/₀) 0.1–0.05 is comparable with the contribution of the delayed neutrons. Thus, it is in principle possible to regulate the criticality of the reactor by exciting fluctuations of the density of a gaseous fuel. Regulation in this manner has decided advantages. Thus, the time in which the reactivity changes which determines the transient processes, is short — of the order of one period of the fluctuation. Moreover, there is practically no danger of accidents, since the reactivity falls as soon as the fluctuations cease. The amplitude of the fluctuation of the neutron flux (see, for example, the expression (20)) always exceeds the amplitude of the fluctuations in the fuel density by (k–1)^–1/2. This circumstance may be exploited to obtain a neutron flux pulsating with a large amplitude.This effect of a growth in thereactivity as a result of fluctuations of the fuel density may prove important in the study of the possibility of self-oscillatory conditions of operation in reactors with a high neutron flux.Translated from Atomnaya Énergiya, Vol. 27, No. 2, pp. 107–111, August, 1969.     

Role of separate factors in the development of the chernobyl accident

NIKIÉT. Translated from Atomnaya Énergiya, Vol. 75, No. 5, pp. 336-341, November, 1993.     

32P Accumulation in Fish in the Enisei River and Reconstruction of the Irradiation Dose to the Public

The results of experimental and theoretical investigations of the behavior in the Enisei River of ³²P entering the river for more than 30 yr with discharges from the Krasnoyarsk Integrated Mining–Chemical Plant are presented. It is shown that ³²P is accumulated actively by water organisms. Its concentration in fish is a thousand times higher than in water. The ³²P content in fish depends little on the type of food ingested by the fish but depends strongly on season, reaching its maximum value in August. A model of the dynamics of the ³²P contamination of fish in the Enisei River over a 25-yr period of operation of the plant (1975–2000) is constructed and verified. The computational estimates show that the irradiation dose due to ³²P to the critical group of the population living in the near zone (fishermen and members of their families) was 0.4–1.6 mSv/yr in 1975–1992 (the maximum value occurred in 1977 and the minimum value occurred in 1992). For the rural population which was not part of the critical group, the irradiation dose from ³²P during the same years was in the range 0.14–0.5 mSv/yr.     

Health assessment of participants in the liquidation of the consequences of the chernobyl accident

The results of an analysis of the health of the participants in the liquidation of the consequences of the Chernobyl accident on the basis of the mortality indicator for the participants are reported. The computational results obtained for the harm due to mortality using estimation of the loss of life due to premature death are presented. It is shown that the relative risk of these losses for certain classes of diseases and dose groups depends on the social position of the liquidators of the accident. Recommendations are made for improving measures for their medical and social rehabilitation. 1 figure, 6 tables, 20 references. National Science Center of the Russian Federation—Institute of Biophysics. Translated from Atomnaya énergiya, Vol. 86, No. 3, pp. 232–238, March, 1999.     

Calculation of radionuclide migration in the top layers of the earth's lithosphere

Atoménergoproekt. M. V. Lomonosov Moscow State University. Translated from Atomnaya Énergiya, Vol. 74, No. 3, pp. 253–256, March, 1993.     

Automated monitoring of the environment in the region of the Kozlodui Atomic Power Plant

NIII Énergoproekt, Sofia. Translated from Atomnaya Énergiya, Vol. 67, No. 1, pp. 57–58, July, 1989.     

Transitional modelling of the neutral gas in the JET neutraliser

Effective understanding of gas flow is important to ensure efficient operation of gas neutraliser systems such as that used at Joint European Torus (JET), which form part of neutral beam heating systems for nuclear fusion experiments. Offering a means of neutralising the charge of initially ionic beams, gas neutralisers permit the injection of beams of neutral particles into the tokamak vessel, which serve to both heat the plasma and drive plasma current. Within the JET neutraliser, gas flow encompasses both the continuum-transition and molecular flow regimes, encouraging the application of novel techniques. The first application of the Augmented Burnett Equations to these systems is presented with results compared to experimental pressure profile data. The results demonstrate that the application of the Augmented Burnett Equations is a valid modelling approach. The strong dependence of accuracy upon outlet Kn is noted and good agreement found with experiment as rarefaction approaches the molecular limit of Kn=1, beyond the theoretical domain of applicability.     

Gamma spectrometry in continuous monitoring of the impurity concentration in the coolant of a reactor circuit

Institute of Nuclear Energy, Academy of Sciences of the Belorussian SSR. Translated from Atomnaya Énergiya, Vol. 70, No. 3, pp. 176–177, March, 1991.     

Pulse characteristic of the feedback in the IBR-2 reactor

Joint Institute of Nuclear Research. Translated from Atomnaya Énergiya, Vol. 70, No. 5, pp. 326–329, May, 1991.     

Estimation of the inventory of the radioactive wastes in Fukushima Daiichi NPS with a radionuclide transport model in the contaminated water

Quantification of the radioactive waste inventory remaining inside the reactors at Fukushima Daiichi NPS is necessary to effectively plan their recovery, treatment, and disposal. Analysis of radionuclide concentrations and secondary wastes in the contaminated water treatment system can provide a means to estimate the radioactive waste inventory, which is not possible by more direct methods due to problems of accessibility and high levels of radiation. A predictive model has therefore been developed to estimate the radioactive waste inventory from the radionuclide concentrations and throughputs in the contaminated water. Model fitting has enabled the estimation of the key parameters, such as the initial radionuclide concentration C₀, the continuous release rate F, and inventory of source of continuous release I_S0. An estimated one-third of the total ¹³⁷Cs inventory has already made its way into the water treatment system as secondary wastes, whereas half still remains inside the damaged reactors as of 13 March 2014.     

Stored energy in the graphite stack of the IR reactor

Storage of Wigner energy and the nature of stored energy release were investigated in the graphite stacks of the IR reactor. The investigations were carried out on graphite bricks removed from the reactor stack as the latter was being dismantled. Other samples were cut out from the reactor stack with the aid of a special drill cutter during the two years after the stack was dismantled, when an additional integral flux of thermal neutrons 2.2 ·10²¹ neutrons/cm² developed. The samples were so chosen that the pattern of stored-energy distribution throughout the stack might be obtained. Stored Wigner energy was determined by the technique of two successive heatings of the samples to temperatures of 600–650 ° C in vacuum calorimeters, making possible an energy release during the anneal. The total quantity of stored energy was determined by combustion of the graphite in a standard solid fuel testing calorimeter.