Search

Radioactive wastes are formed during the production of uranium-plutonium nuclear fuel at enterprises. In the present article the concentration ranges for uranium, plutonium, and neptunium in liquid and cemented wastes corresponding to different radioactivity classes are determined. The concentration ranges are determined for wastes formed in the production of nitride fuel for the initial load, as well as for waste formed on use of recycled uranium, plutonium, and neptunium in production. The effect of 241Am accumulation on the classification of radwaste is determined. The estimated cost of transferring the wastes formed on fabrication of mixed nitride fuel to the national operator for disposal is presented. The technological methods of reducing the cost of waste disposal, including the possibility of forming class-3 wastes for which surface disposal is admissible, are presented. The maximum concentration of plutonium and americium in liquid wastes at which the solidified forms of wastes correspond to class-3 is determined.

The article presents a comparison of technologies for liquid radioactive waste bottom sediment processing from NPPs with WWER-1200 reactor units. Vitrifi cation and cementing methods were compared based on the state of art in the development of the Unifi ed State System for Radioactive Waste Management, as well as engineering and design study of various processing methods. The research demonstrates that industrial use of the vitrifi cation method can be seen as a promising one when it comes to the processing of liquid radioactive waste from NPPs and radiochemical plants.

The possibilities of minimizing the volume of waste are examined for the reprocessing of spent nuclear fuel from VVER-1000 and the matrix material for high-level wastes. The analysis takes into account the designbasis isotopic composition of VVER-1000 spent fuel and the current normative base in the sphere of waste management. It is shown that deep underground disposal of radioactive wastes cannot be avoided at the present stage of development of the reprocessing technologies for the spent fuel from thermal reactors and with the existing legislation associated with the conditions of use of matrices for solidification of wastes and the conditions of waste disposal. Variant methods for decreasing the volume of underground disposal of radwaste are proposed.

The results of studies of the physical and chemical properties of samples obtained during solidification of simulators of spent ion-exchange resin pulps with the use of polymer binders are presented. Investigations were conducted for pulps simulating heterogeneous radioactive wastes from the Kursk NPP. It is shown that the physical and chemical properties of the final compounds and the technological processes used to obtain them correspond to the requirements of solidified radioactive waste sent to storage or disposal. The surface of the samples is uniform and the components are distributed uniformly. Water resistance and radiation resistance tests showed that the mechanical strength of the tested samples is almost identical to the initial strength. It is shown that the mechanical load at which plastic deformation of the polymer compound occurs is a factor of two larger than and the leach rate does not exceed the established value.

The formation of tritium in reactors, its behavior in nitride fuel and possibility of bonding with fission products, and the characteristics of migration out of the fuel-element cladding are examined. It is shown by a computational method that owing to diffusion through the steel cladding the stationary content of tritium in a fuel element is established over several hours of operation and most of the formed tritium escapes through the cladding, some being retained in it. The presence of hydrogen (tritium) in structural reactor materials in the course of operation of the reactor and thermal vibrations of the structure can significantly degrade the strength of steel structural materials. In this connection, in the BREST facility, the emphasis on the problem of catching tritium is shifted from reprocessing of spent nuclear fuel to handling the lead coolant and the gas medium in the interior of the reactor.

Salt cake radioactive waste is a remnant solid salt concentrate after deep evaporation of radioactive evaporator concentrate at WWER NPP’s. The traditional cementing of borate-containing liquid radioactive waste, to which the salt cake belongs, leads to a significant increase in the volume of the final product. This work describes borosilicate vitreous wasteforms developed to immobilize radioactive salt cake waste and comprises data on both glass synthesis and characterization. The composition of glass selected for the purpose of immobilisation of the salt cake radioactive waste allows to include up to 40 wt. % of the oxides contained in the salt cake and to reduce the volume of the final product by more than 2 times compared with the cement compound. The batches were melted in a cold crucible melter at 1200 °C. The normalized cesium leaching rate of the vitrified wasteform product was within range 3.0·10-5 – 3.7·10-6 g/(cm2·day).

The operation of a linear crystallizer, which performs crystallization extraction of uranium from a nitric acid solution of uranyl nitrate during nuclear reprocessing, is analyzed. Equations for the evaluation of the characteristics of the continuous operation of the apparatus are given, namely, the extraction efficiency of the crystal phase and the filling time of the storage container of the apparatus with the crystals of uranyl nitrate hexahydrate. The estimates are compared with the results of computer calculations and experimental data.

14C enters the atmosphere in amounts equivalent to 1.4 PBq/yr with total accumulation 140 PBq via cosmic radiation. As a result of nuclear explosions (1950–1969), its activity in the atmosphere exceeded 200 PBq. At present, 14C has been completely removed into bottom waters and sedimentary rocks in the ocean. The activity of the 14C entering the atmosphere from all operating nuclear reactors equals ~0.3 PBq/yr and the amount from all spent fuel reprocessing facilities equals ~0.06 PBq/yr. The admissible levels of 14C emissions must not exceed levels corresponding to peroral intake dose 10 μSv/yr. This is can be accomplished by means of a system of measures: reduction of the volume of technogenic gases and their 12CO2 content, combining high-efficiency purification with dispersion through high exhaust-stacks, and developing new technologies and reagents binding 14C in compact forms.

The USG-1 facility was developed to incinerate spent reactor graphite. It is equipped with a monitoring and control system; its maximum capacity is 10 kg/h. Trial combustion of a batch of unirradiated graphite was conducted. The tests showed that the units in the facility are serviceable and irradiated reactor graphite can be incinerated directly in an air flow. For a 1.5 kg load of graphite, the burn rate at 900°C was equal to 0.3 kg/h. The burn rate increases with increasing load. The incineration of irradiated graphite bushings of the EI-2 reactor in the USG-1 incinerator was studied at PDC UGR. The completeness of incineration was 95% and the 137Cs catching efficiency was 95%. With modification of the gas purification unit, the USG-1 incinerator can be used to burn irradiated graphite contaminated by traces of nuclear fuel and in monitoring the atmospheric emissions of 14CO2.

A mathematical model of the crystallization of uranium in a continuous linear crystallizer, designed for the crystallization separation of desired products in the processing of an irradiated nuclear fuel, is proposed. This model defines the dynamics of growth/dissolution of uranyl nitrate hexahydrate crystals in a nitric acid solution of uranyl nitrate. Results of a numerical simulation of the indicated process, pointing to the existence of stationary conditions in the working space of the crystallizer, are presented. On the basis of these results, the characteristic time of establishment of the stationary regime at different parameters of the process was estimated. The mathematical model proposed was validated on the basis of a comparison of the results of calculations carried out within its framework with experimental data.

A technology for reprocessing mixed uranium–plutonium nitride fiel (MUPN) from BREST reactor is considered. The technology should ensure reprocessing of spent nuclear fuel with the storage time after irradiation of no more than 1 year, 10–15% content of fissile materials (FM), and burn-up of 10% of heavy atoms. The target product of the technology is a mixture of actinide oxides separated from fission products with the separation factor of ~106. A PH (Pyro–Hydro) process was suggested for MUPN SNF reprocessing. It involves pyroelectrochemical fuel reprocessing with separation of U, Np, and Pu from the major fraction of fission products responsible for the heat release from the fuel and for the radiation load on process media, a series of hydrometallurgical operations for final purification of the target products (U–Pu–Np–Am), and radioactive waste (RW) management. The PH process is being developed since 2011 by the teams from the Bochvar High-Tech Research Institute of Inorganic Materials, Khlopin Radium Institute, and Research Institute of Atomic Reactors with active participation of the Leading Research Institute of Chemical Technology, Siberian Chemical Combine, and institutes of the Russian Academy of Sciences, primarily Frumkin Institute of Physical Chemistry and Electrochemistry and Vernadsky Institute of Geochemistry and Analytical Chemistry.

Crystallization refining is a technological operation that can separate and purity desired products (fissile materials) during the reprocessing of spent nuclear fuel. A mathematic model presented in this article describes the stationary operating regime of a linear crystallizer and makes it possible to determine the parameters of the process that ensure the most efficient separation of the desired products.

Russian Federation is developing the key technologies for closed nuclear fuel cycle with FR used mixed uranium-plutonium nitride or oxide (MOX) fuel within the framework of the project “Proryv”. This is a new integrated comprehensive product for nuclear power, which provides in the future - no accumulation of spent nuclear fuel; - radioactive waste management based on the principles of radiation-equivalent disposal; - technological support for the non-proliferation treaty; - competitiveness with other large-scale power technologies. The experimental and demonstration energy complex is under construction now on the site of Siberian Chemical Combine for the industrial development of the closed nuclear fuel cycle. ODEC will include a fast reactor BREST-OD-300 with lead coolant, facility for fabricating/refabrication of nitride fuel and the spent nuclear fuel processing facility. Up today, the key technology elements were demonstrated using macro quantities U, Pu, Np, irradiated mixed nitride fuel and real high-level waste. Within the framework of the project “Proryv” a prototype of the fuel cycle of fast reactors is developing.

The incineration of reactor graphite in an air stream is studied. Thermogravimetric analysis showed that in air disperse graphite starts to burn at 843 K. The burn rate reaches a maximum at 1023 K and remains constant above this temperature. The logarithm of the burn rate was found to be a linear function of the reciprocal of the temperature: logv = –(2.75 ± 0.35)·104/T. It was found that the burn rate at 1173 K per unit surface area for graphite samples with initial surface area from 600 to 1800 mm2 is almost the same for all samples and equals (0.74 ± 0.15)·10–3 kg/(m2·sec).

A mathematical description of the refined shape of the absorption lines in the Mossbauer spectrum that takes into account the distortion of the shape of the lines as a result of the effect of apparatus factors is suggested. Within the framework of the mathematical model suggested, processing of the absorption spectrum of iron in beryllium was done. The results may be used in the Mossbauer analysis of the phase composition of solid bodies with the aim of early identification of new phases or pre-phase precipitates.

The precipitation of the dispersed phase on the bottom of a melter accompanying vitrification of model solutions of high-level wastes was analyzed and a procedure was proposed for determining the macroscopic parameter characterizing the diffusion of small inclusions of the dispersed phase. The maximum sizes of the conglomerates of the dispersed phase near the bottom of an EP-500 melter and the characteristic time over which the impurity is removed from the melt as a result of sedimentation of the heterogeneous phases were determined on the basis of the results. It was shown that these two characteristics of the dispersed phase have virtually no effect on the depth of the melt of the glass phase. For real furnaces used for vitrification with Joule heating, the results obtained could mean that in the hypothetical case when there is no convection and no temperature gradient in the melter, the precipitating dispersed phases based on fission products will settle almost entirely on the bottom of the melter in the form of a dense layer of precipitate.

Distribution functions of the electric charges of alpha-active particles in a bipolar atmosphere are calculated. A detailed balance of the charge states of particles is performed. Under conditions of alpha decay of the constituent nuclei of the aerosol material, approximately 40 secondary electrons emanate from micron-size particles; as a result, a particle acquires a positive charge. Therefore, multiple charge transfers between charge states are also included in the analysis. 3 refs.

The objective of this study was to develop a method for calculating the charge distribution functions over radioactive aerosol particles (beta emitters) under conditions of single and double charge transfers. An analytic form of the distribution function for both low and high energy beta-active particles was obtained and evaluated, and good agreement with experiment was obtained. Future plans to extend the method to alpha-active aerosols was noted.

Dynamics of the mortality and the mortality radiation risks among male emergency workers of 1986-1987 years of entrance to the Chernobyl zone is analyzed. The average dose of external gamma-exposure for this cohort equals 128 mGy. The size of the cohort at the beginning of the follow-up in 1992 was 47820 persons. For the follow-up period 1992-2006 statistically significant radiation risks of death rates have been estimated: for the mortality from all causes, the excess relative risk per Gy (ERR/Gy) equals 0.42 with 95% confidence interval (95% CI) (0.14-0.72); for the mortality from solid cancers ERR/Gy = 0.74, 95% CI (0.03-1.76); and for the mortality from the circulatory system diseases ERR/Gy = 1.01, 95% CI (0.51-1.57). Based on these estimates the risk groups were ranked among all Russian emergency workers (160 thousand persons): the group of the potential radiation risk with doses more than 150 mGy (33488 persons) and the group of the high radiation risk with doses more than 240 mGy (6054 persons).

The influence of heterogeneity in individual radiosensitivity on estimation of ageing using survival curve is considered. Quadratic deviation of the rate of ageing from the true value in estimated by imitation modeling techniques. The Gompertz model for spontaneous mortality and gamma-frailty model for heterogeneity are used. Simulation performed at different values of radiation effect and heterogeneity variance. It is shown that inclusion heterogeneity in the model is not efficient for large values of heterogeneity variance. For moderate values of heterogeneity variance model with heterogeneity produces more accurate results in comparison with the model without heterogeneity.

Transport processes are investigated by means of the lattice gas model with nearest and nextnearest neighbour attractive and repulsive interactions. The temperature and concentration dependences of self-diffusion coefficient and electroconductivity in the disordered homogeneous phase of these systems are calculated by the cluster approximation. The regions of deviation from the Arrhenius law are determined. The spatial-time distributions of migrating particles are obtained. The influence of strong short-range interactions on the relaxation time of the diffusion process is investigated. Several experimental results of diffusion in systems with strong shortrange correlations are discussed by the theory proposed. Die Transportprozesse in Kristallen vom KDP-Typ werden im Rahmen eines Gittergasmodells beschrieben. AbstoBende und anziehende Wechselwirkungen zwischen nachsten und ubernachsten lonen der Gitterpunkte werden in Betracht gezogen. Die Temperatur- und Konzentrationsab-hangigkeiten der Selbstdiffusions- und Leitfahigkeitskoeffizienten der ungeordneten homogenen Phase dieser Systeme werden mit der Methode der Clusternaherung berechnet. In diesen Kristallen werden Bereiche gefunden, die Abweichungen vom Arrhenius Gesetz aufweisen. Die zeitliche und raumliche Teilchenverteilungen werden fur diese Systeme bestimmt. Der Einflus einer Nahordnung auf die Relaxationszeit des Diffusionsprozesses wird behandelt. Die experimentellen Diffusions-ergebnisse werden im Rahmen der entwickelten Theorie analysiert.

A vast amount of research articles devoted to the increase in childhood thyroid cancer incidence in the most contaminated by radionuclides territories of Belarus, Russia and Ukraine affected by the Chernobyl accident were published recent years. However, the amount of research studies of thyroid cancer incidence among the Chernobyl emergency workers (liquidators) is quite scanty. In the article results of the study of thyroid cancer incidence in the cohort of the Chernobyl liquidators (103427 persons) residing in 6 administrative regions of Russia (North-West, Volgo-Vyatsky, Central-Chernozemny, Povolzhsky, North-Caucasus and Urals) are described and discussed. For the period 1986-2003 eighty seven cases of thyroid cancer were detected in the cohort. Statistically significant excess of the incidence among liquidators over baseline incidence, SIR = 3.39 (95% CI: 2.73; 4.16), among men of Russia has been found. The highest thyroid cancer incidence (SIR = 6.49) was registered among liquidators who had been involved in mitigation works during April-July 1986. At the same time no statistically significant relationship between the incidence rate and external radiation dose, ERR = 1.68 (95% CI: -0.95; 6.46), was detected.

The work focuses on the results of the analysis of the cancer incidence among the Chernobyl emergency workers residing in Russia during 1991-2001. The analysis is based on the data for the cohort of male emergency workers from 6 regions of Russia including 55718 persons with documented external radiation doses in the range of 0.001-0.3 Gy who worked within the 30-km zone in 1986-1987. The mean age at exposure for these persons was 34.8 years old and the mean external radiation dose 0.13 Gy. In this cohort 1370 cases of solid cancer were diagnosed. Three follow-up periods were considered: 1991-1995, 1996-2001 and 1991-2001. The second follow-up period was chosen to allow for a minimum latency period of 10 years. Risk assessments were performed for two control groups: the first control group ("external") represented incidence rates for corresponding ages in Russia in general and the second control group ("internal") consisted of emergency workers. The estimated standardized incidence ratio (SIR) is in good agreement with that of the control within 95% CI. The values of the excess relative risk per unit dose 1 Gy (ERR/Gy) for solid malignant neoplasms have been estimated to be 0.33 (95% CI: -0.39, 1.22) (internal control) for the follow-up period 1991-2001 and 0.19 (95% CI: -0.66, 1.27) for 1996-2001. The analysis of cancer morbidity was carried out for the cohort of 29003 emergency workers who took part in liquidation of the consequences of the Chernobyl accident from 26 April 1986 to 25 April 1987. It was shown that the excess relative risk of cancer deaths per unit dose 1 Sv (ERR/Sv) is equal to 1.52 (95% CI: 0.20, 2.85).

The paper describes the drainage systems developed by the Medinstrument Research Production Association, such as nephropyelostomic catheters, drainage tubes of the Saratoga type, surgical aspiration instruments (tips) made of flexible medical PVC of various modifications. Their testing in the leading clinics of the Russian Federation has shown that the instruments will find a wide application in urological and surgical units. Their use will take some burden from medical personnel and have its therapeutical, social, and economic impact.

In the mode–mode coupling approximation the critical exponente (CE) are calculated for the damping and frequency shift of soft optic modes and acoustic phonons at the structural transition point for crystals with dimensions d = 1, 2, 3. The CE are traced back to the anharmonic interaction of phonons taking into account the intrinsic dynamic central peak of any nature. Anharmonisms of all order are considered. [Russian Text Ignored].

A robotic set (the machine-tool/robot unit) comprised of a numerically controlled lathe and a multi-purpose microcomputer-based robot is described. Programs for the lathe servoing by the robot are also described. Such programs that supply robots with professional skills considerably simplity the task of robot programming. Due to these programs robots can recognize the manufacturing situations by basing on the sensor data and perform the required operations under hindrances. An example of using the robotic set for production of a specific part is presented.

The damping and frequency shifts of the longitudinal and transverse phonons are derived in the right neighbourhood of the Curie point using the microscopic theory for ferroelectrics described by the pseudospin Ising model with transverse field. The scattering of phonons both on the soft modes and on the central peak gives the same contributions to the critical anomalies. The long-range contributions to the effective “exchange integral” are also taken into account. The results coincide with predictions of the phenomenological theory. [Russian Text Ignored.]

In first-order perturbation theory it is shown with respect to the Hamiltonian of the magnon–magnon interaction that for a linear ferromagnetic XY chain with large spins the frequency renormalization is proportional to the energy of noninteracting magnons. In higher order with respect to the same interaction the momentum and temperature dependence of the magnon damping is obtained and weakly damped magnons are shown to exist, provided their wavelength is much shorter than the correlation length. [Russian Text Ignored.]

The problem of inelastic scattering of Mossbauer radiation on the order-parameter fluctuations near phase transitions is considered by means of restricted scaling. Expressions for the scattering intensities that are valid for a wide class of objects with gapless dispersion of the fluctuation spectrum are obtained. In extreme cases (i.e. hydrodynamic and critical ones) the line shape of the resonance nuclear absorption is analysed depending on the temperature and the collimations of radiation beams.

There is particular importance in the storage of high-level wastes (for example, vitrified ones) in the stability of the solid matrix (glass) containing radionuclides. This paper examines the most rapid process in glass component redistribution near inhomogeneities (inclusions, pores, cracks, etc.), as these inevitably arise during vitrification. The authors consider two model problems, whose solutions enable one to estimate the changes in component concentrations near inhomogeneities.

For a classical system of interacting particles with on-site cubic or quartic anharmonicity explicit analytic solutions of the d'Alembert equation are obtained in the form of kinks in the presence of dissipation (viscous or Rayleigh) and a constant force. These kinks will be asymptotically stable in the case of quartic anharmonicity and unstable in the case cubic anharmonicity.

In the mode—mode coupling approximation the critical exponents (CE) are calculated for the dampings and frequency shifts of soft optic modes and acoustic phonons (in uniaxial ferroelectrics) and for the dampings of soft acoustic phonons (in cubic crystals) in the structural transition point. The CE are traced back to the anharmonic interaction (of all orders) of soft phonons with the intrinsic dynamic central peak of any nature. [Russion Text Ignored]

The authors construct a geochemical and hydrological flow model for a salt deposit destined as a disposal site for radioactive wastes which depicts the temperature-dependent dissolution, diffusion, and migration of brines and salt mineral inclusions which have come into thermal or direct contact with the waste material. The model also incorporates the effect of insoluble admixtures to the wastes on the inhibition of radionuclide migration throughout the deposit.

The momentum and temperature dependence of the central peak (CP) width is found for the Ising model with a transverse field in the right neighbourhood of the Curie point. The width of CP in the critical and hydrodynamic limits is described by a scaling-type relation. During deuteration the width of CP diminishes as a squared tunneling frequency. [Russian Text Ignored].