Examination of the first unit at the armenian nuclear power station after the end of operation

The lifetime of a nuclear reactor is limited for technical and economic reasons, and after its service life has been exhausted, a reactor must be decommissioned. When a reactor is disassembled, a large volume of radioactive wastes is produced. The radioactivity of the materials from the disassembled reactor is determined by the induced activity (activation of the materials and equipment irradiated with neutron fluxes in the course of operation) and radioactive contamination by activated products of corrosion and fission products (radioactive deposits on the surface of the equipment, constructional, protective, and building materials) as a result of rupture and accidents in the technological-loop system of the reactor. Estimates of the radioactivity and volume of the materials which are freed when a reactor is decommissioned are presented in, for example, [1][2][3][4][5].The complete or partial disassembly of the buildings and technological systems of modern reactors results in the formation of hundreds of thousands of tons of wastes [4, 5]. More than 90% of this mass consists of reinforced concrete. Only a small fraction of these materials is contaminated and (or) activated up to a high level and must be treated as radioactive wastes that must be buried. Most of the constructional and building materials removed from the operation of the reactors have very little residual radioactivity (of the order of 1 Bq/g and less) or is nonradioactive.For this reason, it is helpful to consider a variant of recycling of some of the wastes, and secondary utilization of these wastes in different industrial production processes or burial as nonradioactive wastes. Of course, all of this work must be performed with a specially organized, strict radiation monitoring of their residual radioactivity. The peculiarity of this type of monitoring is that the dose rate of the ionizing radiation which is due to the residual radioactivity of the wastes is extremely low -a fraction of the natural background.It is obvious that when these materials are further utilized in different industrial processes, the individual and collective irradiation dose to the population should not exceed the admissable limit. The limiting criterion for the individual effective equivalent dose is commonly taken to be 0.01 of the natural background (10 /zZv/yr); for skin the limit is 50 times higher; and, for the collective equivalent dose the limit is I man-Zv/yr from an individual source [6, 7].Investigations are now being conducted abroad on the development of standards in order to do away with the regulatory control of materials with low residual radioactivity [6][7][8][9][10].The lack of a general government standardized base in our country is an impediment to repeated widespread use of materials with low residual radioactivity and to achieving a significant economic savings by reuse of and decrease in the volume of wastes buried as radioactive wastes.A relation between the degree of contamination and the irradiation dose is customarily determined by means of a...

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BBER-500 reactor as a source of induced activity resulting from decommissioning

Borisov¹,

Kudryavtseva²,

Leshchenko³

et al. 1994

At Energy

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The future development of nuclear power requires the development of a new of generation of reactors that meet the modern international reliability and safety requirements. An example of such reactors is the promising power-generating unit with enhanced safety with a 1800 MW(th) water-moderated water-cooled BBER-500 reactor [1]. This plant employs the principle of self-shielding and is a further development of the BBR (PWR) plants, widely used in the world, with the traditional loop arrangement of the first loop.After power plants have reached their service life, they must be decommissioned [2, 3]. According to estimates made by the IAEA, by the year 2010 approximately 200 of the currently operating power generating units with an equivalent electric power of 1000 MW each will be decommissioned and dismantled [4].The disassembly costs are equal to 20-30% of the total construction costs of the power plants [3]. All components, included in the dismantling process will be radioactive to a greater or lesser degree. For accident-free standard operation, the induced activity exceeds 99% of the total activity neglecting the activity of the fuel [5, 6]. Long-lived induced activity is of practical interest, since disassembly is performed at least no earlier than two years after the reactor is shut down.Our objective in this work is to make a two-dimensional investigation of the long-lived induced activity of the structures and materials of a BBER-500 reactor after decommissioning.The BBER-500 reactor consists of the following basic units: a thick-wall metallic vessel, the top block with the safety and control rod drives, intravessel units (shaft, recess), and a core with an equivalent radius of 158 cm and a height of 355 cm.The reactor vessel consists of a vertical vessel, whose inner surface is covered with a 0.7 cm thick stainless anticorrosion facing. In the horizontal plane, passing through the center of the core, the equivalent thickness of the recess is 15.5 cm, the thickness of the shaft is 6.5 cm, and the thickness of the reactor vessel walls is 19.25 cm. The shielding beyond the vessel consists of concrete. A dry side shielding, consisting of serpentinite concrete with a thickness of 73.85 cm with a lining, followed by the standard concrete shielding, is installed on the right side. in the radial direction, at the level of the core.The service life of the reactor is taken to be 50 years with a power utilization coefficient of 0.8. The construction of the main unit of the BBER-500 reactor is planned for the Leningrad nuclear power plant.The construction described above corresponds to the layout of the BBER-500 reactor displayed in Fig, 1. An approximation along the radius r in the horizontal plane is displayed in Fig. 2. Here. r = 0 is the center of the core.The induced activity in the (r, z) geometry was calculated using the AKTIVATSIYA-2 program-constant system [7, 8], which includes the KASKAD-1 program [9, 10] with the DLC-23/CASK library of constants [11]. This system is designed for computational investigati...

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Examination of the first unit at the armenian nuclear power station after the end of operation

Cited by 4 publications

References 2 publications

Fast engineering methods for forecasting the induced activity in the materials of reactors when they are decommissioned

Fast engineering methods for forecasting the induced activity in the materials of reactors when they are decommissioned

Substantiation of the admissable concentration of radionuclides in the utilization of concrete from disassembled reactors

BBER-500 reactor as a source of induced activity resulting from decommissioning

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