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Vol 121, No 1 (2016)

Dedicated to the 60th Anniversary of the Journal Atomnaya Energiya

Lessons from Chernobyl and Fukushima and Advanced Control Concepts for Severe Accidents

Bol’shov L.A.

Abstract

The year 2016 marks the 30th anniversary of the accident in the No. 4 unit of the Chernobyl NPP and the 5th anniversary of the accident at the Fukushima NPP in Japan. The Chernobyl accident substantially changed the public’s attitude toward severe accidents at NPPs, promoting on the one hand modernization and improvement of safety systems and on the other hand a higher safety culture by harmonization of standards and regulations, and adoption of deeply echeloned protection and a scientifically validated approach to the analysis of accidents. The Fukushima accident revealed a new class of accidents – extreme actions caused by naturally occurring cataclysms and/or different external actions, which actually are identical to loss of a large part or all of the means for controlling an accident. The present article examines the main lessons on accidents in terms of understanding the phenomenology of the events occurring during severe accidents and confirms the importance of the deterministic component of the safety concept. At the same time, it emphasizes that special attention must be given to hydrogen safety, systems for prolonged removal of residual heat, emergency readiness, and emergency response under the extreme conditions of severe accidents. The computational means used to develop accident counter-measures must be properly set to take account of the design features of the reactor facility, the containment of the NPP, and the adjoining territories in order to determine the time required to implement the procedures for controlling accidents and mitigating the consequences.

Atomic Energy. 2016;121(1):1-9
pages 1-9 views

Article

High-Priority R&D Problems of Advanced Fast Sodium Reactors

Poplavskii V.M., Bagdasarov Y.E.

Abstract

The transition to new design and circuitry requires careful validation of the efficacy of the new solutions. For the sodium-water BN-1200 macro-modular steam generator, the damage is determined by the failure of the structural material in the zone of a water leak into the sodium and the amount of water entering the coolant. The parameter that ultimately determines the magnitude of the damage is the time interval between the start of a small leak and the actuation of the steam generator’s protection system. Acoustic methods are effective for decreasing the lag of the indication system. The design is based on the use of two-frequency ranges – vibro-acoustic (0.1–40 kHz) and ultrasonic (40–500 kHz) – of high-sensitivity acoustic sensors, and fast software-hardware methods of analyzing acoustic signals in real-time. The presence of thermal insulation and protective jackets on the sodium equipment and pipelines strongly affects the character of the outflow and burning of the sodium and eliminates dispersal. Analysis shows that there are strong grounds for reducing the conservatism (safety margins) in studying emergency regimes associated with sodium leaks.

Atomic Energy. 2016;121(1):10-17
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History and Operation of the First Two Units of the Beloyarskaya NPP

Kochetkov L.A.

Abstract

The history and development are presented of the unique power-generating units at the Beloyarskaya NPP with in-reactor steam superheating with AMB reactors that are thermal channel reactors with graphite moderator, whose core consisted of evaporation channels (2/3 of the core) with tubular fuel elements with heat removal by boiling water under pressure 13 MPa and steam superheating channels (1/3 of the core) with tubular fuel elements with heat removal by superheat steam. A description is given of the particularities of the thermal scheme, the problems associated with the development and testing of the primary equipment used in a power-generating unit, and the experimental research conducted on loop setups and experimental stands built at the Obninsk NPP and setups of the Institute of Physics and Power Engineering. The results of computational and experimental research performed in validation of the power-generating units and startup operations at the Beloyarskaya NPP are presented. Emergency situations arising during startup are described. The experience gained in developing the first two units of the Beloyarskaya NPP is used in the development of a series of RBMK-type reactor facilities.

Atomic Energy. 2016;121(1):18-21
pages 18-21 views

Materials Science Aspects of Operational Safety Enhancement of Advanced VVER Based on Vessel Steel Improvements

Karzov G.P., Margolin B.Z., Teplukhina I.V., Piminov V.A.

Abstract

The materials science aspects of increasing the operational safety of advanced VVER reactors are described. The requirements of the materials for increasing the operational safety of the reactor vessel are formulated. The use of 15Kh2NMFA class 1 steel and 15Kh2MFA-A mod A and mod B steels for fabricating reactor vessels with enhanced operational reliability is analyzed. The results of investigations of the radiation and thermal embrittlement of the improved steels 15Kh2MFA-A mod A and mod B are presented.

Atomic Energy. 2016;121(1):29-42
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Purification of Regenerated Uranium in a Two-Cascade Scheme Using Intermediate Product Extraction in One of the Cascades

Palkin V.A.

Abstract

The efficiency of two-cascade schemes for purification of regenerated uranium is investigated on the basis of a computational experiment. In the first cascade, by shifting the feed toward the waste the waste flow is purified by removing 232U with 235U enrichment to 5%. In the second cascade, the flow is additionally purified by removing 232,234,236U in the intermediate product flow and natural raw material is fed into the main feed flow and low-enrichment commercial-grade uranium is obtained in the main product flow. It is shown that purification can be conducted by feeding it into the step minimizing the total feed flow of the steps or into the first step of the cascade. Low-enrichment commercial-grade uranium hexafluoride meeting ASTM specifications in terms of 232,234,236U can be produced from the purified product obtained in the intermediate product flow.

Atomic Energy. 2016;121(1):43-48
pages 43-48 views

Corrosion Effect on Concrete Barrier Life of a Decommissioned AD Reactor

Antonenko M.V., Chubreev D.O., Kuznetsov G.V.

Abstract

A mathematical model of diffusion of calcium hydroxide in the system concrete barrier–ambient environment was developed to determine the influence of corrosion processes of the first and second kinds, engendered by water and radionuclides, on the lifetime of a concrete barrier of a decommissioned commercial uranium-graphite reactor. The CaOH distribution over the thickness of the barrier in a single crack was determined. Calculations were performed to determine the CaOH concentration over the barrier thickness and to analyze the effect of corrosion and the use of S-3 superplasticizer in concrete on the lifetime of the barrier. The superplasticizer can extend the operating lifetime of the concrete barrier to 800 years.

Atomic Energy. 2016;121(1):49-55
pages 49-55 views

Dynamics of a Charged-Particle Bunch in a Travelling Wave Field with Focusing by a Uniform Magnetic Field

Baev V.K.

Abstract

This work is devoted to charged-particle dynamics in a traveling wave field that is central to the theory of the resonance method of acceleration. The equations of longitudinal and transverse motions of a bunch, focused by a longitudinal uniform magnetic field, are derived, for the first time, within the framework of the theory of envelopes. The Lagrangian of the longitudinal and transverse motions is central to the method used; the derivation of these functions is based on the following assumptions: the emittance of a bunch is approximated by an ellipse and the bunch itself in the configuration space is approximated by an ellipsoid of revolution. The solutions of test problems in which the results obtained by the method of individual particles are compared with the results obtained with the derived equations show satisfactory agreement. The equations of the envelopes could find application in the design of accelerating systems of linear resonance accelerators with focusing by a uniform magnetic field. This pertains to, first and foremost, linear electron accelerators in which focusing of this kind is often used.

Atomic Energy. 2016;121(1):56-62
pages 56-62 views

Life Extension with Ultrasonic Treatment of the Weld Connections of Npp Equipment

Trofimov A.I., Trofimov M.A., Minin S.I., Talabanov M.G., Murachev E.G.
Atomic Energy. 2016;121(1):70-74
pages 70-74 views

Articles

Use of Enriched Uranium in a Fast Reactor with Lead Coolant

Volkov I.A., Simonenko V.A., Makeeva I.R., Dyrda N.D., Belonogov M.N., Trapeznikov M.A.

Abstract

The transition of a lead-cooled reactor initially fueled with enriched uranium into an equilibrium operating regime is examined. Regenerated fuel is used consistently upon closure of the fuel cycle. The defi ciency of recycled fissile material is compensated by enriched uranium. The time to the equilibrium regime is 45 years. The breeding ratio reaches 1 in approximately 38 years. The neutron-physical characteristics were calculated using the multigroup diffusion code Arktika and the PRIZMA spectral code, which employs the Monte Carlo method. The RISK code was used to calculate the evolution of the nuclide composition. The change in the nuclide composition in the external fuel cycle was calculated after each microrun.

Atomic Energy. 2016;121(1):22-28
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Scientific and Technical Communications

Uranium-Plutonium Fuel Cycle of a Fast Molten-Salt Reactor

Ponomarev L.I., Fedorov Y.S., Miroslavov A.E., Degtyarev A.M.
Atomic Energy. 2016;121(1):63-69
pages 63-69 views

Letters to the Editor

pages 75-78 views