Hybrid fusion reactor for production of nuclear fuel with minimum radioactive contamination of the fuel cycle

The paper presents the results of the system research on the coordinated development of nuclear and fusion power engineering in the current century. Considering the increasing problems of resource procurement, including limited natural uranium resources, it seems reasonable to use fusion reactors as high-power neutron sources for production of nuclear fuel in a blanket. It is shown that the share of fusion sources in this structural configuration of the energy system can be relatively small. A fundamentally important aspect of this solution to the problem of closure of the fuel cycle is that recycling of highly active spent fuel can be abandoned. Radioactivity released during the recycling of the spent fuel from the hybrid reactor blanket is at least two orders of magnitude lower than during the production of the same number of fissile isotopes after the recycling of the spent fuel from a fast reactor.     

Variants of closing the nuclear fuel cycle

Influence of the nuclear energy structure, the conditions of fuel burnup, and accumulation of new fissile isotopes from the raw isotopes on the main parameters of a closed fuel cycle is considered. The effects of the breeding ratio, the cooling time of the spent fuel in the external fuel cycle, and the separation of the breeding area and the fissile isotope burning area on the parameters of the fuel cycle are analyzed.     

Improved analysis on multiple recycling of fuel in prototype fast breeder reactor in a closed fuel cycle

An FBR closed fuel cycle involves recycling of the discharge fuel, after reprocessing and refabrication, to utilize the unburnt fuel remains and the freshly bred fissile material. Our previous study in this regard for the PFBR indicated a comfortable feasibility of multiple recycling with selfsufficiency. In the present work, more refined estimations are done using the most recent nuclear data, viz. ENDF/B-VII.0, and with the most recent specification of the fuel composition. Among others, this paper brings out the importance of taking into account the energy self-shielding effects in the cross-section averages used in the study. While self-shielded averages lead to realistic predictions, unshielded averages significantly overpredict breeding in the blankets and underpredict loss in the cores.     

Experiments on plasma-physical aspects of closed cycle MHD power generation

In this paper, important laboratory experiments in closed-cycle magneto-hydrodynamic (MHD) generator plasmas are discussed. The following aspects are treated: electron temperature elevation and nonequilibrium ionization, fluctuations and nonuniformity, streamers as the nonlinear appearance of ionization instability, inlet relaxation, and fully ionized seed as a concept to suppress ionization instability. Conclusions are presented on electrical transport parameters in nonuniform plasmas, streamer fine structure, streamer velocity, streamer initiation in relation to inlet relaxation, and the fully ionized seed concept.     

Proton radioactivity half-lives with nuclear asymmetry factor

The dependence of proton emission half-lives on the nuclear asymmetry parameter is investigated using the WKB method and two types of empirical formula.Using the single-folding formalism with asymmetry-depend-ent nuclear radius and surface diffuseness of nuclear matter,the nuclear potential and consequently the half-life are functions of the asymmetry factor.Despite small values of asymmetry in neutron-deficient proton emitters,notice-able changes in the half-lives are observed.The addition of an asymmetry parameter term to the two forms of empir-ical formulas leads to a reduction in the rms error for ground state and isomeric transitions.A noticeable reduction of about 43%is obtained for isomeric transitions in the second form of the empirical formula.Considering ground state transitions in two categories,odd-even and odd-odd emitters,and adopting deformation and asymmetry-dependent empirical formulas,the rms decreases remarkably.The low est values of rms errors,viz.0.1492,0.2312,and 0.1999,are obtained for the aforementioned empirical formulas for ground state transitions of odd-even and odd-odd emit-ters and for all isomeric transitions,respectively.     

Operation of CANDU power reactor in thorium self-sufficient fuel cycle

This paper presents the results of calculations for CANDU reactor operation in thorium fuel cycle. Calculations are performed to estimate the feasibility of operation of heavy-water thermal neutron power reactor in self-sufficient thorium cycle. Parameters of active core and scheme of fuel reloading were considered to be the same as for standard operation in uranium cycle. Two modes of operations are discussed in the paper: mode of preliminary accumulation of ²³³U and mode of operation in self-sufficient cycle. For the mode of accumulation of ²³³U it was assumed for calculations that plutonium can be used as additional fissile material to provide neutrons for ²³³U production. Plutonium was placed in fuel channels, while ²³²Th was located in target channels. Maximum content of ²³³U in target channels was estimated to be ∼13 kg/t of ThO₂. This was achieved by irradiation for six years. The start of the reactor operation in the self-sufficient mode requires ²³³U content to be not less than 12 kg/t. For the mode of operation in self-sufficient cycle, it was assumed that all channels were loaded with identical fuel assemblies containing ThO₂ and certain amount of ²³³U. It is shown that nonuniform distribution of ²³³U in fuel assembly is preferable.      

核电站最小安全系统电磁脉冲效应试验研究

高空电磁脉冲(HEMP)可通过线缆、孔缝等耦合通道进入电子设备,对各种电子化设备造成暂时甚至永久损伤。考虑到核电站的安全防护等级要求极高,因此有必要研究强电磁脉冲作用下核电站内电子系统的易损性和薄弱环节。首先确定并搭建了核电站最小安全系统模拟试验系统,包括电气、仪控系统和时钟同步系统; 搭建满足GJB 8848-2016规定的威胁级辐照试验平台; 然后对核电站最小安全系统进行辐照效应试验。利用试验数据及效应现象,初步分析了核电站最小安全系统在强电磁脉冲作用下的效应规律,发现HEMP对核电站最小安全系统具有一定程度的威胁,但未影响其核心关键职能。通过总结效应现象、分析薄弱环节和效应阈值,为接下来核电站最小安全系统的易损性评估和防护策略的制定提供依据。     

Density outbursts in a food web model with a closed nutrient cycle

A spatial three level food web model with a closed nutrient cycle is presented and analyzed via Monte Carlo simulations. The food web consists of three trophic levels. The basal level species (called resources  , R$R$) corresponds to primary producers in real ecosystems. The species at an intermediate level (consumers  , C$C$) relates to herbivores. It feeds on the resources. The consumers themselves constitute food for the top level species (predators  , P$P$), which corresponds to carnivores. The remains of the consumers and predators (detritus  , D$D$) provide nutrient for the resources. The time evolution of the model reveals two asymptotic states: an absorbing one with all species being extinct, and a coexisting one, in which concentrations of all species are non-zero. There are two possible ways for the system to reach the absorbing state. In some cases the densities increase very quickly at the beginning of a simulation and then decline slowly and almost monotonically. In others, well pronounced peaks in the R$R$, C$C$ and D$D$ densities appear regularly before the extinction. Those peaks correspond to density outbursts (waves) traveling through the system. We investigate the mechanisms leading to the waves. In particular, we show that the percolation of the detritus (i.e. the accumulation of nutrients) is necessary for the emergence of the waves. Moreover, our results corroborate the hypothesis that top-level predators play an essential role in maintaining the stability of a food web (top-down control).     

On the feasibility of production of microkelvin temperature by nuclear demagnetisation

Nuclear demagnetisation as a means of refrigeration has been proposed and achieved long ago. In this paper an attempt has been made to show that PrBe₁₃, a Van-Vleck paramagnet, can be used to produce a lattice temperature of 10μK. or lower. Such a calculation can be used for a computer simulation of the process.     

On the role of fusion neutron source with thorium blanket in forming the nuclide composition of the nuclear fuel cycle of the Russian Federation

The possible role of available thorium resources of the Russian Federation in utilization of thorium in the closed (U–Pu)-fuel cycle of nuclear power is considered. The efficiency of application of fusion neutron sources with thorium blanket for economical use of available thorium resources is demonstrated. The objective of this study is the search for a solution of such major tasks of nuclear power as reduction of the amount of front-end operations in the nuclear fuel cycle and enhancement of its protection against uncontrolled proliferation of fissile materials with the smallest possible alterations in the fuel cycle. The earlier results are analyzed, new information on the amount of thorium resources of the Russian Federation is used, and additional estimates are made. The following basic results obtained on the basis of the assumption of involving fusion reactors with Th-blanket in future nuclear power for generation of the light uranium fraction ^232+233+234U and ²³¹Pa are formulated. (1) The fuel cycle would shift from fissile ²³⁵U to ²³³U, which is more attractive for thermal power reactors. (2) The light uranium fraction is the most “protected” in the uranium fuel component, and being mixed with regenerated uranium, it would become reduced-enrichment uranium fuel, which would relieve the problem of nonproliferation of the fissile material. (3) The addition of ²³¹Pa into the fuel would stabilize its neutron-multiplying properties, thus making it possible to implement a long fuel residence time and, as a consequence, increase the export potential of the whole nuclear power technology. (4) The available thorium resource in the vicinity of Krasnoufimsk is sufficient for operation of the large-scale nuclear power industry of the Russian Federation with an electric power of 70 GW for more than one quarter of a century. The general conclusion is that involvement of a small number of fusion reactors with Th-blanket in the future nuclear power industry of the Russian Federation would to a large extent solve its problems and increase its export potential.     

Optical spectrum of a closed cycle MHD generator plasma

The spectra of argon-cesium plasmas, used as working fluids of closed-cycle MHD generators, were investigated in the visible and near-i.r. regions by using a Hilger-Watts medium quartz spectrograph. A number of argon and cesium lines was observed, as well as some lines originating from the impurities present in the cesium capsule. The molecular bands of aluminum monoxide have also been detected. The population temperatures estimated from relative intensities of cesium lines lie below those obtained by using either the line-reversal method or recombination-radiation measurements. The intensities of some neutral cesium lines follow the Boltzmann population relation at the population temperature. The Zeeman effect and reversed profiles of cesium resonance lines were not observed because of low resolution of the spectrograph used and because of light scattering on the film.     

Formation of nuclear molecules in cluster radioactivity on interpretation of the cluster radioactivity mechanism

The basis for cluster radioactivity is the property of nuclei of light isotopes of elements heavier than lead to spontaneously form clusters—nuclei of light elements—from valence nucleons, which gives rise to asymmetric nuclear molecules. The cluster formation proceeds through successive excitation-free transfer of valence nucleons to the α particle and to subsequent light nuclei. Nuclear molecule formation is accompanied by a considerable amount of released energy, which allows quantum-mechanical penetration of the cluster through the exit Coulomb barrier.     

On the minimum mass of a monopole

Russian Physics Journal -     

Impact of proliferation strategies on food web viability in a model with closed nutrient cycle

A food web model with a closed nutrient cycle is presented and analyzed via Monte Carlo simulations. The model consists of three trophic levels, each of which is populated by animals of one distinct species. While the species at the intermediate level feeds on the basal species, and is eaten by the predators living at the highest level, the basal species itself uses the detritus of animals from higher levels as the food resource. The individual organisms remain localized, but the species can invade new lattice areas via proliferation. The impact of different proliferation strategies on the viability of the system is investigated. From the phase diagrams generated in the simulations it follows that in general a strategy with the intermediate level species searching for food is the best for the survival of the system. The results indicate that both the intermediate and top level species play a critical role in maintaining the structure of the system.     

On combustion in a closed rectangular channel with initial vorticity

This article examines the detailed combustion process in a theoretical model with applicability to combustion in a wave rotor or wave disc engine. The model comprises a single channel into which an initial loading of methane and air is admitted and ignited after all inlet and exit ports have been closed. Combustion takes place at constant volume. However, the initial gaseous mixture in the channel is not at rest. The initial opening and closing of the ports generates significant vorticity which influences the evolution of the combustion process. Numerical evaluations are provided for the detailed flame shape for simplified (one-step) chemistry and a simulation using the detailed 235-step San Diego scheme. Quantities examined are the evolution of vorticity, pressure fluctuations, mass consumption rate, flame surface area and the influences on combustion of adiabatic and non-adiabatic channel walls. Combustion regimes are identified and compared with simpler model studies (no initial flow). Pointwise quantities are examined to describe the various stages of burning in the channel. The focus of the study is directed towards quantities that influence overall burning rate and completeness of combustion.     

Plutonium and minor actinides management in the nuclear fuel cycle: assessing and controlling the inventory

The mastering of the plutonium and minor actinides inventory in the French Nuclear Cycle is based on a progressive approach from the present status, dealing with the partial reprocessing of spent fuels and the recycling of Pu in the MOX assemblies loaded in the 20 licensed PWRs. This strategy keeps the door open long-term, for example, for the eventual multirecycling of excess Pu in dedicated new assemblies, such as APA or CORAIL in order to stabilise the Pu inventory in the fuel cycle or allow its utilization in new types of fast reactors. Presently, in the framework of 1991 law, scenario studies relying on present and/or innovative technologies are carried out in order to transmute both Pu and minor actinides, thus minimising the quantities to be for disposal. To cite this article: H. Mouney, C. R. Physique 3 (2002) 773–782.     

Computer simulation of a combined cycle power plant

This paper presents the simulation procedure developed to predict the performance of a combined cycle power plant from given performance characteristics of its main components. In order that the procedure could be validated, the simulation technique has been applied to a typical combined cycle power plant (having a dual pressure bottoming cycle) manufactured by a prominent company. The characteristics of the standard equipment like the air compressor, steam and gas turbines, various pumps, etc. have been taken from the manufacturer's catalogues and converted into appropriate equations based on theoretical understanding. The performance of various heat exchangers (like economizers, superheaters, evaporators, etc.) has been determined by using the effectiveness concept after evaluating the overall heat transfer coefficient by using appropriate correlations from literature. The strategy of system simulation is obtained by judiciously interlinking the information flow diagrams of various components and thus the task is finally reduced to that of solving nine non-linear equations for nine variables. The predicted performance of the system is seen to be in good agreement with in good agreement with its rated performance.     

Prospects for and problems of using light-water supercritical-pressure coolant in nuclear reactors in order to increase the efficiency of the nuclear fuel cycle

Trends in the development of the power sector of the Russian and world power industries both at present time and in the near future are analyzed. Trends in the rise of prices for reserves of fossil and nuclear fuels used for electricity production are compared. An analysis of the competitiveness of electricity production at nuclear power plants as compared to the competitiveness of electricity produced at coal-fired and natural-gas-fired thermal power plants is performed. The efficiency of the open nuclear fuel cycle and various versions of the closed nuclear fuel cycle is discussed. The requirements on light-water reactors under the scenario of dynamic development of the nuclear power industry in Russia are determined. Results of analyzing the efficiency of fuel utilization for various versions of vessel-type light-water reactors with supercritical coolant are given. Advantages and problems of reactors with supercritical-pressure water are listed.