The superconducting induction pump is a pumping system which moves electro-conductive liquid by using electromagnetism. It has the potential to be applied as the power system for the submarine ...propulsion and the pumping system for nuclear reactors. Since alternating current may generate more heat in the superconducting winding, it is extremely essential to analyze AC loss characteristics of the pumping system to avoid quenching phenomenon of superconducting tapes. In this article, a 2D-axisymmetric model of an annular linear induction pump which is composed of superconducting coils has been established by using T-A formulation. AC loss of superconducting coils under self-field and external alternating magnetic field have been studied. Meanwhile, the influence of some essential parameters such as the transmission current, coil turns have been analyzed as well. Results show that the arrangement position of coils in the pump plays an important role in determining the the AC loss of the superconducting winding. Meanwhile, self-field of the superconducting coils seems to have larger influence on the AC loss characteristics than the external alternating field. In conclusion, mechanism and relevant action laws of AC loss characteristics in the superconducting linear induction pump transported with three-phase alternating current and under the condition of external background AC field have been found in this article.
Knowledge of the formation conditions of Francevillian uranium and manganese ore deposits as well as natural fission reactors sheds light on the early evolution of the atmosphere between 1950 and ...2150 Ma ago. The model explaining the formation of the Oklo uranium deposits suggests that at the time of sediment deposition in the Franceville basin 2150 million years ago, the oxygen deficient atmosphere would have inhibited uranium dissolution. Dissolution of uranium was only possible during later diagenesis, approximately 1950 Ma. Reduction reactions in the presence of hydrocarbons allowed precipitation of dissolved uranium to U
4+, forming deposits with high enough uranium contents to trigger subsequent nuclear fission reactions. Such a model is in agreement with earlier suggestions that oxygen contents in atmosphere increased during a ‘transition phase’ some 2450–2100 Ma ago. The manganese deposits were formed before the uranium deposits, during the deposition of the black shales and very early diagenesis, and thus at a time when oxygen content in atmosphere was very low. Carbon isotopes data of organic matter show decrease of δ
13C upward in the Francevillian series (−20 to −46% PDB) reflecting the high CH
4 and low O
2 contents in the atmosphere during sediment deposition. This favoured anoxic conditions during deposition of the basinal FB black shales and likewise the migration of Mn over long distances. The manganese precipitated first as Mn-oxides at the shallow edges of the Franceville basin, in photic zones, where photosynthetic organisms flourished. Mn-oxides were then reduced in the black shales forming Mn-carbonates when conditions became more reducing during transgression episodes and/or the first stages of burial. In the black shales, reducing conditions prevailed until recent weathering, allowing the good preservation of organic matter and the Mn deposits. The present-day alteration is responsible for the dissolution of Mn-carbonates and precipitation of Mn-oxides at the water table to form the high grade Mn ore (45–50% Mn). Development of photosynthesizing organisms, a volcanic source of the Mn, and favourable palaeogeography of the Francevillian basins are all important parameters for the formation of the Mn deposits. For the occurrence of the natural nuclear reactors, the age of 2.0 Ga is the main parameter that controls the abundance of fissile
235U and the critical mass. Before 2.0 Ga the
235U/
238U ratio was sufficiently high for fission reactions to occur but conditions favourable for forming high grade uranium ores were not achieved. Then, after 2.0 Ga the increase of oxygen in the atmosphere commonly led to the formation of high grade uranium ores in which the
235U/
238U ratio was too low to support criticality.
The main objectives and principles in nuclear fission reactor safety are presented, e.g. the defence in depth strategy and technical principles such as redundancy, diversity and physical separation. ...After a brief historical review of the continuous development of safety improvement, the most recent international discussion is presented. This includes mainly the international activities within IAEA and its International Nuclear Safety Advisory Group (INSAG). The safety improvement, presented in recommendations of IAEA and INSAG is expressed as an improvement of all elements and all levels of the defence in depth concept. Special emphasis is put on improvement of the highest level, which requires the implementation of means to mitigate consequences of accidents with severe core damage. The different future concepts are briefly characterised. Some examples from the French–German safety approach are taken to demonstrate how requirements for safety improvement by means of an enhancement of the defence in depth principle are developed.
Reactors and Accelerators Morrissey, David J; Seaborg, Glenn T; Loveland, Walter D
Modern Nuclear Chemistry,
2017, 2017-03-27
Book Chapter
This chapter considers the general features of nuclear fission reactors, followed by the general features of charged‐particle accelerators, magnetic spectrometers, and the production of beams of ...radioactive nuclei. Nuclear fission reactors are devices that use controlled neutron‐induced fission to generate energy. The neutron inventory in a reactor is regulated by inserting control rods that contain a neutron‐absorbing material such as cadmium or boron in the fissioning assembly. The chapter considers three classes of ion sources that are used to produce positively charged ions and important features of nuclear collisions. Commercial neutron generators are compact charged‐particle accelerators designed to produce a beam of neutrons by an appropriate nuclear reaction. Positively charged particles must be accelerated to kinetic energies on the order of millions of electron volts (MeV) in order to overcome the Coulomb repulsion of another nucleus and induce a nuclear reaction.
Since the publication in 1964 of Techniques for Underwater Nuclear Power (NCEL TN-545), considerable research and development has been done which has changed the picture regarding the feasibility of ...using isolated reactors on the ocean bottom. This study considers in some detail the work on fouling, corrosion, and heat transfer accomplished by the C. F. Braun Company, Alhambra, California, under contract NBy-32274 (AD-626 185). Also considered are additional problems which might be encountered in using radioisotope decay heat in large (multi-kilowatt) generators or fuel cells in the deep ocean environment. A cursory up-dating of the known arts related in the earlier study is made, especially in referencing material which has recently become available. Possible areas for further investigation are delineated.
The McMaster Nuclear Reactor is a conventional pool-type research reactor. The reactor is currently licensed to operate at a maximum power level of one megawatt. The design power level is five ...megawatts. However, cooling capacity has been installed for only one megawatt. The reactor is fueled with 18 plate MTR type fuel elements. Each standard fuel element contains approximately 196 grams of U235 at 93% by weight enrichment.
► Fuel cladding is safety barrier and its material selection is reviewed. ► Design constraints include neutron absorption, radiation resistance and temperature. ► The effective neutron absorption was ...calculated for selected materials. ► Metallic and ceramic systems (Be, C, Mg, Zr, O, and Si) are potential new materials. ► We discussed the new candidate materials for various GIV reactors.
The growing understanding of the link between carbon emissions and global warming has been promoting a discussion on the environmental and safety viability of nuclear power generation. Current open fuel cycle reactors, however, result in low energy efficiency and produce large volumes of nuclear waste. More advanced nuclear reactors, which are currently under investigation, are expected to allow more efficient and safer use of nuclear energy. In all these cases, the fuel cladding is the most important safety barrier in fission nuclear reactors, as it restrains most of the radioactive fission products within its volume. The selection of fuel cladding material is based on many design constraints, such as neutron absorption cross section, service temperature, mechanical strength, toughness, neutron radiation resistance, thermal expansion, thermal conductivity, and chemical compatibility. The present paper reviews the selection of nuclear fuel cladding materials since the early reactors, illustrating some of the main failure modes and briefly discussing the challenges facing the development of fuel cladding materials for generation IV reactors.
Integrated surface heat flux data from each planet in our solar system plus over 50 stars, including our Sun, was plotted against each object's known mass to generate a continuous exponential curve ...at an R-squared value of 0.99. The unexpected yet undeniable implication of this study is that all planets and celestial objects have a similar mode of energy production. It is widely accepted that proton-proton reactions require hydrogen gas at temperatures of about 15 million degrees, neither of which can plausibly exist inside a terrestrial planet. Hence, this paper proposes a nuclear fission mechanism for all luminous celestial objects, and uses this mechanism to further suggest a developmental narrative for all celestial bodies, including our Sun. This narrative was deduced from an exponential curve drawn adjacent to the first and passing through the Earth's solid core (as a known prototype). This trend line was used to predict the core masses for each planet as a function of its luminosity.
•There is a common mass-luminosity relationship for planets, the Sun, and other stars.•This paper includes an exponential graph illustrating the functional similarity between all the planets in our solar system and over fifty other stars.•This research also produced another graph, which provided the deduced core masses of all the planets and stars that were examined.•The energy production mechanisms for all celestial objects are internal core fission reactors of diverse masses.
Ion beam analysis of materials in the PBMR reactor Malherbe, Johan B.; Friedland, E.; van der Berg, N.G.
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
April 2008, 2008-04-00, Letnik:
266, Številka:
8
Journal Article
Recenzirano
South Africa is developing a new type of high temperature nuclear reactor, the so-called pebble bed modular reactor (PBMR). The planned reactor outlet temperature of this gas-cooled reactor is ...approximately 900°C. This high temperature places some severe restrictions on materials, which can be used. The name of the reactor is derived from the form of the fuel elements, which are in the form of pebbles, each with a diameter of 60mm. Each pebble is composed of several thousands of coated fuel particles. The coated particle consists of a nucleus of UO2 surrounded by several layers of different carbons and SiC. The diameter of the fuel particles is 0.92mm. A brief review will be given of the advantages of this nuclear reactor, of the materials in the fuel elements and their analysis using ion beam techniques.
The present work aims at initiating the conceptual design of a small nuclear reactor intended to provide sufficient electrical power (˜150 kW) to maintain the "hotel" load of the Victoria-class ...submarine and extend her operational envelope. The scope of the design is to provide the nuclear reactor system with sufficient inherent safety features as to permit the operation of the nuclear reactor by crews with minimal training for automatic operation. Several constraints provide the framework for carrying out the design work, such as, among others, maintaining the excess reactivity of the reactor at safe values at all times, providing enough fuel and reactivity for meeting operational requirements, and keeping the size of the reactor core and shielding such as to fit within the hull of the existing vessel.
The final reactor concept, named the Near Boiling reactor, employs TRISO fuel particles in zirconium-sheathed fuel rods. The reactor is light water moderated and cooled. The core life is specifically designed to coincide with the refit cycle of the Victoria-class submarine. The reactor employs a simple and reliable control and shutdown system that requires little intervention on the part of the submarine's crew. Also, a kinetic model is developed that demonstrates the inherent safety features of the reactor during several accident scenarios. The low steady-state flux level of the reactor during normal operation results in very low negative reactivity after shutdown and eliminates any reactor dead time. The reactor is designed for automatic unattended control and does not require extensive training for its operators.
