SYSTEM STUDIES OF FISSION-FUSION HYBRID MOLTEN SALT REACTORS

This work proposes and evaluates a Fission-Fusion Hybrid Molten Salt Reactor (FFHMSR), combining two subsystems, a deuterium + tritium (DT) fusion reactor surrounded by a neutron-absorbing Fusion Blanket (FB) and a critical Molten Salt fission Reactor (MSR). The molten salt, which contains dissolved actinides, circulates at a high rate between them. As envisioned the MSR exhibits the large Conversion Ratio of graphite moderated reactors having small fissile and large fertile inventories. DT fusion neutrons irradiating actinides in the molten salt release additional neutrons which increase isotope conversion and fission. Actinide fuel is continually added while fission products are continually removed so the system\u27s operation never requires refueling interruptions. The choice of molten salt as a eutectic mixture of the fluorides of lithium, sodium, and actinide fuel is explained by eliminating other options. System behavior is explored through simulations invoking modules from the Scale 6.1 code package. Modules include ORIGEN which simulates evolution over time of an isotope inventory and others for neutronics transport, criticality and cross section weighting. The simulation automatically adjusts the ratio of fission to fusion power to maintain MSR criticality, implemented through FORTRAN codes and associated files developed as part of this work. Simulations showed actinide inventories stabilizing to steady levels while fresh actinide fuel from feedstocks of Spent Nuclear Fuel or uranium-238 or thorium-232 continued to be added and fissioned. Required fusion was less than 1% of total power and adequate tritium breeding was obtained. The non-removal strategy was also tried with long-lived fission products (FPs) with the mixed results that some inventories stabilized while others did not. FFHMSR benefits of consuming all actinides and some long-lived FPs are that waste issues are ameliorated while available fission energy is increased by two orders of magnitude. Proliferation resistance is enhanced by the absence of fuel reprocessing and related transportation, by low fissile inventories and by denaturing all fissile by nonfissile isotopes. Safety is enhanced by liquid fuel characteristics allowing emergency draining of fuel to a passively cooled safe location while also providing a stronger negative power coefficient than feasible with solid fuel

Optimal Designs of Mobile Nuclear Engines to Power Manned Vehicles On Mars

This work develops original conceptual designs for compact nuclear fission reactor engines to power robust mobile equipment operating on the surface of the planet Mars. This is a nuclear application area not well explored in previous publications. Some novel analytical approaches are developed herein, including the application of optimal control theory to minimize radiation shielding mass. This work also provides the first study of using another planet\u27s atmosphere to implement open-cycle thermal conversion systems. To power equipment on Mars for extended durations at sustained power levels ranging from one hundred horsepower to several thousand horsepower, there is no practical alternative to a nuclear fission heat source. Design difficulties arise from mobility\u27s need to restrict engine size and mass, each of which is, in turn, determined by the schemes chosen for thermal conversion waste heat rejection and for neutron and gamma radiation shielding. The conceptual design solutions pursued herein entirely avoid a large waste heat rejection radiator or low pressure heat exchanger by instead using the martian air directly as the thermal conversion fluid. This Open Brayton Cycle implementation unconventionally employs large-diameter radial-flow compressor/turbine designs for the lower pressure air-flow stages in order to obtain sufficient efficiency from the low pressure martian air. Design prescriptions and analyses for these rotating components are included. The radiation shielding mass has been minimized by numerical algorithms developed as part of this work to solve the Euler-Lagrange equations for a minimum mass shield meeting stated radiation leakage requirements. In addition, a risk-balancing approach is taken to setting those radiation requirements in order to avoid excessive conservatism

Transcendental

“The past exists only in our memories, the future only in our plans. The present is our only reality. The tree that you are aware of intellectually, because of that small time lag, is always in the past and therefore is always unreal. Any intellectually conceived object is always in the past and therefore unreal. Reality is always the moment of vision before the intellectualization takes place. There is no other reality.” (Pirsig, 247) The world comes to us though our senses. Sight, sound, smell, touch, and taste allow us to bridge the gap between the physical elements that exist in this universe. This physical interaction solidifies and confirms our reality. How do we know we are really ourselves and not some figment of our own imaginations? Quite simply, because we can see, hear, feel, etc

Definition of spacecraft standard interfaces by the NASA Space Assembly and Servicing Working Group (SASWG)

The purpose of the NASA Space Assembly and Servicing Working Group (SASWG) is to study enabling technologies for on-orbit spacecraft maintenance and servicing. One key technology required for effective space logistics activity is the development of standard spacecraft interfaces, including the 'Basic Set' defined by NASA, the U.S. Space Command, and industry panelists to be the following: (1) navigation aids; (2) grasping, berthing, and docking; and (3) utility connections for power, data, and fluids. Draft standards have been prepared and referred to professional standards organizations, including the AIAA, EIA, and SAE space standards committee. The objective of the SASWG is to support these committees with the technical expertise required to prepare standards, guidelines, and recommended practices which will be accepted by the ANSI and international standards organizations, including the ISO, IEC, and PASC

Adaptive Locomotion: The Cylindabot Robot

Adaptive locomotion is an emerging field of robotics due to the complex interaction between the robot and its environment. Hybrid locomotion is where a robot has more than one mode of locomotion and potentially delivers the benefits of both, however, these advantages are often not quantified or applied to new scenarios. The classic approach is to design robots with a high number of degrees of freedom and a complex control system, whereas an intelligent morphology can simplify the problem and maintain capabilities. Cylindabot is designed to be a minimally actuated hybrid robot with strong terrain crossing capabilities. By limiting the number of motors, this reduces the robot's weight and means less reinforcement is needed for the physical frame or drive system. Cylindabot uses different drive directions to transform between using wheels or legs. Cylindabot is able to climb a slope of 32 degrees and a step ratio of 1.43 while only being driven by two motors. A physical prototype and simulation models show that adaptation is optimal for a range of terrain (slopes, steps, ridges and gaps). Cylindabot successfully adapts to a map environment where there are several routes to the target location. These results show that a hybrid robot can increase its terrain capabilities when changing how it moves and that this adaptation can be applied to wider environments. This is an important step to have hybrid robots being deployed to real situations

The Bauschinger effect

If a work-hardenable metal is deformed plastically by a tensile stress +σ₀ and unloaded, its mechanical properties become anisotropic; in particular, though its tensile yield stress is now +σ₀, it will deform plastically if compression stresses numerically smaller than σ₀ are applied. This is known as the Bauschinger effect (Bauschinger 1886). When this research was commenced, very few experiments had previously been carried out to elucidate the effect as a function of the several possible variables and there was practically no satisfactory theory, except perhaps that of Masing (1923), which in any case could be severely criticised on purely theoretical grounds. It was clear that various classes of metals would probably show different types of effect. In particular the metals with face-centred and body-centred cubic lattices which deform by slip only, should show a very different effect from that exhibited by the metals of hexagonal lattice, where twinning plays an important part in the deformation. Single crystals might well show a different effect from polycrystals. In nominally pure metals the effect might well depend on grain size, elastic anisotropy, amount of previous work-hardening, temperature, purity, magnetic properties, degree of preferred orientation of a polycrystal, and orientation of a single crystal. In alloys the situation might be even more complex, especially if more than one phase were present. For the purposes of this present research it was decided to examine the effect thoroughly and systematically in polycrystalline metals deforming entirely by slip, and to carry out exploratory experiments on other metals and in other conditions, including in particular, polycrystalline hexagonal metals and single crystals. Studies of macroscopic mechanical properties alone are not usually very conclusive in establishing the mechanism of the physical processes occurring, and it seemed very desirable to obtain additional information by examining the accompanying changes of other physical properties. Some experiments on these lines are discussed in sections III and V. The exploratory experiments of sections III, V, VI and VIII were deliberately restricted usually to one metal under well-defined conditions, in view of limitations of time. It is hoped to extend these experiments in the near future

A Novel Demountable TF Joint Design for Low Aspect Ratio Spherical Torus Tokamaks

A novel shaped design for the radial conductors and demountable electrical joints connecting inner and outer legs of copper TF system conductors in low aspect ratio tokamaks is described and analysis results are presented. Specially shaped designs can optimize profiles of electrical current density, magnetic force, heating, and mechanical stress

The development of an improved kinetic flow technique and its application to the pyrolysis of methyl bromide

The first object of this work was to produce a technique of analysing continuously the exit gases of flow reactors under conditions where the extent of decomposition is small, and to do this with particular reference to the small changes in reactant concentration. This was preferred to analysis for products since the translation of the data for the latter into kinetic rate equations requires a knowledge or assumptions of the stoichiometry. The second aim of the work was to apply the technique to typical systems as used for bond dissociation energy determinations and test the method on a reaction of importance. 2, Details have been given of the development of the system where the analyses can be performed mass spectrometrically and continuously on both the inlet and exit gases, with about 30 seconds between each sampling. The technique minimises the chance that variations in flow conditions or changes in reactor efficiency will pass undetected, it permits also variations in kinetic parameters to be studied without opening up the reactor but merely by altering the variables and waiting for new steady state conditions. In order to deal with the small variations in the large signals given by the reactant decomposition, an electrical backing off device was used after sufficient stability had been obtained. The details of this have been given. 3. In order to check the flexibility of the technique, the thermal decomposition of methyl bromide in excess toluene, previously investigated by Szwarc, was carried out in the flow system. 4. It was shown experimentally that the rate of decomposition of the methyl bromide was given by: -d [MeBr]/dt = {k₀ + k[sub]T[Toluene] + K[sub]A[Argon]} [MeBr] when using up to 0.1 mm CH₃Er in about 1 mm of toluene and 1 mm of argon carrier gas. The reaction was shown to be surface dependent and was studied in two furnaces of different S/V ratio. 5. Methods of analysis of the data have yielded k₀, k[sub]T and k[sub]A. The temperature coefficient of k₀ has been shown to be k₀ = 10 ¹¹·⁸⁶ exp (-66,700/RT) sec ⁻¹ in the range 960° 1090° . The activation energy from the K[sub]T temperature variation is 63.2 k.cals/mole. 6. The kinetic data-have been discussed and k₀ is ascribed to the first order decomposition process while the second term has been considered to be a surface reaction. The snail increase of the rate with rise in argon pressure is thought to be caused by increases in the steady state concentration of hydrogen atoms, due to argon impeding the partial wall removal of this entity, 7. The activation energy of 66,7 k.cals/mole for the unimolecular decomposition has been compared with other data on D(CH₃ - Br). 8. Finally, suggestions have been made for further work in the study of this reaction to aid a more complete understanding of the apparently complex mechanism involved

HadISD: a quality-controlled global synoptic report database for selected variables at long-term stations from 1973--2011

[Abridged] This paper describes the creation of HadISD: an automatically quality-controlled synoptic resolution dataset of temperature, dewpoint temperature, sea-level pressure, wind speed, wind direction and cloud cover from global weather stations for 1973--2011. The full dataset consists of over 6000 stations, with 3427 long-term stations deemed to have sufficient sampling and quality for climate applications requiring sub-daily resolution. As with other surface datasets, coverage is heavily skewed towards Northern Hemisphere mid-latitudes. The dataset is constructed from a large pre-existing ASCII flatfile data bank that represents over a decade of substantial effort at data retrieval, reformatting and provision. These raw data have had varying levels of quality control applied to them by individual data providers. The work proceeded in several steps: merging stations with multiple reporting identifiers; reformatting to netCDF; quality control; and then filtering to form a final dataset. Particular attention has been paid to maintaining true extreme values where possible within an automated, objective process. Detailed validation has been performed on a subset of global stations and also on UK data using known extreme events to help finalise the QC tests. Further validation was performed on a selection of extreme events world-wide (Hurricane Katrina in 2005, the cold snap in Alaska in 1989 and heat waves in SE Australia in 2009). Although the filtering has removed the poorest station records, no attempt has been made to homogenise the data thus far. Hence non-climatic, time-varying errors may still exist in many of the individual station records and care is needed in inferring long-term trends from these data. A version-control system has been constructed for this dataset to allow for the clear documentation of any updates and corrections in the future.Comment: Published in Climate of the Past, www.clim-past.net/8/1649/2012/. 31 pages, 23 figures, 9 pages. For data see http://www.metoffice.gov.uk/hadobs/hadis