Calculations of the Electron Energy Distribution Function in a Uranium Plasma by Analytic and Monte Carlo Techniques

Electron energy distribution functions were calculated in a U235 plasma at 1 atmosphere for various plasma temperatures and neutron fluxes. The distributions are assumed to be a summation of a high energy tail and a Maxwellian distribution. The sources of energetic electrons considered are the fission-fragment induced ionization of uranium and the electron induced ionization of uranium. The calculation of the high energy tail is reduced to an electron slowing down calculation, from the most energetic source to the energy where the electron is assumed to be incorporated into the Maxwellian distribution. The pertinent collisional processes are electron-electron scattering and electron induced ionization and excitation of uranium. Two distinct methods were employed in the calculation of the distributions. One method is based upon the assumption of continuous slowing and yields a distribution inversely proportional to the stopping power. An iteration scheme is utilized to include the secondary electron avalanche. In the other method, a governing equation is derived without assuming continuous electron slowing. This equation is solved by a Monte Carlo technique

The TITAN oscillating-field current-drive system

The TITAN study uses oscillating-field current drive (OFCD) for steady-state operation in a reversed-field-pinch (RFP) fusion reactor. A circuit model which simulates the plasma, first wall, blanket, and coils has been developed and applied to two TITAN reactor designs to assess OFCD efficiency and power-supply requirements. Methods for optimizing current-drive efficiency and minimizing power-supply requirements have been identified. 15 refs

The TITAN magnet configuration

The TITAN study uses copper-alloy ohmic-heating coils (OHC) to startup inductively a reversed-field-pinch (RFP) fusion reactor. The plasma equilibrium is maintained with a pair of superconducting equilibrium-field coils (EFCs). A second pair of copper EFCs provides the necessary trimming of the equilibrium field during plasma transients. A compact toroidal-field-coil (TFC) set is provided by an integrated blanket/coil (IBC). The IBC concept also is applied to the toroidal-field divertor coils. Steady-state operation is achieved with oscillating-field current drive, which oscillates at low amplitude and frequency the OHCs, EFCs, the TFCs, and divertor coils about their steady-state currents. An integrated magnet design, which uses low-field, low technology coils, and the related design basis is given. 18 refs

A preliminary systems assessment of the Starlite Demo candidates

The Starlite project has evaluated the following five tokamaks as candidates for the US Demo Power Plant: (1) steady state, first stability regime; (2) pulsed, first stability regime; (3) steady state, second stability regime; (4) steady state, reversed shear; and (5) steady state, low aspect ratio. Systems analysis of these candidates has played an important role in the selection of a reversed-shear tokamak for further conceptual design as a US Demo Power Plant. The cost-based systems analysis that led to the selection of a reversed-shear tokamak is described herein

Modeling of Nonseasonal Quarterly Earnings Data: Working Paper Series--05-17

We present new empirical evidence on the predictive power of statistically-based quarterly earnings expectation models for firms which exhibit nonseasonal quarterly earnings patterns. In marked contrast to extant work we find: 1) a considerably greater frequency of nonseasonal firms (36%) when compared to Lorek and Bathke (1984) (12%) and Brown and Han (2000) (17%), 2) the random walk model (RW) provides significantly more accurate pooled, one-step ahead quarterly earnings predictions across 40 quarters in the 1994-2003 holdout period than the first-order autoregressive model (AR1) popularized by Lorek and Bathke and Brown and Han, and 3) the RW model provides significantly more accurate quarterly earnings predictions for large nonseasonal firms than smaller nonseasonal firms. The latter finding documents a size-effect with respect to predictive ability for nonseasonal firms similar to that evidenced for seasonal firms. These findings are particularly salient to researchers in search of efficient statistically-based quarterly earnings expectation models since 129 of 296 (43.6%) sample firms are not covered by security analysts

EBTR design-point selection

The procedure used to select the design point for the ELMO Bumpy Torus Reactor (EBTR) study is described. The models used in each phase of the selection process are described, with an emphasis placed on the parametric design curves produced by each model. The tradeoffs related to burn physics, stability/equilibrium, electron-ring physics, and magnetics design are discussed. The resulting design point indicates a plasma with a 35-m major radius and a 1-m minor radium operating at an average core-plasma beta of 0.17, which at approx. 30 keV produces an average neutron wall loading of 1.4 MW/m/sup 2/ while maintaining key magnet (< 10 T) and total power (less than or equal to 4000 MWt) constraints

Magnetic divertor design for the compact reversed-field pinch reactor

A recently completed design of a pumped-limiter-based Compact Reversed-Field Pinch Reactor is used to estimate for the first time the impact of magnetic divertors. A range of divertor options for the low-toroidal-field RFP is examined, and a design selection is made constrained by consideration of field ripple (magnetic island), blanket displacement, recirculating power, cost, heat flux, and access. Design choices based on diversion of minority (toroidal) field lead to a preference for (poloidally) symmetric or bundle divertor geometries

Public perception and knowledge on nanotechnology: A study based on a citizen science approach

Even with the widespread use of nanomaterials (NMs) in everyday life, consumer knowledge about the functionality, benefits, and possible dangers of nanotechnology (NT) is still modest. As with any developing technology, its public perception has direct implications on future policies and has to be taken into account by academia and industry alike. As part of the “Nan-O-Style” interdisciplinary research project, an online survey was conducted using a Citizen Science-guided approach. The main goal was to evaluate the current levels of knowledge and the attitude towards NT among the general Austrian public and to determine how differing sociodemographic factors may affect these. Over the course of 17 months, a total of 1067 responses were collected and quantitatively analysed. We found that while Austrians display a generally optimistic view and a positive attitude towards NT, there are still remaining concerns about its safety and possible risks. Participants expressed great desire for more information about NT and its applications, as well as for clear labelling and transparency of products containing NMs. Notably, we found that age did not affect the general attitude towards NT nor the levels of NT awareness. While participants with a university degree were generally more knowledgeable on this specific topic, surprisingly, there were no significant differences in the attitude towards NT among people from different educational backgrounds. Similar to previous studies, we observed that male participants demonstrated a more positive attitude towards NT and scored slightly higher in our NT quiz compared to female participants. However, female participants voiced greater desire for more information and transparency regarding NMs. Interestingly, while participants with a negative attitude towards NT scored lowest on the NT quiz, they also expressed the least interest in receiving more NT-related information. This illustrates a difficulty in mitigating public aversion solely by providing more information

Reduction of worldwide plutonium inventories using conventional reactors and advanced fuels: A systems study

The potential for reducing plutonium inventories in the civilian nuclear fuel cycle through recycle in LWRs of a variety of mixed-oxide forms is examined by means of a cost-based plutonium-flow systems model that includes an approximate measure of proliferation risk. The impact of plutonium recycle in a number of forms is examined, including the introduction of nonfertile fuels into conventional (LWR) reactors to reduce net plutonium generation, to increase plutonium burnup, and to reduce exo-reactor plutonium inventories