We discuss here theoretical studies of magnetic acceleration of Compact Torus plasma rings in a coaxial, rail-gun accelerator. The rings are formed using a magnetized coaxial plasma gun and are accelerated by injection of B/sub theta/ flux from an accelerator bank. After acceleration, the rings enter a focusing cone where the ring is decelerated and reduced in radius. As the ring radius decreases, the ring magnetic energy increases until it equals the entering kinetic energy and the ring stagnates. Scaling laws and numerical calculations of acceleration using a O-D numerical code are presented. 2-D, MHD simulations are shown which demonstrate ring formation, acceleration, and focusing. Finally, 3-D calculations are discussed which determine the ideal MHD stability of the accelerated ring.

Americium-241 is widely used as a radiation source, but it also has some potential risk if taken into the body. Although the radiotoxicity of americium-241 is small compared to other transuranic actinides, its effects on the reproductive system and on development of the placenta are more damaging than the effects of plutonium-239. A previous report based on a worst-case scenario involving a hypothetical fire accident in a contaminated facility indicated that there could have been a significant impact on nearby residents from a unit release of americium-241 via atmospheric dispersion. However, because the facility is located in a rural region where most drinking water supplies are drawn from private wells, it is believed that deposition of americium-241 from the atmosphere might also have impacts via the groundwater pathway by infiltration of rainwater. In this analysis, a three-dimensional analytical mathematical model is used to assess several aspects of americium-241 contamination of groundwater, including radioactive transformation, advection, dispersion, and soil sorption. Simulation results indicate that no significant radiological impacts would occur to the nearby residents via the groundwater pathway. 15 refs., 2 figs., 2 tabs.

The calculation of kerma factors from known cross sections is not as simple as is often implied. The kerma factors are strongly influenced by the reaction mechanism assumed. An important example of this dependence on the reaction mechanism is the contribution of the /sup 12/C(n,n')3..cap alpha.. reaction to the total kerma in carbon. First, a short review will be given of the ENDF/B-V carbon cross sections which were used in the calculation of carbon kerma factors. Using the reaction channels implied in the ENDF/B-V evaluation, the contribution of various reactions to the total kerma factors in carbon will be given. A detailed analysis of the reaction mechanisms which could contribute to the (n,n')3..cap alpha.. reaction in carbon has been carried out. First their contribution to kerma, independent of cross section, will be calculated and then the initial spectra of alpha particles produced by the various reaction mechanisms will be given. A discussion of possible ways of experimentally distinguishing the reaction mechanisms will be made by comparing their different initial spectra and their variation in kerma with neutron energy. Finally, the event-size spectra for tissue-equivalent proportional counters will be presented, giving only the contributions from the (n,n')3..cap alpha.. reaction and its …

Large-diameter boreholes drilled at the Nevada Test Site for the Department of Energy frequently exhibit an elongation in response to the regional stress field. Single-axis, decentralized logging tools invariably migrate to the long axis of the hole while logging. The long axis is the roughest and is more frequently washed out. The design of these tools therefore ensures that the worst possible side of the borehole is being logged. A new line of geophysical logging tools has been developed at the suggestion of EG and G, Energy Measurements, Inc., to overcome the effect of borehole elongation. A pair of orienting arms set at 90/sup 0/ to the measurement axis effectively turn the tool so that measurements are always recorded on the smoother, short side of the borehole. 3 refs., 5 figs.

The three-dimensional diagnostic wind field model (MATHEW) and the particle-in-cell atmospheric transport and diffusion model (ADPIC) are used by the Atmospheric Release Advisory Capability to estimate the environmental consequences of accidental releases of radioactivity into the atmosphere. These models have undergone extensive evaluations against field experiments conducted in a variety of environmental settings ranging from relatively flat to very complex terrain areas. Simulations of tracer experiments conducted in a complex mountain valley setting revealed that 35 to 50% of the comparisons between calculated and measured tracer concentrations were within a factor of 5. This may be compared with a factor of 2 for 50% of the comparisons for relatively flat terrain. This degradation of results in complex terrain is due to a variety of factors such as the limited representativeness of measurements in complex terrain, the limited spatial resolution afforded by the models, and the turbulence parameterization based on sigma/sub theta/ measurements to evaluate the eddy diffusivities. Measurements of sigma/sub theta/ in complex terrain exceed those measured over flat terrain by a factor of 2 to 3 leading to eddy diffusivities that are unrealistically high. The results of model evaluations are very sensitive to the quality and the representativeness of …