When target and projectile nuclei have a difference in neutron to proton ratio (N/Z), the quasiprojectiles formed in a deep inelastic collision (DIC) should have a mean N/Z between the N/Z of the target and the N/Z of the projectile, depending on the amount of N/Z equilibration that occurred. Data from six reaction systems at two beam energies (32 and 45 MeV/nucleon) were collected. The systems in order of increasing difference between target and projectile N/Z (shown in parentheses) are 40Ar + 112Sn (∆N/Z = 0.018), 48Ca + 124Sn (∆N/Z = 0.080), 48Ca + 112Sn (∆N/Z = 0.160), 40Ca + 112Sn (∆N/Z = 0.240), 40Ar + 124Sn (∆N/Z = 0.258) and 40Ca + 124Sn (∆N/Z = 0.480). The quasiprojectile N/Z was determined by two techniques. The first technique used the isotopically resolved fragments to reconstruct the quasiprojectile N/Z. The second technique, developed in this thesis, used fragment yield ratios and a simple equation to simultaneously fit all six systems to determine the quasiprojectile N/Z. Simulations and a filter of the FAUST (Forward Array Using Silicon Technology) acceptance were used to calculate neutron loss; this accounted for the difference between the two techniques. To study the fragmentation of quasiprojectiles the fragment yields were used to calculate the isobaric, isotopic, fractional and mean N/Z yields. The results showed that as neutron richness increased, more neutron-rich fragments were produced. In addition observation showed evidence for an inhomogeneous distribution of N/Z between the light charged particles (LCPs Z less than 3) and intermediate mass fragments (IMFs Z greater than 2). The theoretical results, which used different values of the symmetry energy, were compared to experimental data to determine which symmetry energy best represents the experimental data. The comparison showed the experimental data was the overall best fit with a lower value of the symmetry energy. These results were not conclusive and further investigation is required.

The effective Skyrme type interactions have been used in the mean-field models for several decades, and many different parameterizations of the interaction have been realized to better reproduce nuclear masses, radii, and various other data. Today, there are more experimental data of nuclei far from the B stability line. It is time to improve the prediction power of the Skyrme type effective nucleon-nucleon interactions. In this dissertation, we present the procedure of the fitting of the mean-field results to an extensive set of experimental data with some constraints on the Skyrme parameters and some approximations in the Hartree-Fock mean-field to obtain the parameters of the new Skyrme type effective interactions, namely, KDE and KDE0. We investigate the long-standing discrepancy of more than 20% between the values of the incompressibility coefficient Kn:m: obtained within relativistic and non-relativistic models. We show that this difference is basically due to the differences in values of the symmetry energy coefficient J and its slope L associated with the relativistic and non-relativistic models. We also present the results of fully self-consistent Hartree-Fock based Random Phase Approximation calculations for the centroid energies of the breathing modes in four nuclei, namely, 90Zr, 116Sn, 144Sm, 208Pb, obtained with our new Skyrme interaction KDE0. A good agreement with the experimental data is achieved.

This paper assesses the uncertainty associated with the utilization and implementation of advanced fuel cycles to control plutonium inventories. The specific fuel cycles investigated are a partially closed cycle utilizing MOX reactors and completely closed one-tier fuel cycles utilizing fast reactors. Multiple methods for assessing these uncertainties were utilized. A scenario approach that varied the time and number of the implementation of the advanced reactors was used. It was found that the implementation of 3 FR/yr with a CR of 0.5 could reduce the amount of Pu by over 36% in reference to building 3 LWR/yr. In addition to reducing the inventory with respect to the reference LWR case, the growth rate can be reduced from an initial 22 tons Pu/ year growth to 5 tons Pu / year growth with the 2030 actual initial Pu inventory implementation cases. The MOX cases keep the Pu/ TWhe inventory slightly above 1 ton Pu/TWhe and the extremely low CR FR cases even lower than that value. Thus from this work the extremely low CR FR scenarios show the greatest ability to control the growing Pu inventory. In addition to the scenario approach a Monte Carlo uncertainty model was developed and analyzed. The uncertainty analysis showed the high burn up cases are comparable with the of the low CR FR cases in there ability to control the Pu inventory with the Pu inventories ranging from 2500 tons of Pu to 7500 tons of Pu. However, for the high burn up cases the majority of the Pu is Out-Of-Pile as opposed to the FR cases where a considerable amount of the Pu is In-Pile. From a proliferation stand point, the low CR FR case is better at the controlling the Pu inventory because the total inventories are relatively the same for the majority of the runs, and the FR cases keep most of the Pu In-Pile rather than the high burn up cases which keep most of it Out-Of-Pile. Lastly, a brief economic uncertainty model was developed. The economic results show that the once-through cycle is the cheapest with over 50% of the test cases coming in cheaper than all of the FR and MOX cases. The FR cases come out to be the next cheapest with the MOX cases being the most expensive.

Cavitation is a significant concern for the reliable operation of a centrifugal pump. Liquid metal flow loops are used in nuclear, chemical, metal forming, and liquid metal dynamo applications. Understanding of the cavitation characteristics of liquid metals is increasingly important to the design and operation of these facilities. One recent field of cavitation research has developed for mercury flow in spallation targets used in neutron sources. To further the understanding of mercury cavitation, a review of the existing literature on water cavitation, liquid metal cavitation, and mercury cavitation is performed. The mechanics of cavitation and the analytical methods applied to cavitation problems are discussed and analyzed. Acoustic data from the centrifugal pump for the mercury flow loop at the Spallation Neutron Source in Oak Ridge National Laboratory are examined.

The hydrocyclone is commonly used to separate oil from water, and particulates from fluid streams in various process industries. Two-fluid hydrodynamic theory is used here to develop a model for hydrocyclone performance in the application of separation of helium bubbles larger than 30 micron in diameter from liquid mercury at system pressure near 1 bar. The application is related to high power liquid metal target development for proton beams used in spallation neutron sources.

The use of Bonner Sphere Spectrometer (BSS) is a well-established method of measuring the energy distribution of neutron emission sources. The purpose of this research is to apply the Generalized Regression Neural Network (GRNN), a kind of Artificial Neural Network (ANN), to predict the neutron spectrum using the count rate data from a BSS. The BSS system was simulated with the MCNP5 Monte-Carlo code to calculate the response to neutrons of different energies for each combination of thermal neutron detector and polyethylene sphere. One hundred and sixty-three different types of neutron spectra were then investigated. GRNN Training and testing was carried out in the MATLAB environment. In the GRNN testing, eight-one predicted spectra were obtained as outputs of the GRNN. Comparison with standard spectra shows that 97.5% of the prediction errors were controlled below 1%, indicating ANN could be used as an alternative with high accuracy in neutron spectrum unfolding methodologies. Advantages and further improvements of this technique are also discussed.

ANSI/ANS 8.3 “Criticality Accident Alarm System”, Appendix B states “Determining the adequacy of criticality alarm detector placement is far from an exact process”. With this statement in mind a novel method for establishing areas of acceptable Criticality Accident Alarm System (CAAS) coverage was developed and demonstrated utilizing Los Alamos’ Monte Carlo N-Particle Code 5 (MCNP5) in multigroup Adjoint. Validation of the methodology was shown in the comparison of benchmark calculations with empirical results of Sandia testing and with hand calculations utilizing ANS 8.3. Demonstration involved the determination of zones of CAAS coverage from detector sensitivity maps generated by MCNP5 for a conceptual geometry of a new storage facility involving homogenized concrete and BoroBond® slabs. Multiple detector coverage was further demonstrated through the superimposing of several maps corresponding to differing detector locations.

Thesis (MSc)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University OF MICHIGAN.

Thesis--University of Illinois. / Photocopy (positive) made by University Microfilms. Vita. Includes bibliographical references.