No description available.

No description available.

W. B. Nottingham. / "September 9, 1960." / Includes bibliographies. / Army Signal Corps Contract DA36-039-sc-78108. Dept. of the Army Task 3-99-20-001 and Project 3-99-00-000.

A transient code (TFETC) for calculating the temperature distribution throughout the radial and axial positions of a thermionic fuel element (TFE) has been successfully developed. It accommodates the variations of temperatures, thermal power, electrical power, voltage, and current density throughout the TFE as a function of time as well as the variations of heat fluxes arising from radiation, conduction, electron cooling, and collector heating. The thermionic fuel element transient code (TFETC) is designed to calculate all the above variables for three different cases namely: 1) Start-up; 2) Loss of flow accident; and 3) Shut down. The results show that this design is suitable for space applications and does not show any deficiency in the performance. It enhances the safety factor in the case of a loss of flow accident (LOFA). In LOFA, it has been found that if the mass flow rate decreases exponentially by a -0.033t, where t is a reactor transient time in seconds, the fuel temperature does not exceed the melting point right after the complete pump failures but rather allows some time, about 34 seconds, before taking an action. If the reactor is not shut down within 34 seconds, the fuel temperature may keep increasing until the melting point of the fuel is attained. On the other hand, the coolant temperature attains its boiling point, 1057 ��K, in the case of a complete pump failure and may exceed it unless a proper action to trip the reactor is taken. For 1/2, 1/3, and 1/4 pump failures, the coolant temperatures are below the boiling point of the coolant. / Graduation date: 1994

Graduation date: 1994

No description available.

An overall systems design code was developed to model an advanced in-core thermionic energy conversion based nuclear reactor system for space applications at power levels of 10 to 50 kWe. The purpose of this work was to provide the overall shell for the systems code and to also provide the detailed neutronic analysis section of the code. The design code that was developed is to be used to evaluate a reactor system based upon a single cell thermionic fuel element which uses advanced technology to enhance the performance of single cell thermionic fuel elements. A literature survey provided information concerning how other organizations performed system studies on similar space reactor designs. / Graduation date: 1994

Incore thermionic space reactor design concepts which operate at a nominal power output range of 20 to 50 kWe are described. Details of the neutronic, thermionic, thermal hydraulics and shielding performance are presented. Due to the strong absorption of thermal neutrons by natural tungsten, and the large amount of that material within the reactor core, two designs are considered. An overall system design code has been developed at Oregon State University to model advanced incore thermionic energy conversion based nuclear reactor systems for space applications. The code modules include neutronics and core criticality, a thermionic fuel element performance module with integral thermal hydraulics calculation capability, a radiation shielding module, and a module for the waste heat rejection. The results show that the driverless single cell ATI configuration, which does not have driver rods, proved to be more efficient than the driven core, which has driver rods. It also shows that the inclusion of the true axial and radial power distribution decrease the overall conversion efficiency. The flattening of the radial power distribution by three different methods would lead to a higher efficiency. The results show that only one thermionic fuel element (TFE) works at the optimum emitter temperature; all other TFEs are off the optimum performance and result in 40 % decrease of the efficiency of the overall system. / Graduation date: 1993

Preliminary nuclear design studies have been completed on ten configurations of nuclear reactors for low power (1-30 kWe) space applications utilizing thermionic energy conversion. Additional design studies have been conducted on the TRICE multimegawatt in-core thermionic reactor configuration. In each of the cases, a reactor configuration has been determined which has the potential for operating 7 years with sufficient reactivity margin. Additional safety evaluations have been conducted on these configurations including the determination of sufficient shutdown reactivity, and consideration of water immersion, water flooding, sand burial, and reactor compaction accident scenarios. It has been found, within the analysis conducted using the MCNP Monte Carlo neutron transport code, that there are configurations which are feasible and deserve further analysis. It has also been found that solid core reactors which rely solely on conduction for heat removal as well as pin type cores immersed in a liquid metal bath have merit. The solid cores look attractive when flooding and compaction accident scenarios are considered as there is little chance for water to enter the core and cause significant neutron moderation. A fuel volume fraction effect has also been found in the consideration of the sand burial cases for the SP-100 derived configurations. / Graduation date: 1994

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. Description based on print version record. Includes bibliographical references.