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oai:www.ideals.illinois.edu:2142/72834 2023-07-11 col_2142_5131 col_2142_14837 com_2142_5130 com_2142_14836 com_2142_234

Kozlowski, Tomasz McKenzie, George 2015-01-21T19:48:42Z 2015-01-21T19:48:42Z 2014-12 2015-01-21 2014-12 The Rossi-α method determines the prompt neutron decay constant in a nuclear fissioning system at or near delayed critical. Knowledge of the prompt neutron decay constant is important for a critical system as it is a major contributor to the dynamic system behavior. The classical method for the Rossi experiment used gated circuitry to track the time when a neutron was incident upon the detector. The downside of this method is that the circuitry was complex and only one single fission chain could be measured at a time. The modern method allows many chains to be measured simultaneously by a pulse time tagging system such as the LANL custom designed List-mode module. This thesis examines the implementation of the modern Rossi-α method on the all highly enriched uranium, HEU, Zeus experiment. Measurements are taken at several subcritical configurations, at critical in the presence of a source, and at one supercritical point. During the experiment, the List-mode module generates time tags of incoming neutron pulses. After the experiment, this list of neutron pulses is complied using custom software into a histogram. This histogram is fit using off the shelf graphing software to determine the value of α. The subcritical measurements of α are used to extrapolate α at delayed critical. The extrapolation determined the value of α at delayed critical to be α = 89910 s-1. This value is compared to the measured value of α at delayed critical which is determined to be α = 90408.4 s-1. These values differ by 0.55% which is remarkably good agreement. This thesis also examines the expected value of α using a Monte Carlo transport code, MCNP. MCNP determined the value of α at delayed critical to be 100048 ± 0.584 s-1. This result differs by 11.3% from the extrapolated value of α determined experimentally. When compared to systems with similar neutron spectra, the measured value of α fits well in comparison to historical measurements. Item withdrawn by Laura Spradlin (lspradl2@illinois.edu) on 2014-12-10T21:12:45Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 McKenzie_George.pdf: 1220634 bytes, checksum: eb6220761da0faa1a5da059a26934873 (MD5) McKenzie_George.pdf: 1223696 bytes, checksum: 32b0e33192cb0d0fe5300257eaaa142a (MD5) Made available in DSpace on 2015-01-21T19:48:42Z (GMT). No. of bitstreams: 1 George_McKenzie.pdf: 1223696 bytes, checksum: 32b0e33192cb0d0fe5300257eaaa142a (MD5) http://hdl.handle.net/2142/72834 en Copyright 2014 George McKenzie Reactor Physics Rossi Alpha Zeus Experiment Neutron Measurements Modern Rossi alpha measurements text Nuclear, Plasma, & Rad Engr 1973 Nuclear, Plasma, Radiolgc Engr 5183 University of Illinois at Urbana-Champaign Thesis M.S. MS: Nucl, Plasma, Rad Eng-UIUC 10KS5183MS