Delayed critical unreflected and unmoderated uranium metal single cylinder and interacting cylinders (two) for evaluation of a neutron transport method and associated cross-section data

Author

Robert H. Elwood

Date of Award

8-2001

Degree Type

Thesis

Degree Name

Master of Science

Major

Nuclear Engineering

Major Professor

John T. Mihalczo

Abstract

A variety of critical experiments were constructed with unreflected and unmoderated highly enriched uranium during the 1960s and 1970s at the Oak Ridge Critical Experiments Facility in support of criticality safety of the Y-12 National Security Complex. Of these hundreds of delayed critical assemblies, thirteen assemblies of two interacting cylinders with 11-in. diameters and five solid cylinders with diameters varying from 7 to 15 in. are documented here in much more detail than previously. The data presented here are used to verify calculation methods. The measured neutron multiplication factors K_eff, values, have an experimental uncertainty of less than Δke_eff= ±6.20E-04. The experiments are modeled using SCALE with KENO-VI. Three cross-section libraries and the KENO-VI Monte Carlo code are evaluated using these unreflected and unmoderated highly enriched uranium metal cylinders: Hansen-Roach, the 27-group, and the 238-group libraries. A fourth evaluation used the 238-group library with all known impurities. The statistical uncertainty of the calculations is less than or equal to Δke_eff= ± 0.0003. An examination of a comparison of the calculations shows rather small deviation from measured ke_eff values, with the largest deviation of a calculation from a measurement being Δke_eff= ± 0.0062. The average deviations of ke_eff values obtained with the Hansen- Roach, 27-group, and 238-group cross-section libraries from the measured values are - 0.0021, +0.0039, and -0.0042, respectively. With impurities explicitly modeled utilizing the 238-group cross-section library, the average deviation of ke_eff values is -0.0039. This evaluation shows the usefulness of this experimental data for verifying neutron transport methods and cross-section libraries.

Recommended Citation

Elwood, Robert H., "Delayed critical unreflected and unmoderated uranium metal single cylinder and interacting cylinders (two) for evaluation of a neutron transport method and associated cross-section data. " Master's Thesis, University of Tennessee, 2001.
https://trace.tennessee.edu/utk_gradthes/9607