Peter J. Jaegers

Analysis of the first three Zeus critical experiments

Abstract The Zeus experiments have been designed to test the adequacy of 235U cross sections in the intermediate-energy range. Detailed models of the three Zeus critical experiments are developed for the MCNP Monte Carlo code, and calculated results, based on cross sections derived from ENDF/B-V and ENDF/B-VI, are presented and assessed. A series of modeling simplifications then is described that transforms the detailed representations into benchmark configurations, and the reactivity impact of each of those simplifications is assessed.

Criticality characteristics of mixtures of plutonium, silicon dioxide, Nevada tuff, and water

The parameters that determine when critical mixtures of {sup 239}Pu, SiO{sub 2}, and water and mixtures of {sup 239}Pu, Nevada tuff, and water are capable of sustaining an increasing neutron chain reaction as may be caused by a positive void coefficient at constant temperature are established. A single canister is considered that is loaded with up to 75 kg of {sup 239}Pu. A survey of critical spherical mixtures of plutonium, SiO{sub 2}, tuff, and water at constant temperature is created and these results are examined to determine the mixtures that might be autocatalytic. Regions of criticality instability are identified that have the possibility of autocatalytic power behavior. A positive void coefficient is possible for a very limited range of wet systems.

Critical mass experiment using U-235 foils-SiO{sub 2}-polyethylene plates

Fissile material in waste is frequently encountered in decontamination and decommissioning activities. Thousands of drums containing radioactive waste are stored in storage facilities throughout the DOE complex. The amount of fissile material in each drum is generally small because of the criticality safety limits that have been calculated using neutron transport computer codes such as MCNP, KENO, or ONEDANT. No experimental critical data are available to assure the correctiveness of the calculations for those systems containing fissile material (U-235, U-233, and Pu-239) in contact with matrix material (Al{sub 2}O{sub 3}, CaO, MgO, and SiO{sub 2}) in the drums. The purpose of the U-235 foil-SiO{sub 2}-polyethylene experiment is to provide experimental data to validate the computer transport codes and the cross section data.