Critical Experiment Design Phase 1 Report for Integral Request 441

This report documents the analytical methods used in the first phase of critical experiment design (CED-1) conducted as part of integral experiment request (IER) 441. The purpose of IER-441 is to develop a capability to test the epithermal/intermediate cross sections of materials at the Sandia National Laboratories (SNL) critical experiment facility using low enriched uranium oxide fuel. This effort determined that the capability can be achieved using a varying number of test samples placed in a central test region of a hexagonally pitched lattice driven with a more moderated exterior region. In general, the results show that it is possible to develop sufficient worth to measure any nuclear data deficiencies, as well as the ability to shift the neutron spectrum for dysprosium, hafnium, silver, tantalum, indium, cobalt, tungsten, and antimony. There is marginal capability to test manganese due to its relatively low worth at higher boron concentrations. At this stage, there is interest in identifying the material or materials of greatest interest to the nuclear data community so that this project can proceed to CED-2 with a clear goal.