Critical Experiment Design Phase 2 Report for Integral Request 304

Abstract

This report documents the second phase of critical experiment design (CED-2) 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's) 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 in a central test region of a hexagonally pitched lattice driven with a more moderated exterior region. The hollow test region can be changed to either contain a pure aluminum wall or a wall that incorporates a cadmium thermal flux filter. This report documents the development of final anticipated critical configurations using tantalum as the test sample material. Using the anticipated critical configurations, estimates of the experimental uncertainties and sensitivities of materials are performed in keeping with the CEdT process. A list of the new hardware necessary to perform the experiment is included.

Integral Experiment Request 554 CED-1 Summary Report

“…This is proven by several previously published benchmarks in the ICSBEP Handbook as LEU-COMP-THERM-78 (LCT-78) [5] and the forthcoming LCT-102 [6]. Other efforts are ongoing to design new experiments, such as IER-304 [7] and IER-441 [8], in different steps of the CEdT integral experiment request process [9]. Therefore, adding these B 4 C experiments to the ICSBEP Handbook [2] would greatly benefit the community.…”

“…Ten critical configurations are described in this report, each with a different neutron absorber plate inserted in its center or a different lattice configuration. The starting rod configuration of the assembly is based on the IER-304 CED-2 report [7], case 9 of which shows a critical configuration using the 7uPCX fuel rods, with six central horizontal rows of fuel rods removed and replaced with water. In the first nine configurations described in this report, the neutron absorber plates are inserted in this central water channel.…”

“…Figure 2 shows the fuel rod layout in this assembly for case 9 of IER-304 CED-2 report [7], which is the s starting point of this study. The neutron absorber plates are placed vertically in the central channel, thus decreasing the assembly reactivity, and the fuel rod configuration is arranged to achieve criticality.…”