Verification of the ADDER Fuel Management Code for MITR-II Fuel Management Analysis

Abstract

The Massachusetts Institute of Technology Reactor (MITR-II) is a 6 MWth research reactor with highly enriched uranium fuel. Due to the proliferation concerns of civilian HEU use, the MIT Nuclear Reactor Laboratory is actively participating in the US High Performance Research Reactor (USHPRR) program, which seeks to transition the remaining HEU fueled research reactors to newly developed LEU fuel. As part of the USHPRR program, the Advanced Dimensional Depletion for Engineering of Reactors (ADDER) software is being developed at Argonne National Laboratory for research reactor fuel management, and is being analyzed here as a replacement for the MCODE-FM currently used for MITR-II fuel management. This work performed code-to code comparison of MCODE and ADDER for actually operated core configurations, expanding on previous work done on fresh HEU and LEU core configurations. This study showed satisfactory agreement between MCODE and ADDER results. While the predicted critical bank heights at each time step were subtly different between the codes, the differences are nearly all within the 200 pcm acceptance band set in the criticality search algorithms, and are less than the differences between modeled and actual bank heights, so are acceptable. All runs showed an end of cycle U-235 mass discrepancy between MCODE and ADDER less than 0.5 g per element, and no other isotope had a discrepancy greater than 3% per element. Neutron flux and fission density had similarly minor differences. This overall close agreement indicates that for actual fuel management tasks, ADDER is a suitable replacement for MCODE.