Developing Experimental and Computational Nuclear Forensics Signals of Fast Neutron Irradiation Facility At TRIGA Reactor

Developing Experimental and Computational Nuclear Forensics Signals of Fast Neutron Irradiation Facility at TRIGA Reactor

Ian Schwerdt, Joseph Levinthal, Chris Dances, Dong-OK Choe, Haori Yang, and Tatjana Jevremovic

Nuclear Engineering Program, The University of Utah

Abstract

Over 230 research reactors are operating on campuses and labs across the globe. These research reactors are diverse in their design, fuel type, power, and fuel enrichment.  Most TRIGA reactors use Uranium Zirconium Hydride (UZrH) fuel that initially was designed to contain High-Enriched Uranium (HEU). Majority have been converted into low-enriched uranium (LEU) fuel. Fast neutrons can be used in several applications such as neutron hardness experiments for electronics and material tests. Accurate neutron flux and radiation dose measurements and computational estimates in reactors’ irradiation facilities are of great importance for producing accurate nuclear signals of interest to nuclear forensics.

The University of Utah houses a 100 kW TRIGA reactor (UUTR), with one of four irradiators such as the Fast Neutron Irradiation Facility (FNIF), thermal irradiation facility (TI) and other ports. The FNIF provides a neutron spectrum that approximates a fission spectrum. This paper presents experimental measurement and GEANT4 simulation of the neutron flux map in the UUTR’s FNIF, therefore creates a signature of this facility for future experiments and sample irradiation data analysis. The measurements were based on the activation of sulfur pellets positioned at the core side of the FNIF. These values are directly correlated to neutron flux and allows its mapping of the FNIF. The GEANT4 model of the FNIF provided neutron flux distribution with good agreement in comparison to the measured flux map. Further work will consist of a more detailed reactor model in GEANT4 and further data analysis of the P-32 samples to develop reliable and functional data to provide accurate nuclear forensics signatures.

Key words: nuclear forensics, research reactor, TRIGA, fast neutron transport, GEANT4, flux map