(552c) GEANT4 Simulation of Irradiation Facilities and Neutron Sources At University of Utah TRIGA for Nuclear Forensics and Detection

¹Andrew Steven Voyles, ²Haori Yang and ³Tatjana Jevremovic

Utah Nuclear Engineering Program (UNEP), The University of Utah,

50 S Central Campus Dr, MEB 2298, Salt Lake City, UT 84112

¹Undergraduate student in Nuclear Engineering Minor, ²Assistant Professor, ³Chair Professor and UNEP Director

¹andrew.voyles@utah.edu, ²haori.yang@utah.edu, ³tatjana.jevremovic@utah.edu

INTRODUCTION

GEANT4 (GEometry ANd Tracking, release 4) high-energy physics simulation toolkit was used to simulate neutron source signatures, as well as various irradiation ports of the University of Utah TRIGA facility (UUTR): central irradiator, thermal irradiator, fast neutron irradiation facility and some peripheral ports and components, such as fuel elements. Each of these ports has unique geometry and different neutron and gamma flux. Preliminary results for thermal irradiator and central irradiator, as well as for neutron sources are discussed in this paper, while the modeling of the remaining ports is underway.

Being able to quickly and accurately determine the source of various nuclear materials through known nuclear signatures is an essential requirement for successful nuclear forensics.  As a part of an ongoing project at UUTR, using GEANT4, we are developing comprehensive nuclear signature data sets and benchmark against corresponding nuclear experiments. This paper will discuss signatures of the various irradiation ports and samples irradiated in such ports at UUTR, signatures for the UUTR fuel element assemblies, and signatures of shielded and unshielded neutron and gamma sources.

RESULTS

Modeling of the thermal irradiation facility in GEANT4 has displayed successful planar neutron source, with correct physics and transport. As an example calculation, at 25cm from the sample, the absorbed dose for 0.154 μs irradiation time of aluminum sample from thermal irradiator is 1.39 · 10^4mrem/_hr.  The central irradiator model displays the similar results, for a cylindrical neutron source.

GEANT4 simulations of the Pu-Be neutron source shielded with paraffin and lead have been created. It is clear that the  paraffin and lead do an excellent job of shielding the neutrons and gammas

Conclusion

                A preliminary GEANT4 model (coupled with MCNP5 simulation for accurate representation of the neutron flux) was developed for the central irradiation port and thermal irradiation port at Utah TRIGA facility, as well as shielded Pu-Be neutron and gamma sources. Using MCNP5 to calculate flux-per-particle, our current GEANT4 model can simulate the irradiation of various samples. The next step is to expand the current model to include the fast neutron irradiation facility at Utah TRIGA facility. In addition, simulation results will be benchmarked against experimental results, to help make this application suitable for export, in the use of helping benchmark experiments in new facilities. Finally, histograms of energy spectra from samples will be implemented, to be able to export spectra for the nuclear signatures.

REFERENCES

1. Geant4: a toolkit for the simulation of the passage of particles through matter. CERN - the European Organization for Nuclear Research, 2011.

http://www.geant4.org/geant4/

2. OpenGL - The Industry’s Foundation for High Performance Graphics. Khronos Group, 2010.

http://www.opengl.org/

3. HepRep: a Generic Interface Definition for HEP Event Display Representables. Joseph Perl, Stanford Linear Accelerator Center, 2009. http://www.slac.stanford.edu/~perl/heprep/index.html

4. MCNP - A General Monte Carlo N-Particle Transport Code - Version 5. Monte Carlo Codes Group, Los Alamos National Laboratory, 2006.

http://mcnp-green.lanl.gov/