The Design of an Imager to Safeguard Spent Fuel Using Passive Fast Neutron Emission Tomography

Author

Anagha Srikanth Iyengar, University of TennesseeFollow

Date of Award

5-2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Energy Science and Engineering

Major Professor

Jason Hayward

Committee Members

Paul Hausladen, Lawrence Heilbronn, Howard Hall

Abstract

Safeguarding spent fuel in spent fuel pools, during transportation, and at dry cask storage sites has been a continuing priority for the International Atomic Energy Agency (IAEA.) The IAEA implements partial defect testing on all easily dismountable fuel before transfer to difficult-to-access storage. This project is focused on developing a new imaging capability using fast neutron emission tomography in support of the IAEA’s mission. The capability is intended to address the buildup of spent fuel inventories around the world from decommissioning activities by creating an efficient and effective tool for verification of a variety of fuel types for long-term disposition.While the sensitivity of gamma emission tomography is limited by self-attenuation, neutron measurements may have better sensitivity for resolving individual pins toward the center of larger fuel assemblies. Because the neutron signal originates primarily from ²⁴⁴Cm, which is sensitive to exposure, this method could also be sensitive to assemblies containing fuel pins replaced after a single cycle in the reactor and subsequently irradiated in the core. This work describes a set of simulation and measurement work completed in order to investigate and converge on the final design of a fast neutron emission tomography system for imaging a spent nuclear fuel assembly. To conduct a constrained optimization for the design, a range of imager design parameters were identified to be varied, and MCNP was used to build hundreds of geometries to investigate. The analysis was split in two components for gamma or neutron analysis. Simulations and proof-of-concept measurements presented here suggest that it is viable to build a compact equivalent to a parallel slit collimator imager that has sufficient spatial resolution to image spent fuel pins. Furthermore, it is expected to be able to withstand the high photon rates present in the relevant environment. Recommended future work is also discussed.

Recommended Citation

Iyengar, Anagha Srikanth, "The Design of an Imager to Safeguard Spent Fuel Using Passive Fast Neutron Emission Tomography. " PhD diss., University of Tennessee, 2019.
https://trace.tennessee.edu/utk_graddiss/5343