Simulation and experiments on the feasibility of using gamma tomography for void fraction measurements in nuclear fuel bundle mock-ups

Abstract

The High-Resolution Gamma Tomography System (HRGTS) facility is under development at the University of Michigan. This system is planned generally for application to two-phase flow loops representing nuclear fuel bundles. These measurements should provide insight into fluid dynamics phenomena and high resolution data for validation of computational fluid dynamics (CFD) codes. The HRGTS is planned to be deployed in the Michigan Advanced Rod Bundle fLow Experiment (MARBLE). an adiabatic test loop consisting of an 8x8 square lattice arrangement. Simulations modeling MARBLE were performed to study how the counting statistics of the imaging process propagate into void fraction uncertainty. The simulation results showed that an accuracy of around 1% is expected with imaging times of 1 min. Computed tomography measurements were performed on partial mockups of the bundle geometry, which confirmed that the technique can be used to obtain accurate subchannel void fraction data in complicated and challenging measurement scenarios.