Performance Testing of Dysprosium-Based Scintillation Screens and Demonstration of Digital Transfer Method Neutron Radiography of Highly Radioactive Samples

Abstract

Scintillator screens consisting of a dysprosium neutron converter and various scintillator materials were tested in the Heinz Maier-Leibnitz Zentrum Forschungsreaktor München II (FRM II) ANTARES cold neutron beam with the goal of finding a suitable screen for digital transfer method neutron radiography. This work explores the cold neutron response of 16 scintillator screens, 7 of which were previously tested with thermal neutrons. Light yield, signal-to-noise ratio (SNR), and spatial resolution were measured to compare the scintillator screens and determine which were best suited for digital transfer method neutron radiography. Screens with a zinc sulfide (ZnS:Cu) scintillator were most suitable for digital transfer method radiography based on light output, spatial resolution, SNR, and gamma-ray insensitivity. Spatial resolutions between 65 and 220 μm were measured. The top-performing screens were then used to demonstrate the feasibility of a new digital transfer method neutron radiography to image highly radioactive (8.84 Sv/h at ≈1 cm) nuclear fuel at Idaho National Laboratory's Neutron Radiography reactor (NRAD). These results suggest that digital transfer method neutron radiography can be used to indirectly image highly radioactive objects and/or use neutron beams with a large gamma-ray content on a timescale of ~10 min/image (~144 images/day), much faster than the >10 h required using the current transfer method with film (limited to ~14 radiographs/day at NRAD).