Passive Gamma-Ray Detection With Compact Lightweight Imager for Nuclear Safeguards

• Published in: IEEE transactions on nuclear science Vol. 69; no. 6; pp. 1336 - 1343
• Main Authors: Boo, Jihwan, Hammig, Mark D., Jeong, Manhee
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-06-2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aluminum; Ambient dose equivalent; Apertures; Arrays; Californium isotopes; Cameras; Cerium; coded aperture; Depleted uranium; Emitters; Energy resolution; Field of view; Gadolinium; Gallium; Gamma rays; gamma-ray imaging; Isotopes; mixed neutron-gamma environment; Neutrons; Nuclear accidents & safety; Nuclear energy; Nuclear safety; Power management; Radiation; Radiation dosage; Radioisotopes; Safety; Scintillation counters; Scintillators; Security; special nuclear material (SNM); Uranium
• DOI: 10.1109/TNS.2022.3167379
• EISSN: 1558-1578
• ISSN: 0018-9499

Localizing and quantifying special nuclear materials (SNMs) is desired for effective nuclear security and robust nuclear power management. Here, we demonstrate a compact radiation imaging system based on a coded aperture that allows one to form a quantified radionuclide distribution map for small amounts of SNM. The imager is based on the active scintillating medium: cerium-doped gadolinium aluminum gallium garnet [Gd 3 Al 2 Ga 3 O 12 (Ce) or GAGG(Ce)], which even in arrayed form exhibits excellent detection efficiency and good energy resolution over a wide energy range. With a <inline-formula> <tex-math notation="LaTeX">12 \times12 </tex-math></inline-formula> array of <inline-formula> <tex-math notation="LaTeX">4\times 4\times20 </tex-math></inline-formula> mm 3 pixels, the instrument can image, at a target-to-imager separation of 1 m, 1 g of highly enriched uranium (HEU) in 4 min, 75 g of depleted uranium (DU) within 11 min, and 100 g of uranyl nitrate hexahydrate (UNH) within 11 min. The instrument, termed EPSILON-G , can also measure the ambient dose equivalent, H*(10), for radionuclides inside the unit's 45° field of view (FOV), allowing one to accurately reconstruct the radiation dose map inside buildings. The system provides a precise determination of the H*(10) within a short acquisition time when compared to a Geiger-Muller (GM) survey meter due to the sizable area of the GAGG(Ce) scintillator array and its high density and <inline-formula> <tex-math notation="LaTeX">Z_{\text {eff}} </tex-math></inline-formula>. Furthermore, one can identify, in real time, by means of gamma-ray detection, the accurate locations of neutron-gamma sources, as demonstrated with mixed emitters 252 Cf, 239 PuBe, and 241 AmLi all while maintaining a gamma-ray analytical capability.