Experimental evaluation of fuel rod pattern analysis in fuel assembly using Yonsei single-photon emission computed tomography (YSECT)

Optimization of Yonsei Single-Photon Emission Computed Tomography (YSECT) Detector for Fast Inspection of Spent Nuclear Fuel in Water Storage

“…It might be due to the relatively poor image spatial resolution caused by the utilization of larger-sized GAGG scintillators instead of small-sized semiconductors. However, we expect that these unexpected image intensities visible near the true source positions can be removed by applying the machine-learning-based de-noised image reconstruction technique or a threshold method that displays pixels only for intensities higher than a specific threshold, as proposed in our previous study [8,9]. With the present results, we confirmed that YSECT.v.2 can be employed for much-higher-speed inspection of SNF assemblies in water than would be possible with PGET while providing similar source discrimination probability.…”

“…In our previous study, we designed a highly sensitive bismuth germanate (BGO) scintillator-based GET detector using Monte Carlo (MC) simulation [7]; later, we developed a machine-learning-based de-noised image reconstruction technique to improve poor tomographic image spatial resolution caused by utilization of larger-sized BGO scintillators instead of small-sized semiconductors [8]. Through both of these studies, we experimentally validated the feasibility of rod-by-rod verification of a test fuel assembly with our prototype GET system, named Yonsei single-photon emission computed tomography (YSECT), which consists of 64-channel trapezoidal-shaped BGO scintillator-based detectors with parallel-hole tungsten collimators [9]. Despite the suc-cessful proof-of-principle, these studies [7][8][9] also have limitations for the on-site application in nuclear power plants.…”

“…In our previous study, the scintillator geometry of YSECT.v.1 was designed for high gamma-detection probability for the 137 Cs source in air and for high OP-collection efficiency when coupled with a commercial 3 mm × 3 mm SiPM. Based on the results, we determined the width, length, and front and back heights of the scintillators as 3, 40, 40, and 3 mm, respectively [7,9]. The 30 mm × 70 mm plane-shaped 137 Cs source emitted 662 keV gammas toward the scintillator in a box filled with water.…”

“…Through both of these studies, we experimentally validated the feasibility of rod-by-rod verification of a test fuel assembly with our prototype GET system, named Yonsei single-photon emission computed tomography (YSECT), which consists of 64-channel trapezoidal-shaped BGO scintillator-based detectors with parallel-hole tungsten collimators [9]. Despite the suc-cessful proof-of-principle, these studies [7][8][9] also have limitations for the on-site application in nuclear power plants. As shown in our MC simulation study [7], it was difficult to discriminate the SNF source distribution in the central region of the assembly in water with the YSECT detector, due to the high attenuation and scatter probability of the emitted gammas and the lack of any correction technique.…”