• Journal of Radiation Protection and Research
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• v.46 no.4
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• pp.204-212
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• 2021

Background: Identification of radioisotopes for plastic scintillation detectors is challenging because their spectra have poor energy resolutions and lack photo peaks. To overcome this weakness, many researchers have conducted radioisotope identification studies using machine learning algorithms; however, the effect of data normalization on radioisotope identification has not been addressed yet. Furthermore, studies on machine learning-based radioisotope identifiers for plastic scintillation detectors are limited. Materials and Methods: In this study, machine learning-based radioisotope identifiers were implemented, and their performances according to data normalization methods were compared. Eight classes of radioisotopes consisting of combinations of ²²Na, ⁶⁰Co, and ¹³⁷Cs, and the background, were defined. The training set was generated by the random sampling technique based on probabilistic density functions acquired by experiments and simulations, and test set was acquired by experiments. Support vector machine (SVM), artificial neural network (ANN), and convolutional neural network (CNN) were implemented as radioisotope identifiers with six data normalization methods, and trained using the generated training set. Results and Discussion: The implemented identifiers were evaluated by test sets acquired by experiments with and without gain shifts to confirm the robustness of the identifiers against the gain shift effect. Among the three machine learning-based radioisotope identifiers, prediction accuracy followed the order SVM > ANN > CNN, while the training time followed the order SVM > ANN > CNN. Conclusion: The prediction accuracy for the combined test sets was highest with the SVM. The CNN exhibited a minimum variation in prediction accuracy for each class, even though it had the lowest prediction accuracy for the combined test sets among three identifiers. The SVM exhibited the highest prediction accuracy for the combined test sets, and its training time was the shortest among three identifiers.

• Nuclear Engineering and Technology
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• v.49 no.7
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• pp.1369-1378
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• 2017

The present paper reports the development of a computational code based on the Adaptive Group of Ink Drop Spread (AGIDS) for reconstruction of the neutron noise sources in reactor cores. AGIDS algorithm was developed as a fuzzy inference system based on the active learning method. The main idea of the active learning method is to break a multiple input-single output system into a single input-single output system. This leads to the ability to simulate a large system with high accuracy. In the present study, vibrating absorber-type neutron noise source in an International Atomic Energy Agency-two dimensional reactor core is considered in neutron noise calculation. The neutron noise distribution in the detectors was calculated using the Galerkin finite element method. Linear approximation of the shape function in each triangle element was used in the Galerkin finite element method. Both the real and imaginary parts of the calculated neutron distribution of the detectors were considered input data in the developed computational code based on AGIDS. The output of the computational code is the strength, frequency, and position (X and Y coordinates) of the neutron noise sources. The calculated fraction of variance unexplained error for output parameters including strength, frequency, and X and Y coordinates of the considered neutron noise sources were $0.002682{\sharp}/cm^3s$, 0.002682 Hz, and 0.004254 cm and 0.006140 cm, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.5
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• pp.639-642
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• 2013

In this paper, proposed NED(nuclear event detectors) for detection of a transient radiation. Nuclear event detector was blocked of power temporary for defence of critical damage at a electric device when a induced transient radiation. Conventional NED consist of BJT, resistors and capacitors. The NED supply voltage of 5V and MCM(Multi Chip Module) structures. The proposed NED were designed for low supply voltage using 0.18um CMOS process. The response time of proposed NED was 34.8ns. In addition, pulse radiation experiments using a electron beam accelerator, the output signal has occurred.

• Nuclear Engineering and Technology
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• v.31 no.4
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• pp.423-431
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• 1999

A radiotracer technique has been developed to monitor the rotational movement of two piston rings in one cylinder during engine operation. The rings were labeled with two different kinds of radioisotopes, i.e. $^{60}$ Co and $^{192}$ Ir, for identification of the top ring from the second ring. The radiotracers were implanted in a small hole bored on the inner side of each piston ring. The rings were installed in a single cylinder hydrogen engine and three Nal scintillation detectors were mounted around the engine block to measure the gamma radiation. The angle of ring-gap orientation was determined from the radiation counts measured with the three detectors during engine operation. Two windows (upper window for $^{60}$ Co and lower window for $^{192}$ Ir) were set on each ratemeter to count radiation from the two isotopes separately. Procedure to convert the radiation counts to the position of the ring gap was established. With the software programmed with MS-Visualbasic, radiation counts were compared with the reference responses that were measured at angular intervals of 10$^{\circ}$for each piston ring in advance of the experiment. The result was used for the evaluation of the relationship between the orientation of ring-gaps and oil consumption. It was found that an increase in the oil consumption rate of a specific operation condition was closely related to the relative phase angle of the two piston rings.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.128.2-128.2
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• 2014

Long-wave infrared detectors using the type-II InAs/GaSb strained superlattice (T2SL) material system with the nBn structure were designed and fabricated. The band gap energy of the T2SL material was calculated as a function of the thickness of the InAs and GaSb layers by the Kronig-Penney model. Growth of the barrier material (Al0.2Ga0.8Sb) incorporated Te doping to reduce the dark current. The full width at half maximum (FWHM) of the 1st satellite superlattice peak from the X-ray diffraction was around 45 arc sec. The cutoff wavelength of the fabricated device was ${\sim}10.2{\mu}m$ (0.12eV) at 80 K while under an applied bias of -1.4V. The measured activation energy of the device was ~0.128 eV. The dark current density was shown to be $1.2{\times}10^{-5}A/cm^2$ at 80 K and with a bias -1.4 V. The responsivity was 1.9 A/W at $7.5{\mu}m$ at 80K and with a bias of -1.9V.

• Transactions on Electrical and Electronic Materials
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• v.17 no.4
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• pp.227-230
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• 2016

Zn_xMn_3-xO₄ (0.95≤x≤1.20) specimens were prepared using a conventional solid state reaction method. All specimens were sintered in air at 1,200℃ for 12 h, cooled at a rate of 2℃/min to 800℃, and subsequently quenched to room temperature. We investigated the electrical properties of Zn_xMn_3-xO₄ specimens with various amounts of ZnO for use as IR detectors. At a composition of x≥1.15, the ZnO phase precipitates beside the spinel structure. The electrical resistivity at room temperature, activation energy, responsivity, and detectivity of a Zn_1.10Mn_1.90O₄ specimen are 653.2 kΩ-cm, 0.392 eV, 0.016 V/W, and 7.52×10³ cmHz^1/2/W, respectively.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2640-2645
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• 2021

We report the development of a gamma-ray imaging device, named Large-Area Hybrid Gamma Imager (LAHGI), featuring high imaging sensitivity and good imaging resolution over a broad energy range. A hybrid collimation method, which combines mechanical and electronic collimation, is employed for a stable imaging performance based on large-area scintillation detectors for high imaging sensitivity. The system comprises two monolithic position-sensitive NaI(Tl) scintillation detectors with a crystal area of 27 × 27 cm² and a tungsten coded aperture mask with a modified uniformly redundant array (MURA) pattern. The performance of the system was evaluated under several source conditions. The system showed good imaging resolution (i.e., 6.0-8.9° FWHM) for the entire energy range of 59.5-1330 keV considered in the present study. It also showed very high imaging sensitivity, successfully imaging a 253 µCi ¹³⁷Cs source located 15 m away in 1 min; this performance is notable considering that the dose rate at the front surface of the system, due to the existence of the ¹³⁷Cs source, was only 0.003 µSv/h, which corresponds to ~3% of the background level.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4220-4225
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• 2022

Monte Carlo (MC) simulations are increasingly being used as an alternative or supplement to the gamma spectrometric method in determining the full energy peak efficiency (FEPE) necessary for radionuclide identification and quantification. The MC method is more advantageous than the experimental method in terms of both cost and time. Experimental calibration with standard sources is difficult, especially for specimens with unusually shaped geometries. However, with MC, efficiency values can be obtained by modeling the geometry as desired without using any calibration source. Modeling the detector with the correct parameters is critical in the MC method. These parameters given to the user by the manufacturer are especially the dimensions of the crystal and its front edge, the thickness of the dead layer, dimensions, and materials of the detector components. This study aimed to investigate the effect of the front edge geometry of the detector crystal on efficiency, so the effect of rounded and sharp modeled front edges on the FEPE was investigated for <300 keV with three different HPGe detectors in point and volume source geometries using PHITS MC code. All results showed that the crystal should be modeled as a rounded edge, especially for gamma-ray energies below 100 keV.

• Nuclear Engineering and Technology
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• v.56 no.10
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• pp.4355-4364
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• 2024

Fluid pipelines, commonly utilized in the oil industry, often face efficiency and reliability issues due to sediment buildup causing erosion, corrosion, and pipe wall thinning. Traditional assessment methods involve disruptive measures like cutting or creating holes and temporarily taking pipelines out of service. A non-destructive alternative, Limited-Number-Detector Computed Tomography (LNDCT), proves cost-effective and superior. Our proposed algorithm enhances data acquisition and projections using discrete detectors, employing Co-60 as a gamma-ray source and thallium-doped sodium iodide, NaI(Tl), detectors in an arc configuration. Monte Carlo simulations aligned closely with experimental data. Optimization involved adjusting the detector aperture angle based on a primary-to-scatter ratio of gamma-ray photons. We investigated the utility of various isotopes (Co-60, Cs-137, Am-241, Ir-192) to determine optimal projection signal amplitude. The algorithm generates a large sinogram matrix, and a filtered back-projection algorithm with a Hamming filter maximizes image quality while ensuring acceptable calculation volume and time. Using four phantoms, including pipelines filled to different scales, our study evaluates LNDCT configuration, performance, and validation. The results highlight its potential for efficiently evaluating sediment in pipelines, confirming the correctness and accuracy of our proposed algorithm.

• Journal of Radiation Protection and Research
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• v.35 no.2
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• pp.81-84
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• 2010

A CSA(Charge Sensitive Amplifier) was designed and fabricated for application in a radiation detection system based on a semiconductor detector such as Si, SiC, CdZnTe and etc.. A fabricated hybrid.type CSA was evaluated by comparison with a commercially available CSA. A comparison was performed by using calculation of ENC (Equivalent Noise Charge) and by using energy resolutions of fabricated radiation detectors based on Si. In energy resolution comparison, a fabricated CSA showed almost the same performance compared with a commercial one. In this study, feasibility of a fabricated CSA was discussed.