Nuclear Science and Technology

Thermoluminescence characteristics of in-house synthesized K2GdF5:Tb powder for photon and neutron

Van Toan Phan — 2024-07-04

This work presents an in-house synthesis process of K₂GdF₅:Tb thermoluminescence (TL) powder by using the solid-state reaction method. The K₂GdF₅:Tb powder TL glow curves (called as TL spectra), responded to photons (i.e., X-ray beams, gammas) and neutrons, have been investigated to optimize the setting parameters of the TL reader. Batch homogeneity of the in-house synthesized K₂GdF₅:Tb powder has been investigated to study the feasibility in photon and neutron personal dosimetry. The batch homogeneity of the in-house synthesized K₂GdF₅:Tb powder was investigated as less than 27.0%, which satisfied the requirement of the IEC and the ISO criteria (maximum of 30.0% is acceptable).

Evaluation and Comparison of AAA and AXB Dose Calculation Algorithms for Lung SBRT on TrueBeam STx with Eclipse 13.6

Hong Lam Pham — 2024-07-04

This study aims to comprehensively evaluate and compare lung Stereotactic Body Radiation Therapy (SBRT) dose distribution using the Eclipse v13.6 treatment planning system and TrueBeam STx linac data, employing two dose calculation algorithms: Analytical Anisotropic Algorithm (AAA) and Acuros External Beam (AXB). Utilizing thirty-five 4DCT lung SBRT datasets, dose calculations were performed with both algorithms, maintaining consistent setup conditions except for the varied calculation algorithm. Evaluation criteria included tumor dose distribution Conformity Index (CI), Homogeneity Index (HI), Gradient Index (GI), D2cm, V105%, Dmax and organs-at-risk (OAR) doses, assessed via Dose Volume Histogram (DVH) analysis. Additionally, linac parameters such as Monitor Unit (MU) and Beam on Time (BoT) were analyzed. Both algorithms met dose criteria for tumors and OAR tolerance. Minor differences were observed in tumor distribution indices, with AXB's Gradient Index showing proximity to ideal values. Although AXB exhibited slightly higher OAR doses, differences were statistically insignificant. AXB also demonstrated reduced average MUs and BoT. This comparative analysis underscores the efficacy of both AAA and AXB algorithms in ensuring dose conformity and OAR tolerance in lung SBRT planning, with AXB potentially offering improvements in efficiency and patient safety.

Development of a Compact Digital Multichannel Analyzer based on FPGA

Hoai Phuong Pham — 2024-07-04

In this work, we designed and built a digital multichannel analyzer (DMCA) using field-programmable gate array (FPGA), which is used to build a spectroscopic measurement system for a tomography device. DMCA's hardware was built with an ADC with 14-bit resolution and a sampling rate of 105 million samples per second (MSPs) combined with an FPGA board. The models of three functional blocks in DMCA, including pulse shaping filter, peak detection, and spectrum histogram processing, were simulated and optimized in the Matlab environment before they were integrated on the FPGA chip. The performance of DMCA was evaluated based on the high purity germanium (HPGe) detector with standard sources ⁶⁰Co and ¹³⁷Cs. The spectrum measured on the DMCA system showed that the drift of the spectral peak over time (100 hours) was of less than 1% and a resolution of 2.6 keV was at 1332 keV ⁶⁰Co. The DMCA developed in this work demonstrated various advantages: stability, compactness, versatility, and cost effectiveness.

A study on the application of artificial neural network to predict k-eff and peaking factor of a small modular PWR

Tran Chung Le — 2024-07-04

Machine learning (ML) using artificial neural network (ANN) methods is being applied to predict required parameters for nuclear reactors based on learning from big data sets. The ML models usually give faster calculation speed while the accuracy is good agreement with physical simulators. In this work, a multi-layer perceptron network was built and trained to predict k-eff and peaking factor of a small modular pressurized water reactor (PWR). The results are compared with those obtained by using a reactor physics code system, i.e. SRAC2006. The comparison shows good agreement accuracy and higher performance of the ML models.

Study on the repeatability and reproducibility of low-level radioactivity measurements using the analysis of variance tool

Van Hoang Dao — 2024-07-04

The repeatability and reproducibility need to be investigated to evaluate the stability of low-level radioactivity measurements with respect to an analysis method, as well as their dependence on measuring parameters. In this study, the procedures for gross alpha/beta and gamma-ray activity measurements were investigated in the Department of Radiation and Environment Safety at the Center for Nuclear Technologies (CNT). Moreover, an interlaboratory comparison was organized with other institutions, i.e. Dalat Nuclear Research Institute (DNRI), Institute for Nuclear Science and Technology (INST), and Institute of Public Health in HCM (IPH-HCM). To evaluate the repeatability and reproducibility of measures undertaken by the low-level radioactivity measurements, the certified reference materials (CRM), i.e. IAEA-CRM-385 (Natural and artificial radionuclides in sediment from the Irish Sea), NIST-SRM-4322c (Americium-241 Radioactivity Standard), and IAEA-CRM-RGK-1, together with 6 collected real samples were analyzed for ²³⁸U, ²³²Th, ²²⁶Ra, ²²⁸Ra, ²¹⁰Pb and ⁴⁰K. The analysis of variance (ANOVA) tool with respect to the average, standard deviation, F, p-value, and F-crit parameters was applied for the evaluation. The obtained results in the study revealed that the repeatability and reproducibility were stable for the low-level radioactivity measurements at the CNT which meets the laboratory’s quality management requirements.

Study on column leaching process of rare earths from ion adsorption clays by ammonium sulfate

Van Tung Nguyen — 2024-07-04

This report presents the results of study on the column leaching process of rare earths from ion adsorption clay by ammonium sulfate at laboratory scale. Total rare earths content in ion adsorption clay about 350 - 550 ppm. The influence of factors such as solution concentration (NH₄)₂SO₄, time leaching, solid/liquid ratio, number of stage washing ... on the rare earth recovery efficiency was evaluated. The obtained results showed that the rare earth recovery efficiency was up to about 90% under optimal conditions. The obtained technological parameters will re-evaluated at pilot scale (500 kg/batch) to assess the possibility of larger scale development.