Nuclear Science and Technology

Design of a FPGA-based digital reactivity meter for Dalat Nuclear Research Reactor

Van Tai Vo, Nguyen Van Kien, Nguyen Nhi Dien, Le Van Hiep — Fri, 13 Jan 2023 00:00:00 +0700

This paper describes a digital reactivity meter module based on solving the inverse kinetics equations and the time behavior of the output pulse frequency from the amplifier, which is proportional to the power of the Dalat Nuclear Research Reactor (DNRR). The designed reactivity meter, which operates online with real-time calculation, was tested using the PGT-17R simulator signals in comparison with the existing imported module PNO-121R5 of the DNRR’s control and protection system. The experimental results show that the technical characteristics and functions of the two modules are equivalent.

Performance Comparison of ANN-Based Model and Empirical Correlations for Void Fraction Prediction of Subcooled Boiling Flow in Vertical Upward Channel

Ngoc Dat Nguyen, Van Thai Nguyen — Thu, 30 Dec 2021 00:00:00 +0700

The accurate prediction of void fraction parameter in subcooled boiling flow is very important for nuclear safety since it has significant influences on the mass flow rate, the onset of two-phase flow instability, and the heat transfer characteristics in a nuclear reactor core. Many different models and empirical correlations have been established over a variety of input conditions; however, this classical approach could lead to unsatisfactory prediction due to the uncertainties of model parameter and model forms. To cope with these limitations, Artificial Neural Network (ANN) is a powerful machine learning tool for modeling and solving non-linear and complicated physical problems. Therefore, this work is aim at developing an ANN-based model to predict the local void fraction of subcooled boiling flows. The comparison results of the performance between the ANN-based model and empirical correlations for the void fraction prediction of subcooled boiling in vertical upward channel showed the potential use of ANN-based model in the Computational Fluid Dynamics (CFD) codes to accurately simulate the subcooled boiling phenomena.

Identification of Cold-Leg Break Size in LOCA Accident using Artificial Neural Networks and Simulation Database

Le Thi Hong Ngoc, Nguyen Ngoc Dat, Nguyen Van Thai — Fri, 13 Jan 2023 00:00:00 +0700

The most widely studied LOCA (Loss of Coolant Accidents) is a rupture of a cold leg pipe causing the Reactor Cooling System to depressurize first, with different break sizes corresponding to the change in trigger signal from the Instrument and Control System (I&C System) such as pressure, temperature, power, pressure vessel water level, etc. is different. Therefore, the response of nuclear power plant varies considerably with the size of break. To mitigate the consequence of LOCA with a given break size, it is necessary to design the emergency core coolant systems so that the fuel is cooled efficiently during all phases of the accident. Therefore, the size of rupture needs to be detected and identified as soon as possible right after reactor scram. To achieve this goal, this study is conducted to investigate the applicability of artificial neural networks (ANN) for recognizing LOCAs, especially identifying the rupture sizes of the LOCAs according to the changes of operational parameters of VVER-1000 nuclear power plant. This study mainly focuses on building, training, and optimizing the artificial neural networks using simulation databases obtained from the RELAP5 simulation program for VVER-1000 reactor technology. Results clearly showed the potential application of ANN-based model for detecting the break size even with uncertainty of input parameters added.

Using ARGOS to simulate radioactive dispersion in the atmosphere from Fangchenggang nuclear power plant to Viet Nam

Fri, 13 Jan 2023 00:00:00 +0700

In this study, ARGOS software was used to simulate the atmospheric radioactive emissions from Fangchenggang nuclear power plant to Viet Nam. The simulated cases are hypothetical accidents with hypothetical source terms equivalent to level 6 of the International Nuclear and radiological Event Scale (INES). The results show the possibility of using ARGOS in simulating atmospheric dispersion, assessing radiation dose to humans from the Fangchenggang nuclear power plant accident to Viet Nam in some accident situations. Furthermore, the obtained results contribute to forecasting and supporting emergency response when an accident occurs in nuclear power plants.

Research and manufacture of cone-beam computed tomography (CBCT) system for industrial use

B. N. Ha, T. K. Tuan, T. N. Toan, T. T. Duong, T. M. Anh, B. T. Hung, M. D. Thuy — Thu, 30 Dec 2021 00:00:00 +0700

Computed tomography is a transmission tomography technique; this technique allows reconstructing the cross-section images or slices of the real object. The CT was developed in the 1970s for medical diagnostic purposes. Today, the CT technique has evolved to the 7th generation using cone-beam configuration (CBCT) and Flat Panel Detector (FPD) instead of fan-beam arrangement and one dimension detector array. CBCT has greater X-ray efficiency and higher spatial resolution than the previous generation; therefore, it can be used in industrial applications such as metrology of precision machined and None-Destructive Testing (NDT). In this research, the first CBCT system in Vietnam was manufactured; this system can acquire and reconstruct three dimensions of a real object with a maximum size of 200 × 300 mm within ten minutes. The resolution of the reconstructed image is around 49 µm.

Effects of carrageenan oligosaccharides prepared by electron beam irradiation on frozen shrimps during storage

Thu, 30 Dec 2021 00:00:00 +0700

1% carrageenan oligosaccharide solutions obtained by electron beam irradiation at the radiation doses of 9 kGy (CO-9) and 30 kGy (CO-30) were applied for shrimps before frozen, and their effects on quality of frozen shrimps were investigated by observing the microstructure of shrimp’s muscle tissue, measuring their weight loss (%), hardness and pH after thawing. Comparison with the shrimps treated by 1% tetrasodium pyrophosphate solution (Na₄P₂O₇, positive control) and distilled water (negative control), the shrimp samples soaked in CO before frozen kept their initial properties, and the shrimps treated by CO-30 solution showed better quality than others after 3 weeks of frozen storage. Specifically, the mean distances of muscle bundles and muscle fibers in the shrimps soaked in CO-30 solution were 23.9 µm and 11.1 µm, respectively, much smaller than 37.9 µm and 14.8 µm in the shrimps treated by Na₄P₂O₇, and 46.7 µm and 19.8 µm in the shrimps soaked in distilled water only. Our results also revealed that the weight loss after thawing and pH of the shrimps soaked in CO-30 solution were 1.55% and 6.40, much lower than that of the positive control sample (2.59% and 6.82) and negative control sample (4.83% and 6.58), respectively. In contrast, the mean of hardness of the sample soaked in CO-30 solution was 20.4, about 20.7 and 36.0% higher than those of positive control (16.9) and negative control (15.0). These results suggested that CO-30 is effective to inhibit the denaturation of shrimp during frozen storage and can be applied to prolong the shelf life and keep the quality of frozen shrimp products.