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Impact-resistant design of RC slabs in nuclear power plant buildings

  • Li, Z.C.;Jia, P.C.;Jia, J.Y.;Wu, H.;Ma, L.L.
    • Nuclear Engineering and Technology
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    • v.54 no.10
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    • pp.3745-3765
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    • 2022
  • The concrete structures related to nuclear safety are threatened by accidental impact loadings, mainly including the low-velocity drop-weight impact (e.g., spent fuel cask and assembly, etc. with the velocity less than 20 m/s) and high-speed projectile impact (e.g., steel pipe, valve, turbine bucket, etc. with the velocity higher than 20 m/s), while the existing studies are still limited in the impact resistant design of nuclear power plant (NPP), especially the primary RC slab. This paper aims to propose the numerical simulation and theoretical approaches to assist the impact-resistant design of RC slab in NPP. Firstly, the continuous surface cap (CSC) model parameters for concrete with the compressive strength of 20-70 MPa are fully calibrated and verified, and the refined numerical simulation approach is proposed. Secondly, the two-degree freedom (TDOF) model with considering the mutual effect of flexural and shear resistance of RC slab are developed. Furthermore, based on the low-velocity drop hammer tests and high-speed soft/hard projectile impact tests on RC slabs, the adopted numerical simulation and TDOF model approaches are fully validated by the flexural and punching shear damage, deflection, and impact force time-histories of RC slabs. Finally, as for the two low-velocity impact scenarios, the design procedure of RC slab based on TDOF model is validated and recommended. Meanwhile, as for the four actual high-speed impact scenarios, the impact-resistant design specification in Chinese code NB/T 20012-2019 is evaluated, the over conservation of which is found, and the proposed numerical approach is recommended. The present work could beneficially guide the impact-resistant design and safety assessment of NPPs against the accidental impact loadings.

Preparation by the double extraction process with preliminary neutron irradiation of yttria or calcia stabilised cubic zirconium dioxide microspheres

  • Brykala, Marcin;Walczak, Rafal;Wawszczak, Danuta;Kilim, Stanislaw;Rogowski, Marcin;Strugalska-Gola, Elzbieta;Olczak, Tadeusz;Smolinski, Tomasz;Szuta, Marcin
    • Nuclear Engineering and Technology
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    • v.53 no.1
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    • pp.188-198
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    • 2021
  • A modern approach to nuclear energy involves reprocessing like transmutations of spent nuclear fuel products to reduce their radiotoxicity and time needed for their storage. For this purpose, they are immobilized in inert matrices made of zirconia and can be "burned" in fast neutron reactor or Accelerator Driven System. These matrices in spherical form can be obtained by sol-gel process. The paper presents a method of microspheres fabrication based on the combined Complex Sol-Gel Process and double extraction process consisting in the preparation of zirconium-ascorbate sol and simultaneous extraction of water and nitrates. The procedure allows obtaining gel microspheres with a diameter of 50 ㎛, which after heat treatment are processed into the final product. The synthesis of zirconia microspheres with Yttrium by internal gelation process is well known for over a decade now. However, the explanation and characterization of synthesis of such material by extraction of water process is rarely found. Parameters such as: pH, viscosity, shape, sphericity and crystal structure have been determined for synthesized products and semi-products. In addition, preliminary research consisting in irradiation of the obtained materials in fast and thermal neutron flux was carried out. The obtained results are presented and described in this work.

A multi-layer approach to DN 50 electric valve fault diagnosis using shallow-deep intelligent models

  • Liu, Yong-kuo;Zhou, Wen;Ayodeji, Abiodun;Zhou, Xin-qiu;Peng, Min-jun;Chao, Nan
    • Nuclear Engineering and Technology
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    • v.53 no.1
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    • pp.148-163
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    • 2021
  • Timely fault identification is important for safe and reliable operation of the electric valve system. Many research works have utilized different data-driven approach for fault diagnosis in complex systems. However, they do not consider specific characteristics of critical control components such as electric valves. This work presents an integrated shallow-deep fault diagnostic model, developed based on signals extracted from DN50 electric valve. First, the local optimal issue of particle swarm optimization algorithm is solved by optimizing the weight search capability, the particle speed, and position update strategy. Then, to develop a shallow diagnostic model, the modified particle swarm algorithm is combined with support vector machine to form a hybrid improved particle swarm-support vector machine (IPs-SVM). To decouple the influence of the background noise, the wavelet packet transform method is used to reconstruct the vibration signal. Thereafter, the IPs-SVM is used to classify phase imbalance and damaged valve faults, and the performance was evaluated against other models developed using the conventional SVM and particle swarm optimized SVM. Secondly, three different deep belief network (DBN) models are developed, using different acoustic signal structures: raw signal, wavelet transformed signal and time-series (sequential) signal. The models are developed to estimate internal leakage sizes in the electric valve. The predictive performance of the DBN and the evaluation results of the proposed IPs-SVM are also presented in this paper.

Effect of mechanical alloying on the microstructural evolution of a ferritic ODS steel with (Y-Ti-Al-Zr) addition processed by Spark Plasma Sintering (SPS)

  • Macia, E.;Garcia-Junceda, A.;Serrano, M.;Hong, S.J.;Campos, M.
    • Nuclear Engineering and Technology
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    • v.53 no.8
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    • pp.2582-2590
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    • 2021
  • The high-energy milling is one of the most extended techniques to produce Oxide dispersion strengthened (ODS) powder steels for nuclear applications. The consequences of the high energy mill process on the final powders can be measured by means of deformation level, size, morphology and alloying degree. In this work, an ODS ferritic steel, Fe-14Cr-5Al-3W-0.4Ti-0.25Y2O3-0.6Zr, was fabricated using two different mechanical alloying (MA) conditions (Mstd and Mact) and subsequently consolidated by Spark Plasma Sintering (SPS). Milling conditions were set to evidence the effectivity of milling by changing the revolutions per minute (rpm) and dwell milling time. Differences on the particle size distribution as well as on the stored plastic deformation were observed, determining the consolidation ability of the material and the achieved microstructure. Since recrystallization depends on the plastic deformation degree, the composition of each particle and the promoted oxide dispersion, a dual grain size distribution was attained after SPS consolidation. Mact showed the highest areas of ultrafine regions when the material is consolidated at 1100 ℃. Microhardness and small punch tests were used to evaluate the material under room temperature and up to 500 ℃. The produced materials have attained remarkable mechanical properties under high temperature conditions.

Images of Nurses Appeared in Media Reports Before and After Outbreak of COVID-19: Text Network Analysis and Topic Modeling (COVID-19 발생 전·후 언론보도에 나타난 간호사 이미지에 대한 텍스트 네트워크 분석 및 토픽 모델링)

  • Park, Min Young;Jeong, Seok Hee;Kim, Hee Sun;Lee, Eun Jee
    • Journal of Korean Academy of Nursing
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    • v.52 no.3
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    • pp.291-307
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    • 2022
  • Purpose: The aims of study were to identify the main keywords, the network structure, and the main topics of press articles related to nurses that have appeared in media reports. Methods: Data were media articles related to the topic "nurse" reported in 16 central media within a one-year period spanning July 1, 2019 to June 30, 2020. Data were collected from the Big Kinds database. A total of 7,800 articles were searched, and 1,038 were used for the final analysis. Text network analysis and topic modeling were performed using NetMiner 4.4. Results: The number of media reports related to nurses increased by 3.86 times after the novel coronavirus (COVID-19) outbreak compared to prior. Pre- and post-COVID-19 network characteristics were density 0.002, 0.001; average degree 4.63, 4.92; and average distance 4.25, 4.01, respectively. Four topics were derived before and after the COVID-19 outbreak, respectively. Pre-COVID-19 example topics are "a nurse who committed suicide because she could not withstand the Taewoom at work" and "a nurse as a perpetrator of a newborn abuse case," while post-COVID-19 examples are "a nurse as a victim of COVID-19," "a nurse working with the support of the people," and "a nurse as a top contributor and a warrior to protect from COVID-19." Conclusion: Topic modeling shows that topics become more positive after the COVID-19 outbreak. Individual nurses and nursing organizations should continuously monitor and conduct further research on nurses' image.

Investigation on the nonintrusive multi-fidelity reduced-order modeling for PWR rod bundles

  • Kang, Huilun;Tian, Zhaofei;Chen, Guangliang;Li, Lei;Chu, Tianhui
    • Nuclear Engineering and Technology
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    • v.54 no.5
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    • pp.1825-1834
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    • 2022
  • Performing high-fidelity computational fluid dynamics (HF-CFD) to predict the flow and heat transfer state of the coolant in the reactor core is expensive, especially in scenarios that require extensive parameter search, such as uncertainty analysis and design optimization. This work investigated the performance of utilizing a multi-fidelity reduced-order model (MF-ROM) in PWR rod bundles simulation. Firstly, basis vectors and basis vector coefficients of high-fidelity and low-fidelity CFD results are extracted separately by the proper orthogonal decomposition (POD) approach. Secondly, a surrogate model is trained to map the relationship between the extracted coefficients from different fidelity results. In the prediction stage, the coefficients of the low-fidelity data under the new operating conditions are extracted by using the obtained POD basis vectors. Then, the trained surrogate model uses the low-fidelity coefficients to regress the high-fidelity coefficients. The predicted high-fidelity data is reconstructed from the product of extracted basis vectors and the regression coefficients. The effectiveness of the MF-ROM is evaluated on a flow and heat transfer problem in PWR fuel rod bundles. Two data-driven algorithms, the Kriging and artificial neural network (ANN), are trained as surrogate models for the MF-ROM to reconstruct the complex flow and heat transfer field downstream of the mixing vanes. The results show good agreements between the data reconstructed with the trained MF-ROM and the high-fidelity CFD simulation result, while the former only requires to taken the computational burden of low-fidelity simulation. The results also show that the performance of the ANN model is slightly better than the Kriging model when using a high number of POD basis vectors for regression. Moreover, the result presented in this paper demonstrates the suitability of the proposed MF-ROM for high-fidelity fixed value initialization to accelerate complex simulation.

X-ray / gamma ray radiation shielding properties of α-Bi2O3 synthesized by low temperature solution combustion method

  • Reddy, B. Chinnappa;Manjunatha, H.C.;Vidya, Y.S.;Sridhar, K.N.;Pasha, U. Mahaboob;Seenappa, L.;Sadashivamurthy, B.;Dhananjaya, N.;Sathish, K.V.;Gupta, P.S. Damodara
    • Nuclear Engineering and Technology
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    • v.54 no.3
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    • pp.1062-1070
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    • 2022
  • In the present communication, pure and stable α-Bismuth Oxide (Bi2O3) nanoparticles (NPs) were synthesized by low temperature solution combustion method using urea as a fuel and calcined at 500℃. The synthesized sample was characterized by using powder X-ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy dispersive X-ray analysis (EDAX), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and UV-Visible absorption spectroscopy. The PXRD pattern confirms the formation of mono-clinic, stable and low temperature phase α-Bi2O3. The direct optical energy band gap was estimated by using Wood and Tauc's relation which was found to be 2.81 eV. The characterized sample was studied for X-ray/gamma ray shielding properties in the energy range 0.081-1.332 MeV using NaI (Tl) detector and multi channel analyzer (MCA). The measured shielding parameters agrees well with the theory, whereas, slight deviation up to 20% is observed below 356 keV. This deviation is mainly due to the influence of atomic size of the target medium. Furthermore an accurate theory is necessary to explain the interaction of X-ray/gamma ray with the NPs.The present work opens new window to use this facile, economical, efficient, low temperature method to synthesize nanomaterials for X-ray/gamma ray shielding purpose.

Calibration of cylindrical NaI(Tl) gamma-ray detector intended for truncated conical radioactive source

  • Badawi, Mohamed S.;Thabet, Abouzeid A.
    • Nuclear Engineering and Technology
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    • v.54 no.4
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    • pp.1421-1430
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    • 2022
  • The computation of the solid angle and the detector efficiency is considering to be one of the most important factors during the measuring process for the radioactivity, especially the cylindrical γ-ray NaI(Tl) detectors nowadays have applications in several fields such as industry, hazardous for health, the gamma-ray radiation detectors grow to be the main essential instruments in radiation protection sector. In the present work, a generic numerical simulation method (NSM) for calculating the efficiency of the γ-ray spectrometry setup is established. The formulas are suitable for any type of source-to-detector shape and can be valuable to determine the full-energy peak and the total efficiencies and P/T ratio of cylindrical γ-ray NaI(Tl) detector setup concerning the truncated conical radioactive source. This methodology is based on estimate the path length of γ-ray radiation inside the detector active medium, inside the source itself, and the self-attenuation correction factors, which typically use to correct the sample attenuation of the original geometry source. The calculations can be completed in general by using extra reasonable and complicate analytical and numerical techniques than the standard models; especially the effective solid angle, and the detector efficiency have to be calculated in case of the truncated conical radioactive source studied condition. Moreover, the (NSM) can be used for the straight calculations of the γ-ray detector efficiency after the computation of improvement that need in the case of γ-γ coincidence summing (CS). The (NSM) confirmation of the development created by the efficiency transfer method has been achieved by comparing the results of the measuring truncated conical radioactive source with certified nuclide activities with the γ-ray NaI(Tl) detector, and a good agreement was obtained after corrections of (CS). The methodology can be unlimited to find the theoretical efficiencies and modifications equivalent to any geometry by essential sufficiently the physical selective considered situation.

Analysis of safety risk factors of fishermen on the Korean tuna purse seiner (우리나라 다랑어선망어선의 어선원 안전 위험요소 분석)

  • KIM, O-Tae;JO, Hyun-Su;CHANG, Ho-Young;LEE, Yoo-Won
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.58 no.3
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    • pp.251-261
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    • 2022
  • Tuna purse seine fishery (TPF) constitute more than 60% of distant water fishery production in Korea based on a statistic of 2018, and 28 ships from four different companies were under operation at the western and central Pacific Ocean. On this research, common risk factors during TPF were investigated via enumeration of five years Korean fisherman's insurance payment statement, followed by some counterplans to diminish the accident rate. The accident rate of TPF on the Pacific Ocean peaked by 43.0% in 2014 and constantly decreased to 23.0% until 2018, presenting an average of 33.6%. Meanwhile, the accident rate on the Indian Ocean reached the highest point 55.1% in 2014 and declined to 11.6% in 2016, having an average of 24.7%. The average accident rate of the Indian Ocean scored 8.9% lower than the rate of the Pacific Ocean, but no statistic significance was observed. Depending on the process of operation, 'casting or hauling of net' was the most frequent part that people received an injury (40.4%). When the accidents were classified by their types, 'falling down' was the most recurrent cause of the injuries (28.5%). At the point of severity, the worst injuries were induced by crush hazard. Considering aforementioned accident frequency and severity, all the factors on the accident type list were divided into three different groups including high risk, moderate risk, and common risk. This study is expected to contribute to the reduction of occupational accidents during the work of fishermen and establishment of a safety management system for distance water fishing vessels.

Simulation of a neutron imaging detector prototype based on SiPM array readout

  • Mengjiao Tang;Lianjun Zhang;Bin Tang;Gaokui He;Chang Huang;Jiangbin Zhao;Yang Liu
    • Nuclear Engineering and Technology
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    • v.55 no.9
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    • pp.3133-3139
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    • 2023
  • Neutron imaging technology as a means of non-destructive detection of materials is complementary to X-ray imaging. Silicon photomultiplier (SiPM), a new type of optical readout device, has overcome some shortcomings of traditional photomultiplier tube (PMT), such as high-power consumption, large volume, high price, uneven gain response, and inability to work in strong magnetic fields. Its application in the field of neutron detection will be an irresistible general trend. In this paper, a thermal neutron imaging detector based on 6LiF/ZnS scintillation screen and SiPM array readout was developed. The design of the detector geometry was optimized by geant4 Monte Carlo simulation software. The optimized detector was evaluated with a step wedge sample. The results show that the detector prototype with a 48 mm × 48 mm sensitive area can achieve about 38% detection efficiency and 0.26 mm position resolution when using a 300 ㎛ thick 6LiF/ZnS scintillation screen and a 2 mm thick Bk7 optical guide coupled with SiPM array, and has good neutron imaging capability. It provides effective data support for developing high-performance imaging detectors applied to the China Spallation Neutron Source (CSNS).