Hasil untuk "Nuclear engineering. Atomic power"

Yuanyuan SUN, Xianglu ZHANG, Chunyan LI et al.

The α specific activity of plutonium(Pu) and neptunium(Np) in the uranium trioxide product is an important parameter for the quality control. In this study, a simple and reliable method based on TEVA resin was established for the determination of α specific activity of Pu and Np using α spectrometer measurement in the high-uranium content sample. In this method, the uranium oxide powder was first completely dissolved into 2 mL of 5 mol/L HNO3 with heating at 90 ℃, then 10 mL of 5 mol/L HNO3 was added, followed by the addition of 0.1 mL of 30%(mass fraction) H2O2 to adjust the valence of Pu and Np to +4. Then the Pu and Np with the high-uranium extracted onto TEVA resin on the condition of 5 mol/L HNO3+0.1 mL 30% H2O2 loading, while the most of interfering element U penetrated the resin, and the rest was removed using 10 mL of 5 mol/L HNO3+0.1 mL 30% H2O2 elute. The losses of Pu and Np were between 1% and 6% in the loading and rinsing fraction. Finally, the Pu and Np were simultaneously eluted with 10 mL of 0.3 mol/L HNO3+0.02 mol/L H2C2O4 at a flow rate of 1 mL/min. The results show that more than 99% of U is removed through the resin separate ion: the decontamination factor of U is greater than 3.2×104 using the method. And the overall recoveries of Np and Pu are ＞90%, illustrating that the developed method is suitable for the α specific activity measurement of Pu and Np in 0.1-0.5 g of uranium trioxide sample. For the analysis of six spiked samples with known amounts of Pu and Np activities, the measured values are consistent with the expected ones, the relative deviations are between −2% and 5%, indicating the robust and reliable of the developed method. The analysis of the blank procedure shows that the measurement results of Pu and Np are between 0.8 Bq and 1.3 Bq, the detection limit is 2.7 Bq/g for the 0.2 g of uranium trioxide, which meets the requirements of the spent fuel reprocessing process for the determination of α specific activity of Pu and Np in uranium oxide powder. The method has been applied to the determination of Pu and Np impurities in post-treated uranium oxides.

Ghada Yassin, Erik Pönitz, Nina Maria Huittinen et al.

This study presents a comprehensive analysis of the microstructural characteristics and chemical composition of base and weld materials from reactor pressure vessels in the first (units 1 and 2) and second (unit 8) generations of Russian VVER 440 reactors at the Greifswald nuclear power plant. We measured the specific activities of ⁶⁰Co and ¹⁴C in activated samples from units 1 and 2. ⁶⁰Co, with its shorter half-life (t_1/2 = 5.27 a), is a key dose-contributing radionuclide during decommissioning, while ¹⁴C (t_1/2 = 5700 a) plays an important role in a geological repository for low- and intermediate-level radioactive waste. Our findings reveal differences in the proportions of trace elements between the base and weld materials as well as between the two reactor generations. Microstructural analysis identified Mo-rich precipitates and (Mn, S)-rich inclusions containing secondary micro-inclusions in the unit 1 and 2 samples. Raman spectroscopy confirmed iron oxides (γ-Fe₂O₃, Fe₃O₄), silicates (Mn-SiO₃), and Cr₂O₃/NiCr₂O₄ in the base metal as well as MnFe₂O₃ in the weld metal. X-ray photoelectron spectroscopy identified Mn inclusions as MnS, MnS₂, or mixed Mn, Fe sulfides, and the Mo precipitates as MoSi₂. These findings offer valuable insights into the speciation of elements and the potential release of radionuclides through corrosion processes under repository conditions.

Shulong Huang, Kewei Jiang, Jinjie Zhao et al.

Dry ice blasting, a decontamination method with no secondary waste, is widely used in industry. Its safety is crucial in nuclear power plants. In this study, we carried out dry ice blasting treatment on five materials commonly used in nuclear power plants, and successively carried out mass damage research, surface erosion morphology research and mechanical property research. The results show that dry ice blasting is safe for 304 and 316 stainless steel, and brass, but not for aluminum and PVC. The maximum peeling mass for stainless steel and brass was found to be 6.15 g/m2 and 15.38 g/m2, respectively, both within China's energy industry standard (NB/T20142-2012). The process increases surface roughness but doesn't affect the material's microstructure. We recommend lower air pressure and a smaller impact angle for operational equipment to minimize damage, and higher pressures and larger angles for decommissioned equipment to enhance the decontamination effect.

Songlin Lyu, Francesco Amodio, Giovanni De Gregorio et al.

We present the results of the application of a nuclear potential consisting of two- and three-nucleon contact interactions in nuclear structure investigations. The nuclear Hamiltonian has been derived for a very low-energy regime within the framework of the effective field theory, its low-energy constants have been fitted to a few low-energy nucleon-nucleon experimental observables and the deuteron and 3H binding energies. Our goal is to validate the ability of this Hamiltonian to reproduce some important features of open-shell nuclei, and to this end we derive effective shell-model Hamiltonians for nuclei in the p- and sd-shell mass regions. The results of shell-model calculations with these effective Hamiltonians are then compared with experiment, and also with those obtained with a nuclear Hamiltonian derived within chiral perturbation theory, that includes also terms with one- and two-pion exchanges.

YANG Shiqi1, 2, LIU Jinhui1, 2, , YANG Yihan3, LI Peng3, XU Qi3, LI Guanghui3

CO2+O2 uranium leaching process is the third generation of uranium mining and smelting technology in China, in the leaching process of uranium from the ore after the interaction between the leaching agent and the minerals of the ore-bearing layer, the uranium leaches from the ore at the same time, due to the increasing salinity of groundwater, chemical precipitation will generate, resulting in the blockage of the ore-bearing layer. However, in the past, the hydrogeochemical simulation of ore-bearing layer plugging explored the dissolution and precipitation characteristics of minerals through forward simulation, and qualitatively studied the characteristics of ore-bearing layer blockage. In this paper, based on indoor static leaching test (normal temperature and pressure) and the field dynamic leaching test data of the Nalinggou uranium mine with CO2+O2 process, PHREEQC software was used to simulate the mineral dissolution and precipitation, the dissolution and precipitation characteristics of ore-bearing minerals were discussed, and the hydrogeochemical mechanism of the ore-bearing layer blockage of Nalinggou uranium mine was explored. The simulation results show that during the leaching process, potassium feldspar, albite and anorthite dissolve during uranium leaching, under indoor leaching conditions, their dissolution amounts for 60-170 d are 0.2-0.26, 2.91-3.26, and 4.58-5.39 mmol/L, respectively. The dissolution amounts under field leaching conditions are 0.14-1.42, 0.27-1.68, and 0.23-0.75 mmol/L, respectively. Illite, calcite, and gibbsite form precipitates, under indoor leaching conditions, the precipitation amounts for 60-170 d are 5.36-5.9, 9.77-11.7, and 0.40-0.53 mmol/L, respectively. Under field leaching conditions, the precipitation amounts are 0.35-2.79, 0.05-1.34, and 0.39-2.84 mmol/L, respectively, and part of CO2(g) is overflowed. Compared with the indoor leaching test, the dissolution amounts of albite, potassium feldspar and calcite in the rock ore in the field leaching test are relatively lower than that of illite and calcite. The above results indicate that the blocking minerals in the ore-bearing layer in the process of CO2+O2 uranium leaching are mainly illite, calcite and gibbsite. The formation of illite is the result of clayification and alteration of feldspar minerals, calcite and gibbsite are mainly affected by the concentration of Ca2+, Al3+ and pH of the leaching agent, and the higher concentration of Ca2+ and Al3+ and the increase of pH will lead to the precipitation of calcite and gibbsite. Clayification alteration and calcite precipitation of feldspar are important mechanisms for the ore-bearing layer blockage.

LE Dongdong, DENG Qixiang, DU Ansong et al.

BackgroundIn uranium mining and smelting, a significant amount of uranium-containing wastewater is generated, which can easily cause groundwater pollution. In polluted groundwater, uranium often combines with carbonates to form more diffusive and migratory uranyl carbonate complexes, making uranium removal more difficult.PurposeThis study aims to consider the performance of a three-dimensional electrochemical system of rGO/BB hydrogel particle electrodes on uranyl carbonate, and implement an efficient method for removing uranium-containing solutions.MethodsFirstly, graphene oxide (go) samples were prepared by modified Hummers method, then, the effects of electrolyte (sodium nitrate) concentration, applied voltage, electrode spacing, pH value, particle electrode dosage, and initial uranium concentration on the adsorption performance of uranyl carbonate ions by a three-dimensional electrochemical system were investigated, and the recycling performance of the system was studied. Finally, the adsorption mechanism of uranium was analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS).ResultsExperimental results show that under the conditions of pH value of 4~8, electrode spacing of 4 cm, voltage of 5 V, and rGO/BB hydrogel dosage of 90 mg, 200 mL of uranyl carbonate with a concentration of 1~1 000 mg∙L-1 exhibits good adsorption efficiency. Even when the uranyl carbonate concentration is 1 000 mg∙L-1, the adsorption rate can reach 87.56% in 14 h. After five cycles of adsorption and desorption, the adsorption rate remains above 87%, thus showing good recycling performance. The addition and use of rGO/BB hydrogel particle electrodes significantly improves the adsorption capacity of the electrochemical system for uranium, in which carboxyl and hydroxyl groups play a major role in uranium adsorption.ConclusionsThe results of this study show that the three-dimensional electrochemical system based on rGO/BB hydrogel particle electrodes has great application potential for removing uranyl carbonate ions.

Jiwoong Jung, Yong Choi, Seunghun Back et al.

Time-of-flight (TOF) PET detectors with fast-rise-time scintillators and fast-single photon time resolution silicon photomultiplier (SiPM) have been developed to improve the coincidence timing resolution (CTR) to sub-100 ps. The CTR can be further improved with an optimal bandwidth and minimized electronic noise in the readout circuit and this helps reduce the distortion of the fast signals generated from the TOF-PET detector. The purpose of this study was to develop an ultra-high frequency and fully-differential (UF-FD) readout circuit that minimizes distortion in the fast signals produced using TOF-PET detectors, and suppresses the impact of the electronic noise generated from the detector and front-end readout circuits. The proposed UF-FD readout circuit is composed of two differential amplifiers (time) and a current feedback operational amplifier (energy). The ultra-high frequency differential (7 GHz) amplifiers can reduce the common ground noise in the fully-differential mode and minimize the distortion in the fast signal. The CTR and energy resolution were measured to evaluate the performance of the UF-FD readout circuit. These results were compared with those obtained from a high-frequency and single ended readout circuit. The experiment results indicated that the UF-FD readout circuit proposed in this study could substantially improve the best achievable CTR of TOF-PET detectors.

Jae-Yoon Kim, Je-Hoon Jang, Jin-Ha Hwang et al.

When wall-thinning occurs in nuclear Class 2 and 3 pipes, reinforcement is typically applied rather than replacement. To analyze the structural integrity of reinforced wall-thinned pipe, stress analysis results using full 3-D FE analysis are not compatible to the design code equation, ASME BPVC Sec. III NC/ND-3650. Therefore, the efficient stress evaluation method for the reinforced wall-thinned pipe, compatible to the design code equation, needs to be developed. In this paper, stress evaluation methods for the reinforced wall-thinned pipe are proposed using the equivalent straight pipe concept. Furthermore, for fatigue analysis of the reinforced wall-thinned pipe, the stress intensification factor of reinforced wall-thinned pipe is presented using the structural stress method given in ASME BPVC Sec. VIII Div.2.

Mohammed F. Alotaibi, Khalid N. Alharbi, Eid M. Alosime et al.

Keeping track of radiation levels within human-inhabited areas is imperative to prevent public exposure. The human body is subjected to out-of-control radiation doses of approximately 82%, resulting from radiation sources such as earthly, cosmic, and internal radiation exposure. One public health issue is the radionuclide contamination in water and soil. In this paper, an overview of radionuclides contamination for some selected radionuclides in waters and soils has been conducted in all Saudi regions to better understand the sources and status of contamination. This review shows certain radioactive elements, such as 238U, 232Th, 226Ra, 40K, and 137Cs, in soil and water, which may have originated from natural or human-made sources. However, the available literature covers radionuclide levels in soil and water across all regions of Saudi Arabia, including the northern, southern, eastern, western, and central parts.

Saeideh Izadi Yazdi, Mahdi Sadeghi, Elham Saeedzadeh et al.

One important issue in using radiopharmaceuticals as therapeutic and imaging agents is predicting different organ absorbed dose following their injection. The present study aims at extrapolating dosimetry estimates to a female phantom from the animal data of 89Zr radionuclide accumulation using the Sparks-Idogan relationship. The absorbed dose of 89Zr radionuclide in different organs of the human body was calculated based on its distribution data in mice using both MIRD method and the MCNP simulation code. In this study, breasts, liver, heart wall, stomach, kidneys, lungs and spleen were considered as source and target organs. The highest and the lowest absorbed doses were respectively delivered to the liver (4.00E-02 and 3.43E-02 mGy/MBq) and the stomach (1.83E-03 and 1.66E-03 mGy/MBq). Moreover, there was a good agreement between the results obtained from both MIRD and MCNP methods. Therefore, according to the dosimetry results, [89Zr] DFO-CR011-PET/CT seems to be a suitable for diagnostic imaging of the breast anomalies for CDX-011 targeting gpNMB in patients with TNBC in the future.

Vladimir Slugen, Jana Simeg Veternikova, Jarmila Degmova et al.

The paper briefly reviews our positron annihilation studies performed on Eurofer97 steel and its ODS variant, performed in the last about 20 years. Various aspects of radiation environments foreseen for these materials were experimentally simulated via ion implantation and studied by a combination of non-destructive characterization techniques. The primary characterization tools in these studies were two techniques based on positron annihilation, namely positron annihilation lifetime spectroscopy (PALS) and Coincidence Doppler Broadening (CDB) technique. In addition to bulk studies utilizing conventional radioisotope positron sources, ion-implanted specimens were analysed using slow positron beams. This review summarizes the key findings of these techniques concerning the nature of the radiation resistance of EUROFER/ODS steels.

Mingi Eom, Sukwon Youn, Sung-Joon Ye

Miniaturized tissue equivalent proportional counters (mini-TEPCs) are proper for radiation dosimetry in medical application because the small size of the dosimeter could prevent pile-up effect under the high intensity of therapeutic beam. However, traditional methods of calibrating mini-TEPCs using internal alpha sources are not feasible due to their small size. In this study, we investigated the use of electron and proton edges on Monte Carlo-generated lineal energy spectra as markers for calibrating a 0.9 mm diameter and length mini-TEPC. Three possible markers for each spectrum were calculated and compared using different simulation tools. Our simulations showed that the electron edge markers were more consistent across different simulation tools than the proton edge markers, which showed greater variation due to differences in the microdosimetric spectra. In most cases, the second marker, yδδ, had the smallest uncertainty. Our findings suggest that the lineal energy spectra from mini-TEPCs can be calibrated using Monte Carlo simulations that closely resemble real-world detector and source geometries.

Charles Qi, Yi Wang, Hui Wang et al.

State-of-art NPUs are typically architected as a self-contained sub-system with multiple heterogeneous hardware computing modules, and a dataflow-driven programming model. There lacks well-established methodology and tools in the industry to evaluate and compare the performance of NPUs from different architectures. We present an event-based performance modeling framework, VPU-EM, targeting scalable performance evaluation of modern NPUs across diversified AI workloads. The framework adopts high-level event-based system-simulation methodology to abstract away design details for speed, while maintaining hardware pipelining, concurrency and interaction with software task scheduling. It is natively developed in Python and built to interface directly with AI frameworks such as Tensorflow, PyTorch, ONNX and OpenVINO, linking various in-house NPU graph compilers to achieve optimized full model performance. Furthermore, VPU-EM also provides the capability to model power characteristics of NPU in Power-EM mode to enable joint performance/power analysis. Using VPU-EM, we conduct performance/power analysis of models from representative neural network architecture. We demonstrate that even though this framework is developed for Intel VPU, an Intel in-house NPU IP technology, the methodology can be generalized for analysis of modern NPUs.

Jin Won Lee, Seungkook Roh

Charu Sharma, Puspalata Rajesh, R.P. Behera et al.

FU Yuanguang;LIU Peng;LI Rui;WANG Xin;DENG Li

During the source iteration process of Monte Carlo criticality calculation with particle parallel, there exists stochastic fluctuate which may cause unbalanced allocation of number of fission banks. Without inducing bank adjustment algorithm, a fewer particle number per cycle with more cycles would lead to a poorer load balance. The MasterSlave algorithm keeps one process to gather, reallocate and broadcast all fission banks from and to other running process at the end of each iteration cycle, which would guarantee an equal load allocation. However, large amount of data transmission and frequent operations of gather and broadcast would cause a low parallel efficiency. A poor acceleration ratio is found especially in the case with fewer particle numbers per cycle and more cycles for MasterSlave. Instead, for the Nearest Neighbor algorithm, one process keeps a great proportion of particles locally, and only sends a small proportion to its nearest adjacent processes, which greatly reduce the amount of data to transfer. A better acceleration ratio was found compared with Master-Slave, which is not sensitive to different settings of particle and cycle number. In this work, a new load balanced algorithm was proposed. Instead of transmitting data among processes, this algorithm uses weight adjustment scheme. In this algorithm, total particle weight is split equally to each process at the beginning of simulation. The local total weight always keeps being constant as cycles proceed, but the local single particle born weight is adjusted based on the number of local fission banks in each process. As each process deals with equal particle weight, a good load balance can be achieved. As each process does operations separately, no fission bank data need to be transmitted, which leads to a good parallel efficiency. The defect is that it cannot keep consistency between serial and parallel results, which is not a severe case to stochastic simulation. A simple PWR pincell problem and a 2×2 PWR assembly problem were used to test acceleration ability of different algorithm, with single process to 120 processes was used. It is found that new algorithm achieves a higher acceleration ratio compared to MasterSlave and Nearest Neighbor in different settings of particle and cycle number. Further, BEAVRS whole core problem was used on TianheⅡ supercomputer to test the weak and strong scaling parallel efficiency of the new algorithm, with 9254% and 8147% respectively of 4 800 processes relative to 128 processes.

Valeria Galeano, Yuly Meneses, Harvey Aguirre et al.

La dosimetría Fricke es una técnica con múltiples aplicaciones, desde la industria alimentaria hasta la medicina. En las actividades cotidianas de la planta de  irradiación gamma del Servicio Geológico Colombiano (SGC) se usan diferentes sistemas dosimétricos para el estudio de las dosis absorbidas en los materiales, entre ellos el sistema dosimétrico Fricke. En este trabajo se realizó la comparación de la dosis absorbida determinada en el Laboratorio  Secundario de Calibración Dosimétrica (LSCD), a partir de  patrones trazables calibrados en el Organismo Internacional de Energía Atómica (OIEA), y la aplicación del  protocolo IAEA TRS 398, en el irradiador G100 Hopewell  Design que contiene una fuente de Co-60, con las dosis  obtenidas mediante el sistema Fricke usado rutinariamente. Se aplicaron los protocolos establecidos en la norma ISO-STM 51026 “Práctica estándar para el uso del sistema de  dosimetría Fricke”. Se elaboró la curva de calibración de los  dosímetros Fricke, de la cual se obtuvo el parámetro experimental para el cálculo de la dosis absorbida en las  condiciones ambientales particulares de la instalación; el  sistema mostró un comportamiento lineal en el rango de  100 Gy a 350 Gy. Teniendo en cuenta el valor experimental de dosis obtenido con dicho sistema, se realizó la intercomparación con la dosis conocida determinada en el LSCD obteniendo una diferencia en el rango de dosis mencionado no mayor al 3,7 % y una incertidumbre del 3 % con una confiabilidad del 95 %. A partir del valor experimental encontrado y que la  instalación planta irradiación gamma se encuentra en  similares condiciones ambientales que el laboratorio  secundario de calibración y que los irradiadores de estas  instalaciones suministran sus dosis de manera similar, se  puede construir un procedimiento propio para el cálculo de  la dosis, el cual permitirá mayor precisión y operatividad a la dosimetría de la instalación.

Sarah J. Mazaro, Angela Kinoshita, Patricia Nicolucci et al.

New treatments in radiotherapy have some difficulties, among them, the geometric and dosimetric characterization of the radiation beam and the use of small radiation fields. Determination of the prescribed dose in the target volume in cases of small fields is difficult due to the absence of lateral electronic equilibrium and the sharp dose gradient at the edges of the fields. In this way, the choice of the radiation detector becomes relevant when performing the dosimetry of small fields. Alanine dosimeters have proven to be a good option for measurements of high radiation doses in these field sizes. This work aims to characterize the alanine detector through dosimetric tests for the VMAT (Volumetric Modulated Arc Therapy) technique in cases of SBRT (Stereotactic Body Radiation Therapy) to demonstrate the feasibility of using the alanine dosimetric system for use in quality control. End-to-End test was performed in a phantom, simulating two situations: homogeneous and heterogeneous regions. The response of L-alanine showed a strong linear correlation with dose (R2 = 0.99997), and insignificant dependence to dose rate. In the End-to-End test for a planned dose of 18 Gy, the doses obtained in alanine presented expanded uncertainty of 4.60% at 95% confidence level. Therefore, this work demonstrated that alanine dosimeter is suitable for quality control of SBRT with the VMAT technique in routine applications.

Sanghoun Joung, Balho H. Kim

A. Nwachukwu, F. C. Ikeagwuani, A. O. Adeboje

This study investigated the background ionizing radiation of Abakaliki rice mills. The requirement to monitor this site is because the prevalent activities in the site suggest that it is a source of ionizing radiation. The activities include fuel stations and excavation sites. Other sources are various chemicals and agrochemicals (like Phosphate, Uranium, Thorium, and Radium) used during the planting of the different rice species. There is, therefore, an urgent need to investigate the radiation level of Abakaliki rice mills in Ebonyi state, Nigeria to ascertain if it has passed the safety standards. The investigation was carried out using the Radalert 100 radiation monitor and a geographical positioning system (Garmin GPSMAP 765). The studied site was split into different points with each representing a mill that houses different grinding plants. This study included all the sections of the mill. The mean background radiation exposure rate ranges from 0.014mRhr-1to 0.0204mRhr-1. The obtained values are higher than the world standard limit of 0.013mRhr-1 recommended by ICRP except point 7 which corresponds to the top of the rice husk dumpsite. The calculated absorbed dose rates for the various sections of the mill ranged from 99.18 nGh-1 to 177.48 nGyh-1. These values of absorbed dose rates were observed to be far higher than the world permissible value of 89 nGyh-1. The annual effective dose equivalent (AEDE) for the exposure values ranged from 0.122 mSvy-1 to 0.218 mSvy-1 which are far lower than the ICRP permissible limits of 1.00 mSvlyr for the public and therefore implies absence of any immediate radiological risk. The excess lifetime cancer risk for the mill users were all above the 0.29 × 10-3 world recommended value. This suggests a possibility of the rice mill workers developing radiation-related illnesses over time.