Annals of Nuclear Energy最新文献

Nuclear power plants are crucial to meeting net zero emission goals and achieving energy sustainability. Integrating these plants with clean energy technologies such as high-temperature steam electrolysis (HTSE) may improve the efficiency and economic competitiveness of these plants. The current study investigates the design and operation of a thermal power dispatch (TPD) system for coupling boiling water reactors (BWRs) to HTSE plants. The TPD system extracts a portion of the steam from the reactor’s main steam line and transfers its thermal energy to an HTSE plant through a power transport loop. A TPD system for 5 % steam extraction has been designed and the system performance during steady and transient operations has been analyzed. The TPD system dispatched a total of 197 MW thermal energy to the HTSE plant under nominal design conditions. Saturated steam at 7.17 MPa from the BWR plant was condensed and subcooled to a temperature of 168 °C, while a mass flow rate of 91.1 kg/s of superheated steam was dispatched to the HTSE plant. Furthermore, the system performance during transient operation showed a continuous transition from the initial hot standby mode to the nominal power dispatch level. The transient simulation results emphasized the importance of investigating component level performance for the TPD system design. The current results will guide future works on the development of integrated energy systems for hydrogen production or process heat applications.

In this work, the local low-cost materials from Nigeria were companied together to produce a lead-free concrete that can be used in shielding the ionizing γ-rays. This work investigated the impacts of partially replacing coarse aggregates (crushed granite) with a crushed waste glass on the chemical, physical, and radiation shielding characteristics. The developed concretes’ density was measured experimentally, and the fabricated concretes’ elemental chemical composition was determined utilizing a Thermo-Scientific X-ray fluorescence connected to an ARL-QUANT’X-EDXRF-Analyzer. The increase in the waste glass/granite (WG/G) substitution ratio between 0 and 17.6 % decreases the density of the produced concrete from 2.4 g/cm³ to 2.33 g/cm³. On the other hand, the absorption per unit mass (MAC) of the produced concretes increased by raising the WG/G ratio, where there was a 0.217–0.247 cm²/g increase in the MAC at 0.081 MeV, by raising the WG/G ratio between 0 and 17.6 %. Simultaneously, the study shows that the radiation protection efficiency (RPE) at 2.506 MeV for a 10 cm thickness of the fabricated concrete reaches 53.49, 61.14, 54.98, and 55.29 % for concretes with WG/G content of 0.0, 5.3, 11.1, and 17.6 % with the same order, respectively. Therefore, the thicker thicknesses of the developed concretes can offer high shielding capacity to be applied in radiation protection applications.

As a crucial parameter for the design of micro reactors, the neutron spectrum directly impacts the k_eff, the critical size, burnup characteristics, reactivity temperature coefficients and so on. When considering the optimization of the reactor size, designs utilizing thermal neutron spectrum and fast neutron spectrum each present their unique advantages and challenges. To investigate the impact of energy spectrum on the reactor performance, a micro lead-based reactor with annular channel fuel elements is proposed and the study of the influence of varying the volume ratio of moderator and fuel (the M/F ratio) on the k_eff, the critical size, burnup characteristic and reactivity temperature coefficients by using the Reactor Monte Carlo code (RMC code) is conducted. The results show that for the micro lead-based reactor proposed, when the reactor energy output demand is greater than 350 MWt·years, the design with fast neutron spectrum (without moderator) exhibits the minimum size. While the reactor energy output demand is less than 350 MWt·years, the design with a thermal neutron spectrum (with moderator) achieves the minimum size. Moreover, to ensure the negative reactivity temperature effect, the M/F ratio should be maintained below 3.4. The insights presented in this paper will serve as valuable references for the design of the micro reactor.

The management of radioactive waste poses a significant challenge to the sustainable development of nuclear energy. Efficient transmutation of nuclear wastes is crucial to minimize their accumulation. A small modular chloride salt fast reactor (sm-MCFR) capable of transmuting transuranic elements (TRU) is proposed in this paper, combining the advantages of the small modular reactor (SMR) and the molten salt reactor (MSR). The sm-MCFR is characterized by a high fuel loading and a compact core structure that can be quickly deployed around large commercial reactors to achieve TRU transmutation. To evaluate the TRU burnup capability of the sm-MCFR, several fuel salts and reprocessing modes were analyzed using the internally developed TRITON MODEC Coupled Burnup Code (TMCBurnup) tool. NaCl-MgCl₃ with 98 % enrichment in ³⁷Cl is chosen as carrier salt for the sm-MCFR, which can achieve 76.7 % TRU transmutation rate in average and 355 kg·GW⁻¹·a⁻¹ TRU transmutation quality at a continuous reprocessing rate of 10 L/d for 50 operation years. The optimized sm-MCFR reduced the radioactive toxicity of TRU by 84 %, thereby simplifying waste reprocessing. In addition, the sm-MCFR has a negative temperature feedback coefficient of −7.195 pcm/K, favoring safe reactor operation.

We propose a “quasistatic” asymptotic limit for reactor kinetics in which the material properties vary much more slowly in time than the solution itself. We further develop an asymptotic approximation of the solution in this limit using the method of multiple scales that, to leading order, takes the form of the product of a function that depends only on time and a function that depends on all independent variables but varies on the same time scale as the material properties. Determining when an approximation of this form is valid is of interest as several methods for performing reactor-kinetics calculation rely on such a representation of the solution. With an example reactor-kinetics problem, we demonstrate our asymptotic approximation becomes more accurate as the material properties vary more slowly in time, as expected.

The flow instability phenomenon in the helically coiled steam generator may cause continuous large oscillations in flow rate and wall temperature. An experimental and calculation study was carried out to investigate the flow instability behavior of a helically coiled heat exchanger. The flow instability threshold with thermal power within 0.6 MW–2.3 MW is obtained. The increase of inlet throttling and thermal power stabilize the system. Both of the tube-side and shell-side parameters, such as flow rate, temperature, and pressure affect the flow instability thresholds. In addition, the SGTH-1D code is used to simulate the flow instability threshold of the heat exchanger. The SGTH-1D code can accurately estimate the flow instability threshold of the heat exchanger. Finally, a new 3D flow instability map is proposed using the phase change number, the modified subcooled number and the inlet throttling number to estimate the flow instability threshold in the heat exchanger.

This paper presents the development and evaluation of the Coarse Mesh Finite Difference (CMFD) acceleration method to The Random Ray Method (TRRM). We demonstrate its effectiveness in accelerating the convergence of the fission sources and reducing the real statistical error in neutron transport calculations. TRRM treats the angular variable of the neutron flux stochastically and performs batch sampling of characteristic rays to transform the Method of Characteristics (MOC) into a stochastic process, that is capable of making significant strides in memory efficiency and computational performance for some problems. Despite its advantages, TRRM exhibits a potential challenge with a large number of inactive cycles and inherent inter-cycle correlation much like the Monte Carlo method. To address this, the CMFD acceleration method is explored and demonstrated to dramatically reduce the number of required inactive cycles and diminish inter-cycle correlation. Results from the numerical analysis of a 2D C5G7 core problem indicate that the application of CMFD leads to enhanced convergence, with the integration of a CMFD acceleration step every cycle offering the most substantial reduction in statistical noise and error. The study reveals that applying CMFD with every cycle effectively resolves the issue of needing inactive cycles and significantly lowers the inter-cycle correlation, thereby providing a more accurate estimation of standard deviation for pin power distributions. We conclude that using CMFD not only minimizes the number of inactive cycles of TRRM – much like normal Monte Carlo transport – but also lowers real statistical error effectively. For a targeted maximum standard deviation of 0.1% in the pin power, the addition of CMFD can decrease the number of necessary active cycles by 41% compared to standard TRRM, as demonstrated by the 2D C5G7 benchmark analysis.

Lead–bismuth-cooled reactor nuclear power equipment is severely affected by marine environments, causing operational attitude changes such as heeling and rolling. Conventional controllers cannot track set points rapidly. Therefore, this paper proposes an Adaptive Fuzzy Tracking Supervisory Control method. Firstly, the reactor mathematical model based on fuzzy basis functions is obtained through fuzzy mathematics. Secondly, a coolant average temperature tracking controller is designed on Lyapunov stability theory. To ensure the system returns to stable domain, supervisory compensatory control algorithm is developed. Next, the parameters of fuzzy model are adjusted using Fuzzy universal approximation theorem. By introducing discrepancies between actual system and fuzzy model outputs, parameter adaptive law is designed through Lyapunov theorem. This enables real-time parameter adjustment for fuzzy model and fuzzy tracking supervisory controller, enhancing load tracking performance of coolant’s average temperature. Finally, simulation experiments demonstrate that adaptive fuzzy tracking supervisory controller has stronger adaptability to multiple operating conditions under marine environments.