Abstract The Molten Salt Fast Reactor (MSFR), a prominent Generation IV reactor design, offers improved safety by eliminating graphite as a moderator and incorporating a passive safety system. ...Understanding the fuel salt relocation mechanism is crucial in ensuring the reactor’s safety and performance. This study presents a particle-based approach using the Semi-Implicit Moving Particle (MPS) method, which accurately represents fluid as particles carrying essential physical properties. We validate the MPS method as an alternative tool for investigating fuel salt relocation in the MSFR, comparing its results with the well-established δ-SPH method for verification. The simulations encompass scenarios with and without obstacles, involving water-PEO fluids known for their distinct densities and propensity to induce splashing phenomena. The obstacles used are made in several size variations, such as semicircular, rectangular, and triangular obstacles. The excellent alignment of MPS method results with δ-SPH method outcomes confirms its effectiveness in predicting freeze plug melting and fuel salt relocation in the MSFR, providing valuable insights into the passive safety mechanisms. This research contributes to enhancing the safety and efficiency of advanced molten salt reactor designs. Where it can be concluded that the simulation results of the MPS method are almost the same as the simulation results of the δ-SPH method.
Osteoporosis is a serious health issue among aging postmenopausal women. The majority of postmenopausal women with osteoporosis have bone loss related to estrogen deficiency. The rapid bone loss ...results from an increase in bone turnover with an imbalance between bone resorption and bone formation. Osteoporosis can also result from excessive glucocorticoid usage, which induces bone demineralization with significant changes of spatial heterogeneities of bone at microscale, indicating potential risk of fracture. This review is a summary of current literature about the molecular mechanisms of actions, the risk factors, and treatment of estrogen deficiency related osteoporosis (EDOP) and glucocorticoid induced osteoporosis (GIOP). Estrogen binds with estrogen receptor to promote the expression of osteoprotegerin (OPG), and to suppress the action of nuclear factor-κβ ligand (RANKL), thus inhibiting osteoclast formation and bone resorptive activity. It can also activate Wnt/β-catenin signaling to increase osteogenesis, and upregulate BMP signaling to promote mesenchymal stem cell differentiation from pre-osteoblasts to osteoblasts, rather than adipocytes. The lack of estrogen will alter the expression of estrogen target genes, increasing the secretion of IL-1, IL-6, and tumor necrosis factor (TNF). On the other hand, excessive glucocorticoids interfere the canonical BMP pathway and inhibit Wnt protein production, causing mesenchymal progenitor cells to differentiate toward adipocytes rather than osteoblasts. It can also increase RANKL/OPG ratio to promote bone resorption by enhancing the maturation and activation of osteoclast. Moreover, excess glucocorticoids are associated with osteoblast and osteocyte apoptosis, resulting in declined bone formation. The main focuses of treatment for EDOP and GIOP are somewhat different. Avoiding excessive glucocorticoid use is mandatory in patients with GIOP. In contrast, appropriate estrogen supplement is deemed the primary treatment for females with EDOP of various causes. Other pharmacological treatments include bisphosphonate, teriparatide, and RANKL inhibitors. Nevertheless, more detailed actions of EDOP and GIOP along with the safety and effectiveness of medications for treating osteoporosis warrant further investigation.
•Summarizes a realistic high burnup core design.•Used DOE tools to evaluate steady state and transient high burnup fuel performance.•Estimated total core mass susceptible to pulverization.•Evaluated ...pre-transient and transient fuel conditions (temperature and stress).
Abstract This paper explores the phenomenon of open-phase fault of nuclear power plants for preferred power supply, focusing on three distinct scenarios, normal operation, start, and overhaul. For ...each scenario, the paper discusses the responses of existing relay protection devices, which are crucial for detecting and mitigating open-phase faults. These responses vary depending on the impedance at the fault location and the load rate of the plant. This paper highlights that open-phase faults can lead to three-phase imbalances in the power system, but their impact on voltage levels is not always straightforward due to the transformer and motor compensation effects. Additionally, the paper identifies blind zones in open-phase fault detection, where existing relays may fail to respond effectively, leading the plant to enter a station blackout state. In conclusion, the research underscores the importance of open-phase fault detection and protection in nuclear power plants. It reveals potential vulnerabilities in existing relay configurations and emphasizes the need for enhanced monitoring and safety measures to prevent extended plant operation under open-phase fault conditions.
Nuclear waste from small modular reactors Krall, Lindsay M; Macfarlane, Allison M; Ewing, Rodney C
Proceedings of the National Academy of Sciences - PNAS,
06/2022, Volume:
119, Issue:
23
Journal Article
Peer reviewed
Open access
SignificanceSmall modular reactors (SMRs), proposed as the future of nuclear energy, have purported cost and safety advantages over existing gigawatt-scale light water reactors (LWRs). However, few ...studies have assessed the implications of SMRs for the back end of the nuclear fuel cycle. The low-, intermediate-, and high-level waste stream characterization presented here reveals that SMRs will produce more voluminous and chemically/physically reactive waste than LWRs, which will impact options for the management and disposal of this waste. Although the analysis focuses on only three of dozens of proposed SMR designs, the intrinsically higher neutron leakage associated with SMRs suggests that most designs are inferior to LWRs with respect to the generation, management, and final disposal of key radionuclides in nuclear waste.
•The safe storage of Spent Nuclear Fuel (SNF) within a dry cask system must be guaranteed for any operating condition.•The influence of a partial to complete blockage of air inlet openings on the PCT ...is assessed for the HI-STORM 100S system.•The cooling and the safe storage of the SNF seem to be ensured also in out-of-the ordinary situations.•The results from the adiabatic (most extreme) case indicate the importance of a tempestive accident management.•MELCOR showed good adaptability and flexibility, even in simulating scenarios out of its natural domain of application.
The safe storage of Spent Nuclear Fuel (SNF) within a dry cask system must be guaranteed for any operating condition. In particular, the Peak Cladding Temperature (PCT) is currently employed as a measure of the fuel integrity in normal conditions. The same fuel integrity has to be ensured also in off-normal and accidental conditions by keeping the PCT below the regulatory limits. In this regard, the work proposed in this paper aims at evaluating the performance of a concrete-based dry cask in off-normal and accidental conditions. More specifically, the influence of a partial to complete blockage of the air inlet openings on the PCT is assessed by means of a MELCOR model of the HI-STORM 100S cask. Attention is also paid to the temperature of the external concrete cask in order to check the integrity of the concrete itself.
The EUROfusion Safety and Environmental Work Package (WPSAE) has the scope to progress the safety studies for the future EU DEMO reactor. A Generic Site Safety Report (GSSR) has been prepared to ...include all the steps necessary to cover the safety issues of the nuclear fusion plant, from the definition of principles and requirements, through the detection of the source terms at risk, selecting the postulated initiating events, analyzing the accidents, quantifying the doses to the population and investigating waste production and its management. Eleven GSSR volumes collate the studies performed. The final goal is to prepare safety documentation, as complete as possible, to initiate a preliminary safety report when the plant site is selected.
In parallel, the safety studies are supporting the maturation of the design of DEMO, providing feedback on the technical choices for the machine, the selection of materials, the use of space, the equipment necessary to correctly manage the safety risks through continuous collaboration with the design teams of other DEMO Work Packages.
The GSSR focused on safety and environmental issues, it did not encompass security issues that could impact the design and hence the safety performance of DEMO. Consideration of the interactions between safety and security will be needed in the development of the DEMO detailed design and its associate Preliminary Safety Analysis Report (PSAR).
The main achievements of the Pre-Concept Phase are presented in this paper, by summarizing the contents of GSSR volumes. Completion of the work is foreseen during the future Concept Design Phase (2021–2027).
Liquid metal embrittlement (LME) has been reported in many structural materials including steel, aluminum, brass, and nickel during hot-working processes e.g. welding, hot-deformation, brazing, ...heat-treatment, or in-service time. In many of the applications, such as automotive, aerospace, nuclear industries, LME is considered as a serious safety concern. Over the last decades, research activities have grown considerably striving to understand the abnormal LME phenomenon. However, a fundamental understanding of LME has not yet been unraveled due to the diverse, contradicting proposed mechanisms in different processing routes and materials. In the present overview, first various proposed mechanisms are integrated into a systematic manner. Revisiting the proposed mechanisms based on the most-recent experimental discoveries reveals that the stress-assisted grain boundary diffusion mechanism is a viable LME mechanism. The connection between sub-atomic (electronic) structure modification and the embrittlement at grain boundaries provides insights into the grain boundary decohesion during LME. In a bottom-up approach, then this overview selects Zn-induced embrittlement during assembly welding as an example case of LME. Explanations are provided to show why LME cracks are both seen to degrade and be innocuous to material’s performance. Finally, this review outlines recommended directions for future research steps to overcome LME-cracking risk, both from material and process aspects.
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