Large Nuclear Power Plants Research Articles

Study on seismic performance of SRC leaning beam-column exterior joints in the main workshop of CAP1400 nuclear power plant

This paper focuses on the seismic performance of steel reinforced concrete (SRC) leaning beam-column exterior joints in the main workshop of a large capacity nuclear power plant. Quasi-static tests of three specimens with different inclination angles in 1/4 scale of prototype model were carried out. The specimen’ mechanical characteristics, failure modes, hysteresis performance, and energy dissipation capacity were investigated. Based on the quasi-static tests of SRC leaning beam-column exterior joints, the nonlinear test process was simulated and analyzed using ABAQUS software. Besides, the inclination angle of the leaning beam, yield strength of shaped steel, volume-stirrup ratio, and steel content on seismic performance of joints were analyzed by the validated finite element model (FEM). The joint’s carrying capacity and deformation performance can match the seismic design requirements when the inclination angle of the leaning beam was less than 10°. Furthermore, the increase of steel content can enhance the carrying capacity and deformation performance in joints. When the steel content of column and leaning beam was 5.83% and 5.78%, respectively, the ultimate bearing capacity of the joint was increased by about 31% compared with steel content ρc = 2.98% and ρb = 2.97%.

Determination of Emergency Planning Zones distances and scaling-based comparison criteria for downsized Nuclear Power Plants

Nuclear Small Modular Reactors (SMR) present innovative features in design and safety compared to existing Nuclear Power Plants (NPP). Some of these features may turn into a reduction in radioactive releases –both in magnitude and frequency.It seems reasonable to think that smaller plants, i.e. featuring lower power levels, should present lower radioactive releases and offsite consequences. However, how small is small enough cannot be addressed through direct comparison. Furthermore, since multiple nuclear sites to compensate for the same amount of power provided by a single, large nuclear site, might be needed, such direct comparison is ill-conceived.Scaling-based criteria to facilitate comparison of radioactive releases between plants of different size –i.e. power– are proposed. Such criteria set limits to radioactive releases and offsite radioactive risk for SMRs so that offsite consequences of replacing large NPPs by a wider set of SMR sites are not exceeded when assessed globally, i.e. in terms of power generation.The first, deterministic-oriented criterion looks at the radioactive source strength of the SMR based on the maximum size of the SMR Emergency Planning Zone (EPZ) in order not to exceed the EPZ of another NPP when normalizing the EPZ to the power generating unit. The second, risk-informed criterion, looks at the sum of the radioactive harm caused by any event considered under probabilistic analysis application weighted by its frequency, i.e. standard definition of risk.Aside from these two scaling-based criteria for offsite nuclear hazard comparison between nuclear sites of different size, this paper presents two different methods for the determination of EPZ distances. The first method is straightforward based on plant-specific data for dose-consequence calculation, whereas the second, inverse method, builds on extrapolating the EPZ distance of a reference, large NPP down to the SMR.The scaling-based criteria and the methods for the determination of the EPZ distance are put into practice in an application exercise for an integral Pressurized Water Reactor (PWR) SMR.

Reliability and redundancy allocation analysis applied to a nuclear protection system

Brazil is constructing with national technology two small nuclear reactors for propulsion and for radioisotope production with thermal power levels between 20 and 50 MW. These nuclear reactors fit more in the class of small modular reactors (SMR) than in the class of large nuclear power plants. In this article we apply the design approach of SMRs to propose an architecture of reactor protection systems for the small reactor under construction in the country. To do that the probabilistic analysis of the architecture of a nuclear reactor protection system is evaluated to determine the sensitivity of the components through an Reliability Block Diagram modeling. It was evaluated the modification of the architecture and the addition of redundancies when using components with lower life time than the components usually used for this purpose. The results showed that after one year of operation, the reference RPS system presents a failure probability of 0.17 %. The modified system, with components with lower life time, presents a point reliability value only 0.070 % lower than the reference one, but this difference grows exponentially over time, and in 10 years of operation it can reach values above 95%. Using equipment with lower life time characteristics implies a greater number of redundancies and, additionally, a greater number of maintenance procedures and spare parts. Therefore, this technical feasibility analysis should consider a RAM simulation as well.

NEA Framing Nuclear Megaproject “Pathologies”: Vices of the Modern Western Society?

The nuclear sector finds itself at a critical juncture, in part because recent large nuclear power plant projects in Europe and the United States have suffered from what some scholars have called megaproject “pathologies,” that is, the chronic failure of large, complex infrastructure projects to fulfill the “iron triangle” criteria of project performance: cost, timetable, and predefined project prescriptions. To explore the framings of such problems within the nuclear community, this paper analyzes the ways in which 19 experts at the Nuclear Energy Agency (NEA), under the Organisation for Economic Co-operation and Development (OECD) diagnose such problems and their underlying causes. The analysis draws on framing theory and on the scholarship on megaprojects, with semistructured interviews providing the empirical material. The identified four frames highlight as key explanations for pathologies the “vicious circle” of lacking investment, erosion of skills, and construction problems; “bureaucratization and contractualization”; “broken markets”; and “complexity and nuclear-sector exceptionality.” Two overarching metaframes attribute the ultimate reasons to factors outside the projects and the nuclear community, notably to the lack of political leadership and the inability of the modern Western society to identify and pursue its own interest. The NEA frames bear significant resemblance to the alternative megaproject literature, which calls into question the very notion of pathology; stresses the complex, open systems character of megaprojects; and calls for flexibility and adaptability to better align megaprojects with their evolving context. However, the vital need to ensure and maintain an appropriate fit between nuclear-sector megaprojects and their ever-evolving environment deserves greater attention. Toward this end, introduction of OECD-style country peer reviews could constitute an opportunity toward collective “frame reflection,” in interaction with communities offering competing framings of the pathologies. Further research would be welcome on the role of the NEA in framing processes within the nuclear community and on the relationships between megaprojects and modernity in this high-risk industry.

From forests to factories: How modern slavery deepens the crisis of climate change

Globally those in slavery, though small in absolute numbers (est. 40.2 million), contribute disproportionately to environmental destruction and carbon emissions. If modern slaves were a country, they would be the third largest emitter of carbon dioxide in the world, after China and the United States. Concurrently, anthropogenic changes to the global ecosystem have significant impacts on human life, creating vulnerability and displacement that drive modern slavery. This circular relationship is explored through the interaction of contemporary slavery with multiple anthropogenic processes recognized as “planetary boundaries.” It is a key assertion that the study of human rights (and slavery in particular), and the study of anthropogenic impacts, have been falsely seen as distinct and separate issues. In this Perspective, we map an unfolding and extremely troubling nexus between slavery, environmental degradation, and carbon emissions. We break this challenge down into the interconnected processes of extreme weather, deforestation, biodiversity loss, and pollution from manufacturing and resource extraction. We discuss how climate change is a threat multiplier to slavery, but also how slavery is a threat multiplier to the causes of climate change. We conclude by offering compelling policy implications to address these threat multipliers, to help guide future research and policy pathways. Abolishing slavery is shown to be one of the most effective instruments for climate change mitigation, especially given that the costs of ending slavery seem on par to about $20 billion, or the expense of a single large nuclear power plant.

Small Modular and Advanced Nuclear Reactors: A Reality Check

Nuclear power has been declining in importance over the last quarter century, with its share of global electrical energy generation decreasing from 17.5 percent in 1996 to around 10 percent in 2019. Small modular and advanced nuclear reactors have been proposed as potential ways of dealing with the problems-specifically economic competitiveness, risk of accidents, link to proliferation and production of waste-confronting nuclear power technology. This perspective article examines whether these new designs can indeed solve these problems, with a particular focus on the economic challenges. It briefly discusses the technical challenges confronting advanced reactor designs and the many decades it might take for these to be commercialized, if ever. The article explains why the higher construction and operational costs per unit of electricity generation capacity will make electricity from small modular reactors more expensive than electricity from large nuclear power plants, which are themselves not competitive in today's electricity markets. Next, it examines the potential savings from learning and modular construction, and explains why the historical record suggests that these savings will be inadequate to compensate for the economic challenges resulting from the lower generation capacity. It then critically examines arguments offered by advocates of these technologies about job creation and other potential uses of energy generated from these plants to justify subsidizing and constructing these kinds of nuclear plants. It concludes with an assessment of the markets for these technologies, suggesting that these are inadequate to justify constructing the necessary manufacturing facilities.

A threefold empirical analysis of the relationship between regional income inequality and water equity using Tapio decoupling model, WPAT equation, and the local dissimilarity index: evidence from Bulgaria.

This study utilizes a threefold empirical analysis in order to examine the relationship between income and water equity in Bulgaria, the fastest shrinking country in the world in terms of population, and the most unequal member of the EU in terms of regional income distribution. First, in line with this goal, the income elasticity of regional water demand in the country is calculated using the Tapio decoupling model. Second, the WPAT equation which measures the weighted impacts of population, per capita income and intensity on water demand, is utilized. And finally, using the local dissimilarity index, spatial differences in access to water by region are measured. Underscoring the essence of regional level analyses based on specific decomposed sub-groups, findings are thus compatible with the economic and demographic characteristics of the regions handled in the study. In the northern regions where income and population levels are relatively low, during periods when income and water demand both increase, the rise in water demand is usually higher than the increase in income; conversely, when income decreases, the water demand also falls. The effect of population dominates the changes in water demand in the northern regions, with the exception of the Northwestern Region, where water intensity is the leading factor, possibly because the Balkans' largest nuclear power plant is located in the region. In the southern regions where income is higher, income has been the most important determinant of water demand, particularly in recent years.

Subwavelength seismic metamaterial with an ultra-low frequency bandgap

A subwavelength seismic metamaterial (SM) consisting of a three-component SM plate (SMP) and a half space is proposed to attenuate ultra-low frequency seismic surface waves. The design concept and models are verified first by lab-scale experiments on the SM consisting of a two-component SMP and a half space. Then, we calculate the band structures of one-dimensional and two-dimensional subwavelength SMs and evaluate their ability to attenuate Rayleigh waves. A wide ultra-low frequency bandgap can be found, and the Rayleigh waves are deflected by the subwavelength SM and converted into bulk waves in the frequency range of this bandgap. When the number of unit cells of the subwavelength SM is sufficient, the transmission distance and deflection angle of the Rayleigh waves are constant at the same frequency. This discovery is expected to open up the possibility of pragmatic seismic protection for large nuclear power plants, ancient buildings, and metropolitan areas.

Island Operations of Electric Generators Connected to One Substation

<span lang="EN-GB">While increasing integration of renewable energy sources (RES), which are unregulated and difficult to predict, a large system of nuclear power plants must provide balancing peaks in the production of renewable energy. </span><span><span lang="EN">It is also important to simulate </span></span><span lang="EN-GB">the rapid changes in the power of individual </span><span lang="EN">large Nuclear Power Plant</span><span lang="EN-GB"> (NPP) units, and for these regimes to train operators of nuclear units. Therefore the paper is aimed to i<span>sland operations of more parallel electric</span></span><span><span lang="EN">synchronous generators</span></span><span lang="EN"> c<span>onnected to one</span> s<span>ubstation of a power grid.</span></span>

European decision support modelling of long-term external doses received in inhabited areas contaminated by a nuclear power plant accident – 2: Post deposition contaminant mobility on outdoor surfaces

To enable estimation of time-integrated external doses to persons staying in an inhabited area radioactively contaminated by aerosols and gases released in connection with a large nuclear power plant accident, additional knowledge to that described in the first part of this paper is needed on the post-deposition migration of different types of contaminants on the various relevant types of environmental surface. This part of the paper describes how the migration processes are modelled dynamically in the European standard inhabited area dose model, ERMIN, and presents the newest parametric datasets. It is explained how the total information in both parts of the paper may be used to estimate doses received over time by populations in radioactively contaminated inhabited areas.

Development of High Efficiency and Cost Effective Energy Generation Novel Technology

During last, many years the electrical energy is generated in large Thermal Power Plants (TPP) and Nuclear Power Plants (NPP). Thermal Power Plants are the main electricity generating stations that are functioning based on the principle of thermal energy conversion into mechanical and finally into electrical energy. The noted conversion is accomplished by the condensation type of thermodynamic cycle that is called “Rankin” cycle. There are in use Co - generation heat and power plants too, which are functioning based on “Bryton” thermodynamic combined cycle. These plants are assigned for simultaneous generation and distribution of thermal and electrical energy. For this reason, they are more efficient. However, all mentioned cycles and conforming to them power plants serving for generation and distribution of large quantity of electricity from energy generating centralized stations to large number of consumers, which are located in significantly long distance from generating stations. The analysis of existing practice of use of mentioned types of electricity generating powerful centralized stations because of large losses of energy are not enough efficient and cost effective. For instance, the COP of electricity generating station, working by well-known Rankin cycle, makes only 30%, because about 70% of produced thermal energy should be lost to the surrounding environment for providing required conditions of electricity production. It is obvious that such big energy loses extremely pollute the environment, provoke global climate change and forces Governments adopting more forceful approaches to reduce carbon and other harmful gases rejections, increase efficiency of energy generation and improve environmental situation. For this reason, after having studied the potential possibilities of reduction of harmful gases rejections and increase of energy efficiency of electricity generation conventional mods the authors of this article became convinced in impossibility of assigned task and have decided to suggest novel and higher efficiency technology for electric energy generation. From this, point of view this article may become a guideline that can help to improve the present environmental and economic situations.

Radionuclide disposal using the pyrochlore supergroup of minerals as a host matrix-A review.

Since the first large scale commercial nuclear power plant became operational in 1958, the nuclear power industry has been faced with the growing problem of disposal of radionuclides produced from nuclear fission. The current global production of high level nuclear waste is approximately 10,000 metric tons p.a., consisting predominantly of uranium, plutonium, actinides and other minor radionuclides. Developing a safe and cost-effective method for long term storage and disposal of nuclear waste is a key issue of concern to the nuclear power industry. A promising approach to radionuclide disposal is incorporation of the nuclear waste into refractory oxide host minerals or mineral matrices. This technique offers lower leaching rates when compared to the commonly used glass-based vitrification approaches. The refractory pyrochlore supergroup of minerals are particularly attractive for this purpose as they can incorporate considerable amounts of the radionuclides: 93Zr, 133Ba, 135Cs, Th, U, 238Pu, and 244Cm, while demonstrating very low leachability. This review examines the structural, compositional and chemical properties of radionuclide-containing pyrochlore supergroup minerals. Compiled leaching data for radionuclides hosted in pyrochlores demonstrates that these materials offer a high degree of aqueous durability making them strong candidates for radionuclide disposal, offering a viable storage alternative to traditional vitrification methods.

Variable Reactivity Control in Small Modular High Temperature Reactors Using Moderation Manipulation Techniques

With extensive research being undertaken into small modular reactor design concepts, this has brought new challenges to the industry. One key challenge is to be able to compete with large scale nuclear power plants economically. In this article, a novel approach is applied to reduce the overall dependence on fixed burnable poisons during high reactivity periods within a high temperature graphite moderated reactor. To reduce the excess activity, we aim to harden the flux spectrum across the core by removing part of the central moderation column, thus breeding more plutonium, in a later period the flux spectrum is softened again to utilise this plutonium again. This provides a neutron storage effect within the 238U and the resulting breeding of Plutonium. Due to the small size and the annular design of the high temperature reactor, the central reflector is key to the thermalization process. By removing a large proportion of the central reflector, the fuel within the proximity of the central reflector are less likely to receive neutrons within the thermal energy range. In addition to this, the fuel at the extremities of the core have a higher chance of fission due to the higher number of neutrons reaching them. This works as a method of balancing the power distribution between the central and outside fuel pins. During points of low reactivity, such as the end of the fuel cycle, the central reflector can be reinserted and the additionally bred plutonium and U235 at the centre of the core will encounter a higher probability of fission due to more thermal neutrons within this region. By removing the central reflector, this provided a 320 pcm reactivity drop for the duration of the fuel cycle. The plutonium buildup provided additional fissile material up until the central reflector was reinserted. The described method created a two-fold benefit. The overall full power days within the core was increased by ~31 days due to the additional fissile material within the core and secondly the highest loaded power pins saw a 30% power reduction during the removal of the central reflector column.

Seismic response of base isolated nuclear power plants considering impact to moat walls

Seismic isolation can be an effective strategy to protect critical facilities including Nuclear Power Plants (NPPs) from the damaging effects of horizontal earthquake ground shaking. The increased flexibility at the base and resulting elongation of the natural vibration period of the structure leads to significant reductions in forces and acceleration transmitted to the structure above the isolation level at the expense of displacements concentrated in the isolation system. Displacement demands can be large at sites of moderate to high seismic hazard and can be accommodated by a horizontal clearance or moat at the isolation level, typically located in the basement of a structure. A surrounding moat wall can function as a stop to limit isolation system displacements and prevent bearing failure under beyond design basis shaking. However, impact of the isolated structure against the moat wall is of concern due to potential amplification in response of the superstructure. Design guidelines aim to prevent impact by specifying a required minimum clearance to stop (CS) with a low annual frequency of exceedance. A CS below the required value can be justified through analysis considering impact to the moat wall or stop. However, little guidance is available on how to model impact to the moat wall and resulting effects on the NPP superstructure. This study proposes a simplified model for impact simulation that captures the impact forces and the effects of impact on the response of seismically isolated NPPs. Variable clearance to the stop and a range of properties for the moat wall and isolation system are considered to identify parameters that influence the response. Results of these studies indicate that large NPP plants as considered here can have significant penetration into the moat wall, and thus not fully limit displacements in the isolation system, while having considerable increases in accelerations throughout the height of the NPP model.

Developing an Optimum Management Model for Turbomachines

Turbomachinery is an essential part of many industrial processes, from small combustion engines to large nuclear power plants. The efficient management of turbomachines is a complex task because of many parameters to consider, such as flow, pressure, system boundary conditions, etc. Several research studies have been conducted in this direction in order to propose optimal management models. In our study, we have developed an optimization model for turbomachinery management. The model developed is based on genetic algorithms, it saves the energy consumed by turbomachines, and it ensures the proper hydraulic operation of the entire pumping system. The application of the model on the Sidi Aich Ighaouzene drinking water pumping station in the Bejaia wilaya has shown that the model has saved about 14.4% of the cost of energy operation compared to the continuous pumping used. by the water services.

Alternative Fueling Scheme for the Indonesian Experimental Power Reactor (10 MWth Pebble-Bed HTGR)

The National Nuclear Energy Agency of Indonesia (BATAN) is launching a plan (2014) to build an 10 MWth Experimental Power Reactor (Reaktor Daya Eksperimental, RDE) in the Agency’s largest Research Center site, i.e. the Puspiptek Complex, Serpong, South Tangerang, Banten, as a first strategic milestone for the introduction of large scale nuclear power plant fleets into the country. The main objective of the plan is to demonstrate safe and reliable electricity and process heat generation from a nuclear reactor. The RDE is a very small sized pebble-bed high temperature gas-cooled reactor (HTGR) with low enriched uranium (LEU) UO2 TRISO fuel. Following our previous design study with multipass fueling scheme, a scoping study on fuel composition parameters, namely heavy metal (HM) loading per pebble and uranium enrichment was conducted for the simpler once-through-then-out (OTTO) fueling scheme. No need of burnup measurement devices and refueling mechanism to send back discharged fuel pebbles into the core, low power and power density, and simple operation of the RDE become strongest motivation for the present work. The objective function for the optimization is the fissile loading requirement per energy generated (kg/GWd). The optimal heavy metal loading was found around 8 g/pebble while the uranium enrichment corresponding to the 80 GWd/t discharge burnup constraint is approximately 13.7 w/o. Compared with the burnup calculations results of multipass fueling scheme, OTTO fueling scheme burnup performance is slightly inferior in that slightly higher enrichment and fissile loading per pebble are required to achieved the same average discharge burnup.

Impacts of nuclear plant shutdown on coal-fired power generation and infant health in the Tennessee Valley in the 1980s

The Fukushima nuclear accident in March 2011 generated deep public anxiety and uncertainty about the future of nuclear energy. However, differently to fossil fuel plants, nuclear plants produce virtually no greenhouse gas emissions or air pollutants during power generation. Here we show the effect on air pollution and infant health in the context of the temporary closure of nuclear plants by the Tennessee Valley Authority (TVA) in the 1980s. After the Three Mile Island accident in 1979, the US Nuclear Regulatory Commission intensified inspections throughout the nation, leading to the shutdown of two large nuclear power plants in the TVA area. In response to that shutdown, electricity generation shifted one to one to coal-fired power plants within TVA, increasing particle pollution in counties where they were located. Consequently, infant health may have deteriorated in the most affected places, indicating deleterious effects to public health. Nuclear accidents generate vast echoes in public opinion, and often determine policy decisions to suspend nuclear programs. This study shows the unintended implications of nuclear plant shutdown in Tennessee Valley between 1983 and 1986, demonstrating deleterious consequences for public health.

Improving power and desalination capabilities of a large nuclear power plant with supercritical CO2 power technology

To response to the increasing demands for clean water, a large pressurized water reactor (PWR) with a desalination capability has been studied and demonstrated its potential so far. However, the electricity production of the large nuclear reactor decreases by 10% due to steam bypass for desalination. In this study, the authors evaluate the possibility of a large PWR with a capability of producing both electric power and clean water by using the supercritical CO2 (S-CO2) Brayton cycle technology. The S-CO2 power technology is adopted to minimize the decrease in the electricity production capacity due to desalination process. Two concepts which replace the existing steam based power conversion system with a S-CO2 Brayton cycle were proposed. The first concept is that the low pressure steam turbine section of the power conversion system is replaced with the S-CO2 Brayton cycle. The second concept is that the whole steam based power conversion system is replaced with the S-CO2 Brayton cycle. Several S-CO2 cycle options were considered in terms of power production and the desalination capacity and conducted a comparative analysis of selected layouts and the optimal operating conditions of the suggested layouts were identified.

Thinking big? Ghana, small reactors, and nuclear power

Ghana has been seen as a potential market for small nuclear reactors and Ghanaian nuclear officials have, on occasion, expressed an interest in such reactors. However, Ghana seems to be heading towards procuring a reactor from Russia with a capacity of 1000–1200MW. A power plant with such a large power generation capacity is not appropriate to Ghana’s limited electricity grid or its financial circumstances. This paper examines the likely reasons for this focus and argues that despite greater government interest in setting up nuclear reactors, Ghana’s nuclear establishment may not have the political clout to force through the purchase of a reactor, and has therefore attempted to position itself as a complete, one-stop solution to Ghana’s electricity crisis, by calling for the construction of just one or two large nuclear power plants. The paper draws on the role of discursive elements in energy policy making, discusses the policy implications of this reactor choice, and offers evidence for the proposition that decision about nuclear power are not made on the basis of merely techno-economic considerations but are driven by a range of social and political factors.

Modularity in nuclear power plants: a review

PurposeModularity in design and construction of nuclear power plants (NPPs) is widely used for reduction in project construction time and cost. This paper aims to improve understanding of existence, rationale, relevance, types and definitions of modularity in NPPs.Design/methodology/approachThe paper approaches study of modularity in NPPs through review of existing literature. The objective of this paper is to answer the questions such as “what is the meaning of module in the context of NPPs?”, “what is the meaning of modularity in the context of NPPs?”, “why modularity is considered in the design and construction of NPPs?”, “what are the types of modules and modularity?” and “what are the emerging trends?”FindingsFindings of the paper indicate towards widespread use of modularity to reduce construction time and cost, improve safety performance and enable smarter applications of NPPs. Large NPPs tend to use modularity to shorten the project gestation period, and thereby reduce capital cost. Small and medium size NPPs plan to use modularity for simpler and safer reactors that can be factory manufactured, transported, installed and scaled up as permitted by the economic environment.Research limitations/implicationsThis being a review, it has the usual limitations associated with the literature review papers.Practical implicationsFindings of the paper may influence policy regarding option, type, size, design, engineering, procurement and construction of NPPs.Social implicationsFindings of the paper may influence the safety, cost, time and quality performance of future NPPs and facilitate cheaper and more reliable supply of electricity to consumers.Originality/valueThe systematic literature review presents issues and emerging trends in modularity of NPPs, enabling the future work to progress as modularity continues to develop and evolve. The paper also proposes a comprehensive classification and definitions of modules and modularity in NPPs that may facilitate understanding of these terms precisely and uniformly by researchers and practitioners alike.