Roles of nuclear energy in Japan's future energy systems

The roles of nuclear energy in Japan's future energy systems were analyzed from the viewpoint of securing stable energy supply and reducing carbon dioxide (CO₂) emissions. The MARKAL model, developed in the Energy Technology Systems Analysis Programme (ETSAP) of the IEA, was used for establishing several energy scenarios with different assumptions on the availability of nuclear energy, natural gas, and a CO₂ disposal option. Nuclear energy was assumed to apply for synthetic fuel production as well as for conventional electric power generation. By comparing the CO₂ emission and system costs between these energy scenarios, following results were obtained. Without nuclear energy, the CO₂ emissions will hardly be reduced because of substantial increases in coal utilization. CO₂ disposal will be effective in reducing the emissions, however at much higher costs than the case with nuclear energy. The expansion of natural gas imports, if alone, will not reduce the emissions at enough low levels.     

Importance of nuclear generation in the struggles to reduce CO2 emission at Kansai Electric Power Co.

It has been pointed out in recent years that the potential impacts of global warming has been becoming more and more serious because of the rapid increase of anthropogenic CO₂ emission.

Japan's annual CO₂ emissions (fiscal 1994) amounted to 343 million tons of carbon. Although CO₂ emissions caused by fossil-fuel power generation accounted for 29.4% of total, on a sector basis, those directly from the energy conversion sector accounted for only 7.7%. Most CO₂ emissions (21.7% of total) resulted from electric power use in the industrial, commercial and domestic sectors. Thus, the reduction of CO₂ emissions caused by the use of electricity is a nationwide subject.

Understanding that both supply side and demand side approaches are necessary, Kansai Electric has been deploying “New ERA Strategy” as a comprehensive strategy to seek a potential for CO₂ reduction more broadly and deeply. Among a number of action items are the promotion of nuclear power generation, and improvement of overall energy efficiency, besides such demand side measures as leveling off the peak load.

The effectiveness of action items of the New ERA Strategy was evaluated in terms of CO₂ reduction. As a result, estimated CO₂ reduction related to nuclear power amounted to 88% of the total for fiscal 1995 in comparison with 1990, and that expected in 2000 is 84%. These results reconfirm that nuclear power is always the key to practical CO₂ reduction at present and in the future.

Comparison with candidate technology alternatives revealed that photovoltaic power generation needed 7 times greater rated capacity and 280 times larger area than nuclear power, so it is not realistic as a central power station alternative. The comparison also clarified that if wind power stations were constructed at all feasible sites in the Kansai region, they would not be a viable alternative to a single nuclear unit from CO₂ reduction viewpoint.     

The role of nuclear power in the sustainable energy future of Korea

The purpose of this study is to analyze the role of nuclear power in the sustainable energy supply future of Korea. For this purpose, an energy-economy interaction model of the computational general equilibrium (CGE) approach, the Korean Energy and Environmental Policy model(KEEP) was adapted. The model is a non-linear optimization model that maximizes the discounted value of Korean economic utility. The model operates over the time horizon of 1995–2040 in annual steps.

Some scenarios are established in accordance with three possible nuclear growth rate and the strength of the carbon tax imposed. At first, business as usual(BAU) nuclear growth scenario was set up and maintaining the current installed capacity and phasing out the nuclear power options are considered. After that, the investigation has been done on each scenario in the case that a tax for CO₂ emission regulation was imposed.

Results show that limiting CO₂ emissions with a nuclear phase out scenario will have the most serious impact on the economic welfare compared with the other scenarios. If the CO₂ emission target will be imposed in Korea in the foreseeable future, nuclear power will play an important role in mitigating the economic impacts.

This analysis gives us a chance to consider the trade-offs between the most important energy issues of today-concerns with the risk of nuclear power, those involving future climate change, and energy security.     

Synergistic hydrogen production by nuclear-heated steam reforming of fossil fuels

Processes and technologies to produce hydrogen synergistically by the nuclear-heated steam reforming reaction of fossil fuels are reviewed. Formulas of chemical reactions, required heats for reactions, saving of fuel consumption, reduction of carbon dioxide emission, and possible processes are investigated for such fossil fuels as natural gas, petroleum and coal.

In this investigation, examined are the steam reforming processes using the “membrane reformer” and adopting the recirculation of reaction products in a closed loop configuration. The recirculation-type membrane reformer process is considered to be the most advantageous among various synergistic hydrogen production processes. Typical merits of this process are; nuclear heat supply at medium temperature around 550°C, compact plant size and membrane area for hydrogen production, efficient conversion of a feed fossil fuel, appreciable reduction of carbon dioxide emission, high purity hydrogen without any additional process, and ease of separating carbon dioxide for future sequestration requirements.

The synergistic hydrogen production using fossil fuels and nuclear energy can be an effective solution in this century for the world which has to use fossil fuels to some extent, according to various estimates of global energy supply, while reducing carbon dioxide emission.     

Nuclear energy system for the global environmental regulation in Korea— Energy-economy interaction model analysis

Global environmental regulation such as limits on CO₂ emissions will change the energy cost as well as energy mix, and it will eventually affect the potential economic growth and future energy demand. The rise of energy price from the environmental regulation will encourage the efficiency increase of energy use, fuel switching and the substitution between the energy and the other factors of production like labour and capital. Such situations can be successfully simulated through an energy-economy model which permits two-way interaction between energy and economy.

An analysis on the role of nuclear energy system for meeting the global environmental constraint like CO₂ emission regulation, has been performed through an energy-economy interaction model - EFOM-MACRO-KOREA.

In case carbon taxation which is a widely discussed policy measure for CO₂ abatement should be introduced, the role of nuclear energy in the domestic sustainable energy system as well as the economic impacts has been assessed. For the analysis, various scenarios in tax rate have been considered. Levying carbon tax will decrease future economic growth, and the decrease will be bigger in case that there are some restrictions on nuclear installation. It is shown that nuclear energy system will play an important role in Korean sustainable development up to 2040 in most cases.     

CO_2 conversion by thermal plasma with carbon as reducing agent: high CO yield and energy efficiency

A key problem in CO_2 conversion by thermal plasma is suppressing the inverse reactions,CO?+?O?→?CO_2 and CO?+?0.5O_2?→?CO_2, to simultaneously obtain high CO yield and energy efficiency. This can be done by quickly quenching the decomposed gas or rapidly taking away free oxygen from decomposed gas. In this paper, experiments of CO_2 conversion by thermal plasma with carbon as a reducing agent are presented. Carbon quickly devoured free oxygen in thermal plasma decomposed gas, and not only is the inverse reaction completely suppressed, but the discharge energy to form oxygen atoms, oxygen molecular, and thermal energy is also reused.A CO_2 conversion rate of 67%–94% and the corresponding electric energy efficiency of about 70% are achieved, both are much higher than that seen so far by other plasma implementations.     

Futures for hydrogen produced using nuclear energy

What is the future of hydrogen (H₂) produced from nuclear energy? Assuming that economically competitive nuclear H₂ can be produced, production of H₂ may become the primary use of nuclear energy and the basis for both a nuclear-H₂ renewable (solar, wind, etc.) energy economy and a nuclear-H₂ transport system. The technical and economic bases for these conclusions are described. In a nuclear-H₂ renewable energy economy, nuclear energy is used to produce H₂ that is stored and becomes the energy-storage component of the electrical generating system. The stored H₂ replaces piles of coal and tanks of liquid fuel. Capital-intensive renewable energy sources and nuclear reactors produce electricity at their full capacity. The stored H₂ is used in fuel cells to produce the highly variable quantities of electricity needed to fill the gap between the electricity demand by the customer and the electricity generated by the rest of the electrical generating system. Hydrogen is also used to produce the liquid or gaseous transport fuels. This energy-system architecture is a consequence of the fundamental differences between the characteristics of electricity (movement of electrons) and those of H₂ (movement of atoms). Electricity can be generated, transformed, and used economically on either a small or a large scale. However, it is difficult to generate, store, and transform H₂ economically on a small scale. This distinction favors the use of large-scale nuclear systems for H₂ production.     

The strategies of abating emission of CO2 and nuclear energy development in China

In China, annual coal consumption accounts for the first place all over the world in order to meet the high speed development of economy and improvement of the people's living quality. CO₂ emission from coal fire is a main contributor to the climate change. We must abate CO₂ emission besides developing economy for mitigating the global climate change. In the feasible countermeasure to reduce CO₂ emission, which includes improving energy efficiency and developing alternative energy, developing nuclear energy is an important one.     

Nuclear energy for transportation: Paths through electricity, hydrogen and liquid fuels

The transportation sector consumes about a quarter of final energy in Japan and worldwide, and presently most of the energy is supplied by petroleum. For global environment and resources, it is important to seek possibilities of replacing a substantial part of the transportation energy by nuclear energy.

For supplying nuclear energy to the transportation sector, investigated are the paths through such ‘energy carriers’ as electricity, hydrogen and synthetic liquid fuels, to the means of transportation such as automobiles. These energy carriers can be produced from nuclear energy, by itself or synergistically with other primary energies like fossil fuels or biomass.

In this paper, possibilities and impacts of these energy carriers to power transportation means are reviewed, and measures and tasks to supply these energy carriers from nuclear energy are examined.

In converting the primary energies into the energy carriers, the synergistic process may be more advantageous than the individual process. Some of the exploratory processes to produce synthetic liquid fuels from fossil fuels and nuclear energy are presented.     

The role of nuclear energy in 21st century for sustainable development in Korea

With the growing international consensus concerning the harmful health and environmental impact of fossil energy use, there is on the political level recognition of nuclear power's potential role in delivering large quantities of energy without releasing common environmental pollutants and greenhouse gases. The energy consumption in Korea has greatly increased with rapid economic growth and industrialization since 1970. The average annual growth rate was 8% in 1970s and more than 10% in 1980s and 1990s except during the '98 financial crisis.

Due to the lack of domestic energy resource bases, the rapid economic growth and industrialization has to be supported by the imported energy. Thus, the imported energy dependence of total energy supply has rapidly increased from 47.5% in 1970 to 97.5% in 1997. The fossil fuels share of energy consumption grew up to 88.2% in 1997. This resulted to CO2 emission of 140 million ton-C, which account for 1.8% of world greenhouse gases emission. (MOCIE, 2000) Because of rapid industrialization, Korea has relatively higher energy intensive industries compared to most of the developed countries with 3.1 ton-C/capita and 0.49 ton-C/million Won.

Thus, energy policy is being focused on the improvement of energy efficiency and optimum energy mix for the reduction of GHGs. At present, 16 units of Nuclear Power Plant are in operation, 6 units under construction. The nuclear share of electric power generation was 43% last year. This share will be increased up to more than 50% by 2015. In order to meet voluntary GHGs emission target, a drastic switching to non-carbon energy bases would be necessary.     

Sustainability by combining nuclear,fossil, and renewable energy sources

The energy industries face two sustainability challenges: the need to avoid climate change and the need to replace traditional crude oil as the basis of our transport system. Radical changes in our energy system will be required to meet these challenges. These challenges may require tight coupling of different energy sources (nuclear, fossil, and renewable) to produce liquid fuels for transportation, match electricity production to electricity demand, and meet other energy needs. This implies a paradigm shift in which different energy sources are integrated together, rather than being considered separate entities that compete. Several examples of combined-energy systems are described. High-temperature nuclear heat may increase worldwide light crude oil resources by an order of magnitude while reducing greenhouse gas releases from the production of liquid fossil fuels. Nuclear–biomass liquid-fuels production systems could potentially meet world needs for liquid transport fuels. Nuclear–hydrogen peak power systems may enable renewable electricity sources to meet much of the world's electric demand by providing electricity when the wind does not blow and the sun does not shine.     

AP1000 will meet the challenges of near-term deployment

The world demand for energy is growing rapidly, particularly in developing countries that are trying to raise the standard of living for billions of people, many of whom do not have access to electricity or clean water. Climate change and the concern for increased emissions of green house gases have brought into question the future primary reliance of fossil fuels. With the projected worldwide increase in energy demand, concern for the environmental impact of carbon emissions, and the recent price volatility of fossil fuels, nuclear energy is undergoing a rapid resurgence. This “nuclear renaissance” is broad based, reaching across Asia, North America, Europe, as well as selected countries in Africa and South America. Many countries have publicly expressed their intentions to pursue the construction of new nuclear energy plants. Some countries that have previously turned away from commercial nuclear energy are reconsidering the advisability of this decision. This renaissance is facilitated by the availability of more advanced reactor designs than are operating today, with improved safety, economy, and operations.One such design, the Westinghouse AP1000 advanced passive plant, has been a long time in the making! The development of this passive technology started over two decades ago from an embryonic belief that a new approach to design was needed to spawn a nuclear renaissance. The principal challenges were seen as ensuring reactor safety by requiring less reliance on operator actions and overcoming the high plant capital cost of nuclear energy. The AP1000 design is based on the use of innovative passive technology and modular construction, which require significantly less equipment and commodities that facilitate a more rapid construction schedule. Because Westinghouse had the vision and the perseverance to continue the development of this passive technology, the AP1000 design is ready to meet today's challenge of near-term deployment.     

Radiation shielding design of the CFETR polarimeter interferometer and CO2 dispersion interferometer

A three-wave based laser polarimeter/interferometer and a CO₂ laser dispersion interferometer are used to determine the electron and current density profiles on a Chinese fusion engineering test reactor (CFETR). Radiation shielding is designed for the combination of polarimeter/interferometer and CO₂ dispersion interferometer. Furthermore, neutronics models of the two systems are developed based on the engineering-integrated design of CFETR polarimeter/interferometer and CO₂ dispersion interferometer and the major material components of CFETR. The polarimeter/interferometer and CO₂ dispersion interferometer's neutron and photon transport simulations were performed using the Monte Carlo neutral transport code to determine the energy deposition and neutron energy spectrum of the optical mirrors. The energy depositions of the first mirrors on the polarimeter/interferometer are reduced by three orders with the whole shielding. Since the mirrors of CO₂ dispersion interferometer are very close to the diagnostic first wall, shielding space is limited and the CO₂ dispersion interferometer energy deposition is higher than that of the polarimeter/interferometer. The dose rate after shutdown 10⁶ s in the back-drawer structure has been estimated to be 83 μSv h⁻¹ when the radiation shield is filled in the diagnostic shielding modules, which is below the design threshold of 100 μSv h⁻¹. Radiation shielding design plays a key role in successfully applying polarimeter/interferometer and CO₂ dispersive interferometer in CFETR.     

Enhanced CO2 decomposition via metallic foamed electrode packed in self-cooling DBD plasma device

A self-cooling dielectric barrier discharge reactor, packed with foamed Cu and Ni mesh and operated at ambient conditions, was used for the composition of CO₂ into CO and O₂. The influences of power, frequency, and other discharge characteristics were investigated in order to have a better understanding of the effect of the packing materials on CO₂ decomposition. It is found that porous foamed Cu and Ni not only played a role as the carrier of energy transformation and electrode distributed in discharge gaps but also promoted the equilibrium shifting toward the product side to yield more CO by consuming some part of O₂ and O radicals generated from the decomposition of CO₂. The maximum CO₂ decomposition rates of 48.6% and 49.2% and the maximum energy efficiency of 9.71% and 10.18% were obtained in the foamed Ni and Cu mesh, respectively.     

Extraction behavior of Ga(III) and Pd(II) with 2-methyl-8-quinolinol derivatives into supercritical fluid CO2

The extraction behavior of gallium(III) and palladium(II) with 2-methyl-8-quinolinol (HMQ), 2-methyl-5-hexyloxymethyl-8-quinolinol (HMO₆Q) and 5-hexyloxymethyl-8-quinolinol (HO₆Q) from an acidic solution into supercritical fluid (SF) CO₂ were investigated. Furthermore, the pH of an acidic solution contacting with SF CO₂ was spectrophotometrically measured, and the distribution constants of HMO₆Q between SF CO₂ and water were also determined at I = 0.1 M (H, Na)NO₃, 45°C, and 8.6 – 20.4 MPa. Above pH 3, the pH of the aqueous phase in contact with SF CO₂ was levelled to about 3. On the other hand, below pH 3, the pH change is negligibly small. The distribution constant (K_{D,SF CO2} of HMO₆Q between SF CO₂ and water at 20.4 MPa was about one tenth of the K_D for heptane - water system, indicating that the solubility of HMO₆Q in SF CO₂ is remarkably smaller compared with that in heptane. The Ga(III)-HMO₆Q and Ga(III)-HO₆Q complex extracted into SF CO₂ were assigned to be Ga(OH)(MO₆Q)₂ and Ga(O₆Q)₃, respectively. Palladium(II) was extracted with HMQ as Pd(MQ)₂ from a weakly acidic solution. Even in the presence of HMQ, the Pd(II)-HMQ complex extracted from the higher HCl concentration should be H₂PdCl₄.     

Future potential of nuclear heat utilization in energy, economy and environment

In this study quantitative analyses are made to clarify the possible roles of S-HTGRs (Small-sized modular High Temperature Gas-cooled Reactors) in our future energy systems. The results obtained show the good possibility of S-HTGRs to compete economically with L-HTGRs (Large-sized HTGR) taking into account the effects of modularization, learning, mass production, and simplification of safety systems. In the electricity market, S-HTGRs can well compete with coal steam electric power and LWR electric power if they are located close to demand areas. In addition the high temperature nuclear heat from small-sized modular gas-cooled reactors has the potential of contributing to reduce the amount of imported fossil fuels and also SO₂, NO_x, and CO₂ emissions.     

应用于等离子体排灰气处理的甲烷水汽重整反应的热力学分析

Tokamak装置中的等离子体反应一段时间后,需对产生的排灰气进行净化处理,以回收其中的氘氚。目前拟采用甲烷水汽重整反应将化合态的氘氚转化为单质并回收。本文运用Gibbs自由能最小化方法,对应用于等离子体排灰气处理的水汽重整反应进行热力学分析,考查反应温度、原料比例、反应压力、O₂、CO₂、H₂、CO等因素对反应平衡的影响,确定了适宜的反应条件,即反应温度范围650～700 ℃,压力1×105 Pa,水碳比1.5～2.0。此外,原料气中O₂或CO₂的存在有利于减少积碳的生成量,并获得较高的氢同位素平衡转化率;H₂的存在对重整反应的热力学平衡无明显影响;CO的存在会使积碳量增加,对反应产生不利影响,在进入重整反应器前应将其去除。     

Sustainable futures using nuclear energy

We present the role of nuclear energy in a sustainable future. This addresses the social, economic and environmental concerns of us all. Nuclear energy today avoids the emission of nearly two billion tonnes of greenhouse gases (GHGs) each year, thanks to over 400 reactors operating worldwide.

Nevertheless, there is no real recognition of real incentives for large-scale non-emitters like nuclear energy and for emissions avoidance in current Kyoto and other policies. These approaches rely heavily on conservation, renewables and efficiency. These measures alone also will not significantly reduce the atmospheric greenhouse burden, because the world is still growing. Also, our (the world's) future economic growth (in all countries) is tied to energy and electricity use. Our prosperity, the alleviation of poverty and the sustainability of the world depend on having a supply of emissions-free and safe energy.

Recent price hikes in fossil fuels and power blackouts also emphasize our need for reliable, safe and cheap power, as is offered by nuclear energy when coupled with effective and secure waste disposal.

A particularly important role for nuclear power in the future will be its links to the hydrogen economy. It is now recognised that the introduction of hydrogen into the transportation sector will benefit the environment only when low carbon sources, such as nuclear reactors, are the primary energy source for hydrogen production. The future could well be the Hydrogen Age. We show that a major reduction in GHGs worldwide can be obtained by nuclear-electric production of hydrogen, thus alleviating their potential effects on future generations. We also demonstrate a potential key synergism with renewable wind power in the hybrid production of distributed hydrogen. Thus, nuclear energy supports and enables the World in its journey to a sustainable, safe and secure energy future.     

赣杭构造带某铀矿区地下水中铀的存在形式研究北大核心CSCD

为研究铀矿区地下水化学性质对铀的存在形式的影响,本文以赣杭构造带某铀矿区地下水为研究对象,在对9个典型采样点地下水化学成分分析的基础上,采用数理统计软件SPSS 18.0和地球化学模拟软件PHREEQC及llnl.dat数据库,探究了研究区内地下水水化学特征及U的存在形式。结果表明:本研究区地下水水化学类型以HCO_(3)-Na与HCO_(3)-Na·Ca为主,U含量与Ca^(2+)和Mg^(2+)浓度体现出较强正相关性,与SO_(4)^(2-)的相关性次之;地下水中U元素主要以六价为主,几乎占100%,主要存在形式依次为UO_(2)(CO_(3))_(2)^(2-)、UO_(2)(CO_(3))_(3)^(4-)、UO_(2)CO_(3)、UO_(2)(OH)2、UO_(2)(OH)_(3)^(-)、UO_(2)OH^(+)等6种,其中UO_(2)(CO_(3))_(2)^(2-)占绝对优势,整体以碳酸铀酰形式为主,这也与研究区地下水酸碱性相对应。