Reducing future CO2 emissions — The role of nuclear energy

A study was made to analyze the potential of reducing CO₂ emissions and to identify important energy and technology options in future energy systems of Japan. The energy market optimum allocation model MARKAL was used for the analysis with a time horizon from 1990 to 2050.

The analytical procedures were as follows. First, a reference energy system was established by incorporating all important energy sources, energy carriers, and energy technologies that existed already or that might be introduced during the above time horizon. Second, future demand for energy services was estimated based on the two economic growth scenarios, high and low. Also, assumptions were made about the evolution of imported fuel prices, availability of energy resources, and so on. Third, under the above assumptions, the optimum energy and technology options were selected by minimizing a discounted system cost under different carbon tax schemes, and thereby the potential of reducing CO₂ emissions was analyzed.

The following results were obtained by the analysis. Without utilization of nuclear energy, the CO₂ emissions can be hardly stabilized at the 1990 emission level even in the case of the low economic growth and large scale deployment of CO₂ recovery and disposal assumed. A significant amount of fossil fuels will be used for power generation in order to meet the rapidly growing demand for electricity. Nuclear energy, by substituting fossil fuels for electric power generation, is expected to contribute to the reduction of CO₂ emissions. In addition, the average cost of reducing the emissions will be substantially lowered compared with a non nuclear scenario.     

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.     

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.     

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.     

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.     

Plasma-assisted Ru/Zr-MOF catalyst for hydrogenation of CO2 to methane

As an important type of metal–organic framework (MOF), Zr-MOF shows excellent CO₂ adsorption performance. In this work, a Zr-MOF was synthesized by a solvothermal method and adopted to support Ru through simple incipient-wetness impregnation. Then the Ru/Zr-MOF was applied for CO₂ hydrogenation (V_H2 : V_CO2= 4:1) with the assistance of dielectric barrier discharge (DBD) plasma. The hydrogenation of CO₂ results showed that methane was produced selectively under the synergistic effect between plasma and the Ru/Zr-MOF catalyst, and the selectivity and yield of methane reached 94.6% and 39.1%, respectively. The XRD and SEM analyses indicate that the basic crystalline phase structure and morphology of the Zr-MOF and Ru/Zr-MOF remained the same after DBD plasma treatment, suggesting that the catalysts are stable in plasma. The guest molecules in the pores of the Zr-MOF are removed and the Ru³⁺ ions are reduced to metallic Ru⁰ in the reduction atmosphere according to the BET and XPS results, which are responsible for the high performance of plasma with the Ru/Zr-MOF catalyst. In situ optical emission spectra of pure plasma, plasma with Zr-MOF, and plasma with Ru/Zr-MOF were measured, and the active species of C, H and CH for CO₂ hydrogenation were detected. The plasma-assisted Ru/Zr-MOF exhibited high catalytic activity and stability in CO₂ hydrogenation to methane, and it has great guiding significance for CO₂ hydrogenation by using plasma and MOF materials.     

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.     

Study of steam, helium and supercritical CO2 turbine power generations in prototype fusion power reactor

Power generation systems such as steam turbine cycle, helium turbine cycle and supercritical CO₂ (S-CO₂) turbine cycle are examined for the prototype nuclear fusion reactor. Their achievable cycle thermal efficiencies are revealed to be 40%, 34% and 42% levels for the heat source outlet coolant temperature of 480 °C, respectively, if no other restriction is imposed. In the current technology, however, low temperature divertor heat source is included. In this actual case, the steam turbine system and the S-CO₂ turbine system were compared in the light of cycle efficiency and plant cost. The values of cycle efficiency were 37.7% and 36.4% for the steam cycle and S-CO₂ cycle, respectively. The construction cost was estimated by means of component volume. The volume became 16,590 m³ and 7240 m³ for the steam turbine system and S-CO₂ turbine system, respectively. In addition, separation of permeated tritium from the coolant is much easier in S-CO₂ than in H₂O. Therefore, the S-CO₂ turbine system is recommended to the fusion reactor system than the steam turbine system.     

Development of next generation PWR in Japan

The demand for energy in Japan is expected to increase steadily into the future, and it seems that the importance of nuclear power generation will be heightened more when the situation of our country which is not rich in energy resources is taken into account.

Furthermore, when we consider the present situation that the light water reactors have become common, recent outlook for the supply and demand for uranium resources, trends in the development of the fast breeder reactor technology, etc., the light water reactors are expected to remain dominant in the nuclear power generation of our country until at least the second half of the 21st century.

Based on such a background five PWR utilities in Japan (Hokkaido, Kansai, Shikoku, Kyushu, and the Japan Atomic Power), and Mitsubishi Heavy Industries, Ltd. have jointly started researching the Next Generation PWR which is expected to be the leading nuclear power plant taking place of APWR.     

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.     

Role of nuclear energy in environment, economy, and energy issues of the 21st century – Growing energy demand in Asia and role of nuclear

The economic growth of recent Asia is rapid, and the GDP and the energy consumption growth rate are about 8–10% in China and India. The energy consumption forecast of Asia in this century was estimated based on the GDP growth rate by Goldman Sachs. As a result, about twice in India and Association of South East Asian Nations (ASEAN) and about 1.5 times in China of SRES B (Special Report on Emission Scenarios) are forecasted. The simulation was done by Grape Code to analyze the impact of energy increase in Asia. As for the nuclear plant in Asia, it is expected 1500 GWe in 2050 and 2000 GWe in 2100, in the case of the environmental constrain. To achieve this nuclear utilization, there are two important aspects, technically and institutionally.

A. Development of the CANDLE core and/or the Breed and Burn core.

B. The establishment of the stable nuclear fuel supply system like “Asian nuclear fuel supply organization”.

Insulation characteristics of triple mixtures of c-C4F8/N2/CO2 under lightning impulse voltage

This paper has researched the insulation characteristics of 10%c-C₄F₈/N₂/CO₂ mixtures under lightning impulse voltage by experiment. It is shown that the positive and negative lightning impulse breakdown voltages of 10%c-C₄F₈/N₂/CO₂ gas mixtures rise linearly as the electrode gap distance and gas pressure increase and under the same conditions, the positive lightning impulse breakdown voltage of the gas mixtures is always higher than the negative lightning impulse breakdown voltage. As the gas mixtures have a little higher liquefied temperature than SF₆ and the comprehensive GWP is about 5% of SF₆ , and the positive and negative lightning impulse breakdown voltages can both reach 60% of SF₆ , 10%c-C₄F₈/N₂/CO₂ gas mixtures can be applied as insulation gas in electrical equipment such as C-GIS, GIT, GIL and so on.     

Enhancing toluene removal in a plasma photocatalytic system through a black TiO_2 photocatalyst

An efficient toluene removal in air using a plasma photocatalytic system(PPS) not only needs favorable surface reactions over photocatalysts under the action of plasma,but also requires the photocatalysts to efficiently absorb light emitted from the discharge for driving the photocatalytic reactions. We report here that the PPS constructed by integrating a black titania(B-TiO_2)photocatalyst with a dielectric barrier discharge(DBD) can effectively remove toluene with above 70% CO_2 selectivity and remarkably reduced the concentration of secondary pollutants of ozone and nitrogen oxides at a specific energy input of 1500 J·l~(-1),while exhibiting good stability. Photocatalyst characterizations suggest that the B-TiO_2 provides a high concentration of oxygen vacancies for the surface oxidation of toluene in DBD,and efficiently absorbs ultraviolet–visible light emitted from the discharge to induce plasma photocatalytic oxidation of toluene. The presence of B-TiO_2 in the plasma region also results in a high discharge efficiency,facilitating the generation of large numbers of reactive species and thus the oxidation of toluene towards CO_2. The greatly enhanced performance of the PPS integrated with B-TiO_2 in toluene removal offers a promising approach to efficiently remove refractory volatile organic compounds from air at low temperatures.     

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。     

Medium temperature carbon dioxide gas turbine reactor

A carbon dioxide (CO₂) gas turbine reactor with a partial pre-cooling cycle attains comparable cycle efficiencies of 45.8% at medium temperature of 650 °C and pressure of 7 MPa with a typical helium (He) gas turbine reactor of GT-MHR (47.7%) at high temperature of 850 °C. This higher efficiency is ascribed to: reduced compression work around the critical point of CO₂; and consideration of variation in CO₂ specific heat at constant pressure, C_p, with pressure and temperature into cycle configuration. Lowering temperature to 650 °C provides flexibility in choosing materials and eases maintenance through the lower diffusion leak rate of fission products from coated particle fuel by about two orders of magnitude. At medium temperature of 650 °C, less expensive corrosion resistant materials such as type 316 stainless steel are applicable and their performance in CO₂ have been proven during extensive operation in AGRs. In the previous study, the CO₂ cycle gas turbomachinery weight was estimated to be about one-fifth compared with He cycles. The proposed medium temperature CO₂ gas turbine reactor is expected to be an alternative solution to current high-temperature He gas turbine reactors.     

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.     

Operando FT-IR study on basicity improvement of Ni(Mg,Al)O hydrotalcite-derived catalysts promoted by glow plasma discharge

CO₂ adsorption on the surface of hydrotalcite-derived mixed oxide catalysts was investigated under low pressure glow discharge plasma in operando conditions via FT-IR spectroscopy. Nickel catalysts were promoted with various transition metal species (Ce, Fe, La, Zr) to influence their physico-chemical properties. Fe and Zr species were successfully incorporated into hydrotalcite brucite layers. After calcination formed a single phase with Ni(Mg, Al)O mixed oxide, while La and Ce species formed separate phases. This had a consequence in the distribution of surface basic sites as well as in the affinity to CO produced upon CO₂ dissociation in plasma. Plasma treatment activated the surface of prepared materials and changed their properties via the generation of strong basic sites associated with low coordinated surface oxygen anions. Moreover, the CO₂ adsorption capacity of prepared materials increased after plasma treatment.     

复杂混合气体组分在低温活性炭表面的吸附特性

为实现大体积气体中微量放射性气体Kr、Xe同位素的测量,须将混合气体进行浓集并将目标气体吸附于10 mL左右的活性炭源盒中。本实验对混合气体中各组分在活性炭分离柱上的吸附性能进行研究,建立了通过去除其他杂质气体、浓集大体积气体制备放射性Kr和Xe活度源的方法。根据反应堆流出气体和核爆可能生成的气体组分,配制了模拟气体,使用活化的4A分子筛对其中的水和CO₂进行模拟去除,获得了流程中去除水和CO₂的实验条件;选择5个低温点(273、264、255、246、238 K),在低温活性炭柱上对H₂、CO、CH₄、Kr和Xe的吸附特性进行研究,测定了各气体在不同温度下的吸附穿透曲线。结果表明,室温下4A分子筛对水和CO₂有较好的吸附效果。低温下,H₂、CO不易在活性炭表面吸附;CH₄、Kr吸附性质相似;Xe吸附能力较强。低温下难以去除的CH₄可在高温下氧化去除。因此,可根据混合气体中各组分性质的不同实现杂质气体的去除和目标气体Kr、Xe的回收测量。     

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.     

AMS-14C样品制备系统的研制及其性能研究

为了开展加速器质谱仪（accelerator mass spectrometry, AMS）在¹⁴C测量方面的研究,研制了可采用锌法、氢法、氢化钛法制备¹⁴C样品的装置,该制样系统以石英玻璃为主要结构材料,分为以下三个单元：系统真空维护单元、CO₂纯化单元和CO₂还原单元。为验证此装置的可靠性,进行了系列 ¹⁴C样品的制备实验,得到的石墨产率基本达到80%,同时对商业碳粉、树木的含碳量与实验过程中测量区域对应的CO₂量进行了线性拟合,结果呈现明显的线性关系。对一批标准样品和本底样品进行AMS测试,结果显示每个样品¹²C^-的引出束流均大于20 μA,系列空白样品的测量结果表明,¹⁴C/¹²C丰度比平均值为1.061×10^-15,样品制备系统稳定且在制样过程中引入的碳污染较小,符合制样要求,现代木头样品的AMS绝对测量值为（9.13±0.05)×10^-13,与预期值~9.0×10^-13相符合。上述结果表明,该系统结构紧凑,能避免相互污染,高效且便于操作,满足AMS对¹⁴C样品的测试要求。