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Nuclear energy can play a role in carbon free production of electrical energy, thus making it interesting for tomorrow's energy mix. However, several issues have to be addressed. In fission technology, the design of so-called fourth generation reactors show great promise, in particular in addressing materials efficiency and safety issues. If successfully developed, such reactors may have an important and sustainable part in future energy production. Working fusion reactors may be even more materials efficient and environmental friendly, but also need more development and research. The roadmap for development of fourth generation fission and fusion reactors, therefore, asks for attention and research in these fields must be strengthened.

The development of advanced nuclear energy systems, known for their cleanliness and sustainability, is a key strategy for achieving a low-carbon energy transition. Liquid metal (LM)-powered advanced nuclear energy systems demonstrate sustainability and environmental friendliness, as well as being irreplaceable in specific areas. This paper charts a comprehensive scene of applications, challenges, and prospects of LMs in advanced nuclear energy (fusion and fission). First, next-generation fission reactors that use LM coolants, such as sodium or lead, are currently under design and construction. However, the coupling mechanisms of multiphase and multiphysics interactions remain unresolved due to various challenges, including corrosion and lead-water interactions. Second, the exploration of new LM-cooled reactors should emphasize sustainable development while ensuring basic performance. Lastly, the unique properties of LMs, including efficient energy transport and tritium breeding, position them as crucial materials in fusion system design. However, surface characteristics and the magnetohydrodynamic (MHD) effect remain major technical challenges. LMs have already left their mark in nuclear energy and are expected to be an effective solution to overcoming the energy crisis.

Currently, international nuclear fission reactors producing medical isotopes face the problem of shutdown and maintenance, decommissioning, or dismantling, while the production capacity of domestic research reactors for medical radioisotopes is inadequate, and the supply capacity for medical radioisotopes faces major challenges in the future. Fusion reactors are characterized by high neutron energy, high flux density, and the absence of highly radioactive fission fragments. Additionally, compared to fission reactors, the reactivity of the fusion reactor core is not significantly affected by the target material. By building a preliminary model of the China Fusion Engineering Test Reactor (CFETR), a Monte Carlo simulation was performed for particle transport between different target materials at a fusion power of 2 GW. The yields (specific activity) of six medical radioisotopes (14C, 89Sr, 32P, 64Cu, 67Cu, and 99Mo) with various irradiation positions, different target materials, and different irradiation times were studied, and compared with those of other high-flux engineering test reactors (HFETR) and the China Experimental Fast Reactor (CEFR). The results show that this approach not only provides competitive medical isotope yield, but also contributes to the performance of the fusion reactor itself, e.g., tritium self-sustainability and shielding performance.

Thermonuclear fusion of deuterium and tritium constitutes an enormous potential for a safe, environmentally compatible and sustainable energy supply. The fuel source is practically inexhaustible. Further, the safety prospects of a fusion reactor are quite favourable due to the inherently self-limiting fusion process, the limited radiologic toxicity and the passive cooling property. Among a small number of approaches, the concept of toroidal magnetic confinement of fusion plasmas has achieved most impressive scientific and technical progress towards energy release by thermonuclear burn of deuterium-tritium fuels. The status of thermonuclear fusion research activity world-wide is reviewed and present solutions to the complicated physical and technological problems are presented. These problems comprise plasma heating, confinement and exhaust of energy and particles, plasma stability, alpha particle heating, fusion reactor materials, reactor safety and environmental compatibility. The results and the high scientific level of this international research activity provide a sound basis for the realisation of the International Thermonuclear Experimental Reactor (ITER), whose goal is to demonstrate the scientific and technological feasibility of a fusion energy source for peaceful purposes.

Nuclear energy is an environmental issue that needs to be carefully considered regarding its consequences. The environmental effects of nuclear energy encompass a complex interplay of factors, ranging from managing radioactive waste to the potential for accidents, emissions, and resource depletion, necessitating a thorough examination of its impact on our planet. This study examines the relationships between nuclear energy, nuclear fission, nuclear fusion, and load capacity factor for the eight countries (Canada, China, France, Germany, Japan, Russia, Spain, USA) that consumed the most nuclear energy from 1993 to 2018 using the time (Emirmahmutoglu & Kose, 2011) and frequency domain (Croux & Reusens, 2013) panel causality tests. The results differ according to time and frequency domain causality tests. While the time-domain causality test results showed no causal relationship between the nuclear energy consumption, nuclear reactors, and the load capacity factor variables, the frequency-domain causality test revealed that there are causal relationships between these variables in the short, intermediate and long run. According to the frequency-domain causality test results, there is a bidirectional causality relationship between nuclear reactors, energy consumption and load capacity factor. In line with the main findings of this study, it is recommended that these countries implement effective policies to increase environmental quality and make investments and incentives in nuclear energy and technologies.

Theoretical and experimental research on the reversed-field pinch (RFP) is reviewed. The basic theoretical properties of the RFP are considered including equilibrium, toroidal displacement, diffusion, confinement, and ideal and dissipative MHD stability. A general review of RFP experiments is presented including fast experiments, which utilize small-bore insulating tori in which the distribution is usually set up by fast programming on microsecond timescales; and slow experiments, carried out in large metal-walled tori in which the field configuration is set up slowly by self-reversal on millisecond timescales.

The paper examines the prospects of combining MHD generators with nuclear reactors of different types in the USSR. Attention is given to the possibilities of the following combinations: (1) a fast-neutron liquid-metal reactor with a liquid-metal MHD generator, (2) a high-temperature fission-fusion reactor with a nonequilibrium-plasma MHD generator, and (3) a gas-phase fission reactor with an MHD generator using uranium hexafluoride plasma. The feasibility of combining closed-cycle MHD generators with nuclear reactors is assessed.

Direct energy conversion from plasma heat flux has been studied. Since major parts of fusion energy in the advanced fusion reactor are radiation and charged particle energies, the flexible design of the blanket is possible. We discuss the potentiality of the thermoelectric element that generates electricity by temperature gradient in conductors. A strong magnetic field is used to confine the fusion plasma, therefore, it is appropriate to consider the effect of the magnetic field. We propose a new element which is called Nernst element. The new element needs the magnetic field and the temperature gradient. We compare the efficiency of these two elements in a semiconductor model. Finally, a direct energy conversion are mentioned.

Global warming is the ongoing rise in the average temperature of Earth's climate system. Over the past 50 years, the average temperature has increased at the fastest rate in recorded history due to uncontrolled generation of greenhouse gases. Nuclear power is low carbon energy, and it is contributing on a large scale to a low carbon economy and a green energy grid. 442 nuclear power reactors are operating worldwide generating 393 GWe of electricity providing continuous and reliable low carbon power. Nuclear electricity accounts for 11% of total global electricity generation, and this amounts to a third of the low-carbon electricity produced in the world. New innovations are taking place which make nuclear power a more affordable and attractive energy option. These include advances in large reactors, emerging technologies such as advanced fuel and small modular reactors, engineering breakthroughs extending the operational lifetime of existing reactors, and new developments in materials and better waste management. Fast breeder reactor technology has become a commercial reality and it helps not only in generating electricity, but also in producing more fuel than it consumes, besides burning nuclear waste more efficiently compared to any of the existing commercial reactor technologies. The Sun's energy is generated by nuclear fusion. Mastering nuclear fusion technology can guarantee energy security in terms of clean, safe and affordable energy. Nuclear fusion, and plasma physics research of very complex nature are being carried out in many countries. Fusion reactions have been successfully demonstrated although for a fraction of a second and without demonstrating a net gain of electric power. The world's largest international fusion reactor facility called ITER is in an advanced stage of construction with the aim of demonstrating the scientific and technological success of fusion energy research for commercial production. Fusion fuel is plentiful and easily accessible. It is expected that fusion energy is the pathway towards energy security for thousands of years. Nuclear fission and fusion reactors do not emit greenhouse gases into the atmosphere and play a major role in mitigating climate change.

This is a copy of the 2007 report prepared by the DOE/NSF Nuclear Science Advisory Committee in response to the charge from DOE and NSF to "conduct a study of the opportunities and priorities for U.S. nuclear physics research and recommend a long range plan that will provide a framework for coordinated advancement of the nation's nuclear science research programs over the next decade."

Some recent progress and open questions in extracting and understanding the new physics underlying the density dependence of nuclear symmetry energy from laboratory experiments are discussed.

Nuclear reactors are often modeled as inflexible baseload generators with fixed downtimes and restrictive ramping constraints. In practice, however, a reactor's operational flexibility is closely tied to its fuel cycle and associated reactivity margin. A key physical constraint for power maneuverability is xenon poisoning, caused from the transient buildup of neutron-absorbing xenon following a power reduction. This transient can delay or prevent subsequent power ramp-up due to suppressed core reactivity. Additionally, if a reactor is shutdown during periods of low reactivity, restart times can vary significantly, leading to prolonged downtimes. This work introduces a physics-informed modeling framework that embeds fuel cycle dynamics within a unit commitment (UC) formulation. The framework tracks reactivity margin, dynamically enforces xenon induced constraints, and endogenously schedules refueling outages based on core conditions. By capturing intracycle reactivity evolution, the model enables operation dependent nuclear dispatch that reflects both techno-economic requirements and irreducible nuclear physics limits. Application to a representative reactor fleet shows that flexible operation can slow reactivity degradation and extend fuel cycles. Results further demonstrate that different operational modes substantially affect VRE utilization, curtailment, and nuclear fleet capacity factors. These findings highlight the importance of fuel cycle aware flexibility modeling for accurate reactor scheduling and integration of nuclear power into energy system models.

This paper provides a retrospective of the ALPHA (Accelerating Low-cost Plasma Heating and Assembly) fusion program of the Advanced Research Projects Agency-Energy (ARPA-E) of the U.S. Department of Energy. ALPHA's objective was to catalyze research and development efforts to enable substantially lower-cost pathways to economical fusion power. To do this in a targeted, focused program, ALPHA focused on advancing the science and technology of pulsed, intermediate-density fusion approaches, including magneto-inertial fusion and Z-pinch variants, that have the potential to scale to commercially viable fusion power plants. The paper includes a discussion of the origins and framing of the ALPHA program, a summary of project status and outcomes, a description of associated technology-transition activities, and thoughts on a potential follow-on ARPA-E fusion program.

Radiation resistant camera system was constructed for monitoring deuterium plasma discharges in the Large Helical Device (LHD). This system has contributed to safe operation during two experimental campaigns without serious problems due to radiation (neutrons and gamma-rays). The cameras steadily functioned even in the plasma discharge with the maximum neutron emission rate in FY 2017, though some bright specks temporarily appeared on the images. The cameras have been installed in shield boxes which consist of lead boxes covered with 10% borated polyethylene blocks in all directions. For optimizing the design of the shield box, the radiation flux distribution was calculated by MCNP-6 code, which reveals the reduction of the radiation flux and the change of the energy spectra in the shield box. Thanks to the optimization, significant extension of the lifetime of the cameras has been realized. Investigation of the influence of the radiation on the CCD image sensor shows that the number of bright specks generally increases with the radiation flux to the camera, which also indicates that some bright specks disappear by the self-annealing process on the image sensor. This phenomenon also highly contributes to the further extension of the lifetime of the radiation resistant cameras.

Structural materials represent the key for containment of nuclear fuel and fission products as well as reliable and thermodynamically efficient production of electrical energy from nuclear reactors. Similarly, high-performance structural materials will be critical for the future success of proposed fusion energy reactors, which will subject the structures to unprecedented fluxes of high-energy neutrons along with intense thermomechanical stresses. Advanced materials can enable improved reactor performance via increased safety margins and design flexibility, in particular by providing increased strength, thermal creep resistance and superior corrosion and neutron radiation damage resistance. In many cases, a key strategy for designing high-performance radiation-resistant materials is based on the introduction of a high, uniform density of nanoscale particles that simultaneously provide good high temperature strength and neutron radiation damage resistance.