Fission Technology Research Articles

Parametrical Choice of the Optimized Fusion System for a FFHR

Fusion–fission hybrid reactors are concepts of subcritical reactors based on the coupling of fusion and fission devices. In this case, the fusion reactor would work as an external neutron supplier for the fission core of the machine. Such systems could, in principle, operate as multi-purpose machines, such as energy generators, breeders and waste burners. The large availability of fusion and fission technologies makes the choice of devices to couple quite chaotic. In fact, most of the concepts proposed in the literature are based on attempts without real optimization. The purpose of this paper is to propose a parameter which could provide practical information regarding the choice or the design of the fusion system of an FFHR. An engineering approach based on the estimation of the energy efficiency of FFHRs was used. An evaluation of the parameter and some of its possible practical applications are shown. Obtained results indicate that, from a geometrical point of view, compact machines would need lower Q-values to reach high neutron source performance.

ARTISANS—Artificial Intelligence for Simulation of Advanced Nuclear Systems for Nuclear Fission Technology

The objective of this Technical Opinion Paper (TOP) is to provide an overview of the research topics in the ARTISANS (Artificial Intelligence for Simulation of Advanced Nuclear Systems) research group at the North Carolina State University. We will discuss the connections between our research with the key items outlined in the Virtual Special Issues (VSI) Nuclear Fission Technology (NFT) series. NFT is crucial for the global goal of decarbonization, but as outlined by the VSI framework, significant challenges remain that inhibit NFT profitability. Our research addresses some of these challenges, centered around improving the simulation of complex nuclear systems with Artificial Intelligence and Machine Learning (AI/ML). The ARTISANS group specializes in many aspects of applications of AI/ML to nuclear engineering, whose potential impact on NFT continues to grow as AI/ML technologies improve.

From past to future: The role of computational fluid dynamics in advancing nuclear safety in Spain and Portugal

This document explores the role of CFD in nuclear safety studies, with a particular focus on advancements in Spain and Portugal. The field of nuclear safety has increasingly included CFD models to address complex safety–critical phenomena, given their ability to capture three-dimensional behavior with high resolution. While traditional one-dimensional codes remain very valuable, they often rely on conservative approximations, making 3D CFD approaches indispensable for accurate predictions across various nuclear scenarios. In the context of Spain and Portugal, this document shows the contribution to CFD applications for nuclear safety research. The topics covered include code development and validation, combustion studies, simulations of nuclear spent casks, fuel assembly analyses, and investigations into containment safety issues. These advances have mainly contributed to improving the predicting capabilities of CFD models for applications in various safety–critical domains. In addition to detailing the achievements and contributions in the field of CFD in Spain and Portugal, readers will find a comprehensive overview of the current challenges and future perspectives of CFD within the domain of nuclear fission technology.

Achievements of recent research on severe accidents at CEA/IRESNE in support of future nuclear fission technology

In the current context of nuclear revival under the constraint of global warming and an ever-increasing world demand for energy, it is essential to take all precautions in the event of a serious accident during the design phase and to review the severe accident mitigation features of existing plants. The current nuclear revival is accompanied by the development of prototypes based on alternative concepts to light water reactors, such as the Sodium-cooled Fast Reactor (SFR), High Temperature Reactor (HTR), Molten Salt Reactor (MSR), which are also under consideration as reactors of reduced power output, or Small Modular Reactors (SMR). This paper summarizes the main outcomes and achievements of the last five years of experimental and numerical research conducted at CEA/IRESNE into prospective severe accidents within Pressurized Water Reactors (PWR) and SFRs.

The impact of neutral beam parameters on current drive and neutron yield in DEMO-FNS tokamak

DEMO-FNS (DEMO Fusion Neutron Source) will be a hybrid reactor designed to combine fusion and fission technologies. In a hybrid reactor the power is mainly produced by a fission blanket which is exposed to the neutron flux generated by confined fusion plasma used as a Fusion Neutron Source (FNS). The steady-state operation of the FNS is easier to achieve as compared to pure fusion reactors, allowing the FNS to be more compact. The DEMO-FNS will produce 40 MW of fusion power. The neutral beam injectors (NBI) are designed to provide a steady state plasma heating, rotation, fueling, current drive and neutron generation in DEMO-FNS. Four injector units will deliver 30 MW power in deuterium with energy Eb = 500 keV. The NBI concept and main components are inspired from ITER HNBI design implementing acceleration of negative ions with their neutralization on gas.The high density of injected power in DEMO-FNS leads to a very specific operation scenario with ahigher ratio of high-energy ions in the plasma with respect to conventional tokamaks, where the mainpart of neutron flux will result from fusion between hot-tail ions and relatively coldbackground. The current drive and neutron yield produced by the tangentially injected beam in asteady-state operation are strongly affected by magnetic configuration and plasma kineticprofiles. The fast ions deposition and performance in plasma are limited by the losses associatedwith the neutral beam shape and aiming. The main channels of direct beam losses includeshine-through losses, as well as fast ion orbital losses. The detailed evaluation of NB parametersand geometry effects is a necessary step of scenario optimization.BTR code (Beam Transmission or, in earlier versions, Beam Transmission with Reionization) is intended for injector beamlines study, and BTR detailed beam model can be also applied to perform a detailed analysis of beam losses and performance in plasma. The analysis of beam in plasma shows the ways towards higher values of beam driven current (NBCD) and neutral yield; the beam-in-plasma behaviour can be tuned for a given tokamak configuration. The NB tracing model workflow is implemented in the BTOR suite (Beam in TORoids). The results for DEMO-FNS are compared with the NBI performance in ITER tokamak, as both machines are beam-driven and implement a similar NBI concept.

Preface for Special Issue “NFT-09: LT&EE&LV”: Nuclear Fission Technology in Lithuania, Estonia and Latvia

Preface for Special Issue “NFT-09: LT&EE&LV”: Nuclear Fission Technology in Lithuania, Estonia and Latvia

Contribution of IAEA coordinated research projects to light water reactors advanced technology fuel testing and simulation

The Fukushima-Daiichi accident in 2011 highlighted the pressing need for enhanced design and safety analysis of nuclear fuels, especially under accident conditions in nuclear power plants (NPPs). To address this need, the international nuclear fuel community has developed several concepts of Accident Tolerant and Advanced Technology Fuels (ATFs) for light water reactors. The International Atomic Energy Agency (IAEA), at the request of its Member States, has initiated a series of three Coordinated Research Projects (CRPs) to aid in the development and testing of these ATFs. These projects, known as FUMAC, ACTOF, and ATF-TS, focus on the experimentation and simulation of ATFs under various accident conditions, including design basis accidents and design extension conditions. This paper provides a comprehensive overview of the main activities, as well as the achieved or anticipated results of these three CRPs. The insights and advancements gained from these projects will enable IAEA Member States to further refine nuclear fission technology, thereby contributing to efforts aimed at mitigating climate change.

Accident tolerant fuels behavior analysis for Pressurized Water reactor in steady state and transient conditions

Nuclear Fission Technology (NFT) is constantly developing to seek an increasingly safer operation and, consequently, increase the public acceptance of nuclear energy generation. Therefore, the development of new types of nuclear fuels and the search for different materials for cladding fuel rods has been the subject of research mainly to provide better efficiency in to carry energy in nuclear reactors and also to reduce possible damages in accident situations. In this way, this work aimed to compare the thermal response and behavior of Zircaloy 4, SiC reinforced with Hi-Nicalon type S (HNS) and FeCrAl alloy when they were considered as fuel cladding at steady state and transient conditions during operation of a PWR (Pressurized Water Reactor). Two thermal hydraulic models using the RELAP5 MOD3.3 and RELAP5-3D v. 4.3.4 codes and the reference data from the document Final Safety Analysis Report of Angra 2 PWR were used to perform the investigations. The work was developed in two steps. In the first one, the results of the Angra 2 nodalization in steady state conditions were compared with the Angra 2 reference data, obtaining good agreement. In the second step, the thermal response, when the cladding materials were changed, was evaluated in steady state and transient situations. The transients LOFA (Loss of Flow Accident), LBLOCA (Large Break - Loss of Coolant Accident), and coolant channel blockage were simulated in extreme conditions. The results have shown that substituting Zircalloy 4 alloy by FeCrAl or ceramic cladding SiC HNS presented a similar and better thermal response. Moreover, in another simulation, UO2 fuel has been replaced by U3Si2. The results showed lower temperatures at the fuel center in the rods with U3Si2 than those using UO2 as nuclear fuel, demonstrating the advantages of using U3Si2 fuel concerning the radial heat transfer in the rod.

Assessment of alternative nuclear fuel cycles for the Brazilian nuclear energy system

Alternative nuclear fuel cycles could contribute to the future of nuclear fission technology reducing the use of natural resources, waste management and lessening greenhouse gas emissions. To increase understanding of future technologies, analysis of power generation systems are essential and supports long-term decision-making. On this basis, this research presents an evaluation and comparison considering the use of alternative nuclear fuels in Pressurized Water Reactors (PWR) based on the Brazilian nuclear energy system. Assessment results show consumption of resources, inventories of spent fuel, nuclear waste, greenhouse gas emissions and costs of nuclear fuels. Among the main results, Mixed Oxide (MOX) fuel appears as the most promising by multi-criteria analysis considering two of the three evaluated areas. On the other hand, if costs have an importance greater than 55%, the conventional fuel UOX appears as the most advantageous. Thorium-uranium dioxide (TRU-U) and Transuranic-thorium dioxide (TRU-Th) fuels are in intermediate positions, along with Uranium oxide (UOX), and may still be options depending on the intentions of decision-makers.

Economic evaluation of hydrogen production in second and third units of Bushehr nuclear power plant regarding future need of nuclear fission technology

Today, the most important challenge for hydrogen production is the use of suitable energy source for sustainable production. The dual use of nuclear power plants allows them to expand into other markets by eliminating greenhouse gas emissions from processes such as hydrogen production. The significance of this matter especially in countries with ongoing new nuclear power plants is high and shows the future need for nuclear fission technology. In this paper, an economic assessment of hydrogen production in the second and third units of the Bushehr nuclear power plant (BNPP) with the Hydrogen Economy Evaluation Program (HEEP) is carried out and a comparison of CO2 emission in nuclear and non-nuclear methods of hydrogen production is presented. Most nuclear reactors, including Advanced Pressurized WaterReactor (APWR), High Temperature Gas Reactor (HTGR), and Water-Water EnergeticReactor (WWER), can be used as a source of thermal and electrical energy for the process of hydrogen production. In this research, hydrogen production processes based on the Conventional Electrolysis (CE), High Temperature Steam Electrolysis (HTSE), and Sulfur-Iodine (SI) Process using different storage and transportation options are compared to choose the cost-effective method for coupling with the WWER1000 reactor. Hydrogen production, thermal energy, and electricity costs have been calculated and explained in detail. The results showed that the cost-effective option for hydrogen production is using the High Temperature Steam Electrolysis (HTSE) method, Compressed Gas (CG) storage, and pipeline transportation, by 2.88 $/kg. Also, applying this method to produce hydrogen, the nuclear power plant thermal efficiency, and the hydrogen plant efficiency are kept in the best possible conditions by 51.98% and 58.21%, respectively.

Nuclear fission technology in Africa: Assessing challenges and opportunities for future development

Nuclear fission technology offers a potential solution for meeting Africa's increasing energy demands while also supporting economic development and regional cooperation. However, significant challenges such as financing and investment barriers, technical capacity gaps, and public concerns about safety and security persist. This article explores the key opportunities and challenges for nuclear fission technology in Africa, examining current and planned nuclear power projects and analyzing their successes, challenges, and lessons learned. We also discuss strategies for advancing nuclear power programs in African countries, including policy and regulatory reforms, investment and financing mechanisms, human resource development, capacity building, and public engagement and education. The need for further research into the potential environmental, health, and socio-economic impacts of nuclear power plants in African countries is emphasized, as well as the development of innovative and sustainable nuclear technologies tailored to African contexts. Ultimately, achieving sustainable and safe deployment of nuclear fission technology in Africa will require a comprehensive and collaborative approach, with partnerships and collaborations playing a critical role.

Possibility of misleading readings of water level in VVER steam generator during severe accidents with account for the Fukushima lessons

The severe accident at Fukushima Daiichi in 2011 has emphasized the importance of keeping instrumentation reliable in the course of a severe accident, for successful diagnosis of current state of the reactor and adequate decision making. After the electrical current was partially restored several hours into the accident at Unit 1, the readings of the water level in the core have been for a long time misleading. Given the conditions at the Unit, they were clearly contradicting the analytical estimates of coolability and degradation level of the reactor core. In the post-accident investigations this contradiction was explained by TEPCO by the effect of water evaporation in the reference leg due to heat up of the drywell atmosphere around. The water level instrumentation in different vessels of the VVER NPPs like steam generator, pressurizer is very similar to that at Fukushima BWR. Although the VVER and BWR designs are different in many aspects, it is important to verify if the lessons learnt from the Fukushima accident are applicable in case of severe accidents at VVER.This paper presents the results of numerical study for the possibility of misleading readings of water level in VVER steam generator during hypothetical severe accidents. These results demonstrate the importance of learning the lessons from the accidents that have happened at structurally similar NPPs, and their consideration in safety analyses of NPP units in operation and under design process. Accumulation of lessons learnt from previous operation and emergency experience is a very important advantage of nuclear fission technology that allows enhancing the safety of new designs of nuclear reactors.

Current status of MELCOR 2.2 for fusion safety analyses

MELCOR is an integral code developed by Sandia National Laboratories (SNL) for the US Nuclear Regulatory Commission (USNRC) to perform severe accident analyses of Light Water Reactors (LWR). More recently, MELCOR capabilities are being extended also to analyze non-LWR fission technologies. Within the European MELCOR User Group (EMUG), organized in the framework of USNRC Cooperative Severe Accident Research Program (CSARP), an activity on the evaluation of the applicability of MELCOR 2.2 for fusion safety analyses has been launched and it has been coordinated by ENEA. The aim of the activity was to identify the physical models to be possibly implemented in MELCOR 2.2 necessary for fusion safety analyses, and to check if those models are already available in MELCOR 1.8.6 for fusion version, developed by Idaho National Laboratory (INL). From this activity, a list of modeling needs emerged from the safety analyses of fusion-related installations have been identified and described. Then, the importance of the various needs, intended as the priority for model implementation in the MELCOR 2.2 code, has been evaluated according to the technical expert judgement of the authors. In the present paper, the identified modeling needs are discussed. The ultimate goal would be to propose to have a single integrated MELCOR 2.2 code release capable to cover both fission and fusion applications.

Nuclear energy and sustainable development

The dependency on combustion of coal, oil and gas for energy cannot be indefinite. Thus, the process of replacing fossil fuels with many energy technologies cannot be avoided in order to combat this high dependency. Nevertheless, we argue that in the long term, nuclear fission technology is the answer to the ever increasing demand for energy. This entails that nuclear fission has to play a major role in suppling energy in this age and beyond. In achieving this, the major aspect is in switching electrical energy generation from fossil fuels to nuclear fission. This cannot be achieved in a short period of time but in few decades citing France as an example.1 This energy transformation campaign is capable of reducing emissions of carbon dioxide as well as other greenhouse gases at a large scale. In view of this, replacement of coal-fired with gas-fired generating stations will not significantly reduce greenhouse gases emissions. What about the other energy sources such as wind and solar? These may not be an ultimate answer as they will be hard pressed in supply and may fall short in energy supply at very high scale. This is because they depend on backup power or energy storage hence not able to meet the ever growing high demand of energy. Therefore, this paper focuses on the current status of nuclear energy. It also discusses the future prospects of nuclear energy and the activities of the International Atomic Energy Agency (IAEA).

Defining the Challenges—Identifying the Key Poisoning Elements to Be Separated in a Future Integrated Molten Salt Fast Reactor Clean-Up System for iMAGINE

Nuclear fission technologies have the potential to play a significant role in the energy mix of a net-zero and sustainable society. However, to achieve the sustainability goal two significant challenges remain: efficient and sustainable fuel usage and the minimization of long-term nuclear waste. Civil nuclear molten salt systems and technologies offer the opportunity to address both, delivering future reactors at scale for efficient and effective power production and nuclear waste burnup. Potentially, both objectives could be fulfilled in one reactor system, which could significantly improve sustainability indices. The key to this innovation is demand driven development of a significantly reduced fuel cycle with enhanced proliferation resistance which offers further potential for improvement. To achieve these goals, a transformative approach for salt clean-up during molten salt reactor operation is proposed, by concentrating on the detection and removal of key neutron poisoning elements which prevent the reactor from long-term operation. To enable this highly innovative development work, a novel analysis of the evolving elementary fuel composition, their concentrations, and their criticality influence is now provided in this work. This, combined with consideration of the oxidation states of each of these elements then provides the basis for the selection of these key poisons and the development of advanced separation processes and process monitoring. This work also discusses the importance of the effective integration of physics and chemistry when systems modelling in achieving these system development goals.

Do proposed regulatory approaches for commercialfusion energy jeopardize successful technologydeployment?

Fusion energy has long been touted as an energy source capable of producing large amounts of clean energy without the fuel, pollution, siting, and safety constraints of other energy sources. Despite this promise, fusion energy has not come to fruition after six decades of research and development due to continuing scientific and technical challenges. Significant private investment in commercial fusion start-ups signals a renewed interest in the prospects of near-term development of fusion technology. Successful deployment of fusion energy, however, will require an appropriate regulatory framework to ensure public safety and economic viability. Initial discussions and proposals from fusion start-ups (e.g., Commonwealth Fusion Systems, General Fusion, TAE Technologies) and industry associations (e.g., Fusion Industry Association)have advocated the use of risk-informed regulations as the basis for the licensing of commercial fusion technology in the United States. These proposals are based, in part, on regulatory methods used for licensing commercial fission technology that developed in parallel with the commercial fission industry. Risk-informed regulations incorporate risk information from probabilistic safety analyses to ensure that regulations are appropriate for the actual risk of an activity. Proponents of risk-informed regulation believe that these methods can improve the economics and operation of nuclear facilities by focusing regulatory resources on addressing credible accident scenarios that are most likely to pose threats to worker and public safety. In addition to interest from industry, the U.S. Nuclear Regulatory Commission (NRC)has begun an initiative to develop a new risk-informed regulatory framework for the licensing of advanced nuclear fission power plants, but it is unclear if this framework would be applied to fusion. Despite the benefits of adopting a risk-informed framework for a mature fission industry, use of risk-informed regulations for the licensing of first-generation commercial fusion technology could be detrimental to the goal of economic near-term deployment of fusion. Commercial fusion technology has an insufficient operational and regulatory experience base to support the rapid and effective use of risk-informed regulations. More conservative regulatory analyses could instead be used for first-generation fusion facilities to facilitate more rapid deployment, and enable collection of operating experience to support future use of risk-informed regulations. A hybrid regulatory pathway that incorporates seven decades of lessons learned in commercial fission would enable the implementation of regulatory requirements that evolve with the development of commercial fusion technology, from a first-of-a-kind demonstration plant to a mature low-carbon energy source.

Hydrogen explosion mitigation in DEMO vacuum vessel pressure suppression system using passive recombiners

An important issue for the Fusion Reactors is the hydrogen explosion hazard assessment. For this reason, in the Work Package of Safety Analyses and Environment (WPSAE) of the EUROFusion consortium, a task was established to identify the potential for hydrogen production in DEMO vessel in accident situations and to investigate the possible solutions which can prevent the risk of hydrogen and dust explosion. The hydrogen in the Vacuum Vessel (VV) can lead to combustion progressing in deflagration and detonation. Besides, the tungsten dust could enhance the effects of H2 reaction as demonstrated by experiments, however, in this first set of accidents, only the H2 generated by the chemical reaction is accounted for.For these reasons, the solutions to avoid or limit the H2 production and/or to control safely the risk of H2 accumulation and explosion need to be screened starting from the solutions adopted in the fission technology, and later on, adapted and assessed in the Pressure Suppression System (PSS) foreseen in DEMO. One promising idea seems to install passive catalytic recombiners in the PSS.The aim of this paper is firstly to set a range of operating parameters for the PAR functioning and intervention suitable in DEMO PSS configuration. Secondly to verify if the present criteria and parameters work efficiently in mitigating the H2 accumulation a PSS in accidental conditions. To test the theoretical effectiveness of the PAR intervention, two reference accidents have been analyzed: an in-VV Loss Of Coolant Accident (LOCA) in the frame of the Design Basis Accident (DBA) and a Loss Of Flow Accident (LOFA) without active plasma shutdown in the context of the Beyond Design Basis Accidents (BDBA).The results seem promising if the performances of the PAR will be confirmed in sub atmospheric and saturated conditions.

Nuclear Energy and Its History: Past Consequences, Present Inadequacies and a Perspective for Success

An attempt is made to locate nuclear technology within a logical context considering history, risks, societal catastrophes and perspectives: the need is identified for a new direction in the exploitation in order to restore the role in energy production. We depict the situation coming from a marvelous history of discoveries started at the beginning of the XX century; heroes are recalled who made possible something that is inconceivable today: design, construction and production of electricity in a few years; that history was tainted by intentional nuclear explosions, i.e. the original sin that we are now paying. Then, we attempt to show that the societal risk is an inherent part of the civilization. Restoring the public trust (towards nuclear fission technology) by matching nuclear safety with the current technological status and advancers in risk assessment is the key objective. The “independent assessment”, or a principle for the exploitation of nuclear energy already stated in the 50’s of the previous century, shall then re-appear. This is used to erect the signpost for a “dynamic barricade” to further reduce the risk of operation of nuclear reactors and to match the design with current technological capabilities and with the frontiers of the research.

A First Assessment on the Scale-Up Possibilities of Different Electrochemical Techniques for Lithium Isotopic Enrichment

Chemicals enriched in lithium isotopes are of paramount importance in the current nuclear fission technology, in future nuclear fusion technology, and in neutron detectors. Currently, lithium isoto...

Nuclear Energy Development in Bangladesh: A Study of Opportunities and Challenges

It is a challenging task for Bangladesh to meet its increasing demand of energy while its economy is rapidly growing. Though prices of oil, coal, and fossil fuels around the world have been volatile, the price trend in Bangladesh demonstrates a persistent rise in the immediate past. This is further exacerbated by depleting reserves of natural gas. Cumulatively, these two effects heighten Bangladesh’s energy needs. Bangladesh presently mitigates her energy requirements predominantly through natural gas, supplemented by a handful of coal and furnace oil plants. Consequently, due to scarcity of natural gas, oil and coal resources, nuclear power surfaces as a palatable strategic option for Bangladesh’s future development agenda. However, a successful nuclear power program entails an extensive infrastructure. Just like the other nuclear energy-producing countries, Bangladesh also face challenges to safeguard the health and security of nuclear reactors, the proper management for nuclear waste treatment and the security concerns over the safe usage of nuclear materials. Additionally, the development of nuclear energy is also bewildered because of the complex nature of fission technology, lack of efficient human resources, and non-existence of proper legal instruments to guide safe nuclear power production. Moreover, the further challenges include the questions, for example: whether the nuclear power plant project is supported by the mass people or not? What are the strategies for nuclear waste disposal? Whether the recent initiatives for nuclear energy production is necessary or the country should more concern with renewable sources? This paper evaluates the nuclear energy development in Bangladesh. It operates under qualitative methodological framework and utilises secondary sources for analysis. We advance several recommendations in this paper to remedy the highlighted issues: (1) creating a comprehensive legal and regulatory system; (2) fortifying home-based technology of nuclear development and simultaneously localising of foreign-based technology; (3) reducing the cost of nuclear energy production; (4) fast-tracking the procedure of efficient development of nuclear technology; (5) accelerating the procedure of switching to more efficient reactor and nuclear fuel cycle, and (6) conducting effective profile-raising activities to generate greater awareness and spur common acceptance.