The country with the highest nuclear power contribution to its energy matrix is France with 72.28%. The French nuclear history reveals that they trust in reprocessing option since an early stage of ...the nuclear power plants. Therefore, this work is devoted to studying the two options of a fuel cycle, i.e., Open Fuel Cycle (OFC) and Closed Fuel Cycle (CFC) for this country and the economics of each scenario. The assessment begins using the MESSAGE, since the first official registration by the International Atomic Energy Agency (IAEA), which is in 1970 and tries to follow the model until 2016. After that, the MESSAGE adjusts the energy planning to fit best until 2034 remaining the nuclear activity in this country. The results show the best reactor option to supply 50000 MWyr until 2034 using the two fuel cycle models. Finally, it is shown the amount of resources needed to maintain the nuclear power industry in France and justify the French option of the fuel cycle based on the economic results. The results show the use of nuclear resources taking advantage of a closed fuel cycle. The idea is to show the sustainability of a closed fuel cycle, applying this methodology to countries in nuclear development with a different scenario.
•Open Fuel Cycle (OFC) and Closed Fuel Cycle (CFC) choice.•The assessment has been done using the MESSAGE.•It shows the sustainability of a closed fuel cycle.
•The effect of bedrock temperature on the disposal density of LEU, MOX and Th-TRU spent fuels was studied.•A linear relationship between bedrock and maximum temperatures at the canister surface was ...found.•Higher decay heat of reprocessed fuels implies a lower disposal density.•Candidate regions for possible DGR construction in Brazil were identified.
The final stage of the nuclear fuel cycle involves the design of a disposal repository for spent fuel or high-level waste from reprocessing operations. Focusing on the back-end fuel cycle, this study investigated the impact of bedrock temperature on the disposal of traditional low-enriched fuel and two reprocessed fuels, in a hypothetical design of a Brazilian Deep Geological Repository (DGR). The reprocessed fuels taken into consideration in this study were transuranic fuel spiked with thorium oxide and a plutonium/uranium fuel mix. For all fuels, interim storage had previously taken place for 50 years. The appropriate spacing between adjacent canister was determined, and the effect of increasing the bedrock temperature until the maximum allowed temperature at the canister surface were estimated using the ANSYS code. Results showed a linear relationship between the two temperatures. The transuranic fuel cannot be disposed of under assumed conditions, while the plutonium/uranium fuel requires larger disposal areas than traditional low-enriched fuel. We estimated the total area of disposal required for different amounts of spent fuel and identified six regions for further studies based on simulation results, mean bedrock temperature data, and population density, primarily in the southeastern part of Brazil.
•Evaluation of alternative nuclear fuels on a real nuclear energy system.•Assessment of open and closed fuel cycles based on uranium, thorium and reprocessing.•Results concerning the consumption of ...natural resources, performance and costs of fuels.•Multi-criteria decision approach is used to classify fuel cycles for future nuclear technology.•Results encourage the debate on nuclear energy and support decision-making.
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.
•Small-sized subcritical fast reactor with external neutron sources for actinide transmutation has been proposed.•The goal is to verify the actinide transmutation using hybrid systems: ADS-fission ...and fusion-fission.•the subcritical fast reactor is a promising option for actinide transmutation through fission reactions.•It can effectively address the issue of high-level nuclear waste management.
This study proposes an optimized small-sized subcritical fast reactor with an external neutron source for actinide transmutation. The reactor integrates features of Accelerator Driven Systems (ADS) and Fusion-Fission Systems (FFS) based on Tokamak technology. Both external neutron sources were evaluated, one from fusion reactions and the other from spallation reactions in the designed small subcritical fast reactor. The analysis assessed neutron flux and actinide transmutation rates through fuel burnup simulations at 1200 K. The results underscore the significance of external neutron sources in subcritical systems, with the fusion-fission source presenting high actinide transmutation. The SSFR utilizes thorium oxide as fuel and Lead-Bismuth Eutectic (LBE) as coolant. Neutronic parameter comparisons between FFS and ADS neutron sources were conducted, showing advantages for actinide transmutation in the system with the FFS neutron source, which enhances transmutation, minimizing radiotoxicity. The neutronic parameters were obtained using the MCNP, while the MONTEBURNS code, which links the MCNP and the ORIGEN depletion code, was utilized to perform the fuel burnup simulations. The cross-section libraries were generated by the NJOY-2012 using the nuclear data library JEFF-3.3.
•A trigeneration process of H2, electricity and desalinated water was proposed and studied.•It is based on the technologies Na-O-H cycle, SCWR power plant and MED desalination.•Mass, energy and ...exergy balances are applied to evaluate trigeneration thermal performance.•EES software was used to model the studied systems.•Such process has potential to produce 5 kg/s of H2, 400 MWe and 980 kg/s of H2O.
Hydrogen (H2) is a substance with a wide range of applications, especially ammonia (NH3) production. It is the key chemical used to make fertilizers, a pillar of agriculture industry, an important activity for society. H2 can be obtained according to different processes, including the recent method Na-O-H (sodium-oxygen-hydrogen) thermochemical water splitting cycle that produce it by cracking H2O (water) molecules into H2 and O2 (oxygen) through cyclic chemical reactions based on the elements Na, O and H. Such reactions are sustained by a heat source at specified temperature level. In this context, nuclear reactors, such as Supercritical Water Reactor (SCWR), are suitable energy options for this kind of process because they are designed to support electricity together with high temperature applications like H2 production. At the same time, water could be get by means of MED (Multi-Effect Distillation), a desalination method able to harvest waste heat from thermal systems. This approach allows saving the available potable water to be used in essential human needs such as drinking and agriculture while the desalinated one would serve as hydrogen source in the sodium-oxygen-hydrogen technique. Then, H2 production based on the technologies Na-O-H cycle through the heat supplied by SCWR coupled to a MED unit enables the trigeneration of electricity-hydrogen-water, three important goods for current society, what justifies the development of a paper covering this multigeneration approach. So, the main aim of this work is to evaluate the thermodynamic performance of this trigeneration case, a task never done before because those three systems were not coupled together aiming this multigeneration case as it was checked in the literature. It was considered a SCWR with output thermal power equal to 1000 MWth as the heat source to both Na-O-H hydrogen production facility plus MED installation. The work is developed by implementing mass and energy balances in Engineering Equation Solver (EES) software to determine the amount of H2, electricity and desalinated H2O acquired. According to the main results, this trigeneration process has potential to produce a maximum of 5 kg/s of hydrogen, 400 MW of electricity and 960 kg/s of desalinated H2O.
The aim is to analyse the neutron spectrum influence in a hybrid system ADS-fission inducing transuranics (TRUs) transmutation. A simple model consisting of an Accelerator-Driven Subcritical (ADS) ...system containing spallation target, moderator or coolant, and spheres of actinides, “fuel,” at different locations in the system was modelled. The simulation was performed using the MCNPX 2.6.0 particles transport code evaluating capture (n,γ) and fission (n,f) reactions, as well as the burnup of actinides. The goal is to examine the behaviour and influences of the hard neutron spectrum from spallation reactions in the transmutation, without the contribution or interference of multiplier subcritical medium, and compare the results with those obtained from the neutron fission spectrum. The results show that the transmutation efficiency is independent of the spallation target material used, and the neutrons spectrum from spallation does not contribute to increased rates of actinides transmutation even in the vicinity of the target.
Thermochemical water splitting cycles are considered an attractive option to produce H2, a substance with many important applications for society such as ammonia production because they do not ...require fossil fuels. In contrast, they obtain H2 decomposing water by means of cyclic chemical reactions. There are a wide variety of thermochemical ones under research, including the relatively new Na–O–H (sodium–oxygen–hydrogen) cycle proposed in 2012 by a research group. Despite introducing a new potential thermochemical cycle, those previous researchers do not investigate the thermal performance of it. Such task can be done through an exergy analysis. So, the aim of the paper is to evaluate the exergy performance of the Na–O–H cycle and its chemical reactions. This goal is accomplished by implementing in EES (Engineering Equation Solver) software exergy efficiency (ε1) and exergy destroyed (ED_1) balances for the cycle and their reactions considering specific conditions of pressure (p) and temperature (T). This approach allows understanding how these two variables influence the system performance, which could compromise its actual implementation and economic feasibility if it has low thermal efficiency. According to the results: reaction 1 (hydrogen production step) has mean ε1=96% and ED_1 = 8.5 kJ under 100–300 °C at 0–1 bar; reaction 2 (metal separation step) has ED_2 = 280 kJ and ε2=56% at 450 °C considering vacuum condition; hydrolysis step (reaction 3) has average ε3=87% and ED_3 = 18 kJ at 25–200 °C under 0–1 bar. Then, the Na–O–H cycle has overall ε=82% and ED = 306 kJ to produce 1 mol of H2. These values of ε and ED are theoretical and maximized ones. In practical situations, such amounts probably will reduce in function of unavoidable irreversibility present in actual systems such as pressure drop and heat loss that were neglected in the work to facilitate its development. Finally, it concludes the Na–O–H cycle has relatively high exergy efficiency, making it a potential hydrogen production method. However, its practical implementation in the future must overcome some of its drawbacks, by means of more research, like the low thermal efficiency of reaction 2 when compared to reactions 1 and 3 beyond the low pressure needed to perform such step.
•The exergy performance of the 3-step Na–O–H thermochemical cycle is evaluated.•Reaction 1 has an exergy efficiency of 96% with mean exergy destroyed of 8.5 kJ.•Reaction 2 destroys 280 kJ, resulting in an exergy efficiency of 58%.•Reaction 3 has an exergy efficiency of 87% with mean exergy destruction of 18 kJ.•The Na–O–H cycle has an overall exergy efficiency of 82% and destroys 306 kJ.
The main aim of the paper is to determine a theoretical range of operational conditions for the three chemical reactions of the NaOH (sodium-oxygen-hydrogen) thermochemical water splitting cycle by ...performing a Gibbs free energy (ΔG) analysis. ΔG is a thermodynamic parameter that allows determining if a chemical reaction is able to occur due to its enthalpy (ΔH) and entropy (ΔS) changes under specific conditions of pressure (p) and temperature (T). The methodology consists of implementing in Engineering Equation Solver (EES) software equations related to ΔH and ΔS for the three chemical reactions of the NaOH process, considering specific conditions of p and T with proper thermodynamic data to calculate ΔG. The main obtained results are: reaction 1, hydrogen production step, has ΔG < 0 for any values of T and p considered in the study; it can be performed at 100 °C under 1 bar; reaction 2, metal separation step, only can proceed under vacuum atmosphere at around 500 °C; reaction 3, hydrolysis step, always has negative Gibbs free energy despite pressure and temperature values and it can be carried out under 1 bar at 25 °C. Moreover, the methodology described in this paper could be used to investigate operational conditions for thermochemical processes.
•In 2012 were proposed 3 chemical reactions for the NaOH cycle able to produce H2.•It was first analyzed considering few specific conditions of p and T.•A ΔG analysis is performed to determine operational conditions for such cycle.•Reaction 1 and reaction 3 can occur respectively at 100 °C and 25 °C under 1 bar.•Reaction 2 only can proceed under vacuum atmosphere at around 500 °C.
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