Persona: Juárez Mañas, Rafael
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rjuarez@ind.uned.es
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0000-0001-7649-202X
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Juárez Mañas
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Rafael
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Publicación Optimizing Radiation Shielding for Fusion Maintenance Facilities: Insights From a Comprehensive Analysis of ITER Hot Cell(WILEY, 2025-05-19) Martínez Albertos, Pablo; Sauvan, Patrick; Catalán Pérez, Juan Pablo; Belotti, Mario; Javier, François; Germa, Joffrey; Tonqueze, Y. Le; Dammann, Alexis; Juárez Mañas, Rafael; ITER Organization (IO)One of the primary goals of the ITER project is to demonstrate the safety characteristics of a fusion device, particularly in terms of radiation management. Radiation protection during maintenance periods is of special concern, as personnel performing maintenance-like activities will be exposed to delayed gamma fields from numerous and complex radioactive components. Ensuring a safe and equipped environment for such activities is the objective of the ITER hot cell. This facility requires extensive design optimization, balancing spatial and temporal availability constraints, radiation protection, and cost-effectiveness. In this paper, we present a comprehensive assessment of ITER hot cell’s radiation environment to support its efficient design and safe operation. The study evaluates the shielding efficiency of the conceptual design layout from 2021, providing meaningful insights for layout improvement. We show that substantial amounts of concrete (~2900 m3) could be saved from the currently evolving design while respecting radiological requirements. The evaluation of the occupational radiation exposure (ORE) associated with hot cell maintenance activities resulted in 179 man·mSv·year−1, which represents a significant fraction (36%) of the project’s annual budget. This highlights the importance of integrating shielding analysis, accounting for personnel radiation exposure, even in early design phases, to support the optimization of the maintenance plan according to safety requirements.Publicación Nuclear scoping analysis of ITER bioshield top lid toward its preliminary design review(Elsevier, 2023-10-01) Bergman, J.; Loughlin, Martin; Le Tonqueze, Y.; Thompson, M.; Martínez Albertos, Pablo; Sauvan, Patrick; Juárez Mañas, RafaelDuring ITER operations, electronics located in the crane hall, which is above the tokamak, will be exposed to neutron and photon fields from both the plasma and the activated water. To protect the electronics, the implementation of dedicated shielding on the crane hall platform and the bioshield top lid is required. The design demands optimisation attending to constructability, weight limits, and radiation shielding requirements. This work evaluates eight shielding configurations by assessment of the neutron flux and dose accumulated over 4700 h of operation at 500 MW for electronics protection. This corresponds to a neutron wall load of 0.3 MW a/m² as specified in the ITER Project Specification. An intermediate-source approach has been followed with SRC-UNED, considering all relevant radiation sources while minimising the computational time required. Results were presented at the top lid Conceptual Design Review aiming to support decision-making. Further optimisation has since been performed to reach a top lid proposal for its Preliminary Design Review. All outcomes show that radiation levels above the north and south crane hall platforms are compatible with the critical electronics requirements.Publicación Improved radiation shielding analysis considering vector calculus(Wiley, 2020-09-08) Juárez Mañas, Rafael; Loughlin, Michael; López Revelles, Antonio Jesús; Pedroche Sánchez, Gabriel; Kolsek, Aljaz; Sauvan, Patrick; Sanz Gozalo, JavierThe future of nuclear energy in the energy mix faces a permanent scrutiny of safety aspects in conciliation with bridled costs, either fission- or fusion-based. This affects to all the exciting milestones pursued in XXIst. To name few in the field of fission, the deployment of the IVth generation reactors is expected or the definitive solution to the radioactive wastes is sought. A mention apart is made to fusion technology, with ITER as the flagship project. It seeks a virtually infinite energy source, intrinsically safe and with reduced radioactive waste production with respect to fission the first commercial reactor. All these, and many other endeavors, share the operation of sophisticated devices in the presence of intense ionizing radiation fields. Humans and electronics must be protected to ensure safe and reliable performance, while shielding normally represents a large fraction of the budget. This involves nuclear analysis in the design phase to forecast the radiation conditions. The complexity of the simulation of 3D radiation fields that is computationally affordable nowadays is unprecedented. While sophistication in geometries and source definitions has become routine, the resulting complexity of these scalar fields makes their analysis increasingly difficult. The need of enhancement of the analysis techniques is evident today. Vector calculus is proposed following a physical interpretation of the field lines that boosts the analysis capabilities. It identifies the trajectories around which shielding is weakest in an automated errorless and effortless approach. Its power is illustrated with an example relevant to the ITER reactor.Publicación Shielding conceptual designs of ITER TCP ports to protect electronics(Elsevier, 2022-01-18) Martínez Albertos, Pablo; Pedroche Sánchez, Gabriel; Dremel, M.; Pearce, R.; Loughlin, M.; Le Tonqueze, Y.; Sanz Gozalo, Javier; Juárez Mañas, RafaelCritical electronics of ITER Tokamak, hosted in the shielded corners (SC) of the Tokamak Building (B11), must operate under acceptable neutronic flux conditions (≤10 n⋅cm 2⋅s 1) to minimize single event effects. During machine operation and at lower level (B1), both the Torus Cryopumps (TCP) ports location within B11 and their pumping efficiency constraints are factors contributing to the radiation environment in the SC. Although previous studies have addressed the transmission of radiation out the vessel of TCP ports, none of them have assessed the impact of such radiation beyond the Port Cell. In this work, different TCP shielding configurations were evaluated at B1 level of B11 due to plasma neutrons emerging from the six TCP ports only. MCNP and dedicated computational tools were used to perform the radiation transport calculations. Albeit being a partial study, the examination of the compatibility between the TCP plasma neutron flux and the electronics limit in the SC has been addressed, while considering the combined effect of the shielding design and the building walls, lintels and doors in the results. We present a combined shielding case that reduces the neutron flux to a range of 1.3–9.3 n⋅cm 2⋅s 1 depending on the location, which is compatible with the limit while respecting pumping efficiency and assembly difficulty constraintsPublicación Computational study of the Nitrogen-16 source term in the ITER vacuum vessel cooling circuit through the coupling of system-level analysis code and CFD(Elsevier, 2024-08) De Pietri, Marco; Fiorina, C.; Le Tonqueze, Y.; Juárez Mañas, RafaelIn ITER, the evaluation of the activated water radiation source and its impact on the radiological levels is necessary to demonstrate compliance with the safety requirements. The use of simplified or conservative approaches often results in the application of expensive constraints on the installation that impact its economics, operations, and construction schedule. In this work, we propose a novel methodology to calculate the activated water source term with a higher degree of realism. The methodology is based on the coupling of a system-level code with a Computational Fluid Dynamics (CFD) code in an explicit, one-way approach. We apply this methodology to the evaluation of the 16N radioisotope within the ITER Vacuum Vessel Primary Heat Transfer System (VV-PHTS) cooling circuit in a steady-state and transient scenarios. We chose this system since previous analyses of the VV-PHTS were done with simple, ad-hoc calculations that yielded results that differed by up to a factor of five, underscoring a higher level of uncertainty. As a result, we generate a computational model of the source term that can be used to evaluate the radiological condition surrounding the cooling systems during the operations.Publicación Nuclear analysis of the ITER Torus Cryopumps(IOP Publishing, 2019-09-09) Pedroche Sánchez, Gabriel; López Revelles, Antonio Jesús; Kolsek, Aljaz; Dremel, Matthias; Bansal, Gurpreet; Pearce, Robert; Sanz Gozalo, Javier; Juárez Mañas, RafaelThe ITER Tokamak will feature six torus cryopumps (TCP) to maintain the vacuum requirements inside the vacuum vessel for plasma operation. They will be connected to the ITER vacuum vessel through the lower ducts, which have limited shielding to ensure an efficient pumping. Therefore, these ducts will represent a relevant path for radiation to travel from the plasma and affect diverse aspects of the ITER facility, such as the electronics allocation or the maintenance operations during the machine shutdown. Previous analyses have addressed these important aspects. Nonetheless, limitations in those studies and design evolution have justified a new analysis, specifically dedicated to the TCP final design review. The results of the nuclear analysis are presented here focusing on the B1 level port cell #4. The TCP design and the associated and neighboring equipment have evolved and updated models have been considered. The TCP modelling has required an explicit heterogeneous treatment of the internal parts. The radiation source from the divertor cooling water pipes running along the port cell ceiling has been considered with the latest available source definition. In terms of methodology, one major improvement has been the modelling of the radiation transmission from C-model to the Tokamak Complex model. Another important improvement has been the consideration of D1SUNED for the determination of shutdown dose rates, covering a broader fraction of the radioactive inventory than in previous studies. The following quantities have been determined: neutron flux, absorbed dose to silicon, 1 MeV equivalent neutron fluence and shutdown dose rates (SDDR) after 106 s of cooling time. Finally, a set of proposals have been made to considerably mitigate the SDDR after 106 s of cooling. This work represents a realistic and matured source of information of the radiation environment in the ITER TCP port cells as presented in the final design review.Publicación Update in the nuclear responses of the European TBMs for ITER during operation and shutdown(Elsevier, 2018-07-06) Juárez Mañas, Rafael; López Revelles, Antonio Jesús; Sauvan, Patrick; Pedroche Sánchez, Gabriel; Kolsek, Aljaz; Alguacil Orejudo, Javier; Ugolini, Daniele; Vallory, Joelle; Ricapito, Italo; Poitvein, Yves; Calvo, Francisco; Sanz Gozalo, JavierThe depiction of the nuclear responses of the ITER European Test Blanket Modules (TBMs), Helium Cooled Lithium Lead (HCLL) and Helium Cooled Pebbles Bed (HCPB) is presented in this work. Following important components update, and important methodological advances, the nuclear heat and the tritium production have been revisited, giving new estimations 10% higher than the previous evaluation for nuclear heat in both TBMs and to 15% higher for HCPB T production. This has an impact on the thermo-mechanical design of the TBM and the tritium handling. In addition, the Shutdown Dose Rates in the respective port interspace have been characterized in local approach. It shows a performance that could imply compatibility with planned in-situ maintenance activities when analysed in global approach, an improvement with respect to previous evaluations.Publicación Assessment of ITER radiation environment during the remote‑handling operation of In‑Vessel components with D1SUNED(Nature Research, 2023-03-02) Martínez Albertos, Pablo; Sauvan, Patrick; Loughlin, M. J.; Tonqueze, Y. Le; Juárez Mañas, RafaelDuring ITER operational life, a remote-handled cask will be used to transfer In-Vessel components to the Hot Cell for maintenance, storage and decommissioning purposes. Due to the distribution of penetrations for system allocation in the facility, the radiation field of each transfer operation presents a high spatial variability; all operations must be studied independently for workers and electronics protection. In this paper, we present a fully representative approach to describe the radiation environment during the complete remote-handling scenario of In-Vessel components in the ITER facility. The impact of all relevant radiation sources during different stages of the operation is addressed. As-built structures and 2020 baseline designs are considered to produce the most detailed neutronics model of the Tokamak Complex, the 400,000-tonne civil structure hosting the tokamak, up to date. Novel capabilities of the D1SUNED code have allowed to compute the integral dose, the dose rate and the photon-induced neutron flux of both moving and static radiation sources. Time bins are included in the simulations to compute the dose rate caused by In-Vessel components at all positions along the transfer. The time evolution of the dose rate is built in video format with a 1-m resolution, especially valuable for hot-spots identification.Publicación Dust contamination of Divertor Remote Handling System in ITER Hot Cell: A novel approach to model complex superficial radiation sources(ELSEVIER, 2024) Martínez Albertos, Pablo; Sauvan, Patrick; Catalán Pérez, Juan Pablo; F., Javier; Le Tonquèze, Yannick; Hamilton, David Thomas; Juárez Mañas, RafaelActivated dust produced by the erosion of plasma-facing components entails a significant radiation source for ITER and, generally, for all tokamaks aiming for operation under high neutron exposure. In-Vessel remote-handling operations will mobilise the dust, which will be deposited on the remote-handling tools used, for which hands-on maintenance is expected. To ensure safe maintenance of the remote-handling equipment, a dedicated decontamination process in the Hot Cell is required. Evaluating the radiation fields produced by the contaminated equipment is central to minimising radiation exposure to personnel. In this study, we present a nuclear analysis of the Divertor Remote Handling System during its transfer and decontamination process. Past computational limitations regarding superficial sources definition and high uncertainties on the dust model have been overcome by implementing a novel methodology and following an alternative approach. Two surface-dependent dust distributions over the complex geometry surfaces were considered to evaluate the dose rates according to the different contamination levels during the process phases. A scoping analysis was performed to determine the amount of dust that would comply with project requirements in each phase of the process. Improvement margins were identified in the quantification of the amount of dust and Hot Cell layout.Publicación ITER full model in MCNP for radiation safety demonstration(Nature Research, 2024-10-03) Juárez Mañas, Rafael; Belotti, Mario; Kolsek, Aljaz; López Ochoa, Víctor; Alguacil Orejudo, Javier; Pedroche Sánchez, Gabriel; López Revelles, Antonio Jesús; Martínez Albertos, Pablo; De Pietri, Marco; Guijosa Araez, Pol; Tonqueze, Y. Le; Loughlin, M. J.; Polunovskiy, E.; Pampin, R.; Fabbri, M.; Sanz, J.The development of nuclear fusion as a safe and virtually limitless power source is receiving growing attention in the context of looming energy crisis and climate change. ITER project stands as the flagship international initiative and is advancing steadily. The construction of the Tokamak Complex is nearly finished, and the assembly of core components has begun on site. Simultaneously, the design is being finalized, and the safety case is becoming more concrete. Current approaches to radiation safety demonstration using 3D nuclear analysis with the Monte Carlo code MCNP require sophisticated artifacts to sew together simulations in separate models for the Tokamak and the rest of the facility. This results in cumbersome studies and, consequently, challengeable conclusions. To address this issue, we have built the an integral MCNP model of the ITER facility: the ITER full model. Along with improvements to the D1SUNED code, we illustrate its computational practicality and pertinence in two meaningful simulations for ITER safety case. This work represents the culmination of a two-decade-long effort of ITER modelling aiming to demonstrate adequate radiation safety. Beyond supporting the remaining design tasks, this model simplifies the corresponding 3D nuclear analysis and improves the robustness of the ITER safety case.