The IFMIF-DONES facility will irradiate prospective fusion reactor materials using a linear accelerator to collide a deuteron beam with a lithium target in a liquid state. A particularity of the IFMIF-DONES accelerator is the lack of physical separation between the target vacuum chamber (TVC), where liquid Li circulates, and the vacuum chambers of the upstream accelerator components. Loss of Vacuum Accidents (LOVAs) could thus result in the potential transport of material between the TVC and the rest of the accelerator, with the risk of potential reactions with the liquid Li or the mobilisation of radioactive inventory. This paper describes the Multipurpose Vacuum Accident Scenarios (MuVacAS) experimental setup, specifically designed to validate mitigation strategies against of such accidents. MuVacAS replicates the key characteristics of the last 49 m of the IFMIF-DONES accelerator vacuum chambers. It is equipped with modules to reproduce different leak scenarios, including sudden air inrushes or the controlled injection of various gases and water. Initial experimental results from a sudden air inrush scenario are presented, showcasing the capability of MuVacAS to accurately reproduce accident conditions in vacuum systems. Furthermore, the measurement systems were reliable during the tests, ensuring the data were valid and accurate. The planned experimental campaigns aimed at reproducing a variety of LOVAs are also outlined. The data collected in these campaigns will be used to assess the effectiveness of the Fast Safety Isolation Valves (FSIVs) - the primary mitigation devices for these accidents - and to support the design of the IFMIF-DONES safety systems.

The International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source (IFMIF-DONES), under construction in Granada, Spain, will serve as a neutron source to irradiate materials and critical technologies for fusion power plants. It will produce prototypical fusion neutron fluxes capable of generating damage similar to that expected in future fusion reactors. This work presents the evaluation of a current-mode micro-ionization chamber (mu IC) tested under the pulsed radiation environment of the linear IFMIF prototype accelerator (LIPAc) in Rokkasho, Japan. The mu IC, developed for integration into the start-up monitoring module (STUMM) of IFMIF-DONES, is designed to measure gamma radiation as part of the STUMM's overall neutron and gamma field characterization during commissioning. The experiments focused on assessing the performance of the mu IC under radiation conditions simulating IFMIF-DONES operational scenarios. Positioned in the LIPAc high energy beam transport (HEBT) line near the Beam Dump, the current-mode mu IC demonstrated its capability to detect pulsed gamma irradiation.

The IFMIF-DONES project is undertaking the design and construction of a scientific facility near Granada, Spain, intended for the irradiation of fusion materials under a neutron spectrum similar to that found inside a nuclear fusion reactor. Granada is a moderately seismic region within the Iberian Peninsula, which requires an appropriate seismic design strategy to ensure the reliable and safe operation of the facility.The Main Building, which houses the facility's critical systems, consists of a concrete structure seismically isolated from the ground. As the project progressed, more detailed in-situ investigations and a comprehensive Seismic Hazard Assessment refined the understanding of site conditions. These updated analyses suggested that seismic base isolation may not be strictly necessary from a structural perspective and could introduce additional construction complexities. This has enabled the consideration of alternative foundation schemes, although these may influence the performance of the installed equipment.This study presents the results of structural analyses for several substructure options without seismic isolation, including ground improvement techniques and the use of piles. The alternatives are compared based on their impact on the overall building design and the seismic demand transmitted to sensitive internal components, as represented by the Floor Response Spectra (FRS), providing a trade-off analysis of performance and constructability. Finally, for the best-performing alternative, probabilistic FRS are derived to quantify the impact of soil variability on seismic demand.

At the core of IFMIF-DONES is placed the Target System. It generates a high-speed liquid lithium jet (15 m/s, 300°C) acting as the target for a 40 MeV, 125 mA deuterium-based linear accelerator, with the primary aim of qualifying fusion-related materials. The design of the Target System has evolved during the last few years addressing key challenges. Managing the 5 MW of power deposited continuously in the target requires a reliable lithium loop supplying liquid lithium in well-defined conditions. The extreme operational conditions, exposed to high irradiation levels (~25 dpa/year), demand also careful selection of materials and regular replacement strategies for critical components, supported by dedicated Remote Handling systems. Current efforts focus on optimizing the design to meet the requirements for its upcoming construction phase. This includes advanced features to facilitate assembly, installation, and long-term operability. Additionally, attention is being paid to the integration of diagnostics. This contribution highlights the recent R&D and engineering solutions aimed at advancing the Target System toward successful construction, commissioning and subsequent operation.

The IFMIF-DONES facility provides a very high intensity flux of neutrons for research on materials of future fusion reactors and other complementary applications. The generation of those neutrons is driven by stripping reactions between energetic deuteron particles and a liquid lithium jet. The requirements on the deuteron beam are to deliver a 40 MeV beam with a constant current of 125 mA. All the systems involved in the generation, acceleration, transport and shaping of the deuteron beam are grouped in the so-called accelerator systems (AS). The design of this high-power driver has been ongoing for a long time, and many prototypes of the critical technologies have been tested. During the last decade, the design has been consolidated and evolved into an engineering design ready for construction. The overview of the main features of the design and the current status is presented in this article.

IFMIF-DONES is devoted to the irradiation of fusion materials, based on a high energy linear accelerator and a lithium-deuteron stripping reaction, creating the high intensity neutron source which simulates the damage on the 1st wall of the future fusion reactors. The core of the facility are the Accelerator, Lithium and Test Systems hosted inside IFMIF-DONES Facility, in the so-called Main Building (MB). The detailed design of this building was initiated first during the IFMIF-EVEDA activities in the framework of the Broader Approach (EU-Japan Bilateral Agreement) and pursued within EUROfusion for the development of an Early Neutron Source (WPENS). The design has evolved in which the main areas in terms of neutronics shielding are the Accelerator Vault and the Test Cell, where the nuclear reaction takes place and the materials are irradiated. Additional rooms like the Access Cell or the radwaste treatment area, are key in terms of shielding. In this work, it is presented the status of the integration into the design of the MB structure of the safety requirements from the definition of the radiation maps, neutronics studies and heavy concrete vs ordinary concrete capabilities.

The International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source (IFMIF-DONES) will be an installation capable of qualifying materials for use in future fusion power reactors. To do so, a linear accelerator will deliver high-intensity deuteron beam to a liquid Li loop, creating a flow of neutrons that will produce material damage equivalent to that expected in a fusion reactor. The vacuum system must maintain high vacuum conditions during operation with high reliability. For this reason, a careful study of the vacuum has been assessed and implemented in the accelerator project. Vacuum simulations have been performed in order to have a first estimation of the expected pressure profile, and documentation is being produced to standardize the subsystem. Additionally, valuable knowledge from the prototype installation, IFMIF/Engineering Design and Engineering Validation Activities (EVEDA), is being taking into account in engineering design activities. Moreover, two vacuum related prototypes are being manufactured; the Multipurpose Vacuum Accident Scenarios (MuVacAS) prototype will enable experimental studies of air inrush in the last section of the accelerator; and the Quick Disconnecting System (QDS) prototype is being developed to study the feasibility of the remote handling of the interface located between the accelerator beam line and the target chamber. The paper presents the status of the design of the vacuum subsystem of the accelerator and discusses the future challenges.

The International Fusion Materials Irradiation Facility- DEMO Oriented Neutron Source (IFMIF-DONES) is a scientific infrastructure aimed to provide an intense neutron source for the qualification of materials to be used in future fusion power reactors. Its implementation is critical for the construction of the fusion DEMOnstration Power Plant (DEMO).IFMIF-DONES is a unique facility requiring a broad set of technologies. Although most of the necessary technologies have already been validated, there are still some aspects that introduce risks in the evolution of the project.In order to mitigate these risks, a consortium of companies, with the support of research centres and the funding of the CDTI (Centre for the Development of Industrial Technology and Innovation), has launched the DONES EVO Programme, which comprises six lines of research:•Improvement of signal transmission and integrity (planning and integration risks)•Optimisation of RF conditioning processes (planning and reliability risks)•Development of a reliable beam extraction device (reliability risks)•Development of technologies for the production of medical isotopes (reliability risks)•Improvement of critical parts of the lithium purification system (safety and reliability risks)•Validation of the manufacture of critical components with special materials (reliability risk).DONES EVO will focus on developing the appropriate response to the risks identified in the IFMIF-DONES project through research and prototyping around the associated technologies.This contribution will present a discussion of the risks, the proposed response to them and the evolution of the technologies involved, following selected experiments carried out throughout the project.

IFMIF-DONES is a facility under construction in Granada, whose main goal is the validation and characterization of materials under a fusion prototypic irradiation field. This field is created by the interaction of a high energy intense continuous deuteron beam and a flowing liquid lithium target. The requirements imposed on the beam at the interaction point are a complex trade-off among the scientific experimental needs for the materials irradiation defined at the top-level requirements (20 dpa in a volume of 0.3 dm3 and 50 dpa in 0.1 dm3), and the technical constraints of several systems such as the Accelerator Systems, the Lithium Systems, and the Test Systems. Recent simulations with the initial definition of beam-on-target requirements showed the necessity of redefining them in order to fulfill the irradiation needs. This contribution will address the main challenges to gather the inputs for the definition and reassessment of the beam-on-target requirements. A comparison detailing the main changes compared to the previous ones will be given, together with a short overview of the studies ongoing by different systems to analyze the impact of each beam-on-target requirements on the performance of the whole facility.

IFMIF-DONES (International Fusion Materials Irradiation Facility – DEMO Oriented Neutron Source) is a fusion materials testing facility that is currently being designed under the framework of a work package of the EUROfusion Consortium. It will use a 125mA at 40MeV deuteron beam to generate a high neutron flux through Li(d,xn) stripping nuclear reactions in a liquid lithium target. The High Energy Beam Transport line (HEBT), the most upstream system of the IFMIF-DONES accelerator, is responsible for the guidance and shaping of the beam towards the target. Additionally, during commissioning periods, the HEBT is also responsible for diverting the beam, through the Beam Dump Transport Line, to the Beam Dump for testing purposes. The HEBT is spread along different rooms and zones: the Accelerator Vault, the Radiation Interface Zone (RIZ), and Target Interface Room (TIR). The engineering design of the HEBT components situated within the TIR and RIZ has been updated to satisfy new requirements, with a focus on ensuring the protecting of the Fast Isolation Valve (FIV) from the backscattered radiation from the target. These modifications include relocating the FIV from the TIR to the RIZ, adjusting the building layout to accommodate the new FIV module, configuring an enclosure cabinet for the RIZ, and adding local shielding to extend the lifetime of the FIV seal actuators. This work describes the current status of these TIR and RIZ engineering design, including radioprotection, commissioning and maintenance plan, beam diagnostics devices, beam dynamics and new remote handling approaches, as well as the layout and integration of the required components along the beamline. The TIR and RIZ are critical areas for IFMIF-DONES, and their design and operation must be compliant with functional, reliability and safety requirements. The updated design addresses potential issues and enhances the facility’s overall functionality.

IFMIF-DONES will be an irradiation facility based on a 40 MeV deuteron accelerator. Unavoidable beam losses along the accelerator result in deuterium interactions with the beam facing materials of the vacuum beam pipe, some of them leading to material activation. The initial design of the beam pipe was based on stainless steel, but an evaluation of the residual doses from the pipe showed high values after operation of the accelerator. The accelerator beam line must be periodically maintained, and excessive cooling times for reaching acceptable dose levels may result in poorer availability of the facility. A deeper study of the High Energy Beam Transport line (HEBT) showed that a direct reaction between deuterons and iron in steel resulted in the production of Co-56, with a half-life of 77 days. This radioisotope is the main source of the radiation and makes it impractical to wait for a proper attenuation of the radiation field. A redesign of beam line elements has been performed to avoid the presence of stainless steel as a beam facing material and to replace it with aluminum where possible, resulting in faster decay of residual doses. This work contains a summary of the nuclear analysis performed for the computation of residual doses with stainless steel beam pipe, stressing the uncertainties of the calculations, based on the limited availability of nuclear data for the relevant nuclear reaction Fe56 (d,2n). The proposed replacement of element materials is also described, and an updated nuclear analysis shows the reduction of residual radiation, and its impact on possible maintenance operations.

The L inear I nternational Fusion Materials Irradiation Facility P rototype Ac celerator (LIPAc) is under commissioning in Rokkasho Fusion Institute in Japan and aims to accelerate 125 mA D+ at 9 MeV in Continuous Wave mode for validating the IFMIF accelerator design. To ensure a fine characterization and tuning of the machine many beam diagnostics are installed spanning from injector to the beam dump. The beam operations in 1.0 ms pulsed D+ at 5 MeV were successfully completed with a low power beam dump in 2019. Despite the challenges posed by the pandemic, the crucial transition to a new LINAC configuration was also finalized to enable operation in 1.0 ms — CW D+ at 5 MeV with the high-power beam dump. The 1 st beam operation of the configuration was carried out in 2021. The experiences and challenges encountered during these beam campaigns are described in this paper.

This article addresses the challenges associated with the alignment of the equipment within the IFMIF DONES installation and presents the strategy devised to achieve acceptable levels of uncertainty. The primary obstacles stem from the need to align equipment located in different rooms, some of which are inaccessible for manual operations. Additionally, the elevated radiation levels in certain areas impose restrictions on the fiducials that can be employed. The article details the outcomes of implementing the proposed alignment procedure, including the specific equipment used and the achieved levels of uncertainty.

Recent advancements in the neutronics activities of the IFMIF-DONES project, developed within the EUROfusion framework, are presented. These include updates to radiation dose maps during commissioning and normal operation of the accelerator systems; material irradiation analyses and shielding optimization of the test systems; activation inventories of 7Be, 3H, and activated corrosion products in the Li systems; shutdown dose analyses of transportation and storage of radioactive waste, cooling water and atmosphere gas activations, skyshine to the public, etc. The development of simulation tools, nuclear data evaluation, and nuclear experiments for the specific needs of DONES neutronics are highlighted, as well as the nuclear analysis handbook and database. Several challenges for future development are also discussed to ensure the provision of high-quality nuclear analyses.

The Linear IFMIF Prototype Accelerator, LIPAc, is being commissioned aiming at validating the RFQ up to 5 MeV beam acceleration. Eventually, the nominal beam of 5 MeV-125 mA in 1 ms length and 1 Hz rate pulsed mode was achieved in 2019. The beam operation has been resumed since July 2023 after a long maintenance including recovery from unexpected problems in the RFQ-RF system. This new phase aims at the commissioning of the full configuration except SRF LINAC, which is replaced by a temporary beam transport line. Focusing on the RFQ behavior, it will be interesting to operate it at higher duty, especially for longer pulses. Furthermore, a beam simulation study suggested that the beam extracted from the RFQ includes considerable momentum halo when the vane voltage reduces by more than 5 %, with a slight decrease of the mean energy. It can be a potential source of a quench like the mismatched beam in the cryomodule. This could be studied by measuring the energy from the Time -of -Flight among multiple BPMs while monitoring beam loss around the dipole, where momentum halo should be lost. During the beam commissioning phase, we studied them by scanning the RFQ voltage.

This work presents an analysis of the IFMIF-DONES design maturity and the necessary activities to increase it up to the level required to launch the procurement phase. The analysis has been performed using a Technology Readiness Level (TRL) methodology. The TRL scale and definitions employed in EU Horizon programs have been found to be appropriate for this assessment, with some modifications to consider the IFMIF-DONES peculiarities.The level of Technology Readiness needed for launching the procurement of each subsystem or component (“target TRL”) has been established. From the comparison between the present TRL and the target TRL, the elements requiring further development and validation have been identified and the experimental activities needed to increase their maturity have been defined.The results of the TRL assessment for the accelerator, lithium and test systems of the facility are presented together with a brief outline of the most relevant validation needs identified.

In IFMIF-DONES, a deuteron beam will impinge on a flowing liquid lithium target, resulting in an intense neutron source. Other radiation sources will also arise due to the interactions between deuterons and the beam facing accelerator components. These radiation fields may cause some negative effects, such as damage to equipment or the generation of residual radiation sources. The characterization and mitigation of all the radiation sources are crucial for a safe operation and maintenance of the facility. In this study, the optimization and/or implementation of some radiation shields located in critical areas is considered to reduce the doses during operation and shutdown. Three scenarios are assessed: (i) shielding optimization of the High-Power Beam Dump for the accelerator commissioning, (ii) shielding optimization for the scraper of the High Energy Beam Transport line and the Fast Safety Isolation Valves, and (iii) shielding implementation to reduce the radiation transmission through Heating, Ventilation, and Air Conditioning wall penetrations. Radiation maps of the biological dose and the dose to silicon are computed, showing the impact of such shielding elements.