Liquid Lithium Target Research Articles

Update of the 5 MW Beam-on-Target Requirements for improvement of the materials irradiation performance at IFMIF-DONES

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.

Thermal hydraulic and structural analysis of the IFMIF-DONES liquid-lithium target system

In the IFMIF-DONES neutron source a single accelerator line delivers 125 mA of deuterons at 40 MeV to a flowing liquid lithium target with a free surface facing the deuteron beam.Neutrons with fusion-relevant spectrum are generated by a stripping reaction and used for material samples irradiation.This report presents a numerical thermal–hydraulic and structural analysis using updated design of the target system and neutronics analysis results. Simulation scope includes the target assembly, vacuum chamber with beam ducts, outlet channel, quench tank vessel and connecting elements.Simulations have been conducted with the commercial CFD code Simcenter Star-CCM + . The computational domains consist total of 47.4x106 fluid and 14x106 structure cells.The following aspects have been analyzed:•Temperature distribution in lithium and target system structure during beam-on operation;•Transient mixing of lithium in the quench tank with temperature change during the beam switch-on phase.•Thermal displacements and stresses in the TA and QT structures.Simulations using the new distribution of nuclear heating show no significant changes in the temperature field in liquid lithium. Calculated unwanted temperature hotspots in the target structure demonstrate the need for optimization of the target design.

Validation activities at ENEA Brasimone in support of the IFMIF-DONES design

IFMIF-DONES is a powerful neutron source which is being designed with the main purpose of qualifying structural materials (EUROFER being the first candidate) to be used in DEMO and fusion power plants envisaged after it. This source relies on one high current (125 mA) deuterons beam accelerated to 40 MeV which impacts on a liquid lithium target to produce an intense neutron flux through Li(d,n) stripping reactions able to simulate the nuclear responses expected on the first wall of the reactor. The engineering design of IFMIF-DONES is presently being carried out mainly in the framework of the EUROfusion Work Package Early Neutron Source (WPENS). Since 2021, a new phase has started with the launch of the FP9 WPENS workplan whose objective is to continue advancing the engineering design of the facility, putting special effort on the experimental validation of those aspects which still need to be qualified to demonstrate the fulfillment of functional and safety requirements. The ENEA Brasimone Research Centre has been and still is strongly committed in several validation tasks concerned in particular with the lithium systems design and the Remote Handling (RH) maintenance.In this paper, an overview of the most relevant validation activities carried out in recent years or still in progress or planned at the ENEA Brasimone Research Centre in both of the aforementioned areas is presented, including the erosion/corrosion tests in the Lifus 6 loop; the nitrogen-gettering materials qualification in the ANGEL facility; and the RH and prototypes testing in the DRP laboratory for the validation of the High Flux Test Module electric connectors and the pre-heating of the Target Assembly.

Thermal and structural analysis of the DONES target system under steady state and transient loading conditions

One of the crucial steps in the European Roadmap to the realisation of fusion energy is the design and construction of the Demo-orientated NEutron Source (DONES) facility. DONES is a fusion-like neutron source, based on the International Fusion Materials Irradiation Facility (IFMIF) concept, aimed at qualifying and testing the materials to be used in fusion reactors. The Target System (TSY) is a crucial system as it is the component where the interactions between deuterons and a liquid lithium target, flowing on a solid surface (i.e. the Back Plate), take place to produce neutrons for irradiating the testing materials. In this regard, an investigation campaign has been performed to evaluate the thermo-mechanical behaviour of the DONES TSY under selected steady state and transient loading conditions, in light of the most recent design updates (new bellows and connection systems). The first part of the assessment concerned the analysis of the TSY under the normal operation steady state loading scenario. A detailed 3D FEM model has been set up, considering the newest updates of the TSY geometry and of the operational parameters, and a thermo-mechanical analysis has been launched. Results have been mainly checked in terms of TSY global deformation, focusing on the Back Plate and on the connecting bellows displacements, in order to exclude overlapping with the High Flux Test Module and misalignments with the beam footprint. Afterwards, since the lithium inlet temperature has been increased from 250 °C to 300 °C, a transient thermo-mechanical analysis of the TSY under the start-up loading conditions has been performed to check if it is able to withstand the hotter lithium flow according to the RCC-MRx criteria. Therefore, the reference pre-heating strategy has been adopted, assessing the thermal and mechanical behaviour of the TSY, focusing on the Back Plate. The obtained results are presented and critically discussed, suggesting important recommendations for the follow-up of the design.

Shielding optimization to reduce the radiation field in the accelerator systems of IFMIF-DONES

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.

Engineering design status of IFMIF-DONES High Energy Beam Transport line and Beam Dump system inside the TIR and RIZ

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.

Application of the MELCOR for Fusion Code to the Transient Accident Analysis of the IFMIF-DONES Test Cell

According to the European Fusion Roadmap, to demonstrate the feasibility of fusion energy, it is necessary to build a comprehensive database of materials properties to be used in future fusion power plants. This is the objective of the IFMIF-DONES facility, which will drive a deuteron beam on a liquid lithium target to produce high energy neutron fluxes for irradiating candidate fusion materials. Among the several ongoing activities in the frame of the EUROfusion Early Neutron Source Work Package (WPENS) project, deterministic accident analyses play an important role, since they help identifying a set of reference accident scenarios and related safety class components. Some of these scenarios are being studied with the MELCOR-fusion code, an integrated engineering code which is able to perform thermal-hydraulic transient calculations. In this work, the MELCOR-fusion code has been applied to two potential accident scenarios involving the degradation of the primary lithium loop of IFMIF-DONES. A rupture in the Quench Tank and a break in the inlet nozzle to the Target Vacuum Chamber were postulated as the two initiating events followed by a lithium spill into the Test Cell room. The purpose of this study was to obtain different key metrics, such as the maximum pressure and temperature loads reached in the TC room, the amount of the leaked lithium mass, and the time for lithium solidification. The computed results will help identify the safety requirements to be applied to the final design of the TC room.

Beamline and vacuum system design of HEBT for the A-FNS accelerator

The Advanced Fusion Neutron Source (A-FNS) project is progressing at the QST Rokkasho institute, Japan. The A-FNS will conduct fusion neutron irradiation tests of materials for a fusion demonstration reactor (DEMO reactor). For these tests a high intensity deuteron beam accelerator is used to produce a high neutron flux with the neutron energies around 14 MeV. The accelerator system accelerates a deuteron beam to a beam energy of 40 MeV, guides the beam towards a liquid lithium target and shapes the uniform beam at the Li target using a magnet system.Two of the main considerations for the A-FNS high energy beam transport (HEBT) design are protection of the Superconducting Radio-Frequency linear accelerator (SRF) and vacuum system design for the interface of the HEBT and the target system. For the A-FNS, back streaming of Li vapor from the windowless free surface of the Li target is a concern. In addition, widely different vacuum pressure must be maintained between the accelerator system and the target system. This paper shows the detailed design of the A-FNS HEBT section regarding these considerations.

Neutron and isotope production yield from proton and deuteron beams in the 20–45 MeV range on thick liquid gallium-indium and lithium targets

Neutron and isotope production yield from proton and deuteron beams in the 20–45 MeV range on thick liquid gallium-indium and lithium targets

Status of the engineering design of the IFMIF-DONES high energy beam transport line and beam dump system

IFMIF-DONES plant [1] (International Fusion Materials Irradiation Facility – DEMO Oriented Neutron Source) is currently being developed under the framework of a work package of the EUROfusion Consortium. It will be a facility located at the south of Spain in Granada. Its objective and main goal is the testing and qualification of fusion materials by the generation of a neutron flux with a broad energy distribution covering the typical neutron spectrum of a (D-T) fusion reactor. This is achieved by the Li (d,xn) nuclear reactions occurring in a liquid lithium target where a 40 MeV at 125 mA deuteron beam with a variable beam footprint between 200 mm × 50 mm and 100 mm × 50mm collides. The Accelerator Systems is in charge of providing such high energy deuterons to produce the required neutron flux. The High Energy Beam Transport line (HEBT) is the last subsystem of the IFMIF-DONES accelerator, and its main functions are to guide the deuteron beam towards the liquid lithium target and to shape it with the required rectangular reference beam footprints. The HEBT system includes a Beam Dump devoted to stop the beam during commissioning and start-up phases. The present work details the present status of the HEBT engineering design, including beam dynamics, vacuum configuration, radioprotection, beam diagnostics devices and remote handling analyses performed detailing the layout and integration of required components through-out the beamline.

Stellar s-process neutron capture cross sections on ASe and ACe

We report on experiments at the Soreq Applied Research Accelerator Facility Liquid-Lithium Target (SARAF-LiLiT) laboratory dedicated to the study of s-process neutron capture reactions. The kW-power proton beam at 1.92 MeV (1-2 mA) from SARAF Phase I yields high-intensity 30 keV quasi-Maxwellian neutrons (3-5 1010 n/s). The high neutron intensity enables Maxwellian averaged cross sections (MACS) measurements of samples with short-lived decay products. Neutron capture reactions on natSe and natCe were investigated by activation in the LiLiT neutron beam and γ-spectrometry measurements of their decay products.

Particle Accelerator and Vacuum Related Research at Universities

Particle accelerators and vacuum are inseparable. After a description of the situation surrounding the development of particle accelerators at universities, some related research areas are introduced, i.e., the J-PARC ACS linear accelerator, a liquid lithium target system for BNCT (Boron Neutron Capture therapy) and measurements of secondary electron emission coefficients of dielectrics for RF vacuum windows.

The liquid-lithium target at the soreq applied research accelerator facility

The liquid-lithium target at the soreq applied research accelerator facility

Nuclear data libraries for IFMIF-DONES neutronic calculations

International Fusion Materials Irradiation Facility-DEMO Oriented NEutron Source (IFMIF-DONES) is an installation aimed to irradiate with a high neutron flux materials relevant for the construction of the DEMOnstration fusion power plant (DEMO), in order to study the damage due to irradiation. Neutrons are generated using a 40 MeV and 125 mA deuteron beam impinging on a thick liquid lithium target. With these characteristics, damage due to irradiation comparable to that in the first wall of a fusion power reactor is achieved. In this paper we investigate the differences in the neutronic calculations of the IFMIF-DONES design when using different nuclear data libraries. We first studied the differences in neutron production due to Li(d, xn) reactions between different models and evaluations, comparing the different results with experimental data. Additionally, we tested the performance of the MCNP6.2 and Geant4 Monte Carlo codes when using deuteron incident data libraries. Then, we performed neutronic calculations of the IFMIF-DONES design using the most reliable Li(d, xn) neutron production models available, which are the FZK-2005 and JENDL/DEU-2020 evaluations according to the results obtained in the first part of the study. Thus, the differences in these evaluations are propagated to different neutronic calculation results: neutron flux, primary displacement damage, gas production, and heating in the materials to be irradiated. Finally, we also carried out these same neutronic calculations while using different nuclear data libraries for the neutron transport.

Electrochemical hydrogen detection in DONES loop materials

• Design of an electrochemical sensor adequate to RAMI conditions of IFMIF-DONES. • Determination of hydrogen in liquid lithium. • Online electrochemical muliplex monitoring. • Modular design for different extended approaches (impurities, electrochemical procedures, sizes). The radiation-induced degradation of materials in fusion systems is planned to be investigated in IFMIF-DONES ( International Fusion Materials Irradiation Facility - DEMO Oriented NEutron Source ), where fast neutrons are produced by a reaction of deuteron-beams with a liquid lithium target. A by-product as critical impurity is hydrogen, which might affect the reliable and safe operation of the IFMIF-DONES loops. Therefore, an important issue is the measurement and control of the hydrogen impurity concentrations in liquid lithium. Initially, a practically applicable direct measurement of hydrogen concentrations in lithium facilities did not exist. However, one promising approach to manage this issue is based on the electrochemistry of the DONES materials The developed Electro-Chemical Hydrogen Sensor for Liquid Lithium (ECHSLL) allows the measurement of the electromotive Force (EMF) between a reference materials system and the loop lithium melt, and thus the monitoring of the hydrogen impurity concentrations. This article will show backgrounds of non-metallic impurities in liquid metal materials and the specific material stabilities within DONES. Liquid lithium is a very reactive material. Therefore critical issuesareviable materials compatibilities, the interactions with hydrogen and the transport behaviour of H-ions in electrolytes at the applied temperatures. Further issues are also the syntheses of the electrochemical materials, as hydrogen conducting electrolytes, reference electrode systems and the different procedures (heat treatments and conditioning steps). The tests showed the functionality of the developed H-sensor. Beyond that, the used material combinations exhibited reliable behaviour in melts under harsh conditions. Hence, the most critical aspect (stability of the sensor materials in the Li-melt) has been resolved by using niobium sensor heads. The observed experimental EMF potentials are in good accordance compared with calculated models, also in long-time experiments.

Stellar s -process neutron capture cross sections of Ga69,71

The stable gallium isotopes, $^{69,71}$Ga, are mostly produced by the weak slow ($s$) process in massive stars. We report here on measurements of astrophysically-relevant neutron capture cross sections of the $^{69,71}$Ga$(n,\gamma)$ reactions. The experiments were performed by the activation technique using a high-intensity ($3-5\times10^{10}$ n/s), quasi-Maxwellian neutron beam that closely mimics conditions of stellar $s$-process nucleosynthesis at $kT \approx$ 40 keV. The neutron field was produced by a mA proton beam at $E_p=1925$ keV (beam power of 2-3 kW) from the Soreq Applied Research Accelerator Facility (SARAF), bombarding the Liquid-Lithium Target (LiLiT). A 473 mg sample of Ga$_2$O$_3$ of natural isotopic composition was activated in the LiLiT neutron field and the activities of $^{70,72}$Ga were measured by decay counting via $\gamma$-spectrometry with a high-purity germanium detector. The Maxwellian-averaged cross sections at $kT$ = 30 keV of $^{69}$Ga and $^{71}$Ga determined in this work are 136(8) mb and 105(7) mb, respectively, in good agreement with previous experimental values. Astrophysical implications of the measurements are discussed.

Novel experimental techniques for neutron induced charge particle reaction studies in nuclear astrophysics

Neutron induced reaction studies on various unstable and short-lived nuclei play a very important role in understanding the various nucleosynthesis processes occuring in astrophysics scenario. We discuss here our approach to study neutron induced charge particle cross-section for various unstable and short-lived nuclei at effective temperatures of ~1.5-3.5 GK using the 7Li(p, n) reaction as a neutron source with five orders of magnitude higher neutron intensities with respect to currently available neutron time-of-flight facilities, using SARAF accelarator and Liquid Lithium Target (LiLiT) facility.

Wake Shape and Height Profile Measurements in a Concave Open Channel Flow regarding the Target in DONES

Wakes appearing downstream of disturbances on the surface of a water flow in a concave open channel were examined experimentally. The investigated channel geometry was similar to the liquid lithium target in DONES (Demonstration fusion power plant Oriented NEutron Source). The objective of the measurements was to analyze the effect of a disturbance on the downstream layer thickness. For measuring the height profiles in the channel, an optical measurement system based on laser triangulation was developed. It was shown that the wake of the undisturbed flow emerged from the nozzle corner, which was in accordance with analytical solutions. For sufficiently large disturbances at the nozzle edge, the height profiles located downstream showed symmetrical minima and maxima on both sides of the disturbance. The wake depth strongly depended on the diameter and penetration depth of the disturbance, as well as the circumferential position in the channel, which yields to a critical wake depth of one millimeter for the lithium target in DONES.

Conceptual design progress of advanced fusion neutron source

Based on the results of the IFMIF/EVEDA project in the broader approach (BA) activities, the conceptual design of the Advanced Fusion Neutron Source (A-FNS) to obtain irradiation data of DEMO blanket materials is under consideration in Japan.This paper describes the progress of the A-FNS conceptual design, which consists of a 40 MeV, 125 mA deuteron beam, a liquid lithium target system, and a test and post-irradiation test facilities. the main objectives of the A-FNS are the acquisition of RAFM irradiation data up to 2035 and the tritium recovery test on the blanket. In addition, it is expected to be used for various neutron researches.The technical design activities of the A-FNS are focused on improvement of the lithium target design, review of impurity criteria, remote handling, and irradiation application plan.

Comparison between liquid lithium and liquid tin targets in reactor relevant conditions for DEMO and I-DTT

The performance of divertor targets made of liquid metal, either lithium or tin, in highly powered tokamaks is analyzed for the proposed European DEMO and the projected Italian divertor test tokamak (I-DTT). The main tool is the 2D edge code TECXY, together with COREDIV. The results show that both materials are compatible with either DEMO or I-DTT under proper setting of the liquid divertor parameters. In general, operation at a high density is always highly recommended especially if detached conditions are desired. The latter can always be closely approached even when preserving an acceptable plasma purity with a proper setting of the target parameters and with the help of an additional impurity, which is able to radiate significantly inside the scrape-off layer plasma. For this action, Ar is preferred over Ne. Tin usually performs better than lithium for mitigation properties, reducing plasma pollution, material consumption, which in a DEMO-like device could be very high, and a definitely lower chemical affinity to hydrogen.