Liquid Li Target Research Articles

Cleanroom assembly of the IFMIF SRF Linac

In complement to the development activities for fusion reactors (JT-60SA & ITER), Fusion for Energy contributes to the R&D for material characterisation facilities. Within the Broader Approach agreement, different actors from Europe to Japan collaborate to develop and assemble in Japan the LIPAC, a technical demonstrator of a D+ accelerator that will be used to produce neutron by nuclear stripping reaction on a liquid Li target. In 2024, the LIPAC is getting ready for the installation of the SRF cryomodule that will conclude its construction. Started in March 2019, the assembly was paused a first time to solve technical problems on its solenoids. Resumed in August 2022, the assembly was paused a second time after the completion of the cavity/coupler assembly to fix additional issues. In April 2024, the assembly restarted with the completion of the beam line. In this talk, we will present and details the different steps of the cleanroom assembly and how the different technical difficulties were overcome.

DONES Systems identification and requirements allocation

• Systems identification of IFMIF-DONES for work distribution and responsbility allocation. • System-of-Systems to Group-of-Systems type mapping. • Alignment of Systems identification and requirement allocation. The mission of the DONES program is to develop a database of fusion-like neutron irradiation effects in the materials required for the construction of the Demonstration Fusion Power Reactor (DEMO) for benchmarking of radiation response of materials. In order to do this, the DONES facility will be built to provide a neutron source producing high-energy neutrons at sufficient intensity and irradiation volume. DONES will generate a neutron flux with a broad energy distribution covering the typical neutron spectrum of a (d-t) fusion reactor. This is achieved by utilizing Li(d,xn) nuclear reactions taking place in a liquid Li target when bombarded by a deuteron beam. The energy of the deuterons (40 MeV) and the current of the accelerator (125 mA) have been tuned to maximize the neutron flux to get irradiation conditions comparable to those in the first wall of a fusion power reactor. For the success of this mission, the needs of all the stakeholders shall be very clearly stated, considering the whole lifecycle of the facility. Once the needs are clear, they shall be translated into specific requirements, following a top-down approach, to be allocated to the different systems or groups-of-systems (GoS). To do this, it is essential to properly identify which parts shall be treated as a System or GoS, as they shall be designed accordingly, and the requirements allocated in consequence.

Verification of accuracy of contact-probe distance meter for lithium target of fusion neutron source

Abstract An accelerator based intense neutron sources such as the IFMIF, A-FNS and DONES produce neutron flux by a stripping reaction between lithium (Li) and deuteron for testing various materials for fusion reactor. In these fusion neutron sources, a liquid Li free-surface jet is applied as the liquid Li target. For the development of the Li target system, the variation in the thickness of the Li jet was measured using the Li loop of Osaka University. At the Osaka Univ., a lot of knowledge about the surface fluctuation of the Li jet had been obtained by using the electro-contact type distance meter (referred to as the probe apparatus herein). Besides, for the stable and safety operation of the facility, the probe apparatus is planned to be used as a safety interlock system for beam irradiation in actual intense neutron source because of its simple structure. Therefore, it is desirable to verify its accuracy. Especially, it is expected that false detection and undetected waves, which is particular to the contact-type apparatus, could cause errors. Then in this study, the measurement using non-contact type distance meter using optical comb (referred to as the laser probe herein) was conducted, and then the error of the results of the probe apparatus is evaluated by comparing results.

Experimental evaluation of wall shear stress in a double contraction nozzle using a water mock-up of a liquid Li target for an intense fusion neutron source

Herein, the wall shear stress in a double contraction nozzle has been evaluated experimentally to produce a liquid lithium (Li) target as a beam target for intense fusion neutron sources such as the International Fusion Materials Irradiation Facility (IFMIF), the Advanced Fusion Neutron Source (A-FNS), and the DEMO Oriented Neutron Source (DONES). The boundary layer thickness and wall shear stress are essential physical parameters to understand erosion–corrosion by the high-speed liquid Li flow in the nozzle, which is the key component in producing a stable Li target. Therefore, these parameters were experimentally evaluated using an acrylic mock-up of the target assembly. The velocity distribution in the nozzle was measured by a laser-doppler velocimeter and the momentum thickness along the nozzle wall was calculated using an empirical prediction method. The resulting momentum thickness was used to estimate the variation of the wall shear stress along the nozzle wall. Consequently, the wall shear stress was at the maximum in the second convergent section in front of the nozzle exit.

Engineering validation for lithium target facility of the IFMIF under IFMIF/EVEDA project

The International Fusion Materials Irradiation Facility (IFMIF), presently in the Engineering Validation and Engineering Design Activities (EVEDA) phase was started from 2007 under the frame of the Broader Approach (BA) agreement. In the activities, a prototype Li loop with the world's highest flow rate of 3000L/min was constructed in 2010, and it succeeded in generating a 100mm wide and 25mm thick with a free-surface lithium flow along a concave back plate steadily at a high-speed of 15m/s at 250°C for 1300h. In the demonstration operation it was needed to develop the Li flowing measurement system with precious resolution less than 0.1mm, and a new wave height measuring method which is laser-probe method was developed for measurements of the 3D geometry of the liquid Li target surface. Using the device, the stability of the variation in the Li flowing thickness which is required in the IFMIF specification was ±1mm or less as the liquid Li target, and the result was satisfied with it and the feasibility of the long-term stable liquid Li flow was also verified. The results of the other engineering validation tests such as lithium purification tests of lithium target facility have also been evaluated and summarized.

Numerical analysis of high-speed Lithium jet flow under vacuum conditions

The EVEDA Li test loop (ELTL) [1] is aimed at validating the hydraulic stability of the Lithium (Li) target at a velocity up to 20m/s at vacuum (≈10−3Pa). The ELTL has been designed to demonstrate the feasibility of the major components providing a neutron production liquid Li target for IFMIF. The rectangular shaped Li jet (cross-section 25mm×100mm) necessitates for heat removal flow velocities of 15–20m/s along a concave shaped back wall (curvature radius 250mm) towards the outlet pipe, where the Li jet is subjected to vacuum before it finally enters the collecting quench tank. During the validation experiments within the ELTL acoustic waves within the target outlet pipe have been recorded, indicating potential cavitation processes in the jet impinging region, which may cause premature failures.In order to identify potential cavitation phenomena in correlation with the free jet flow in the outlet pipe a numerical study has been performed. The comparison measured and simulated acoustic emissions exhibits that experimentally deduced cavitation area coincides with the location of the jet wall impingement. The simulations further reveal that a part of the fluid after striking the wall even flows opposite to the gravity vector. This reversed flow is inherently unstable and characterized by waves at first growing and then bursting into droplets. The intense generation of small droplets increases significantly the Li free surface area and lead to a production of Li vapour, which is captured by the jet flow and reintroduced in the main flow. As the static pressure is recovered downstream due to jet impact, the vapour bubbles collapse and hence cavitation likely occurs.

Validation of IFMIF liquid Li target for IFMIF/EVEDA project

A liquid-Li free-surface stream flowing at 15m/s under a high vacuum of 10−3Pa is to serve as a beam target for the planned International Fusion Materials Irradiation Facility (IFMIF). The Engineering Validation and Engineering Design Activities (EVEDA) for the IFMIF is implemented under the Broader Approach. As a major activity for the Li target, the EVEDA Li test loop (ELTL) was constructed by the Japan Atomic Energy Agency. The present study demonstrates a stable Li target that satisfies the IFMIF design conditions (250°C, 15m/s, 10−3Pa) and presents the procedure for operating the Li target which consists of seven stages. We used a laser-based method to verify that the Li target is adequately stable. In addition, we examine cavitation occurring during startup of the Li target, and consequently, determine the appropriate startup pressure.

Technical analysis of an early fusion neutron source based on the enhancement of the IFMIF/EVEDA accelerator prototype

In the framework of the Engineering Design and Engineering Validation Activities for the International Fusion Materials Irradiation Facility (IFMIF/EVEDA), three major prototypes have been designed and are being manufactured, commissioned and operated which are firstly the Accelerator Prototype (LIPAc) at Rokkasho, fully representative of the IFMIF low energy (9MeV) accelerator stage, secondly the EVEDA Lithium Test Loop (ELTL) at Oarai, and thirdly critical components of the High Flux Test Modules to be tested in the helium cooling loop (HELOKA-LP) at Karlsruhe. The present paper analyses possibilities from a technical point of view, for combining, modifying, and enhancing, at limited cost, selected components of the prototypes towards the realisation of an early reduced-flux neutron source, able nonetheless to start the testing of candidate DEMO materials and realising by this a first step towards the construction and operation of a complete IFMIF plant.Various options of deuteron beam parameters, such as energy, current and shape are analysed with respect to their technical challenges and the neutron yield resulting from the nuclear reaction with the Li target. Related requirements for the liquid Li target with respect to jet parameters are evaluated and the neutron mapping in the high flux region is presented underlying an analysis of the available volume for testing reduced activation ferritic martensitic (RAFM) steels at relevant structural damage levels.

Screening Potential of 6Li(d,α)4He and 7Li(p,α)4He Reactions in Liquid Lithium

In order to investigate the screening effect of a nuclear reaction in a liquid metal environment, thick-target yields of the 6 Li(d,α) 4 He and 7 Li(p,α) 4 He reactions were measured using a liquid Li target for incident energies between 22.5 and 70 keV. The modified S ( E ) factor [ S * ( E )] for the liquid Li environment was deduced by dividing the measured yield by the energy integration of the penetration factor divided by the stopping power. It was shown that S * ( E ) for the liquid environment is considerably larger than that for the atomic/molecular environment for both reactions. The difference in the screening energy between the two environments was deduced to be Δ U = 235 ±63 ( 6 Li+d) and 140±82 eV ( 7 Li+p), although the screening energy for liquid Li has a large uncertainty with U liq ∼486–776 ( 6 Li+d) and 324–637 eV ( 7 Li+p) owing to the uncertainty of the astrophysical bare S ( E ) factors. This difference in the screening energy should be considered in such a way that, in liquid Li met...

Status of engineering design of liquid lithium target in IFMIF-EVEDA

In International Fusion Materials Irradiation Facility (IFMIF), intense neutron flux (4.5 × 10 17 n/m 2 s) with a peak energy of 14 MeV are produced by means of two deuteron beams with a total current of 250 mA and maximum energy of 40 MeV that strike a liquid Li target circulating in a Li loop. Major design requirement is to provide a stable Li jet at a speed of 10–20 m/s with a surface wave amplitude on the Li flow less than 1 mm for handling of an averaged heat flux of 1 GW/m 2 under a continuous 10 MW deuterium beam deposition. The target system consists of a target assembly, a replaceable back-plate, a Li main loop and a Li purification loop. In July 2007, Engineering Validation and Engineering Design Activities (EVEDA) started under Broader Approach. In this paper, status of the engineering design of the IFMIF Li target system performed in 2007/2008 is described. The future EVEDA tasks to develop the target system are also summarized.

Thickness distribution of high-speed free-surface lithium flow simulating IFMIF target

International Fusion Materials Irradiation Facility (IFMIF) employs liquid lithium as D + beams target. The liquid Li target is formed as flat plane free-surface flow by a nozzle and flows at high speed around 15 m/s. This paper focuses on flatness of the liquid Li target. The Li flow experiment was conducted in Osaka University Li Loop with a test section which was 1/2.5 scaled model of IFMIF. The thickness of the Li flow was measured and obtained by a contact method which was developed for the measurement. Analytical study on Kelvin wake and numerical calculation on the wake near the side wall of the flow channel were also conducted and compared with the experimental results. As a result, the positions of the wake crest obtained from both of the experiment and numerical calculation assuming contact angle 140° agreed well with the iso-phase line of the analytical model. The generation of the wake likely depends on wettability between Li and the structural material which is 304SS in the present study.

Latest design of liquid lithium target in IFMIF

This paper describes the latest design of liquid lithium (Li) target system in International Fusion Materials Irradiation Facility (IFMIF). IFMIF is an accelerator-driven intense neutron source for fusion reactor materials testing. Two 40 MeV deuteron beams with a total current of 250 mA strikes a liquid Li target circulating in a Li loop. The Li target is to provide a stable Li jet at a speed of 10–20 m/s to handle an averaged heat flux of 1 GW/m 2. A concaved Li flow is applied to avoid Li boiling. A cold trap and two kinds of hot trap are applied to control impurities (T, 7Be, C, O, N) below permissible levels. A back wall made of RAFM is located in the most severe region of neutron irradiation (50 dpa/year). System availability requires more than 95% during plant lifetime. EVEDA tasks including Li loop are now being performed under the Broader Approach.

High energy density physics problems related to liquid jet lithium target for Super-FRS fast extraction scheme

The new international facility for antiproton and ion research (FAIR), at Darmstadt, Germany, will accelerate beams of all stable isotopes from protons up to uranium with unprecedented intensities (of the order of 1012 ions per spill). Planned future experiments include production of exotic nuclei by fragmentation/fission of projectile ions of different species with energies up to 1.5 GeV/u at the proposed super conducting fragment separator, Super-FRS. In such experiments, the production target must survive multiple irradiations over an extended period of time, which in case of such beam intensities is highly questionable. Previous work showed that with full intensity of the uranium beam, a solid graphite target will be destroyed after being irradiated once, unless the beam focal spot is made very large that will result in extremely poor transmission and resolution of the secondary isotopes. An alternative to a solid target could be a windowless liquid jet target. We have carried out three-dimensional numerical simulations to study the problem of target heating and propagation of pressure in a liquid Li target. These first calculations have shown that a liquid lithium target may survive the full uranium beam intensity for a reasonable size focal spot.

Latest liquid lithium target design during the key element technology phase in the international fusion materials irradiation facility (IFMIF)

International Fusion Materials Irradiation Facility (IFMIF), being jointly developed by EU, JA, RF and US, is a deuteron–lithium (Li) stripping reaction neutron source for fusion materials testing. In 2002, a 3 year Key Element technology Phase (KEP) to reduce the key technology risk factors was completed. A liquid Li target has been designed to produce intense high energy neutrons (2 MW/m 2) up to 50 dpa/year by 10 MW of deuterium beam deposition which corresponds to an ultra high heat load of 1 GW/m 2. This paper describes the latest design of the liquid Li target system reflecting the KEP results and future prospects.

Activities on IFMIF lithium target at ENEA

The status of R&D activity ongoing at ENEA on the lithium target system of the international fusion materials irradiation facility (IFMIF) is reported. The activity has been launched in year 2000 in the frame of IFMIF key element technology phase in order to reduce the key technology risk factors and to guarantee the required availability and reliability of the IFMIF liquid Li target system. The items discussed in the paper are related to the Li jet flow stability numerical analysis, water flow simulation experiment, backplate remote handling simulation and Li target safety analysis.

Suitability and feasibility of the International Fusion Materials Irradiation Facility (IFMIF) for fusion materials studies

There is a global consensus among materials scientists and engineers that thequalification of materials in an appropriate test environment isindispensable for the design, construction and safe operation ofdemonstration fusion reactors as well as for the calibration of data generated from fission reactor and accelerator irradiations. In anevaluation process based on a series of technical workshops it wasconcluded that an accelerator driven D-Li stripping source would bethe best choice to fulfil the requirements within a realistic timeframe. In response to this need, an international design team withmembers from the European Union, Japan, the United States of America and the Russian Federation has developed, under theauspices of the International Energy Agency during a conceptual design activity phase(1994-1996), a suitable and feasible concept for an accelerator drivenD-Li stripping source. This reference design for the InternationalFusion Materials Irradiation Facility (IFMIF) is based onconservative linac technology and two parallel operating 125 mA,40 MeV deuteron beams that are focused onto a common liquid Litarget with a beam footprint of 50 mm by 200 mm. The materialstesting volume behind the Li target is subdivided into different fluxregions: the high flux test region (0.5 L, 20-55 dpa/full poweryear), the medium flux test region (6 L, 1-20 dpa/full power year), and the lowflux test region (>100 L, <1 dpa/full power year). The design developed was the basis for the conceptual design evaluation phase(1997-1998) and for subsequent engineering oriented activities. On the basis ofcomprehensive neutron transport calculations, an evaluation of theirradiation parameters and the available testing volumes has shown thatthe users' requirements can be fulfilled. Major engineering effortshave been undertaken to establish an IFMIF design that is based onavailable and already proven technologies. The design developedis based on extensive reliability, availability, maintainability andsafety studies and is conceived for long term operation with atotal annual facility availability of at least 70%.