IFMIF Research Articles

Installation and first operation of the International Fusion Materials Irradiation Facility injector at the Rokkasho site.

The International Fusion Materials Irradiation Facility (IFMIF) linear IFMIF prototype accelerator injector dedicated to high intensity deuteron beam production has been designed, built, and tested at CEA/Saclay between 2008 and 2012. After the completion of the acceptance tests at Saclay, the injector has been fully sent to Japan. The re-assembly of the injector has been performed between March and May 2014. Then after the check-out phase, the production of the first proton beam occurred in November 2014. Hydrogen and deuteron beam commissioning is now in progress after having proceeded with the final tests on the entire injector equipment including high power diagnostics. This article reports the different phases of the injector installation pointing out the safety and security needs, as well as the first beam production results in Japan and chopper tests. Detailed operation and commissioning results (with H(+) and D(+) 100 keV beams) are reported in a second article.

Measurement of ion species in high current ECR H⁺/D⁺ ion source for IFMIF (International Fusion Materials Irradiation Facility).

Ion species ratio of high current positive hydrogen/deuterium ion beams extracted from an electron-cyclotron-resonance ion source for International Fusion Materials Irradiation Facility accelerator was measured by the Doppler shift Balmer-α line spectroscopy. The proton (H(+)) ratio at the middle of the low energy beam transport reached 80% at the hydrogen ion beam extraction of 100 keV/160 mA and the deuteron (D(+)) ratio reached 75% at the deuterium ion beam extraction of 100 keV/113 mA. It is found that the H(+) ratio measured by the spectroscopy gives lower than that derived from the phase-space diagram measured by an Allison scanner type emittance monitor. The H(+)/D(+) ratio estimated by the emittance monitor was more than 90% at those extraction currents.

Measurement of lithium target surface velocity in the IFMIF/EVEDA lithium test loop

In the framework of the Engineering Validation and Engineering Design Activities (EVEDA) project of the International Fusion Materials Irradiation Facility (IFMIF), we measured surface velocity fields of a lithium (Li) target at the EVEDA Li test loop under specifically-designated IFMIF conditions (target speeds of 10, 15, and 20m/s, vacuum pressure of 10−3Pa, and Li temperature of 250°C). In the current design of the IFMIF, the free surface of the Li target is under a most severe heat load condition with respect to Li boiling. The objective of this study is to measure the actual free-surface velocity under these IFMIF conditions to evaluate the heat removal performance of the Li target. The measured results (using the surface-wave tracking method that our team developed) showed two-dimensional time-averaged velocity distributions around the IFMIF beam footprint being virtually uniform, and close to the cross-sectional average velocity. The uniformity of the velocity distributions was less than 1m/s. The comparison between the measured and analyzed surface velocity at the beam center showed that the analysis accurately predicts the measurement results within a margin of 3%. Finally, it was confirmed that the Li target delivers adequate heat removal performance in the IFMIF as designed.

Demonstration of Li target facility in IFMIF/EVEDA project: Li target stability in continuous operation of entire system

The International Fusion Materials Irradiation Facility (IFMIF) is an accelerator-based D+-Li neutron source in which two 40-MeV-D+ beams with a total current of 250mA are injected into a liquid Li stream flowing at 15m/s (Li target). The EVEDA Li test loop (ELTL), which simulates the hydraulic conditions of the Li target and a part of the purification system envisaged in IFMIF, is a main activity in the Li target facility of the IFMIF/EVEDA project and has been implemented under the Broader Approach (BA) agreement since 2007. The key issues to be validated in ELTL were as follows: (1) validation of the Li target, Li target diagnostics, and cold trap (CT), and (2) validation of long-term operation. This study describes the stability of the Li target in an integrated long-term operation run of the entire system as a demonstration of the IFMIF Li target facility. The Li target was continuously operated with the CT for 571h, and its stability was evaluated periodically using a high-precision Li target diagnostic. Therefore, the Li target essentially satisfied the stability requirement of <±1mm throughout the continuous operation.

Numerical Analysis of Unsteady Flow Behavior in Flow Conditioner of IFMIF Liquid-Lithium Target

IFMIF (International Fusion Materials Irradiation Facility) is an accelerator based deuteron-lithium (D-Li) neutron source to simulate the neutron irradiation field in a fusion reactor. The target assembly of the IFMIF consists of the flow conditioners and the nozzle, which has to form a stable lithium jet. This work focuses on a numerical study of the flow conditioner efficiency, in which two different types of flow conditioners are compared by means of a detailed numerical analysis with respect to specific hydraulic effects in the pipe elbow and the inflow conditioners. The adequateness of two modelling approaches - Large Eddy Simulation (LES) and Detached Eddy Simulation (DES) - to simulate an unstable flow through a 90° bend of circular cross section has been examined. Both methods investigated exhibit a reasonable agreement with the experimental data, but the DES approach does not require a very fine grid resolution and is less time consuming. The further conducted numerical analysis of the flow conditioner uses a DES approach. The calculations show that a honeycomb-screen combination is not capable to suppress effectively large scale swirl motions emerging from the bend. A frequency analysis of the static pressure fluctuation reveals instabilities in the shear layer between the separation zone and the accelerated outer region, which additionally increase the inhomogeneity of the axial velocity distribution.

The accomplishment of the Engineering Design Activities of IFMIF/EVEDA: The European–Japanese project towards a Li(d,xn) fusion relevant neutron source

The International Fusion Materials Irradiation Facility (IFMIF), presently in its Engineering Validation and Engineering Design Activities (EVEDA) phase under the frame of the Broader Approach Agreement between Europe and Japan, accomplished in summer 2013, on schedule, its EDA phase with the release of the engineering design report of the IFMIF plant, which is here described. Many improvements of the design from former phases are implemented, particularly a reduction of beam losses and operational costs thanks to the superconducting accelerator concept, the re-location of the quench tank outside the test cell (TC) with a reduction of tritium inventory and a simplification on its replacement in case of failure, the separation of the irradiation modules from the shielding block gaining irradiation flexibility and enhancement of the remote handling equipment reliability and cost reduction, and the water cooling of the liner and biological shielding of the TC, enhancing the efficiency and economy of the related sub-systems. In addition, the maintenance strategy has been modified to allow a shorter yearly stop of the irradiation operations and a more careful management of the irradiated samples. The design of the IFMIF plant is intimately linked with the EVA phase carried out since the entry into force of IFMIF/EVEDA in June 2007. These last activities and their on-going accomplishment have been thoroughly described elsewhere (Knaster J et al [19]), which, combined with the present paper, allows a clear understanding of the maturity of the European–Japanese international efforts. This released IFMIF Intermediate Engineering Design Report (IIEDR), which could be complemented if required concurrently with the outcome of the on-going EVA, will allow decision making on its construction and/or serve as the basis for the definition of the next step, aligned with the evolving needs of our fusion community.

The design status of the liquid lithium target facility of IFMIF at the end of the engineering design activities

The International Fusion Material Irradiation Facility (IFMIF) is an experimental facility conceived for qualifying and characterizing structural materials for nuclear fusion applications. The Engineering Validation and Engineering Design Activity (EVEDA) is a fundamental step towards the final design. It presented two mandates: the Engineering Validation Activities (EVA), still on-going, and the Engineering Design Activities (EDA) accomplished on schedule in June 2013. Five main facilities are identified in IFMIF, among which the Lithium Target Facility constituted a technological challenge overcome thanks to the success of the main validation challenges impacting the design. The design of the liquid Lithium Target Facility at the end of the EDA phase is here detailed.

Measurement of Li target thickness in the EVEDA Li Test Loop

A high-speed (nominal: 15m/s, range: 10–16m/s) liquid lithium wall jet is planned to serve as the target for two 40MeV and 125mA deuteron beams in the International Fusion Materials Irradiation Facility (IFMIF). The design requirement of target thickness stability is 25±1mm under a vacuum of 10−3Pa. This paper presents the results of the target thickness measurement conducted in the EVEDA Li Test Loop under a wide range of conditions including the IFMIF condition (target speed of 10, 15, and 20m/s; vacuum pressure of 10−3Pa; and Li temperature of 250°C). For measurement, we use a laser probe method that we developed in advance; this method generates statistical measurements method using a laser distance meter. The measurement results obtained under the IFMIF nominal condition (15m/s, 10−3Pa, 250°C) at the IFMIF beam center are as follows: average target thickness=26.08±0.09mm (2σ), mean wave amplitude=0.26±0.01mm (2σ), and maximum wave amplitude=1.46±0.25mm (2σ). Of the total wave components, 99.7% are within the design requirement. The analytically predicted target thickness is in excellent agreement with the experimental data, resulting in successful characterization of the Li target thickness.

Overview on recent progress toward small specimen test technique

The present status of the small specimen test technique (SSTT) and the engineering design of the post irradiation examination (PIE) facility in the International Fusion Materials Irradiation Facility (IFMIF) were evaluated and summarized as parts of the IFMIF/engineering validation and engineering design activity (EVEDA). SSTT is very important to obtain data mainly for the design of fusion demonstration (DEMO) reactors using the high flux test module (HFTM) of IFMIF. The analysis of brittle–ductile transition behaviors of reduced-activation ferritic/martensitic (RAFM) steels is very important for evaluating the structural integrity of RAFM steels used in the fusion DEMO reactors, and it is necessary to develop new analyses combined with random inhomogeneity analysis and the modified master curve method. Further developed analysis and test equipment developing for small specimen tests are necessary in the establishment of SSTT.

RAMI assessment for IFMIF lithium facility

A RAMI (reliability, availability, maintainability and inspectability) assessment performed on the IFMIF (International Fusion Materials Irradiation Facility) Lithium Facility (LF) is presented. Given the high availability requirements for the IFMIF plant, a target requirement of 94% availability has been attributed to the LF and its feasibility verified for the proposed system design. The LF performance for the foreseen operation mission has been investigated by the mean of failure mode, effect and criticality analysis (FMECA) and reliability block diagrams (RBDs). The first assessment performed on the base of the present design did not satisfy the above target requirement. Then, possible optimizations in design solutions and maintenance policy have been investigated. The RBD analysis shows that with some improvements the LF could be able to comply with the availability target requested, as the obtained mean availability for 10 years of simulation is of 93.4% and the inherent availability more than 99%. The reliability to operate the LF without failure during the yearly scheduled operation time is about 64%. Most critical components in terms of impact on LF reliability and availability, are: (i) the Li loop Target Section (back plate) and electro-magnetic pumps for the main loop, (ii) the getter beds of the hydrogen hot trap and the electromagnetic pump for the impurity control system.

Results of the RAMI analyses performed for the IFMIF accelerator facility in the engineering design phase

This paper presents a summary of the RAMI (Reliability Availability Maintainability Inspectability) analyses done for the IFMIF (International Fusion Materials Irradiation Facility) Accelerator facility in the Engineering Design Phase. The methodology followed, the analyses performed, the results obtained and the conclusions drawn are described. Moreover, the consequences of the incorporation of the RAMI studies in the IFMIF design are presented and the main outcomes of these analyses are shown.

Overview of the IFMIF test facility design in IFMIF/EVEDA phase

The test facility (TF) is one of the three major facilities of the International Fusion Material Irradiation Facility (IFMIF). Engineering designs of TF main systems and key components have been initiated and developed in the IFMIF EVEDA (Engineering Validation and Engineering Design Activities) phase since 2007. The related work covers the designs of a test cell which is the meeting point of the TF and accelerator facility and lithium facility, a series of test modules for experiments under different irradiation conditions, an access cell to accommodate remote handling systems, four test module handling cells for test module processing and assembling, and test facility ancillary systems for engineering support on energy, media, and control infrastructure. This paper summarizes the principle functions, brief specifications, and the current design status of the above mentioned IFMIF TF systems and key components.

The engineering design evolution of IFMIF: From CDR to EDA phase

The International Fusion Materials Irradiation Facility (IFMIF), presently in its Engineering Design and Engineering Validation Activities (EVEDA) phase, started in 2007 under the framework of the Broader Approach (BA) Agreement between Japanese Government and EURATOM. The mandate assigned was to develop an integrated engineering design of IFMIF together with accompanying sub-projects to validate the major technological challenges that included the construction of either full scale prototypes or cleverly devised scaled down facilities, which are essential to reliably face the construction of IFMIF on schedule and cost. The Engineering Design Activities were accomplished on-schedule with the release of its “Intermediate Engineering Design Report (IIEDR)” in June 2013 compliant with our mandate. This paper highlights the design improvements implemented from the previous Conceptual Design Phase.

Certification of contact probe measurement of surface wave of Li jet for IFMIF

The international fusion material irradiation facility (IFMIF) is a neutron source for developing fusion reactor materials. A liquid lithium (Li) jet with free surface is planned as a target to generate intense neutron field. It is important to obtain information on the surface wave characteristic for safety of the facility and efficient neutron generation. Surface wave characteristics experiment using the liquid Li circulation facility is carried out at Osaka University. In our studies, measurement using an electro-contact probe apparatus is conducted and many data about surface wave height were taken. In this experiment, a liquid Li droplet was observed on the probe. To see effect due to droplets on the probe needle, images near the surface of the Li jet including the Li droplet were taken by HSV camera synchronized with probe contact signals, and correlation between the behavior of the Li droplet and signals was evaluated. From the results, when the droplet on the probe contacts of the droplet with the surface, signals obviously different from the regular signal were observed. The influence on the result of frequency was estimated and is approximately <1%. Accuracy of measurement using probe could be increased by carefully deleting false signals.

Re-evaluation of neutron displacement cross sections for silicon carbide by a Monte Carlo approach

Neutron displacement cross sections for SiC are re-evaluated by a Monte Carlo approach, with damage energies of primary recoils calculated by the stopping and range of ions in matter (SRIM) code. The validity of the Monte Carlo model is examined by the case of iron, and the results show good agreement with the reference values. Neutron displacement cross sections for SiC at energies up to 100 MeV are calculated, and averaged over the neutron spectra of a fusion DEMO reactor, the high flux test module of the International Fusion Materials Irradiation Facility, and typical fission test reactors. Gas production is also calculated for those neutron irradiation facilities. Finally, the suitability of the displacement cross sections is discussed. The results on comparison among neutron irradiation of different facilities by the current displacement cross sections are similar to those by results of the previous work. Moreover, since neutron displacement cross sections in this study are calculated with damage energies of primary recoils calculated by SRIM, neutron damage evaluated by our displacement cross sections is suitable for correlation with damage by heavy ions calculated by SRIM.

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.

Chemical reaction of lithium with room temperature atmosphere of various humidities

When replacing lithium target components in the International Fusion Materials Irradiation Facility, the lithium adhering on the surface of components will chemically react with the surrounding atmosphere. In this study, we investigate the chemical reaction of pure lithium in room temperature air, oxygen, nitrogen, and argon of various humidities. In air, oxygen, and argon, the weight gain increases with time and humidity, and no significant difference is observed in these gases. In nitrogen, except for the test with 75% relative humidity (RH), the weight gain accelerates with time, and the weight gain rate decreases with increasing RH. We attribute the weight gain increase observed in low humidity to the acceleration due to lithium nitride formation. Upon increasing the moisture content of the gas, the main lithium reaction becomes lithium hydroxide formation.

Accelerators for Fusion Materials Testing

Fusion materials research is a worldwide endeavor as old as the parallel one working toward the long term stable confinement of ignited plasma. In a fusion reactor, the preservation of the required minimum thermomechanical properties of the in-vessel components exposed to the severe irradiation and heat flux conditions is an indispensable factor for safe operation; it is also an essential goal for the economic viability of fusion. Energy from fusion power will be extracted from the 14 MeV neutron freed as a product of the deuterium–tritium fusion reactions; thus, this kinetic energy must be absorbed and efficiently evacuated and electricity eventually generated by the conventional methods of a thermal power plant. Worldwide technological efforts to understand the degradation of materials exposed to 14 MeV neutron fluxes [Formula: see text] m[Formula: see text]s[Formula: see text], as expected in future fusion power plants, have been intense over the last four decades. Existing neutron sources can reach suitable dpa (“displacement-per-atom”, the figure of merit to assess materials degradation from being exposed to neutron irradiation), but the differences in the neutron spectrum of fission reactors and spallation sources do not allow one to unravel the physics and to anticipate the degradation of materials exposed to fusion neutrons. Fusion irradiation conditions can be achieved through Li (d, xn) nuclear reactions with suitable deuteron beam current and energy, and an adequate flowing lithium screen. This idea triggered in the late 1970s at Los Alamos National Laboratory (LANL) a campaign working toward the feasibility of continuous wave (CW) high current linacs framed by the Fusion Materials Irradiation Test (FMIT) project. These efforts continued with the Low Energy Demonstrating Accelerator (LEDA) (a validating prototype of the canceled Accelerator Production of Tritium (APT) project), which was proposed in 2002 to the fusion community as a 6.7[Formula: see text]MeV, 100[Formula: see text]mA CW beam injector for a Li (d, xn) source to bridge with the International Fusion Materials Irradiation Facility (IFMIF) under discussion at the time. Worldwide technological efforts are maturing soundly and the time for a fusion-relevant neutron source has arrived according to world fusion roadmaps; if decisions are taken we could count the next decade with a powerful source of 14 MeV neutrons thanks to the expected significant results of the Engineering Validation and Engineering Design Activity (EVEDA) phase of the IFMIF project. The accelerator know-how has matured in all possible aspects since the times of FMIT conception in the 1970s; today, operating 125 mA deuteron beam at 40 MeV in CW with high availabilities seems feasible thanks to the understanding of the beam halo physics and the three main technological breakthroughs in accelerator technology: (1) the ECR ion source for light ions developed at Chalk River Laboratories in the early 1990s, (2) the RFQ operation of H[Formula: see text] in CW with 100 mA demonstrated by LEDA in LANL in the late 1990s, and (3) the growing maturity of superconducting resonators for light hadrons and low [Formula: see text] beams achieved in recent years.

Current status of the technology development on lithium safety handling under IFMIF/EVEDA

Studies for establishing technology for the safe handling of lithium was performed in the Engineering Validation and Engineering Design Activities (EVEDA) for the International Fusion Material Irradiation Facility (IFMIF). This research comprises four tasks: (a) extinguishing lithium files, (b) chemical reactions of lithium on the event of a leak, (c) lithium removal from the components, and (d) chemical analysis of impurities in lithium. Tasks (a) and (b), related to functions on the event of a lithium leak, involve selection of the material suitable for extinguishing lithium fires and assessment of corrosive effects of leaked lithium on materials at high temperature, respectively. Task (c) involves evaluation of methods for the replacement and/or decommissioning of the lithium components. Task (d) constitutes the development of high-precision techniques for the determination of impurities in lithium, particularly the dominating corrosive impurity—dissolved nitrogen. Experimental results addressing the objectives of each of the tasks are described in this communication.

Neutronic Analysis of the IFMIF Tritium Release Test Module Based on the EVEDA Design

The International Fusion Materials Irradiation Facility (IFMIF) is an accelerator-based intense neutron source to test fusion reactor materials under irradiation conditions expected to be experienced by a future fusion power plant (DEMO). The Tritium Release Test Module (TRTM) is intended for the irradiation of solid breeder ceramics as well as beryllium involving in-situ tritium release measurements in IFMIF. During the EVEDA (Engineering Validation Engineering Design Activities) phase, a detailed engineering design for the TRTM has been elaborated. A new 3-dimesional Monte Carlo geometry model of TRTM was prepared for a neutronic analysis directly from engineering CAD data using the McCad conversion software developed at KIT. The analysis was performed with the latest version of the Monte Carlo code McDeLicious, an enhancement to MCNP5 for IFMIF neutronics calculations, using a state-of-the-art nuclear data library FENDL-3. The result emphasizes the importance of the neutron reflector which should be placed behind TRTM in order to make the irradiation properties close to the European HCPB DEMO. Although the achievable dpa is lower than that expected in DEMO, the T/dpa and He/dpa values can be simulated very well when the neutron reflector is appropriately designed, in particularly by utilizing beryllium.