Hiroo Kondo

IFMIF/EVEDA lithium test loop: design and fabrication technology of target assembly as a key component

The engineering validation and engineering design activity (EVEDA) for the International Fusion Materials Irradiation Facility (IFMIF) is proceeding as one of the ITER broader approach activities. In the concept of the IFMIF, two 40 MeV deuteron beams are injected into a liquid Li stream (Li target) flowing at a velocity of 15 m s−1. The EVEDA Li test loop (ELTL) is aimed at validating the hydraulic stability of the Li target at a velocity up to 20 m s−1 under a vacuum condition of 10−3 Pa as the most important issue. Construction of the ELTL, which is the largest liquid metal loop possessing 5.0 m3 Li for the fusion research ever, was completed in the O-arai Research & Development Center in the Japan Atomic Energy Agency on 22 November 2010. This paper presents the design and fabrication technology of a target assembly called integrated target assembly, in which the Li target is produced by a contraction nozzle along a concave channel. There are two concepts regarding the target assembly: the integrated target assembly and the bayonet target assembly. Both target assemblies are outlined in this paper, and then the newly proposed design of the integrated target assembly for the ELTL and its fabrication technology are given. The integrated target assembly was processed by a five-axis milling machine and the processing accuracy was measured by 3D measurement tools. Finally, methods applied for the validation of the stability of the Li target are introduced in this paper.

Experimental Study on Wave Propagation Behavior on Free Surface of Lithium Flow for IFMIF

Velocity measurement of surface waves on high-speed liquid lithium (Li) flow was conducted by using the Li circulation loop at Osaka University to support target monitor and diagnostics applications for the International Fusion Materials Irradiation Facility (IFMIF). Free surface shapes were recorded with a high-speed video camera, and surface waves were tracked with the statistical correlations of image intensity patterns over a velocity range of 5 to 15 m/s. As a result, the velocity distribution of surface waves was measured. The development of surface velocity beyond the nozzle edge was clearly measured. The velocity measurement by this method might suffer from some influence from stationary waves, which were generated by a damaged nozzle edge. The measured velocity in a region free from stationary waves was seen to exceed the mean flow velocity, probably due to two-dimensional regular waves. For this case, the measured velocity may consist of the advection velocity of the Li flow and the phase velocity of the wave. For an irregular wave region, the measured velocity was shown to be approximately the same as the mean flow velocity. The present flow velocity measurement can be used in the high-velocity range where random waves are generated.

Design and Construction of IFMIF/EVEDA Lithium Test Loop

The International Fusion Materials Irradiation Facility (IFMIF) is a D + ―Li neutron source aimed at producing an intense high energy neutron flux (2 MW/m 2 ) for testing candidate fusion reactor materials. Under Broader Approach activities, Engineering Validation and Engineering Design Activities (EVEDAs) of IFMIF started on July 2007. Regarding the lithium (Li) target facility, design, construction, and tests of EVEDA Li test loop (ELTL) is a major Japanese activity. The detail design of the loop was started since early 2009. Construction of the loop was started at the middle of 2009, and completion is scheduled at the end of February 2011. This paper focuses on the design of the loop configuration and the major components. ELTL was designed to consist of two major Li loops, which are a main loop and a purification loop including an impurity monitoring loop. The main loop equips a target assembly which produces a high-speed free-surface Li flow to test the flow stability as the D + beam target. The maximum flow rate of an electromagnetic pump in the main loop was set to 3000 l/min, so that flow velocity in the target assembly is 20 m/s at the maximum. Regarding the purification loop, a cold trap and two hot traps and impurity monitors are installed in order to purify and monitor impurities in Li. The configuration of these components in addition to the specification and configuration of the whole loop is presented.

Engineering Validation and Engineering Design of Lithium Target Facility in IFMIF/EVEDA Project

Abstract EVEDA Lithium Test Loop (ELTL) has been designed and constructed, has operated a liquid lithium flow test facility with the world’s highest flow rate and has succeeded in generating a 100-mm-wide and 25-mm-thick free-surface lithium flow along a concave back plate steadily at a high speed of 20 m/s at 300°C for the first time in the world. This result will greatly advance the development of an accelerator-based neutron source to high energy and high density, one of the key objectives of the fusion reactor materials development under the BA (Broader Approach) Activities. Recent related engineering validation and engineering design of the lithium facility has been evaluated.

Engineering Design of Contact-Type Liquid Level Sensor for Measuring Thickness Variation of Liquid Lithium Jet in IFMIF/EVEDA Lithium Test Loop

Abstract In the Engineering Validation and Engineering Design Activities (EVEDA) on the International Fusion Materials Irradiation Facility (IFMIF), hydraulic stability of a liquid Li jet simulating the IFMIF Li target is planned to be validated in the EVEDA Li Test Loop (ELTL). This paper presents the engineering design of a contact-type liquid level sensor for use in ELTL. The sensor is going to be utilized to measure variation of jet thickness in the validation test on hydraulic stability of the Li jet, which is one of the major key tests to be performed in ELTL. A fundamental requirement for the engineering specification of the sensor is to ensure the position accuracy of the measurement probe against the pressure load of approximately 0.1 MPa between the inside and the outside of the test chamber. The calculation result on structural strength of the sensor with a Nastran code showed that the maximum displacement was 0.65 mm and that the sensor has adequate strength against the pressure load. The calculation result on the sensor temperature with an ABAQUS code showed that the probe tip’s temperature can be heated up to approximately the operation temperature with no heaters installed on the sensor.

Experimental Study on Fire-Extinguishing of Lithium

Fire-extinguishing behavior of four fire extinguishants, dry sand, pearlite, Natrex-L and Natrex-M on burning lithium was examined. Temperature and flame increase in chemical reaction between lithium and silicon, which is the major element in the fire extinguishants, were observed for dry sand and pearlite. For Natrex-L, temperature increase was not observed visually, although flame was slightly increased when it was applied to the burning lithium. The effect of lithium pool depth on the fire-extinguishing performance of Natrex-L was investigated on the definite area of the lithium combustion surface because the density of Natrex-L was larger than that of liquid lithium. It was found that the amount (thickness) of fire extinguishant necessary for fire-extinguishing increased as the depth increased. In this experimental condition (combustion area: 270cm2 , lithium depth: 1–2cm), the minimum thickness of the fire extinguishant was 1.5 times the depth of the lithium pool.Copyright

Measurement of Wavy Surface Oscillations on Liquid Metal Lithium Jet for IFMIF Target

The International Fusion Materials Irradiation Facility (IFMIF) has been conceived as a high-flux 14 MeV neutron source for testing candidate fusion reactor materials. In the current design, neutrons are generated by irradiating a target with a deuteron beam and high-speed free-surface flow of liquid metal lithium (Li) is adopted as the target. To reveal the stability of the Li flow, we have examined characteristics of surface waves at a location 175 nm downstream from a nozzle exit, which corresponds to the center of the beam irradiated region. In this study, the characteristics of surface waves just downstream of the nozzle exit were measured experimentally, since the initial growth of surface waves exerts a definite influence on the surface behavior of the Li flow in the downstream region. Experiments were carried out with a focus on surface oscillations of the Li flow using the lithium circulation loop at Osaka University. These oscillations are measured using an electro-contact probe apparatus, which can detect electrically a contact between the probe tip and the Li surface and provide local height data of surface waves. The apparatus was installed at a location 15 mm downstream from the nozzle exit and scanned the Li surface by moving along the liquid-depth direction. The experiments were performed for the velocity range of 3-15 m/s under argon gas atmosphere at a pressure of 0.13 MPa. The contact signal recorded in the experiment was used to analyze the characteristics of surface waves, and then the root-mean-square wave amplitude and the frequency of surface waves were calculated. It was found that the root-mean-square wave amplitudes of surface waves increased with a rise in the flow velocity, and reached approximately 0.18 mm at 14-15 m/s. And also, obtained frequencies were analyzed using a linear stability theory, and the variation of frequencies was examined with the mean flow velocity.

Chemical analysis of hydrogen isotopes dissolved in li and y for hot trap of ifmif target loop

Abstract IFMIF-EVEDA progresses in Japan as one of the EU-Japan Broader Approach Activities. The research is performed to decide whether or not IFMIF is constructed after some uncertainties included in the design are clarified. One of the uncertainties included in the Li purification process is to prove experimentally the removal of 1 weight ppm (wppm) T and 10 wppm D from flowing Li for safety. Our research group is experimentally investigating the recovery of hydrogen isotopes including T not only in static Li but also in fluidized Li. In the past study, hydrofluoric acid (HF) treatment of Y is successful in removing oxide inevitably formed on its surfaces. The recovery of hydrogen isotopes including T less than 1 wppm is successfully proved with use of the HF-treated Y at 300°C, which is the IFMIF hot-trap temperature. Mass-transfer rates of hydrogen isotopes in the liquid Li and Y under stirred conditions were determined. In addition, we developed a way to determine an amount of D or T dissolved in Li and Y by using a dissolution method. The quantitative D analysis is performed by using techniques of HNO3 solution for Y and H2O one for Li. The distribution coefficient between Li and Y is determined as a function of temperature and contact time.

Material Improvement of Hydrogen Isotope Permeation Monitor for Liquid Lithium

Abstract Titanium plates coated by iron were fabricated electrochemically as a candidate hydrogen isotope permeation window for liquid lithium. Contacting the window to liquid lithium containing deuterium between 673 and 873 K, its permeation behavior and resistance to degradation were investigated. The iron-coated window showed less permeability than the bare titanium window as well as good agreement with the theoretical value. Furthermore, the iron layer at the vacuum side surface strongly improved oxidation resistance. Decrease of permeability for 2 hours air exposure could be recovered within 30 hours in the case of the coated window, while that of the bare titanium window could not. The coated permeation window is promising regarding high permeability and antidegradation properties.

Current Status of Design and Construction of IFMIF/EVEDA Lithium Test Loop

The International Fusion Materials Irradiation Facility (IFMIF) is a D+ -Li neutron source aimed at producing an intense high energy neutron flux (2 MW/m2 ) for testing candidate fusion reactor materials. Under Broader Approach activities, Engineering Validation and Engineering Design Activities (EVEDA) of IFMIF started on July 2007. Regarding to the lithium (Li) target facility, design and construction of EVEDA Li Test Loop is a major activity and is in progress. This paper presents the current status of the design and construction of EVEDA Li Test Loop. The EVEDA Li Test Loop consists of a main loop system and a purification loop system. The detail design was started at the early 2009. Fabrication of the loop was started at middle of 2009, and completion is planned at the end of Feb. 2011. Currently, the system diagram of the EVEDA Li Test Loop is finished to be defined. The diagram and function of major components in the main loop system and the purification loop system are described in this paper.Copyright