Mizuho Ida

Thermal-hydraulic characteristics of IFMIF liquid lithium target

Abstract International Fusion Materials Irradiation Facility (IFMIF) is an accelerator-based deuteron–lithium neutron source for testing fusion materials. High-speed flow up to 20 m/s is required for the liquid lithium target to remove high heat load 1 GW/m2 of deuteron beams. Thermal-hydraulic stability of the target system is required during long-term operation of IFMIF. Thermal-hydraulic analyses and simulation experiments with water jets were carried out to verify the stability of the IFMIF target flow. Appropriateness of concept of the high-speed flow on concave back-wall was verified by the analyses. There were enough temperature margins to avoid boiling and a thickness margin of 3 mm in the target. Acceptable range of the back-wall radius was 100–1000 mm. By the experiments with different nozzle wall roughness, main cause of surface waves was found to be boundary layer at the nozzle exit depending on the wall roughness. Cause of increased surface waves in case of the coarse-wall nozzle was a transition from laminar to turbulent boundary layer. Based on the experimental results, a wall roughness less than 6.3 μm was recommended for IFMIF target. These results give stable conditions of the IFMIF target, verify the appropriateness of its design and give guidelines on its fabrication.

Designs of contraction nozzle and concave back-wall for IFMIF target

Abstract For the liquid lithium flow target of International Fusion Materials Irradiation Facility (IFMIF), the double reducer (two-step contraction) nozzle with a high-contraction ratio of 10 which generated high-speed uniform jet flows up to 20xa0m/s was proposed. Multi-dimensional hydraulic analyses were carried out to verify the performance of the proposed nozzle. The analytical results showed that the double reducer nozzle would well generate high-speed uniform flow, while one-step contraction nozzle generated non-uniform flow and resulted in flow thickening at the beam footprint. For the target design, the range of the concave back-wall radius with no lithium boiling due to the centrifugal force and proper component arrangement in the irradiation test cell was determined by the thermal–hydraulic analysis of a free-surface flow. It was verified that the back-wall radius from 0.25 to 10xa0m was acceptable in the velocity range of 10–20xa0m/s.

Lithium free surface flow experiment for IFMIF

Abstract High-speed lithium flow was demonstrated in free surface condition by using the lithium loop facility at Osaka University. The project aims at the verification of hydrodynamic stability of free surface lithium flow of up to 15 m/s. A horizontally aligned test channel was installed in the existing loop. Preliminary results show that the design of the nozzle and of the test channel is considered to be successful in order to realize a high-speed free surface flow of lithium in vacuum.

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

Abstract 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.

Experimental and analytical studies on high-speed plane jet along concave wall simulating IFMIF Li target flow

Abstract As part of the conceptual design activity (CDA) of the international fusion materials irradiation facility (IFMIF), the characteristics of the high-speed liquid lithium (Li) plane jet target flow have been studied by water experiments and numerical analyses for both heating and non-heating conditions. The simulated prototypal-size water jet flows were stable over the entire length of ∼130 mm at the average velocity up to 17 m/s. The jet flow had a specific radial velocity profile, close to that of free-vortex flow, because of a static pressure distribution in the jet thickness due to centrifugal force. Detailed velocity measurement revealed that this flow condition is penetrating into the upstream reducer nozzle up to a distance ≈ the jet thickness. The numerical analyses using a two-dimensional Cartesian-coordinate model were successful to predict the velocity profile transient around the nozzle exit, though underestimated the development of the velocity profile and the jet thickness.

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.

Status of lithium target system for international fusion materials irradiation facility (IFMIF)

The recent status of the lithium target system for the international fusion materials irradiation facility (IFMIF), accelerator-based D-Li neutron source, is described with focus on a low-cost design and a three-stage deployment of the IFMIF. The activities of the key element technology phase (KEP) have also been summarized.

Liquid lithium target under steady state ultra high heat load of 1 GW/m2 range for International Fusion Materials Irradiation Facility (IFMIF)

Abstract International Fusion Materials Irradiation Facility is an accelerator-based neutron source using the D–Li stripping reaction to provide high intensity neutron field with energy of 14 MeV and damage dose rate of around 20 dpa/year for fusion materials development. To handle the intense deuterium beam power up to 10 MW which corresponds to ultra high heat flux of 1 GW/m2, the liquid Li jet flow with a maximum velocity of 20 m/s and a concave flow configuration is necessary. According to thermal–hydraulic analysis, an induced centrifugal force with a radius of concave back wall (25 cm) realized that the Li temperature is lower than the Li boiling point. To confirm the hydraulic characteristics of Li flow, water jet simulation experiment has been done. Moreover, validation experiment in Li loop is under way in Osaka University. In addition, a permissible heat load of the Li flow under a surface heat deposition has been discussed.

Status of activities on the lithium target in the key element technology phase in IFMIF

Abstract This paper describes the status of the liquid lithium (Li) target facility in the key element technology phase (KEP) of the International Fusion Materials Irradiation Facility (IFMIF). The IFMIF is being jointly developed by the European Union (EU), Japan (JA), Russian Federation (RF) and US to provide an accelerator-based D–Li neutron source for testing the candidate materials for fusion reactors. A key issue of the Li target is to obtain a stable liquid Li flow with a speed of 20 m/s under a deuterium beam deposition of 10 MW. In the KEP, 19 tasks for the Li target are proposed and shared by EU, JA and RF. These tasks are a Li simulation experiment by water jet, Li flow experiment, corrosion/erosion, remote handling of the target assembly, and safety analysis. In addition to the KEP tasks, detailed design of the target is being performed.

Water jet flow simulation and lithium free surface flow experiments for the IFMIF target

Abstract A water jet experiment was performed to investigate the influences of nozzle inner wall roughness on the free surface stability of water flow, which simulates the lithium (Li) target jet flow of the International Fusion Materials Irradiation Facility (IFMIF). The effect of a cover gas was investigated further as a possible candidate for the interfacial wave growth because of the Kelvin–Helmholtz instability. The results showed that the jet interfacial roughness was insensitive to the cover gas pressure, but it increased with the wall roughness because of the development of a boundary layer along the wall. This effect was found to be significant when the velocity was higher than 10 m/s. Utilizing these results, a Li open flow experiment is being planned by modifying the Li Loop at Osaka University.