Liquid Breeder Research Articles

Tritium breeding control within liquid metal blankets

A key requirement for DEMO is the on-site breeding of tritium. In order to do this, a robust control system must be employed to ensure enough tritium is being bred to sustain the fusion reactor, whilst not breeding an amount which would exceed the plant's tritium inventory license. A tritium breeding method which is cost effective and reduces radioactive waste for disposal is that of the liquid metal breeder such as those based around LiPB and FLiBe. This paper focuses on the modeling of a simplified fusion reactor design with a LiPb blanket with linked radiation transport, nuclide burn-up and control theory. Two simple models were simulated using the FATI code which incorporated a PID (proportional integral derivative) controller that adjusted the Li6/Li7 ratio in order to increase/decrease tritium production based on the difference between the measured excess tritium inventory and the desired excess inventory. The modelling has initially demonstrated that a linear PID controller has the capability to manage tritium production within a LiPb liquid blanket.

Deuterium Retention in Tungsten-Coated Reduced Activation Ferritic/Martensitic Steel

Tungsten (W) is considered to be a good candidate as plasma-facing material of blanket in fusion reactor because of its good thermal properties and high atomic number. Despite those advantages, tungsten is a very heavy material. In order to solve this problem, tungsten coating on plasma-facing components (PFCs) is being developed. However, the performance of the W coating should be evaluated. Ferritic steel has better compatibility with both liquid metal or solid breeder, and all candidate coolants of fusion reactors, compared to austenitic steel. It also has low thermal expansion coefficient and high thermal conductivity. Moreover, the reduced activation ferritic-martensitic steel F82H (Fe-8Cr-2W) has been developed as candidate structure material for ITER blanket because of its advantages. Hydrogen isotope retention in PFCs affects surface properties, plasma fuelling, and wall conditioning of a fusion reactor and greatly depends on the material. Therefore there is a need to evaluate the deuterium retention/desorption behaviour of the tungsten coating, especially on F82H.

Heat-Pulse Flowmeter for a Liquid Breeder Blanket

Liquid metals Li, Pb-17Li and Sn-20Li are candidate liquid breeders in fusion reactors. The development of a flowmeter that can be applied to high-temperature liquid metals is an important issue. A heat-pulse flowmeter is proposed in the present study. Its basic performance was investigated by means of a loop experiment with Pb17Li and a numerical simulation. The temperature distribution in flowing Pb-17Li was obtained by local transient heating of the outer surface of a loop tube. The temperature distribution gradually changed and resembled the movement of a hot spot, which had a higher temperature than its surroundings. This hot spot moved along the flow and passed through the tips of the thermocouples. The change in temperature distribution with the movement of the hot spot was monitored by three thermocouples exposed to the Pb-17Li flow. The results of the loop experiments were numerically simulated by assuming a certain flow rate, and the temperature profile obtained in the loop experiment was in agreement with the simulation results. The time taken by the hot spot to pass through the tips of the thermocouples was measured and simulated, and the correlation between this time and the average flow velocity was evaluated. The results indicated the average flow velocity can be obtained using the heat-pulse flowmeter proposed in this study. c

Preliminary Study on the Melting and Reaction of Liquid Metal Breeders for a Korean Test Blanket Module in ITER

Korea has developed a liquid breeder blanket and participated in the test blanket module program for ITER. To develop liquid breeder technologies with not only liquid lithium but also lead-lithium (PbLi), an experimental loop for the liquid breeder was constructed at the Korea Atomic Energy Research Institute. The main purposes of the loop are developing components such as an electromagnetic pump, testing the effects of magnetohydrodynamics, and investigating the compatibility between the liquid breeder and other materials. Before operating the loop, the melting and solidifying temperatures of the PbLi and its contamination were experimentally investigated considering cyclic use with the prepared reaction chamber. Melting and solidifying temperatures were ~235°C, and there was no change even with the cyclic test. Because of contamination such as oxidation, however, the composition of PbLi can be changed, which should be considered when operating the loop. The reactions of PbLi and Li with air and water were observed. The PbLi did not react with air or water, but Li showed a severe reaction with them. However, reaction mitigation using nano-particles was found in the experiment.

Progress of Tritium Extraction and Measurement Methods Development from Liquid Breeder Blanket in Korea

To investigate tritium extraction technology for the helium-cooled molten lithium test blanket module, a tritium extraction method in the liquid breeder based on the gas-liquid contactor concept has been studied. Preliminary experimental investigations have been designed and prepared at Korea Atomic Energy Research Institute to develop a measurement of tritium concentration and correlation of bubble diameter for stripping gases in the liquid breeder. An acryl vessel and a stainless chamber were manufactured to observe bubble behavior and to measure bubble size, respectively, with a photography method, and the experimental investigations will be performed in the near future. An annular capsule and a plate type made with very thin membrane walls with porous structure inside were developed to improve response time and operational capability for high pressure conditions, and a permeation sensor test device was manufactured to evaluate the proposed permeation sensors. The hydrogen extraction column has been constructed based on the conceptual design for the preliminary investigations, and the fundamental liquid breeding experiments are planned to obtain various experiences on the hydrogen extraction technology.

Fabrication of a 1/6-Scale Mock-Up for the Korea TBM First Wall in ITER

Korea has developed a liquid breeder blanket for the test blanket module (TBM) program in ITER with a helium-cooled molten lithium concept. Since ferritic martensitic steel is used as the structural material for the TBM first wall (FW), various joining methods have been developed with hot isostatic pressing in order to develop a TBM FW fabrication method. In this study, three small mock-ups were fabricated in order to develop and verify the manufacturing method of the TBM FW through the pressure and helium leak tests. They were successfully fabricated. After fabrication and checking the performance of the mock-ups, a 1/6-scale mock-up was fabricated with a 260-mm height, 444-mm width, and 435-mm depth, in which width and depth were preserved and the number of channels was reduced from 60 to 10. The mock-up has a U-type shape and ten channels with a size of 20-mm height and 10-mm width for cooling. A manifold for flow testing and high heat flux testing of the 1/6-scale mock-up was designed and fabricated to distribute fluid uniformly to the mock-up.

MHD Analysis and Preparation of an Experiment for Developing the Korean Test Blanket Module

To develop a Korean (KO) test blanket module (TBM) for an International Thermonuclear Experimental Reactor (ITER), particularly for a liquid breeder type, a currently developed conventional code, CFX, with an electromagnetic module for analyzing the magnetohydrodynamics (MHD) effect of the liquid breeder under a high magnetic field is numerically validated using a theoretical equation and previous experimental data. From a comparison with the previous data, the code shows its capability to simulate the MHD effect very well. The KO TBM was then analyzed using the code for comparing the velocities and pressure drops when there was a high magnetic field of the ITER condition (5 T) and when there was not. From the analysis, the pressure drop increased from 0.008337 to 486.8 Pa, and the flow became more uniform in the upward region but concentrated in a corner or inlet manifold, which provided the idea to modify the manifold design. Since the pressure drop by the MHD effect will be tested with the constructed experimental loop for the liquid breeder, a preliminary analysis was performed using the installed test section and magnet, which can produce a magnetic field of up to 2.2 T.

Impact of heat treatment on surface chemistry of Al-coated Eurofer for application as anti-corrosion and T-permeation barriers in a flowing Pb–15.7Li environment

The compatibility testing of Eurofer steel in flowing Pb–15.7Li has shown that corrosion attack is a serious concern at least under view of precipitate formation from dissolved steel components in cooler system sections, leading to a high risk of tube blockages. Additionally, the T-permeation from the liquid breeder through the steel structure into the He-cooling system is an important safety issue. Both topics may be reduced by the application of barriers. Hot dip aluminization (HDA) showed that Al scales exhibit such ability but claimed also the development of improved coating technologies.Thus, two electro-chemically-based deposition processes, which exhibit industrial relevance and adjustable layer thickness of deposited Al, were developed, tested and characterized. Both are working with water-free electrolytes of toluene or ionic liquid (IL) base near room temperature (RT). The successfully deposited homogeneous layers need a heat treatment to establish the required protective/functional properties. During this stage, the Al reacts with the steel and forms an Al-enriched zone with a thin protective Al2O3 surface scale. However, the topology is rough and pores are visible. Thus, for optimization of surface structure and scale quality, investigations concerning the required heat treatment were performed including effects coming from the applied coating technology.

Hydrogen transport through interface between gas bubbling and liquid breeders

An experimental study was performed to investigate hydrogen transport under conditions of gas bubbling into the liquid breeders of Li, Pb–17Li and Flinak. Gas of H2 or high-purity Ar at 0.1MPa was injected into the liquid breeders using an I-shape nozzle. Then, the H2 partial pressure in the cover gas under transition state was measured by a solid electrolyte sensor. Variations of the partial pressure in the exhaust gas were compared with a numerical model to describe hydrogen transfer through the bubble–liquid interface. The experimental rates of hydrogen transport in the liquid breeders were correlated in terms of a mass-transfer coefficient for the hydrogen transport under gas bubbling. The overall mass-transfer coefficient for H2 charging was compared with that for Ar purging. The coefficient for the recovery was about 10 times lower than that of the charging in the respective cases of the Pb–17Li and the Flinak.

Code validation and development for MHD analysis of liquid metal flow in Korean TBM

Numerical simulation code such as commercial CFD one, ANSYS-CFX was studied and validated with the previous experimental data for magnetohydrodynamics (MHD) analysis in the liquid metal breeder flow of the Korean Test Blanket Module (TBM) considering the ITER operation conditions. And, a system code for safety analysis was developed with the MARS-FR (Multi-dimensional Analysis Reactor Safety for Fusion Reactor) in this study, whose base code was MARS and it was developed for commercial pressurized water reactor and gas cooled reactor in Korea. First, with the selected benchmarking problem with previous experimental studies and analytic solution, ANSYS-CFX was validated and evaluated. It shows a good agreement with the pressure loss prediction in MHD flow. Second, the system code was developed to predict the MHD effect for the one dimensional flow analysis based on a MHD solution which Miyazaki derived and has semi-implicit scheme to a flow direction. This study shows good agreement between ANSYS-CFX MHD prediction and experimental results as a validation, and the developed system code presents good performance of prediction in MHD pressure loss.

Long-Term Operation and Basic Corrosion Test in an Experimental Loop for Liquid Breeder in Korea

Korea has developed a liquid breeder blanket and participated in the test blanket module (TBM) program within the international thermonuclear experimental reactor group with a helium-cooled molten lithium (Li) concept. Based on this concept, helium and liquid Li were used as a coolant and breeder, respectively. Additionally, ferritic-martensitic steel (FMS) was considered as a structural material. However, according to our strategy for developing a liquid breeder TBM and its more relevant DEMO concept, not only liquid Li breeders, but also lead-Li (PbLi) breeders were considered. An experimental loop for a liquid breeder (ELLI) was constructed for the purpose of validating the design and fabrication of our electromagnetic (EM) pump; testing the effects of the magneto-hydro-dynamics; and investigating the compatibility of PbLi using structural materials such as FMS. In the ELLI, Pb-15.7Li, where Li is 15.7 at % (called PbLi hereafter), is used as the breeding material, and the EM pump circulates it through the loop. The maximum operating pressure and temperature in the loop are 0.5 MPa and 550 °C, respectively. In this paper, performance tests with the EM pump were carried out. During the three separate experiments, the EM pump was operated for 250 h with a speed of 0.16 m/s for corrosion tests. For a material of corrosion test, tubular-type specimens and cylindrical-type specimens were fabricated and installed in three test pots of the loop. After installing the specimens into the loop, the corrosion test was performed while the EM pump was operating with a 0.16 m/s flow rate at 340 °C for 250 h.

R&D activities of the liquid breeder blanket in Korea

Abstract A liquid breeder blanket has been developed in parallel with the International Thermonuclear Experimental Reactor (ITER) Test Blanket Module (TBM) program in Korea. The Korea Atomic Energy Research Institute (KAERI) has developed the common fields of a solid TBM such as design tools, structural material, fabrication methods, and He cooling technology to support this concept for the ITER. Also, other fields such as a liquid breeder technology and tritium extraction have been developed from the designed liquid TBM. For design tools, system codes for safety analysis such as Multi-dimensional Analysis of Reactor Safety (MARS) and GAs Multi-component Mixture Analysis (GAMMA) were developed for He coolant and liquid breeder. For the fabrication methods, Ferritic Martensitic Steel (FMS) to FMS and Be to FMS joinings with a Hot Isostatic Pressing (HIP) were developed and verified with a high heat flux test of up to 0.5–1.0 MW/m 2 . Moreover, three mockups were successfully fabricated and a 10-channel prototype is being fabricated to make a rectangular channel FW. For the integrity of the joining, two high heat flux test facilities were constructed, and one using an electron beam has been constructed. With the 6 MPa nitrogen loop, a basic heat transfer experiment for code validation was performed. From the verification of the components such as preheater and circulator, a 9 MPa He loop was constructed, and it supplies high temperature (500 °C) and pressure (8 MPa) He to the high heat flux test facility. For an electromagnetic (EM) pump development for circulating the liquid breeder, magnetohydrodynamic (MHD) experiment, and flow corrosion test, a PbLi breeder loop was constructed. From the performance test, the EM pump and magnet show their capability, and flow and static corrosion tests including oxide coating for corrosion protection were performed. For tritium extraction from the liquid breeder, a gas–liquid contact method was adopted and a tritium extraction chamber was constructed. For measurement of the tritium amount in the liquid breeder, permeation sensors have been developed.

Compatibility of reduced activation ferritic martensitic steel JLF-1 with liquid metals Li and Pb–17Li

The corrosion of reduced activation ferritic martensitic steel, JLF-1 (Fe–9Cr–2W–0.1C), in high-purity Li was quite small. However, carbon in the steel matrix was depleted by the immersion to the Li. The depletion caused the phase transformation of the steel surface in which the morphology of the steel surface changed to ferrite structure from initial martensite structure. The phase transformation degraded the mechanical property of the steel. However, the carbon depletion and the phase transformation of the steel were suppressed in carbon doped Li. The carbon in the steel was chemically stable and did not dissolve into the Li when the carbon potential in the Li was high. The concentration of nitrogen and oxygen must be kept as low as possible because the corrosion was larger when the concentration of oxygen or nitrogen in the Li was higher. The chemical reaction between the steel and the Li compounds of Li3N and Li2O was also investigated. The corrosion of the JLF-1 steel in Pb–17Li was summarized as the dissolution of Fe and Cr from the steel into the melt. The corrosion of the specimen with Er2O3 coating fabricated by metal organic decomposition process in the Li and the Pb–17Li was investigated. The coating was deformed, cracked and partially exfoliated in the liquid metals, though the oxide itself was chemically stable in the liquid breeders. The damage was probably made by the stress, which was generated by a large difference of the thermal expansion ratio between the solidified Li or Pb–17Li and the coating during a heat up and a cool down process of the corrosion test.

Fusion tritium research facilities in KAERI

Korea Domestic Agency (KODA) is developing a nuclear fusion fuel storage and delivery system (SDS) as one of the Korean procurement packages. Korea Atomic Energy Research Institute (KAERI) is operating the following basic scientific research laboratories for an SDS and tritium supply study: a metal hydride bed preparation laboratory, hydrogen isotope recovery and delivery performance test rig, in-bed calorimetry performance test rig, and tritium shipping container integrity test facility. Furthermore, the development of a test blanket module (TBM) is required to test and validate the design concept of tritium breeding blankets relevant to fusion power plants. KAERI is also operating the following laboratories for the TBM research, such as a tritium extraction performance test rig, High-flux Advanced Neutron Application Reactor (HANARO), and Experimental Loop for Liquid Breeder (ELLI).

High Temperature Mechanical Properties of Pure and Alloyed Group 5 Metals in View of Their Application as Tritium Permeation Materials

Tensile and creep strength of pure V, Nb, Ta, and Nb-9W alloy were examined at 600 °C to assess their applicability as hydrogen permeation material for the recovery of tritium from the high temperature liquid breeder blanket of a fusion reactor. The Nb-9W alloy required a comparatively higher annealing temperature to achieve good ductility. Based on tensile strength results, it is estimated that a permeation wall thickness of 0.1 mm is achievable. According to creep rate of Nb-9W alloy, design stress maybe decreased below 1/3 of yield stress.

Performance Test of the Electromagnetic Pump in an Experimental Liquid Breeder Loop for Developing a KO Test Blanket Module

Korea(KO) has developed liquid a breeder blanket and participated in the Test Blanket Module (TBM) program within the International Thermonuclear Experimental Reactor (ITER) with a Helium Cooled Molten Lithium (HCML) concept. To develop the liquid breeder technologies with not only liquid lithium but also lead-lithium (PbLi), an Experimental Loop for a Liquid breeder (ELLI) was constructed at Korea Atomic Energy Research Institute (KAERI). The main purposes of the loop are developing components such as an electromagnetic (EM) pump, testing the effects of magneto-hydro-dynamics (MHD), and investigating the compatibility between liquid breeder and other materials. In the present study, the measurement results of a magnetic field in the fabricated magnet, and a performance test of the EM pump, were introduced in order to validate their designs; the magnet used for the MHD test with a liquid PbLi was designed to produce about 2 T, and the measurement results show that the maximum field was about 2.2 T with a ferritic martensitic (FM) steel channel. The EM pump was designed to circulate the liquid PbLi at up to 60 Ipm, and was tested for up to 11 lpm. The test showed good agreement with the input power to the EM pump.

Development of an experimental facility for a liquid breeder in Korea

In order to develop a Li-based test blank module (TBM) in the International Thermonuclear Experimental Reactor (ITER), an Experimental Loop for Liquid breeder (ELLI) was constructed and its test operation was completed. The ELLI consists of a sump tank, an electromagnetic (EM) pump, a direct current (DC) magnet, and measurement devices such as a flow meter, pressure transmitters, a differential pressure transmitter, and thermocouples. The magnet used in magneto-hydrodynamics (MHD) tests was prepared with a maximum magnetic field of 2.2 T, and the magnetic field was measured. The EM pump was designed and fabricated to circulate a liquid breeder such as PbLi up to a maximum flow rate of 60 lpm, and measured up to a maximum rate of 10.4 lpm of a mass flow meter. For filling and draining the PbLi before and after experiments more easily, the entire loop was located on a tilting plate, which can incline the loop up to 15°. Jacket-type heaters were installed throughout the entire loop including the sump tank for heating up to 550 °C. The EM pump tests in the ELLI loop were performed using varying pump voltages.

Flow accelerated corrosion and erosion–corrosion of RAFM steel in liquid breeders

Corrosion experiments for RAFM, JLF-1 steel (Fe–9Cr–2W–0.1C) in three types of liquid breeders (i.e. Li, Pb–17Li and Flinak) were performed at 600 °C. The influence of the different experimental parameters, such as a flowing condition, an exposure time and a geometric condition, on the corrosion behavior was investigated. The present study focused on the evaluation of the weight loss of the corroded specimen by the corrosion model based on mass transfer. The dissolution of the metal elements from the steel was accelerated by the fluids. An erosion–corrosion of the steel was caused by the peeling off of the corroded steel surface in the flowing liquid breeders.

Development and qualification of functional materials for the EU Test Blanket Modules: Strategy and R&D activities

Europe has developed two reference tritium breeder blankets concepts for a DEMO fusion reactor: the Helium-Cooled Lithium–Lead and the Helium-Cooled Pebble-Bed. Both will be tested in ITER under the form of Test Blanket Modules (TBMs). The paper reviews the current status of development and qualification of the EU TBMs functional materials; i.e. ceramic solid breeder materials, beryllium/beryllides multiplier materials and Lithium–Lead liquid metal breeder material Pb–15.7Li. For each functional material the main functional/performance requirements with key qualification issues, current status of the R&D activities and the EU development strategy are presented. In the development strategy major steps considered are listed pointing out importance of the ‘Development/qualification/procurement plan’, currently under elaboration, for definition of a roadmap of further activities aiming at delivery of qualified functional materials to be used in the European TBMs in ITER.

Aluminum-Based Barrier Development for Nuclear Fusion Applications

Abstract In the helium-cooled lead-lithium (HCLL) design concept for blanket structures of a future fusion power plant, the eutectic Pb-15.7Li alloy is used as a liquid tritium breeder and is in direct contact with the structural material, e.g., ferritic-martensitic steels. Compatibility tests showed that a high corrosion attack appears and that the dissolved steel elements like Fe and Cr form precipitates, with a high risk of system blockages. Therefore, coatings as corrosion barriers are required for a reliable plant operation. Because of safety reasons, a distinct permeation reduction of the tritium, produced in the Pb-Li alloy by nuclear reactions, into the environment has to be limited, too. Previous developments already showed that Al-based coatings can perform very well as anti-corrosion and tritium permeation (T-permeation) reduction barriers in a PbLi environment. However, industrially relevant coating technologies for fusion application are still missing and/or cannot fulfil low activation criteria. Electrochemical deposition processes are highly flexible and used widely for the production of functional coatings, e.g., for corrosion protection. Nevertheless, because of its unique electrochemistry, Al cannot be deposited from water-based systems. Therefore, the development of two different Al coating processes from nonaqueous systems was initiated and proofed by the successful generation of protective and reproducible scales after heat treatment.