Keisuke Mukai

Kyoto University | Kyodai · Institute of Advanced Energy

Fusion reactions on the cathode surface of glow discharge deuterium–deuterium fusion neutron sources contribute significantly to the neutron production rate (NPR). While the NPR shows a linear relationship with current in the low current regime, a rise in cathode temperature in the high-current regime causes stagnation of the NPR. This tendency may...

The evaluation of activities from radionuclides inside a vacuum vessel is required for the safe maintenance and estimation of the activation level of fusion devices. The Large Helical Device (LHD), Toki, Japan, has been performing deuterium plasma experiments since 2017, and radionuclides have accumulated in components such as vacuum vessels. In th...

Neutron irradiation of a molten salt tritium breeder is planned to evaluate tritium accountancy in the liquid immersion blanket robust accountancy (LIBRA) project at MIT. A sealed-tube deuterium-tritium (DT) fusion neutron generator (NG) will be used for the irradiation. Hence, the NG’s characterization is necessary to evaluate the tritium accounta...

Measurement of thermal and epithermal neutron spatial distribution inside the fusion breeding blanket is essential for evaluating tritium breeding performance. This work aims to establish the method to measure thermal and epithermal neutron fluxes in the breeding blanket by employing a combination of different material foils and utilizing the diffe...

A large amount of Li‐containing ceramic breeder pebbles is packed in the solid breeding blanket of a nuclear fusion reactor. Several pebble fabrication technologies have been proposed in previous studies, including wet process, emulsion method, extrusion spheronization, additive manufacturing, and melt process. However, a simple, energy‐effective,...

Kyoto Fusioneering (KF), a private fusion technology company based in Japan, is exploring the use of FLiBe (a lithium fluoride and beryllium fluoride eutectic mixture) molten salt as a promising breeder-coolant for tritium breeding in fusion reactors. FLiBe has many attractive features, such as: high neutron multiplication, excellent tritium breedi...

Kyoto Fusioneering (KF), a private fusion technology company based in Japan, is exploring the use of FLiBe (a lithium fluoride and beryllium fluoride eutectic mixture) molten salt as a promising breeder-coolant for tritium breeding in fusion reactors. FLiBe has many attractive features, such as: high neutron multiplication, excellent tritium breedi...

Trapping ions, such as deuterium and tritium, inside a potential well to generate neutrons is a well-established technology through electric and magnetic fields via the inertial electrostatic confinement fusion (IECF) and the tokamak, respectively. In the IECF, the straightforward configuration is a concentric cathode connected to a negative bias,...

The use of an electronic descriptor is a high-throughput approach for predicting the chemical reactivities of various materials that has the potential to significantly facilitate the material design of Be intermetallic neutron multipliers for nuclear fusion applications. However, electronic descriptors for Be intermetallics with the desired propert...

This article outlines Kyoto Fusioneering’s (KF’s) initial engineering and development activities for its self-cooled lithium lead-type blanket: Self-Cooled Yuryo Lithium-Lead Advanced (SCYLLA). We provide details on overall design, including an initial tritium breeding ratio (TBR) assessment via neutronics analysis, as well as the status of SCYLLA-...

A glow discharge (GD) fusion neutron source that utilizes nuclear fusion reactions of deuterium has been upgraded. The fusion reactions in this device mainly occur by collisions between the charged or neutral particles and the hydrogen isotopes trapped at the surface of electrodes. In addition, it is known that the metal hydride coating on the elec...

Liquid lithium–lead (Li–Pb) eutectic alloy is one of the candidate liquid tritium breeding materials of fusion blanket and it contains bismuth (Bi) as an initial impurity or transmutation product from lead. The saturated solubility of Bi, $S$ (wt.ppm), in Li–Pb was measured in the temperature range from 508 to 623 K. The measured results were plo...

In a DEMO fusion reactor, it is necessary to continuously extract deuterium and tritium from the unburned fuel gas under divertor panels. For the pumping system in the divertor, a new method of transferring hydrogen isotope using proton conductors has been proposed. In this study, we have constructed a new experimental setup using a proton conducto...

Understanding the permeation behavior of tritium from a pebble bed breeding blanket is essential for establishing a self-sufficient fuel cycle in a nuclear fusion reactor. It is known that double corrosion layers forms on reduced activation ferritic-martensitic (RAFM) steel surface by gas release from a ceramic breeder material, however, its effect...

Climate policy necessitates significant reductions in long-term greenhouse gas (GHG) emissions in most industry sectors. Automobiles, steel, and pharmaceutical sectors are the leading CO2 emitters in in Japanese manufacturing. The Japanese government and major players in these industries have developed a variety of countermeasures to help combat gl...

A discharge-type fusion neutron source generates neutrons by fusion reactions of hydrogen isotope atoms. In order to operate the fusion device based on the deuterium–tritium (D–T) fusion reaction, the tritium inventory is required to be decreased. In the present work, a self-sufficient system was installed into the fusion device for reducing the am...

Japan appears to be on the verge of making the transition to a carbon-neutral (CN) society. Renewables offer significant potential. however, the current energy policy has lagged in terms of environmental action, suggesting that adjustments may not be as straightforward. The Paris Agreement calls for a 50-80% decrease in CO2 emissions worldwide by 2...

Liquid lithium, a candidate material for the target of International Fusion Material Irradiation Facility (IFMIF), easily contains nitrogen. Nitrogen in liquid lithium should be removed as it accelerates corrosion of tubing materials. Hot trapping by iron-titanium alloys is expected to be a practical method. In order to understand the characteristi...

Measuring methods of spatial neutron distribution have been required for the evaluation of TBR inside the blanket. In this paper, neutron transport inside a blanket mock-up, mainly assembled by beryllium neutron multiplying layers and lithium breeding layers, was simulated for measurements of the neutron energy spectrum and the spatial distribution...

Our group is developing an ultra-compact neutron source based on inertial electrostatic confinement (IEC) fusion device for various applications at Kyoto University. This IEC device is configured from a titanium anode and a molybdenum cathode with diameters of 17 and 6 cm, respectively. A high-intensity neutron source operated in a stable pulse sha...

We report a neutronics study of a blanket mock-up using a discharge-type compact fusion neutron source. Deuterium–deuterium fusion neutrons were irradiated to the mock-ups composed of tritium breeder and neutron reflector/moderator. Tritium production rate (TPR) per source neutron was measured by a single-crystal diamond detector (SDD) with a 6Li-e...

Reduced activation ferritic/martensitic steel F82H samples with tritium permeation barriers were annealed in contact with ceramic breeder pebbles at 550 °C and 700 °C for up to 32 days under purge gas. Cr2O3-formed F82H rapidly reacted to form three layers at 550 °C, and pure Fe projections grew with annealing time. Diffusion kinetics of O and Li w...

An inertial electrostatic confinement (IEC) fusion device accelerates ions, such as deuterium (D) or tritium (T), to produce nuclear fusion and generate neutrons. The IEC's straightforward configuration consists of a concentric spherical transparent cathode at a negative bias surrounded by a grounded spherical anode. The effects of cathode properti...

The electrochemical treatment using chloride molten salt was focused as a method for removal and monitoring of oxide impurities in the liquid breeder materials. The anodic reactions on a glassy carbon electrode in a LiCl-KCl eutectic melt contacting with Li-Pb eutectic melt without and with Li2O addition were investigated. The transfer of oxide imp...

The designs of neutron spectrum-shaping assembly (NSSA) composed with various shielding materials with natural isotopic abundance were evaluated to construct the neutron field dominated with thermal neutron or epi-thermal neutron for the application of neutron filed in the torus hall of LHD toward the BNCT research. According to the neutron transpo...

Liquid Li-Pb eutectic alloy and lithium, assumed to be used in a liquid blanket system for fusion reactors, can easily contain light element impurities. It is thought that these impurities have bad influences on compatibility with structural materials. However, an effective reducing method for impurities has not yet been established. In this work,...

Lithium metal and lithium oxides are components of lithium–oxygen (Li–O2) batteries. In order to accurately identify Li-compounds and understand the degradation mechanism, fundamental knowledge on electron structures of constituent elements is vital. However, experimentally-derived occupied states of Li has been missing due to their intrinsic diffi...

Since the low-carbon technology fusion energy is scheduled to be commercialized beyond 2050, the late-mover needs to flexibly and strategically operate for sustainable cash flow responding to the future market mechanism. Carbon sequestration of the fusion–biomass hybrid system by using low-temperature heat is proposed under the two preconditions: t...

Tritium breeding performance of a fusion blanket is a key parameter for the self-sufficient fueling of a fusion reactor, and thus designed to validate the performance of a neutronics experiment. Measuring the 2-D distribution of bred tritium is challenging via conventional methods such as β-ray counting from an irradiated lithium sample using a liq...

Measurement of neutron flux and energy spectrum profile inside the blanket is required for fusion blanket design. An experiment using an imaging plate and activation materials (Dy, In, and Au) was performed to measure spatial distribution of neutron flux. Neutrons were generated by a discharge-type compact fusion neutron source whose neutron produc...

Monoclinic lithium metatitanate, β-Li2TiO3, is a member of the Li2MO3 (M = Ti, Mn, Sn, Ru, and/or Ir) series and an important cation conductor for various energy applications such as Li-ion batteries and nuclear fusion reactors. Comprehensive knowledge of the crystal structure is vital to understand the Li-ion diffusion mechanism, and several possi...

Be-rich intermetallics (beryllides) have gathered wide attentions to be adopted for high temperature environments, particularly as an advanced neutron multiplier in fusion reactors. This study reveals the valence electron structure of Be12M (M = Ti,V) by using soft X-ray emission spectroscopy with ultra-high resolution (~0.22 eV). The Be-Kα spectra...

This paper aims to make an investigation on economic analysis of fusion-biomass hybrid system for clean fuel production. A blanket concept with lithium lead (LiPb) and silicon carbide (SiC) technology such as dual coolant lithium lead (DCLL) is capable of delivering over 600 °C of high temperature heat for endothermic gasification reaction. This te...

Tritium breeding ratio (TBR) is one of the most important parameters determining the tritium self-sufficiency of a deuterium-tritium fusion reactor. A neutronics experiment is planned to measure the spectral neutron fluences two-dimensionally (2D) using a discharge-type compact fusion neutron source and a neutron imaging plate (NIP), respectively....

In a solid breeding blanket, ceramic breeder pebbles are in contact with reduced activation ferritic martensitic (RAFM) steel at high temperatures for years and accordingly form a corrosion layer on the blanket structural steel. Present study focuses on corrosion characteristics of EUROFER97 RAFM steel by an advanced breeder material of Li2TiO3 wit...

Effect of moisture in sweep gas on chemical compatibility between ceramic breeder (Li4SiO4 with 20 mol% of Li2TiO3) and EUROFER97 was examined in this study. These materials were contacted and heated at 623, 823, and 1073K for up to 12 weeks where the H2O concentrations of the outlet gas were 0.13-0.24 vol.%. In the two-phase breeder specimen, Li4S...

Chemical compatibility between ceramic breeder (Li4SiO4 + 20 mol% addition of Li2TiO3) and EUROFER97 steel was examined in this study. These materials were contacted and heated at 623, 823 and 1073 K under He + 0.1% H2 atmosphere for up to 12 weeks. Limited influence was found in the breeder specimens, although losses of the constituent elements ap...

In connection with International Thermonuclear Experimental Reactor (ITER), Japan and Europe are promoting broader approach (BA) activities, which is research and development aimed at early realizing of fusion energy development. As one of the activities, advanced tritium breeder materials (lithium-containing ceramics) have been developed and chara...

Multiple tritium breeder recycling is an attractive option to make a future fusion power reactor ecologically and economically sustainable. This research project aims at exploring the feasibility of multiple breeder ceramics recycling by remelting with regard to the activation behavior. The average activation level of multiple reused breeder pebble...

Enthalpy of Li2TiO3, which was synthesized by a neutralizing method and its Li/Ti ratio was determined to be Li/Ti ratio (mol/mol) = 1.97, was measured by a drop calorimeter, and its heat capacity was derived as a function of temperature. XRD (X-ray diffraction) analysis of the sample before and after the enthalpy measurement indicated no phase cha...

Crystal grain growth and crystallization of lithium metatitanate with excess Li (Li2+xTiO3+y), which is expected as an advanced ceramic breeder for a future DEMO fusion reactor, were studied in this paper. By the observation of sintered pellets using scanning electron microscope, it was shown that the Li2.1TiO3+y specimens, which have small grains...