Coordinating Meeting on R&D for Tritium and Safety Issues in Lead-Lithium Breeders (PbLi-T 2007) Overview of Japanese PbLi-T Research Activities and Related Topics Takayuki Terai University of Tokyo

Japanese PbLi-T Research Activities and Related Topics Japan has not proposed a specific Pb-Li TBM design, but plans to contribute to TBM test by collaboration with other parties. Tritium Behavior in Pb-Li - Diffusivity, Mass-transfer and Permeability by in-pile test (University of Tokyo) - T recovery by permeation window method (University of Tokyo) - Diffusivity and solubility of H and D (Kyushu University) - Permeability in a loop (Kyoto University) Permeation Barrier Coating - Al 2 O 3, Y 2 O 3 coating (University of Tokyo) - Er 2 O 3 coating (NIFS, University of Tokyo, JUPITER-II) Related Topics - Advanced blanket concept based on PbLi – SiC – He combination with a LiPb-He dual coolant loop (Kyoto University) - Conceptual design of ICF reactor “KOYO-F” using PbLi as a coolant and breeder (Osaka University) - Q hehavior in SiC (Shizuoka University)

Gas supply System IC Silica gel Schematic diagram of the irradiation apparatus He + H 2 Water Bubbler Reactor core Container with heater Polyethylene Blocks He + H 2 (HT) Tritium Release Behavior from Liquid breeders under a Blanket -Simulated Condition (under Neutron Irradiation at High Temperature) Pb-17Li, LiF-BeF 2 (Flibe), Sn-20Li K Tritium chemical species (HT, HTO, TF, etc.) Tritium diffusivity Tritium release rate Tritium permeation through piping materials (Tokyo)

Diffusion Coefficient of Tritium in Liquid Pb-17Li Under the condition of He-H 2 (p H2 > 10 3 Pa) purge gas, Diffusion of T in liquid Pb-17Li is dominant, and D / m 2 s -1 = 2.50 x exp ( kJmol -1 / RT) (Terai et al., J. Nucl. Mater. 187 (1992), 247.) (Tokyo)

Mass-transfer Coefficient of Tritium from Liquid Pb-17Li to environmental gas Mass-transfer coefficient increases with p H2 in He-H 2 purge gas, and at p H2 > 10 3 Pa, it is almost constant and given by K D / ms -1 = 2.5 x exp ( kJmol -1 / RT) This process is governed by the T diffusion in liquid-film, and the film thickness is 0.2 mm in this condition. (Terai et al., Fus. Engng. and Des. 17 (1991), 237) (Tokyo)

Tritium Permeation through Piping Materials Facing Liquid Pb-17Li In case of  -Fe, no stable oxide film cannot formed on the surface, and T permeation behavior is described by the T diffusion in  -Fe, while in case of SS316, a stable oxide film of Cr 2 O 3 and FeCr 2 O 4 decreases T permeation rate with a reduction factor of 30 – 300 depending on p H2. (e.g. Terai et al., J. Nucl. Mater. 191 － 194 (1992), 272) (Tokyo)

Experiments of recovery of hydrogen isotopes from Pb- 17Li -Measurement of diffusivity, solubility and isotopic exchange rate constant- S. Fukada, Kyushu University group Li-Pb Fe Experimental apparatus for LiPb-H 2 (D 2 ) systemComparison between experiment and calculation

Dependences of D H and S H on temperature for Pb-17Li-H system and comparison with previous researches S. Fukada, Kyushu University group Hydrogen solubility in Li 0.17 Pb 0.83 Hydrogen diffusivity of Li 0.17 Pb 0.83

Li activity of Li X Pb 1-X -H 2 system eutectic alloy When x Li >0.5, electric charge of Li + is not shielded by Pb atoms, and Li + -H - ionic binding is major in Li X Pb 1-X eutectic alloy. Activity of Li is higher. When x Li <0.5, electric charge of Li + is shielded by Pb atoms, and Li + and H - ions are not combined directly. Activity of Li is the lowest. S. Fukada, Kyushu University group Pb H-H- Li + Pb H-H-

Material balance equation Gas-phase mass-transfer coefficient LiPb-phase mass-transfer coefficient Tritium concentration profile in tritium extraction tower Design of He-LiPb counter-current extraction tower for tritium recovery LiPb in LiPb outHe in He out S. Fukada, Kyushu University group Example of calculation of tritium concentration in a counter-current extraction tower (Flibe case) S. Fukada et al., Fusion Science and Technology, 41 (2002) 1054.) Cited from He-water system

Ceramic Coating R&D for Pb-17Li Properties of ceramic coating for Pb-17Li blanket Tritium permeation resistance Electrical resistance Corrosion resistance Fabrication and properties of ceramic coatings Al 2 O 3 coating fabricated by hot-dipping followed by oxidation (Tokyo) Y 2 O 3 coating fabricated by plasma spray (Tokyo) Al 2 O 3 and Y 2 O 3 coating fabricated by plasma CVD (Tokyo) (Terai et al., Surf. Coat. Tech. 106 (1998), 18.) Er 2 O 3 coating fabricated by Arc-source deposition (NIFS, Tokyo, JUPITER-II)

Al 2 O 3 Coating Fabricated by Hot-Dipping Followed by Oxidation (Tokyo) (Terai et al., SOFT-1994, p.1329) (Terai, J. Nucl. Mater. 248 (1997), 153)

Phase Change of the Coating Fabricated by Hot-dipping Followed by Oxidation

Selection of Er 2 O 3 coating as tritium permeation barrier Thermodynamic stability, corrosion-resistance to liquid breeder, and high compatibility with structural materials → permeation barrier at multi-conditions Fabrication of Er 2 O 3 coatings by several PVD methods Observation on characteristics of coating, （１） Surface observation for cracks and holes (microscope) （２） impurity (XPS, EDS) （３） density (weight change + SEM) （４） crystallinity (XRD) → Selection of coating methods and conditions Hydrogen permeation test （５） Coatings with different grain size and thickness → Evaluation of ability and mechanism for improvement on Er 2 O 3 as a tritium permeation barrier. Er 2 O 3 coating as tritium permeation barrier (NIFS, Tokyo)

RF sputteringReactive sputtering Arc-source deposition Cracks & Holes manymediumfew Impuritylow Densitylowmediumhigh Crystallinity medium to good medium Medium to good (depending on the distance between target and substrate) （ depending on temperature) The coating fabricated by arc-source method is considered to be sutable for tritium permeation barrier coatings. → Hydrogen permeation experiment for the coating fabricated by arc- source method. Characteristics of coatings

Permeation reduction factor to the vanadium substrate: 1/10 6 ～ 1/10 8 PRF to iron or stainless steel : 1/100 ～ 1/10,000 (comparable with Al 2 O 3 coatings) Permeation rate coefficient was affected by the thickness of coatings than crystallinity or grain size Hydrogen permeation rate coefficient (NIFS, Tokyo) Room temp. 10Pa ～ 10 5 Pa  Double layered coating

Objective Kyoto University pursues advanced blanket concept based on LiPb – SiC – He combination to be opearated at 900 degree or above. Research objective includes, -to Establish a possible advanced blanket concept with supporting technology -to Demonstrate the attractiveness of fusion energy with safety and effectiveness i.e. high temperature efficient generation and hydrogen production, minimal waste generation and tritium release, technical feasibility, adoptability to attractive reactor designs. Activity in Kyoto University Research Items Current researtch efforts are on the following tasks Conceptual design with neutronics and thermo-hydraulics, MHD LiPb-SiC-hydrogen system study: compatibility, solubility, permeability LiPb technology : Loop experiment, purity control, high temperature handling SiC component development : cooling panel, tubings, fittings and IHX Mockup development : heat transfer, tritium recovery and control Institute of Advanced Energy, Kyoto University

SiC-LiPb Blanket Concept Outer blanket calculation model Module box temperature made of the RAFS must keep under 500 ºC. Li-Pb outlet temperature target 900 ºC. We propose the new model of active cooling in Li-Pb blanket. This concept is equipped He coolant channels in SiC/SiC composite and provides more efficient isolation between the RAFS and high temperature Li-Pb. We evaluate the feasibility of high temperature blanket in this model. 3.High temp. outlet (~900ºC) 1.RAFS module box (~500ºC) 2.SiC/SiC active cooling panel

LiPb loop operational for heat exchanger with SiC composite development Upgrading for LiPb-He dual coolant loop started in degree He secondary loop will be added in LiPb loop was installed and started operation Major parameters: LiPb inventory : 6 liter flow rate : 0 – 5 liter /min temperature : 250 – 500 degree C (~900 deg C at SiC section) MHD, heat exchange, compatibility, hydrogen permeation studied. LiPb loop in Kyoto University Activity in Kyoto University mm mm 6 mm NITE SiC cooling panel channel SiC cooling panel structure channel structure unit with NITE composite developed for He-LiPb cooling panel. Institute of Advanced Energy, Kyoto University

At Osaka University, brush up of conceptual design reactor KOYO-F and elemental experiments are continued with other universities collaborately Fast ignition KOYO-F Electric output 1283MW System 4 Modular reactors + 1 laser system Compressio n laser 1.1 MJ/pulse, 32 beams, 16Hz Cooled Yb:YAG ceramic Heating laser 0.1 MJ/pulse, 16Hz, Cooled Yb:YAG ceramic Fusion yield200 MJ/pulse, 4 Hz Chamber size 3m radius, 12m high at inner surface Pulse load Peak load Average load Neutro ns 1.4 MJ/m 2 50 PW/m MW/m 2 Alpha 0.7 MJ/m 2 2 TW/m MW/m 2 Basic specifications Wall load at 200 MJ fusion yield

Features of KOYO-F to deal with high  heating Vertically off-set irradiation to simplify the protection scheme of ceiling Cascade surface flow with mixing channel to enhance pumping by cryogenic effect. Tilted first panels to make no stagnation point of ablated vapor Target is enlarged by 150 Critical issues are: 1) Protection of beam ports 2) Aerosols and particles 3) Tritium flow

Elemental study at ILE and collaborations with other universities At ILE, Osaka –Ablation by alpha particles was experimentally simulated with punch-out targets driven by back lighted laser. At Kyushu University –With Dr Y. Kajimura, beam port protection –With Dr. S. Fukada, tritium flow At Kyoto University –With T. Kunugi, stability of cascade flow –With S. Konishi, ablation, aerosols, LiPb loop

Hydrogen isotope behavior in SiC for the insulator in Pb-Li blanket D 2 TDS spectra for SiC at room temperature Implantation temperature dependence on D retention in graphite, SiC and WC In the initial stage, D was trapped by C and after the saturation of C-D, D was trapped by Si. D retention in SiC is reached more than 0.7 D/SiC at room temperature. In the initial stage, D was trapped by C and after the saturation of C-D, D was trapped by Si. D retention in SiC is reached more than 0.7 D/SiC at room temperature. Si-DC-D Y. Oya and K. Okuno Shizuoka University

Only D bound to Si was influenced by He + implantation. By He + implantation, the damaged structure would be introduced. In addition, He retention was observed, although D retention was decreased. Only D bound to Si was influenced by He + implantation. By He + implantation, the damaged structure would be introduced. In addition, He retention was observed, although D retention was decreased. He implantation effects on hydrogen isotope trapping in SiC

TITAN Task 1-2: Tritium Behavior in Blanket Systems Participants: T. Terai, A. Suzuki, H. Nishimura (U. Tokyo) S. Konishi, T. Kamei (Kyoto U.) S. Fukada, K. Munakata, K. Katayama (Kyushu U.) T. Nagasaka, M. Kondo, T. Uda, A. Sagara (NIFS) T. Norimatsu, K. Homma (Osaka U.) T. Sugiyama (Nagoya U.) P. Sharpe, P. Calderoni, D. Petti (INL) D-.K. Sze (UCSD) and others

Key technical items for tritium in liquid blanket systems Solubility in Pb-Li -typical measurements performed at relatively high hydrogenic partial pressure (~ Pa) are extrapolated to much lower partial pressures required for tritium inventory control -deviance from Sievert’s Law is possible (based on other LM results, e.g. Li) -measurements at extremely low concentrations require tritium Recovery methods from Pb-Li (and other liquid breeders) and He flows -inadequate mass transport across liquid-vapor interface for vacuum disengagement or window permeators in PbLi -oxidation or cryogenic systems for He, with structural and power implications -ingenious techniques for high recovery efficiencies are needed Transport barriers resistant to thermal cycling and irradiation -minimum required PRF ~ 100, needs robustness or self-healing attributes -success (or lack thereof) greatly influences direction of blanket system design Permeation behavior at very low partial pressures over metals -linear vs. Sievert’s behavior? transport related to dissociation/recombination rates becomes non-equilibrium? -influence of surface characteristics and treatment

Proposed Research Project Areas for TITAN Task 1-2  Solubility of T in Pb-Li at Blanket Conditions - Low pressure region of hydrogen isotopes using tritium - Confirmation of Sieverts’ Low, Phase diagram of Pb-Li and T system  Concentration Effects of T Permeation in Structural Materials and TPB Coating - Wide T pressure range covering several kinds of liquid breeders - Performance test on SM as well as TPB coating (to be developed in Japan)  Tritium Extraction from Pb-Li and Other Liquid Breeders at Blanket Conditions - Mass transfer kinetics - Permeation window, gas engager, etc. - Performance test on a loop which is constructed inside or outside the budget  Modeling and System Design for Tritium Behavior at Blanket Conditions Selected to provide the basis for the Tritium Behavior in Liquid Blanket Systems of interest to US and Japan