Coordinating Meeting on R&D forTritium and Safety Issues in Lead-Lithium Breeders

(PbLi-T 2007)

Overview of Japanese PbLi-T Research Activities

and Related Topics

Takayuki Teraitera@n.t.u-tokyo.ac.jp

University of Tokyo

Japanese PbLi-T Research Activitiesand 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

- Al2O3, Y2O3 coating (University of Tokyo)

- Er2O3 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 + H2

Water Bubbler

Reactor core

Container with heater

Polyethylene Blocks

He + H2

(HT)

Tritium Release Behavior from Liquid breeders under a Blanket-Simulated Condition (under Neutron Irradiation at High Temperature)

Fast neutron source : 108~109n/cm2s ("YAYOI" of the University of Tokyo) Tritium generaton rate : ~40Bq/g -Li,s Purge gas : pure He, He + 0.001-10%H2, pure H2, He+2%HF irradiation time : for about 150 minutes

Pb-17Li, LiF-BeF2(Flibe), Sn-20Li673-973 KTritium chemical species (HT, HTO, TF, etc.)Tritium diffusivityTritium release rateTritium permeation through piping materials

(Tokyo)

Diffusion Coefficient of Tritium in Liquid Pb-17Li

Under the condition of He-H2 (pH2 > 103 Pa) purge gas, Diffusion of T in liquid Pb-17Li is dominant, and D / m2s-1 = 2.50 x 10-7 exp ( -27.0 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 pH2 in He-H2 purge gas, and at pH2 > 103 Pa, it is almost constant and given by KD / ms-1 = 2.5 x 10-3 exp ( -30.7 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 Cr2O3 and FeCr2O4 decreases T permeation rate with a reduction factor of 30 – 300 depending on pH2.

　　 (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

JL

cLiPbDLiPb HKS pH2up pH2down

2L2

DLiPb H teL2

4Dt e

9L2

4Dt e

25L2

4Dt

Experimental apparatus for LiPb-H2(D2) system

Comparison between experiment and calculation

0 2 4 6 8 100

50

100

150

200

250

300100%-H

2 973K 873K 773K 673K

Con

cent

ratio

n of

hyd

roge

n [p

pm]

Time [h]

Dependences of DH and SH on temperature for Pb-17Li-H system and comparison with previous researches

1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.010-8

10-7

10-6

700 600 500 400 300

105 Pa

104 Pa

5x103 Pa

103 Pa F.Reiter Chan and

Veleckis Katuta Wu

Temperature [oC]

Solu

bilit

y [1

/Pa0.

5 ]

1000/T [1/K]

1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.910-10

10-9

10-8

700 600 500 400 300

105 Pa

104 Pa

5x103 Pa

103 Pa F.Reiter T.Terai Okamoto

Temperature [oC]

Dif

fusi

vity

[m

2 /s]

1000/T [1/K]

S. Fukada, Kyushu University group

Hydrogen solubility in Li0.17Pb0.83

Hydrogen diffusivity of Li0.17Pb0.83

)11590

exp(108.1 8

RTD HLiPb

)18700

exp(101.2 6

RTK HLiPb

Li activity of LiXPb1-X-H2 system eutectic alloy

• When xLi>0.5, electric charge of Li+ is not shielded by Pb atoms, and Li+-H- ionic binding is major in LiXPb1-X eutectic alloy. Activity of Li is higher.

• When xLi<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

PbPb

H-

Li+

Li+

Pb

H-

Pb

• 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 towerfor tritium recovery

LiPb in

LiPb out He in

He out

HG 3.07G0.32

L0.51

GGDG

23

HL 1

430

L

L

0.22 L

LDL

0.5

S. Fukada, Kyushu University group

LdyGdx

kLav Sy yi dzkGaVct x xi dz

yyin

exp 1 KCL

G

z

H 0,L

KCL

G

exp 1 KCLG

h

H 0,L

KCL

G

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

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• Al2O3 coating fabricated by hot-dipping followed by oxidatio

n (Tokyo)• Y2O3 coating fabricated by plasma spray (Tokyo)• Al2O3 and Y2O3 coating fabricated by plasma CVD (Tokyo) (Terai et al., Surf. Coat. Tech. 106 (1998), 18.)• Er2O3 coating fabricated by Arc-source deposition (NIFS, T

okyo, JUPITER-II)

Al2O3 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 Er2O3 coating as tritium permeation barrier

Thermodynamic stability, corrosion-resistance to liquid breeder, and high compatibility with structural materials　　　　→ permeation barrier at multi-conditionsFabrication of Er2O3 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 Er2O3 as a tritium permeation barrier.

Er2O3 coating as tritium permeation barrier(NIFS, Tokyo)

　 RF sputtering Reactive sputteringArc-source deposition

Cracks & Holes

many medium few

Impurity low low low

Density low medium high

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: 1/106 ～ 1/108

• PRF to iron or stainless steel : 1/100 ～ 1/10,000 (comparable with Al2O3 coatings)

• Permeation rate coefficient was affected by the thickness of coatings than crystallinity or grain size

Hydrogen permeation rate coefficient (NIFS, Tokyo)

10-16

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

Φ(m

ol/m

sPa・

1/

2)

1.81.71.61.51.41.31.2

1000/ T

Vanadium Iron SUS304 非加熱 700℃Room temp.

10Pa ～ 105Pa

Er２O３（～１０ｍ）

　 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- 9 -

Institute of Advanced Energy, Kyoto University

SiC-LiPb Blanket ConceptSiC-LiPb Blanket ConceptOuter 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.

Li-Pb Flow

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 2006. 900 degree He secondary loop will be added in 2007.

LiPb loop was installed and started operationMajor 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

15.12 mm

17.89 mm6 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

System4 Modular reactors + 1 laser system

Compression laser

1.1 MJ/pulse, 32 beams, 16HzCooled Yb:YAG ceramic

Heating laser

0.1 MJ/pulse, 16Hz, Cooled Yb:YAG ceramic

Fusion yield 200 MJ/pulse, 4 Hz

Chamber size

3m radius, 12m high at inner surface

Pulse load

Peak load

Average load

Neutrons

1.4 MJ/m2

50 PW/m2

5.6 MW/m2

Alpha0.7 MJ/m2

2 TW/m2

2.8 MW/m2

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 channelto enhance pumping by cryogenic effect.

• Tilted first panels to make no stagnation point of ablated vapor

Target is enlarged by 150Critical issues are:

1) Protection of beam ports

2) Aerosols and particles3) 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

～Tritium permeator

Heat exchanger

Vacuumvessel

Pelletinjector

Vacuum pump

Tritiumrecovery

LiPb flowTritium

Fuelingsystem

Power generator

(2)

(4)

(7)

(10)

(3)

(5)

(6)

(1)

(8)

(9)

400 600 800 1000 12000.0

0.5

1.0

1.5

2.0

Des

orpt

ion

rate

/ 10

19 D

2 m-2 s

-1

Temperature / K

Ion fluence

/ 1022 D+ m-2

1.0 0.50 0.25 0.13

Heating rate: 0.5 K s-1

Hydrogen isotope behavior in SiC for the insulator in Pb-Li blanket

D2 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-D C-D Y. Oya and K. OkunoShizuoka 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

(~101-104 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