Comments on Corrosion R&D Needs for
DCLL
B.A. Pint and P.F. Tortorelli
Presented by S.J. Zinkle
Oak Ridge National Laboratory
US ITER-TBM Meeting
Idaho Falls, ID
August 10-12, 2005
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
1
Compatibility in the DCLL system will likely involve
multiple materials
• In-vessel TBM
– ferritic/martensitic steel, SiC FCI
• External piping
– Ni-base superalloy?
• Tritium processing
– Refractory alloy??, tritium permeation barrier materials??
• Heat exchanger
– Material options??
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
2
Liquid Metal Compatibility is Controlled by several mechanisms
• Dissolution
– Numerous phenomena can affect mass transfer across metal-liquid interface, J=k
(C0-C)
• Laminar vs. turbulent flow (including magnetic field effects)
• Solubility temperature dependence
• Impurity and interstitial transfer
– Very important for refractory metals (and BCC metals in general)
• Alloying between the liquid metal and solid
– Typically eliminated early on in selection process (showstopper)
• Compound reduction
– Often most relevant for ceramics (e.g., SiC insert)
• The last three mechanisms can be roughly evaluated using low-cost
capsule experiments; the 1st mechanism requires flowing loop tests
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
3
There are two major contributors to dissolution mass transfer
J=k (C0-C)
• Static isothermal mechanisms
– Capsule tests can provide initial data on solubilities (infinite
dilution steady-state approximation)
• Flowing, nonisothermal mechanisms
– Rate-controlling steps include surface reaction, liquid-phase
diffusion through boundary layer, and solid state diffusion
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
4
Eventually, Compatibility Issues Need To be
Examined Under Dynamic, DT Conditions
Ji = k(Csol,i – Ci)
 Constant driving force for dissolution
 Positive results from isothermal capsule experiments may
not be reproduced under these conditions
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
5
Current knowledge of candidate materials for DCLL
system is largely limited to static capsule tests
• Substantial experimental database on ferritic steel
compatibility with flowing Pb-Li
– Comprehensive analysis of existing data is needed
• Database for other materials generally does not include
information for nonisothermal flowing systems and effects
of magnetic fields
• Very little is known about potential stress corrosion
cracking mechanisms
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
6
Concluding remarks
• Need to establish reference design (materials, operating
conditions) asap
• Near-term compatibility R&D activities would focus on
analysis of existing compatibility for ferritic/martensitic
steel with flowing Pb-Li
– Also continue limited number of static capsule tests on candidate
piping materials (possibility to avoid coatings or ceramic inserts)
• Medium-term activities would be centered on flowing loop
experiments
– Thermal convection loop
– Other loops?
• Scoping experiments on stress-corrosion cracking should
also be initiated in the near- to medium-term
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
7
Chemical Analyses of the Pb-Li Revealed
Little Reaction With SiC after 1000h
Li
(at.%)
Si
(ppma)
C
(ppma)
O (ppma)
N
(ppma)
Start
n.d.
<40
<170
1270
<40
800˚C
1000h
17.5%
<30
1850
4090
100
1100°C
1000h
16.3%
<30
1160
3550
90
1100˚C
2000h
16.0%
185
1025
7890
200
 No significant mass gains after any capsule test
 Si detected after 2,000h at 1100°C, still less than Kleykamp
 PbLi not analyzed yet for 5,000h 800°C or 1,000h 1200°C
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
8
Specialized Capsule Experiments Have Been Used
For SiC Exposures In Pb-17Li
800 and 1000˚C, 1000 h
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
9
Negligible Change In Specimen Mass Before Or
After Cleaning Was Observed
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
10
Corrosion-Resistant Metallic Coatings for Pb-17Li
• At highest temperatures at and near first wall, SiC flow channel
inserts can provide protection
• Ducting behind this more likely to be made of conventional steels
• Pb-17Li is quite corrosive toward certain ferrous and Ni-based
alloys at temperatures above 450°C
• One possible solution to ducting protection is corrosion-resistant
aluminized coatings on strong conventional alloys: aluminide
surface layers should be stable in Pb-17Li (Hubberstey et al.,
Glasbrenner et al.)
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
11
Al-Containing (Al2O3-forming) Alloys Showed Significantly
Reduced Mass Losses In Pb-17Li
Capsule test: 1000 h, 700˚C, Pb-17Li
Specimen
Capsule
Mass Change
(mg/cm2)
316 SS
316 SS
-0.7
316 SS
Fe
-5.7
316 SS
Mo
-3.8
ODS FeCrAl
Mo
-0.2
Fe-28Al-2Cr+Zr
Mo
-0.2
Ni-42.5Al
Mo
-0.1
0.25 m
*no preoxidation of specimens
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
12
316 SS Results Can Be Understood Based On
Fundamental Dissolution Driving Force
Ji = k(Csol,i – Ci)
• Dissolution continues until saturation is reached
• For specimens of 316 SS, saturation is reached sooner in
a 316 SS capsule because both are contributing solute
(mainly Ni)
• Fe or Mo capsules are relatively inert
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
13
Surface Morphology Of Exposed Stainless Steel
Was Consistent With Dissolution
1 m
316SS in Mo Capsule, 1000 h, 700˚C, Pb-17Li
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
14
Examination Of Cross Sections Confirmed
Some Dissolution Had Occurred in Stainless Steel
10 m
1000 h, 700˚C,
Pb-17Li
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
2 m
15
Nickel Depletion Was Observed in Stainless Steel
Counts
1000 h, 700˚C,
Pb-17Li
10 m
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
Counts
Energy, ev
Ni
Energy, ev
16
Aluminide-Formers Showed Little Mass Loss And
Tended To From Stable, Protective Al-Rich Layers
1000 h, 700˚C,
Pb-17Li
2 m
Ni-42.5Al
in Mo Capsule
2 m
ODS-FeCrAl
in Mo Capsule
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
17
Qualitative Analysis Indicated These Surface Layer
Were Rich in Al and O (Likely Al2O3)
Surface Layer
Al
Counts
Subsurface Alloy
O
Fe
Energy, ev
ODS-FeCrAl in Mo Capsule
1000 h, 700˚C, Pb-17Li
Energy, ev
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
18
Example Cycle Efficiency as a Function of Interface FS/Pb17Li Temperature
-the
max.
η~38.8%,
Tmax,FS<<550oC
for
an
interface FS/LiPb temperature
of 475 oC;
-the
max.
η~41.5%,
Tmax,FS<<563oC
for
an
interface FS/LiPb temperature
of 510 oC.
0.44
Cycle Efficiency
For a fixed maximum
neutron wall loading ~4.7
MW/m2,
0.45
TLiPb,out=700oC;Tmax,FW=800 oC
Tave,FW=700 oC; Ppump/Pthermal << 0.05
0.43
0.42
0.41
0.4
0.39
0.38
0.37
0.36
475
490
510
530
550
Max. Interface FS/LiPb Temperature, oC
OAK RIDGE NATIONAL LABORATORY
U. S. DEPARTMENT OF ENERGY
19