Session 3: Interfaces

Victor Ignatiev and Juergen Konys

Errosion, Corrosion and Diffusion

• Liquid metals – 2

• Molten salts - 2

• Water - 1

Corrosion of structural materials by liquid metals

Damien Féron, “Corrosion of structural materials by liquid metals used in fusion, fission and spallation”

Application Fusion, fission and spallation

Limits of Use Steels (nickel alloys not suitable). The influence of impurities in the liquid metals needs more consideration.

Main Radiation Effects Irradiation effects are not discussed

Research Details

Mainly based on experiments

Major Issues and Challenges

Long term issues (prediction of corrosion performances over 40-60 years)

Coolant Processing and Handling Experimental difficulties linked to the experimental conditions (high temperature, chemical hazards, toxicity…). Modelling and simulation under development.

Others

In liquid sodium, corrosion phenomena, including liquid metal embrittlement are considered under control (authentic SS). In liquid lead and its alloys, corrosion issues may need mitigation strategies (steels). More investigations in liquid lithium (embrittlement & dissolution)

Achievement

Corrosion phenomena & mechanisms

R&D Needs – Experimental (parameters) – Modeling & simulation – Mitigation

Pb-alloy corrosion and advanced mitigation methods

Alfons Weisenburger, “Corrosion in Pb-alloy cooled nuclear reactors and advanced mitigation measures”

Application Fission and spallation, some for fusion

Limits of Use Steels not suitable for temperatures >450°C Coatings, surface alloys, advanced alumina forming steel may extent to 650°C or higher. Oxygen content of Pb-alloy requires specific attention.

Main Radiation Effects Irradiation effects are not discussed

Research Details

Mainly based on experiments

Major Issues and Challenges

High temperature compatibility

Long term issues (prediction of corrosion performances over 40-60 years)

Coolant Processing and Handling Experimental difficulties linked to the experimental conditions (high temperature, chemical hazards, toxicity, …).

Oxygen addition to liquid lead and its alloys, allow use of steels up to 450°C. Localized corrosion hinders use at higher temperatures. At temperatures above 450°C advanced mitigation strategies are required. Alumina forming steels or surface layers are one promising option. Insoluble coatings like alumina by PLD are an other option.

Achievement

Corrosion phenomena & mechanisms

R&D Needs – Experimental (parameters) – Modeling & simulation – proven and optimized mitigation measures

Corrosion of Structural Materials in Molten Fluoride and Chloride Salts

Stephen Raiman, Corrosion of Structural Materials in Molten Fluoride and Chloride Salts

Application Molten Salt Reactors

Research Details

Capsule testing and thermal convection loops are employed for corrosion testing of molten fluoride and chloride salts

Major Issues and Challenges

Lack of data on material compatibility in chloride salts

Coolant Processing and Handling Removal of moisture, metal chlorides, and other oxidizing impurities from salt

R&D Needs – Corrosion data in chloride salts – Controlled salt chemistry – Modeling effort

Sample mounted on capsule lid

Inner and outer capsules

Combined–Environment Performance of Nuclear Structural Materials for MSR Applications

Ondrej Muránsky, “Molten Salt Reactor (MSR) Research in

Australia: High-Temperature, Radiation Effects, and Corrosion Behaviour of Relevant Ni Alloys and Graphite”

Application Fission: Molten Salt Reactor Development

Limits of Use Molten salt: FLiNaK < 750°C

Main Radiation Effects He irradiation and combined irradiation and molten salt effects Ion Irradiation: Au, Ni, He, Fe, Te, ~20dpa, < 700°C, <1.1017 ion/cm2

Research Details

High-temperature creep, molten salt corrosion and radiation damage of structural materials (Hastelloy-N, GH3535, MONICR)

Major Issues and Challenges

Identification of failure mechanisms and acquisition of material data \for design and sustainment of MSR reactors

Coolant Processing and Handling Coolant processing and handling is not discussed

Achievement

Development of understanding of combined effects of high-temperature creep, molten salt corrosion, and radiation damage on material performance

R&D Needs – Understanding structural material performance in extreme environment – MSR NPP design and sustainment

FLiNaK, 700 oC, 190 MPa applied stress

SCC Mapping of SUS316L in Hot Water with DH

Oral : Huang & Kimura, “SCC Mapping of SUS316L in Hot Water Dissolved with Hydrogen and/or Oxygen.”

Application Fusion DEMO

Limits of Use Radiation hardening may accelerate SCC in hot water dissolved with hydrogen isotopes.

Main Radiation Effects Radiation & He embrittlement Radiation induced GB segregation

Research Details

SSRT

Major Issues and Challenges

Effects of hydrogen & test temp. on SCC

SCC mechanism

Coolant Processing and Handling Water chemistry: Controlling content of dissolved hydrogen in hot water

Others Synergism of radiation embrittlement and SCC

Achievement

Mapping of appearance of SCC with hydrogen content and test temperature

R&D Needs Understanding SCC mechanism

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 50 100 150 200 250 300

No SCC

SCC (only suface)

SCC

Dis

solv

ed H

ydro

gen

(ppm

)

Temperature (°C)

IGSCC - TGSCC

TGSCC

Barriers / Coatings for structure

• Liquid metals - 1

• Molten salts - 1

• Nanoceramic coating - 1

Materials issues in heavy liquid metal cooled systems

Massimo Angiolini, “Materials issues in heavy liquid metal cooled systems”

Application HLM cooled systems, ALFRED Lead Reactor

Limits of Use Exposure to HLM at temperatures above 450°C and oxygen concentration 10-8 wt Exposure to neutron irradiation up to 100 dpa

Main Radiation Effects (Unwanted) Differential swelling respect to the substrate, precipitation of unwanted phases, enhanced diffusion in the substrate, deterioration of the swelling behavior of the substrate at the interface

Research Details Corrosion in HLM cooled systems Steels HLM corrosion characterization Development of coatings and surface treatments to face the corrosion issues in HLM cooled systems

Major Issues and Challenges

The main challenge is the lack of irradiation facilities to test the performance under neutron irradiation

Achievement

Aluminizations by pack cementation

Al2O3 coatings by PLD

Mechanical and corrosion testing in molten lead

Heavy ion irradiations characterizations

R&D Needs Careful thermodynamic characterization of the Pb-Steel- O system Neutron irradiation facilities

Permeation reduction in nanoceramic coatings

Oral: Fabio Di Fonzo, “Close to zero permeation in diffusion barrier nanoceramic coatings.”

Achievement

Permeation reduction factor up to 105 (DEMO requirements around 1000)

R&D Needs - Permeation Tests with Tritium - Tests in presence of Pb-16Li

Application Design of diffusion barrier nanoceramic coatings

Limits of Use

- HLM corrosion of breeding blanket components in presence of Pb-16Li

- Permeation of T trough structural steels

Main Radiation Effects No effects under electron irradiation

Research Details

- Exposure to static Pb-16Li eutectic

- Permeation tests with H2 and D under electron irradiation

Major Issues and Challenges

- Chemical compatibility in stagnant and flowing Pb-16Li

- Reduction of permeating gas flux

- Coating/substrate adhesion

- Materials evolution under high-damages radiation levels (ions and neutrons)

Molten Salt Fast Spectrum Reactor System

Aleksander Surenkov, Corrosion phenomena induced by coolant, blanket and fuel salts: focus on stainless steels and high nickel alloys

Application: Mollten salt reactors (MSR)

Limits of Use: Max temperature (700-800°C) of wall in the MSR primary circuit made of selected Ni alloy is mainly limited by the Te intergranular corrosion (IGC) depending on Redox potential of the fuel salt / coolant. Min temperature (550-600°C) of the construction material MSR is determined by the melting point of the fuel salt / coolant, as well as the joint solubility of actinides and lanthanide trifluorides in the melt.

Major Issues and Challenges: • Embrittlement of high Ni alloys by He, which is

formed from 10B and nickel by nuclear reactions; • Diffusion of the of the tellurium fission product

into alloys along grain boundaries led to IGC. Coolant Processing and Handling: Continuous monitoring of the redox potential of the fuel / coolant salts, its composition and impurities, including oxides, free fluorine ions, metal fluorides and tellurium and maintaining them at a low level will be required to minimize the rate of corrosion of structural materials.

R&D Needs: 1) Studies of the kinetics of the boundary diffusion of tellurium in candidate alloys and the mechanism of their tellurium intergranular embrittlement should be carried out under nonisothermal conditions simulating the operation mode in the fuel circuit of the MSR. 2) The metallurgy properties of these alloys should be studied in more detail and especially under irradiation.

Main Radiation Effects: Not considered

Research Details:

NRC KI test Salt in mole %

Nickel alloys

Tspecimen

С

Parameters of IGC Depth cracks

L max, μm

« К »,

pc×μm/сm

73LiF -27BeF2+ 2.0UF4+Te(metal)

Average value [U(IV)/U(III)]= 60

Hastelloy N

HN80МТY

HN80MTW

EM- 721

750

69

NO

NO

117

3500

NO

NO

3380 73LiF -27BeF2+

2.0UF4+Te(metal)

Average value [U(IV)/U(III)]=85

Hastelloy N HN80МТY

HN80MTW

EM 721

800

800

780

800

148

32

126

286

4490

670

5820

5830

Posters

• Water - 1

• Nanoceramics - 1

• Liquid metals- 1

Oxide nanoceramics at extreme radiation levels

Poster: Matteo Vanazzi, “Radiation damage in oxide nanoceramics.”

Application Design of corrosion- and radiation-resistant nanoceramic coatings

Limits of Use HLM corrosion of unprotected structural steels above 450 °C

Main Radiation Effects Crystallization (phases nucleation and grain growth) of initially nanoceramic coatings

Research Details

- Irradiation tests with heavy ions

- Exposure to static Lead before and after irradiation

Major Issues and Challenges

- Chemical compatibility in stagnant and flowing Pb (dissolution/oxidation)

- Mechanical compatibility (erosion, etc.)

- Coating/substrate adhesion

- Materials evolution under high-damages radiation levels (ions and neutrons)

Achievement

Corrosion resistance and mechanical stability after 150 dpa

R&D Needs Irradiation tests with Neutrons

ϒ-Al2O3

α-Al2O3

pristine

150 dpa

SCC Resistance in SUS310S

Poster : Huang & Kimura, “SCC Behavior of SUS316L and SUS310S in Fusion Relevant Environments.”

Application Fusion DEMO

Limits of Use Radiation hardening may accelerate SCC in hot water dissolved with hydrogen isotopes.

Main Radiation Effects Radiation & He embrittlement Radiation induced GB segregation

Research Details

SSRT

Major Issues and Challenges

Suppression of SCC

Coolant Processing and Handling Water chemistry: Controlling content of dissolved hydrogen in hot water

Others Synergism of radiation embrittlement and SCC

Achievement

SUS310S is less susceptible than SUS316L.

R&D Needs Understanding SCC mechanism

SUS316L SUS310S

DH 1.4ppm DH 1.4ppm

Thermodynamic considerations on chemical interactions between liquid metals and steels

Masatoshi KONDO, “Thermodynamic considerations on chemical

interactions between liquid metals and steels”

Application Fission and fusion reactors and ADS system

Limits of Use The effect of non-metal impurities on the steel corrosion in liquid metals has been studied. However, their effects on the corrosion in Pb-Li alloy are quite limited.

Main Effects

Corrosion of the steels in Pb-Li alloys must be influenced by the nitrogen dissolved in

the alloys.

Research Details

Mainly based on experiments

Major Issues and Challenges

High temperature compatibility

Measurement of nitrogen in Pb-Li alloy

Coolant Processing and Handling

The nitrogen concentration in Pb-Li alloy

must be monitored and controlled.

Achievement Effect of nitrogen in Pb-Li alloys on the steel corrosion was newly made clear.

R&D Needs – Experimental (parameters) – Modeling

Pb Li Pb-Li alloy

Corrosion behaviors of steels in Pb-Li alloys must be influenced both by Pb (dissolution type corrosion) and Li (Li-N-Cr reaction corrosion).

Li Pb Pb rich Pb-Li alloy Li rich Pb-Li alloy

Pb-Fe-O

Fe-Cr-O

Oxide lay er

f ormation

JLF-1 steel

H2O

CO2 O

N

NLi

Fe dissolution

N

Dissolution of Cr

by chemical reactionCarbon dissolution

Phase transformation

Li

(Tilt view by FE-SEM

after immersion to Pb-5Li)1μm 1μm(Tilt view by FE-SEM

after immersion to Pb-45Li)

Diffusion of Pb into steel matrix