Corrosion of steels in liquid metals Concetta Fazio
Program Nuclear Safety Research MATGEN IV.2 February 2- 8, 2009 Stockholm – Kiruna, Sweden
Corrosion of steels in liquid metals Concetta Fazio
Program Nuclear Safety Research MATGEN IV.2 February 2- 8, 2009 Stockholm – Kiruna, Sweden
Outline Motivation
The role of Nuclear Energy in an Energy Mix
The Fast Reactor System and its fuel cycle
Transmutation objectives and Scenarios
Fast Reactor Systems and the role of liquid metals as coolant
Examples
Loop type Na cooled FR
Pool Type Pb cooled FR
ADS
Corrosion of steels in liquid metals
What is corrosion?
Parameters affecting corrosion
Corrosion mechanisms in HLM and Na
Experimental evaluation of corrosion mechanisms and rate
Models
Practical applications
Summary and Perspectives
The role of Nuclear Energy in an Energy Mix 0 5 10 15 20 25 30 1990 2000 2010 2020 2030 2040 2050 World Primary Energy Sources (Gtoe) 6 6,5 7 7,5 8 8,5 9 World Population (Billions) Other Renewable Biomass Nuclear Gas Oil Coal Population Source IEA : Energy to 2050 -
Scenarios for a Sustainable Future
Objectives of future implementation of FR in a power park (starting from ~ 2040)
Transmutation Objectives and Scenarios Generic objectives of P/T strategies:
reduce the burden on a geological storage in terms of waste mass minimization, reduction of the heat load and of the source of potential radiotoxicity.
Transmutation Objectives and Scenarios It is a generally agreed conclusion that fast neutron spectrum systems are more appropriate for transmutation of TRU
More specific objectives can be defined according to the specific policy adopted towards nuclear energy and according to specific strategies of reactor development.
Three categories of specific objectives:
Waste minimization and sustainable development of nuclear energy and increased proliferation resistance of the fuel cycle. A transition from a LWR fleet to a FR fleet is foreseen.
Reduction of MA inventory and use of Pu as a resource in LWRs, in the hypothesis of a delayed deployment of fast reactors. Use of dedicated burners (ADS or FR)
Reduction of TRU inventory as unloaded from LWRs: Management of spent fuel inventories, as a legacy of previous operation of nuclear power plants in ADS.
Transmutation Objectives and Scenarios
Among the 6 preferred Gen IV systems, 3 are FRs Very High Temperature Reactor Sodium Fast reactor Supercritical Water Reactor Molten Salt Reactor Lead Fast Reactor Gas Fast Reactor
Examples - Loop type Na cooled FR: JSFR Ref. SMINS, 2007
Loop type Na cooled FR: JSFR Operational conditions K. Mukai, Int. Seminar on coolants and Innovative Reactor Technologies, CEA Cadarache Nov. 2006 Parameters to be considered for material assessment
Examples - Pool type Pb cooled FR: ELSY L. Cinotti, Int. Seminar on coolants and Innovative Reactor Technologies, CEA Cadarache Nov. 2006 Pump
Impeller
Alternative materials for pump impeller under investigation
Maxthal, SiSiC, Noriloy HX - T91 or AISi 316L Vessel – AISI 316L Cladding – T91
Pool type Pb cooled FR: ELSY L. Cinotti, Int. Seminar on coolants and Innovative Reactor Technologies, CEA Cadarache Nov. 2006 Operational conditions Parameters to be considered for material assessment
ADS EFIT XT-ADS
ADS: Operational conditions n.a. ~100 MPa + 40 fatigue cycles/yr stress ~ 1.5 m/s ~ 3 m/s flow Up to 30 Up to 40 dpa/yr 125-190 MPa ~100 MPa stress 80-150 MPa 50-150 MPa stress ~ 1 m/s ~ 1 m/s flow < 0.03 < 0.02 dpa ~ 0.1 m/s ~ 1 m/s flow < 0.003 < 0.02 dpa ~ 2m/s ~ 2m/s flow Up to 100 Up to 160 dpa T T T T 400 – 480 °C 400 – 480 °C 400 – 430 °C 400 – 530 °C EFIT (Pb) 240 - 340 °C Spallation target 300 – 400 °C Heat exchanger 300 – 400 °C Reactor Vessel 300 – 500 °C Core components: mechanical stresses: e.g. Hoop stress on cladding XT-ADS (LBE) EFIT Pump: T= 480 °C; dpa < 0.03; flow = 10 m/s (on impeller)
Liquid Metals Fast reactors have:
Hard neutron spectrum (i.e. limited neutron thermalisation and as small neutron capture as possible)
High power density: need for effective coolant with high thermal exchange capability.
Therefore: liquid metals as coolant. Historically Na and, at a lesser extent, Heavy Liquid Metals (HLM) have been the preferred choices.
Liquid Metals Properties High High 69 845 883 98 23 11 Na High High - Toxicity Moderate as dust Moderate as dust - Chemical reactivity 10150 10520 kg/m3 Density at 450°C 125 327 °C Melting Temperature - 82 - Atomic Number 14 17 W/mK Thermal Conductivity at 450 °C 1670 1745 °C Boiling Temperature - 207 amu Atomic Mass LBE Pb Unit Property
Corrosion of steels in liquid metals What is Corrosion?
Why it is important to study it?
Pitting Corrosion: Corrosion Pits are the primary source of leaks in water handling systems Liquid metal corrosion
Lecor impeller (presented at the ELSY Meeting by ENEA) Active Corrosion on Carbon Steel Manhole „The word corrosion denotes the destruction of metal by chemical or electrochemical action; a familiar example is the rusting of iron” U. R. Evans
Why it is important to study it Ensure Integrity of structures
Avoid Plugging of systems with corrosion products
Ensure thermal conductivity of fuel cladding and functional components
An example for HLM cooled FR:
Stringent safety requirement on the integrity of the cladding material has been put for design basis operating conditions and design extension conditions.
For the chosen temperature regime, the selected cladding material should withstand the combined effect of neutron irradiation, corrosion and mechanical stresses in order to comply with the safety requirements.
Comments