Sodium corrosion studies in support of SFR : state of the art

Transcription

1 GROUPEMENT DE RECHERCHE CEA - CNRS - EDF - AREVA NP 3rd International Topical Seminar JAEA / CEA on Coolant and Innovative Reactor Technologies Sodium corrosion studies in support of SFR : state of the art CEA / DEN / Saclay DPC / SCCME : Behaviour of materials in nuclear, industrial, natural and biological environments, from the understanding of elementary processes up to the development of predictive integrated models for industrial applications, permanents staff : >60, PhD >15, Lab. > 4000 m² LECNA : J-L. Courouau, V. Lorentz, F. Balbaud 1

2 Plan 1- Introduction 2- Short literature review 3- R&D programme 4- Testing device design 5- Prospect and others issues 2

3 Introduction 1 Excellent compatibility of steel with pure liquid sodium, specifically the austenitic steels used in the reactors built up to today in their given operating conditions Context : new needs for the 2020 SFR prototype or for the SFR (materials // operating conditions // alternative coolant for secondary circuit or for energy conversion systems) Components Materials Normal operating conditions Service life time Transient conditions Core Fuel clad: A 15/15-25 Ti, F/M Cr ODS S. Assembly : F/M 9-12 Cr thin thick C Hot peak : 650 C 8-12 m/s [O] < 5 ppm 4 y and more T transient : 850 C(boiling) during a few hours max. number of event to be determined Chemistry transient : [O] = 15 ppm / 100 h Fixed primary structures A 316 LN thick C A few m/s [O] < 5 ppm 60 years T transient : 850 C(boiling) during a few hours max. number of event to be determined Chemistry transient : [O] = 15 ppm / 100 h Hot primary structures and components (pump, heat ex) A 316LN F/M 9-12 Cr thin thick C A few m/s [O] < 5 ppm 10y <&< 60y transient : 850 C(boiling) during a few hours max. number of event to be determined Chemistry transient : [O] = 15 ppm / 100 h Secondary structure and SG A 316 LN F/M 9-12 Cr thin thick C A few m/s [O] < 5 ppm 10y <&< 60y Sodium-water reaction (soda/sodium) [O] = 200 ppm / 2000 h Alternative coolant or energy conversion systems 316L : Na-Ni T91 : Pb- Bi ScCO2 thin C A few m/s 10y <&< 60y A : austenitic steel F/M : Ferritic / martensitic steel 3

4 Literature 1 Generalized corrosion in liquid sodium Main mechanisms (austenitic steel): Wetting by dissolution of native oxides layer = 1st step (cleansing) Weight loss by dissolution leading to a recession depth, depending on temperature, sodium impurities and hydrodynamics mainly (Radio activation transfer = operating Rule / ALARA) Diffusion of interstitials elements (C mainly, N, H, B ) to or from liquid sodium leading to a diffusion layer presenting different mechanical properties Steel sodium Steel Na[O] Cr NaCrO2 ferrite Cr 23 C 6 Ni Na[C] Na[Ni] austenite Depleted Austenite Fe Na-Fe-O Predictive models: weight loss + recession depth Empirical models : Phenomenological model (?): A???? n T-To r? k? v? O?e r? Sh(Re, Sc). D. d H ( a( s)? a( l )) Use restricted in time, temperature, material, Re : interpolation Extrapolation possible 4

5 Literature 3 Data Required data : Solubilities in liquid sodium (metallic and non-metallic elements) Free energies of formation of elements combination Diffusivities in liquid sodium and materials S (ppm) Fe Ni Cr Mo Mn T ( C) S (ppm) O H C T ( C) Missing data : Solubilities V, Nb, B, W, Al, Apparent solubilities of Fe 10 5 discrepancy assessed Fe d + FeO x + FeO y Na t + FeC z Na 4 FeO 3 =? (FeO)(Na 2 O) 2 ) thermodynamic data (Fe Na - C O) system Diffusivities (all except Mn [Sudha, 2006]) [Gnanasekaran, 1986] 5

6 Literature 4 main parameters Oxygen [Kolster et al., 1984]. Hydrodynamic [Weeks, 1973] Temperature & Oxygen [Thorley et al., 1967]. Alloying element effect: + Ni : lower ferritic layer on austenitic steel, so lower corrosion rate +B, +P : increase the corrosion rate 6

7 Literature 5 Austenitic steels : T, O, Re, leaching of element,? (Mo),? (TT), voids (? ), restructuration (?->? ), GB, C, n flux? GD-MS measurement and cross section for X8 CrNiMoVNb after 5000 h 700 C. Steel (15-15 Ti B) carburizing conditions, 5 m/s Mechanical properties kept constant (C uptake replaced B loss) Baqué semi empirical model : Borgstedt, model validity? 316L C - 8 m/s - 1 ppm C Needs : 60 years service life time & thin components Steels others than 316L (15-15Ti A800 AA) Predictive model including interstitials for normal and transient operating modes affected depths, µm % of 500 µm recession phase transformation affected by corrosion years A 316Ti x x C 620 C 7

8 Literature 6 ferritic/martensitic steels non ODS Similar mechanism to austenitic steel - Parameters : T, O, v, C, Kinetics of weight loss = or lower No modification of the chemical composition, but depths affected by phase transformation in large grains x10 sometimes observed More sensitive to [O] by internal oxidation along GB + grain leaching (>20-40 pm) Decarburization sensitive : stabilizing element (Cr, V, Nb, Ti) & thermal treatment Flux n? Phase transformation? ->? in case of Ni transfer via Na Needs : Not critical for use at T<550 C, low [O] Phase transformation for to be verified, interstitials elements and behaviors during the transient as regard oxidation Long term prediction as well 9Cr1Mo C, few m/s, ppm O h Internal oxidation >> 316L Baqué_1981 EM C, 2 m/s, 1 ppm O h Restructuration in large grains Weight loss <= 316L Crouch_1978 8

9 Literature 7 - ODS steels Kinetics lower / 316 (weight gain by Ni) More sensitive to Carbon transfer? Phase transformation due to Nickel transfer (heater) No change in mechanical properties Needs : Oxidation data (ODS with very small grains : lower oxidation rate expected?) Phase transformation (Obstacles as a prevention?) Long term prediction for normal and transient operating conditions [Suzuki et al., 1988] [Yoshida et al., 2004] 9

10 R&D programme Objective : corrosion modeling for steels operated in liquid sodium to be able to assess the limits of use (Service life time, Tmax, ) Literature review: 1- F/M steels ODS or not : data required (short term ) and modeling (longer term) 2- A steels : modeling for larger parameters (steels, T, O) including transient (long term >2011) 2007 Specific testing device required Saclay Lab. Scale experiment: Mechanisms & Modeling : Well adapted for parametric testing over extended operating conditions including transients Temperature - time - Re - [O] 2009 Cadarache Pilot scale experiment : validation Coupling effects T t - Re - [O] close to normal operating conditions

11 Corrosion testing device 1 CORRONa (CORROsion Na) Principle: thermal well with rotating cylinders and sodium mini-loop for chemistry control - thermal well in gloves box for T control - inert crucible in contact with Na at high T to avoid any contamination - Na recirculation (mini loop) for chemistry control - rotating cylinders to control hydrodynamics Constraints : - make sodium fire a negligible risk (double confinement, leaks detection, very low volume) - thermal control (cooling of the flange) A A? Moteur? Recirculation Cylindre éprouvette 1 ière barrière Purificati on Purification Moteur 2 ième barrière LIBS Recirculation A Purificati on Purification Cylindre éprouvette A CEA Saclay - Bat 458 pièce 3 2 complementarily testing devices Na = 3.1 kg each Operating conditions: T = C (designed for 750 C) v = tr/min (Re) [O] = 0,7 à 38 ppm Mini-loop : 1 l/h, C with cold trap (= reactor circuits) Crucible : Molybdenum (MLR 0.7% La2O3) Well : Nickel base alloy

12 Laser LIBS (hublots) Corrosion testing device 2 Moteur Brushless Argon Laser Moteur des cylindres tournants Détection entré air (Zirox) Plancher BàG Bride d accostage puits Accouplement magnétique Mini boucle de recirculation Joints Mini piège froid : 1 dl Mini pompe Electro magnétique 1 l/h Mécanisme tournant Boites à huile (thermocryostat) Plaques de coupure thermiques Isolant céramique Bac de rétention + Détection de fuite Na Puits Coupons Creuset en Mo Na Cylindres Détection de fuite Na Four Calorifuge Air Accostage Creuset Na et internes 12

13 Corrosion testing device 3 Change of cylinder : 13

14 Corrosion testing device 4 Cooling fluid circuits Traversée étanche sur Kf 40 Zone interne Zone de refroidissement du palier Zone de refroidissement du couvercle Bride de jonction Bride d accostage Zone externe C2? C1? R2? R1? BàG? Zone de refroidissement de la bride C2? C1? Zone de refroidissement du pot R1? R2? BàG? XT750 Vanne réglante bypasse XT150 2 thermocryostats 14

15 Corrosion testing device 5 Sodium mini loop for chemistry control Préchauffages Vannes de la purge Lignes de siphonage h = 100 h = 100 Lignes de Gaz Raccords swagelok ou SPG S PEM Piège froid Bac de rétention +Détection de fuite Na par collier CT EM P Depressurization line (sodium/oil reaction) PEM Filtre à vapeur Disques de rupture Filtre à vapeur Vue de haut Clapet anti retour 15

16 Prospect and others issues CORRONA : 1 st test on well? planned for October 2009 (625 C 1000h - Re=0 - low [O]) Materials program (priorities) : CEA ODS steels (3 nuances) : never tested in sodium, mechanism, modeling Fe-9Cr : little tested in Na, mechanism, modeling Austenitic : model strengthening Collaborations /other development support / support from GD-MS measurement (M. Tabarant) for sodium sampling analysis - Saclay DPC /LRSI LIBS (D. L hermite, JB. Sirven) for on line chemistry monitoring - Saclay DPC /LRSI Oxygen electrochemical measurement (V. Ghetta, C. Steil, J. Fouletier) - LEPMI/LPSC Grenoble Electrochemical similitude, CFD modeling, EMP (A. Alemany SIMAP ) (V. Botton, C. Dumont) - INSA Lyon Mechanical properties with liquid metal interaction by Small punch test - Université de Lille (I. Serre, J-B. Vogt) Mechanical properties with liquid metal interaction ECP (T. Auger) Others issues : Hot concentrated acid corrosion for waste processing Fissions products corrosion (internal fuel clad corrosion) Water oxidation at high temperature for the steam generator component NaOH corrosion (aqueous, concentrated, hot) (stress corrosion cracking) Corrosion by other medias (Pb-Bi, scco2) Hydrogen et materials (embrittlement, tritium) Water corrosion during storage before processing Other kind of corrosion 16