Oxidation and degradation of Zircaloy-4 in nitrogen- oxygen-steam - - PowerPoint PPT Presentation

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Oxidation and degradation of Zircaloy-4 in nitrogen- oxygen-steam - - PowerPoint PPT Presentation

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Oxidation and degradation of Zircaloy-4 in nitrogen- oxygen-steam mixtures at 850C DENOPI Project High Temperature Corrosion (GRS), July 8-9 2017 Mathilde Gestin, Olivia Coindreau, Michle Pijolat, Christian Duriez, Vronique Peres Work

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Institut Mines-Télécom

Oxidation and degradation

  • f Zircaloy-4 in nitrogen-
  • xygen-steam mixtures at

850°C

DENOPI Project

High Temperature Corrosion (GRS), July 8-9 2017

Mathilde Gestin, Olivia Coindreau, Michèle Pijolat, Christian Duriez, Véronique Peres

Work performed in the frame of the DENOPI project, funded by the French government as part

  • f the “Investment for the Future” Program

reference ANR-11-RSNR-0006

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Context

24/07/2017

École des Mines de Saint-Étienne 2 “Special Report on the nuclear accident at the Fukushima Daiichi nuclear power station, 2011” Report INPO 11-005, Institute of Nuclear Power Operations, Atlanta, GA, USA

cylindrical fuel pellets fuel rod cladding fuel assembly

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Context

24/07/2017

École des Mines de Saint-Étienne 3

Post Fukushima French DENOPI Project

In SFPs Zircaloy fuel clad = only barrier

Fukushima The vulnerability of the spent nuclear fuel pools (SFPs)

“Status Report on Spent Fuel Pools under Loss-of-Cooling and Loss-of-Coolant Accident Conditions”, NEA Final Report, CSNI/R(2015)2, May 2015

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State of the art,

Zircaloy-4 in air at 850°C

24/07/2017

École des Mines de Saint-Étienne 4

  • M. Lassere et al, “Study of Zircaloy-4 cladding air degradation at high temperature” Proceedings of the 2013 21st International Conference on Nuclear

Engineering ICONE21 July 29- August 2, 2013, Chengdu, China

Nitrogen effect on mass and kinetic rate

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State of the art,

Zircaloy-4 in air/steam at 900°C

24/07/2017

École des Mines de Saint-Étienne 5 Steinbruck et al. Journal of Nuclear Materials 392 (2009) 531–544

Formation of Zirconium nitride (gold colour)

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State of the art,

Zircaloy-4 pre-oxidized in air at 850°C

24/07/2017

École des Mines de Saint-Étienne 6 Kasperski et al, Oxidation of Metals January 2017 pp 1–13

Protective effect of pre-oxide High temperature

  • xidation

→ new oxide scale formed Normal operation in reactor → oxide scale formed

As received Pre-oxidized After oxidation in air at 850°C

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High temperature

  • xidation

→ new oxide scale formed Normal operation in reactor → oxide scale formed

Aims of the study

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École des Mines de Saint-Étienne 7

Research focus: Oxidation of Zircaloy-4 pre-oxizided in nitrogen-oxygen-steam mixtures at HT Aims of the study: → Understanding the corrosion mechanism → Kinetic analysis for modeling the kinetic rate as a function of the temperature and partial pressures P(O2), P(N2), P(H2O)

As received Pre-oxidized After oxidation in air at 850°C

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Experimental protocol

Material

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École des Mines de Saint-Étienne 8

Zy-4 Alloy (wt.%) Sn 1,32 - 1,35 Fe 0,21 O 0,123 - 0,129 Cr 0,11

Pre-oxide Metal

  • Zircaloy-4: 15*10*0,5 mm
  • Pre-oxidation: 250 days O2 + H2O (15% vol.) at 425°C
  • Pre-oxide thickness ≈ 30µm
  • [H] ≈ 280 ppm
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flowing mixture entrance furnace measuring device flowing mixture exit sample

Experimental protocol

Apparatus

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École des Mines de Saint-Étienne 9

Experimental conditions: Thermogravimetric analysis Flow rate 6L/h Temperature 850°C Pressure P(O2) = 80 hPa P(N2) = 320 hPa P(H2O) = 50 hPa Carrier gas He (balance) Rate 10°C/min Time 1-10 hours

100 200 300 400 500 600 700 800 900 20 40 60 80 100 120 140 160 180 200 5000 10000 15000 20000 Temperature ( C) Δm/S (g.m-2) Time (s)

Isothermal and isobaric conditions

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24/07/2017

École des Mines de Saint-Étienne 10

Results

Thermogravimetric analysis, effect of time

0,005 0,01 0,015 0,02 0,025 0,03 0,035 5000 10000 15000 20000 25000 30000 100 200 300 400 500 600 700 800 900 d(Δm/S)/dt (g.m-2.s-1) Time(s) Temperature ( C) Temperature 2h05 isothermal 0,005 0,01 0,015 0,02 0,025 0,03 0,035 5000 10000 15000 20000 25000 30000 100 200 300 400 500 600 700 800 900 d(Δm/S)/dt (g.m-2.s-1) Time(s) Temperature ( C) Temperature 2h05 isothermal 4h15 isothermal 0,005 0,01 0,015 0,02 0,025 0,03 0,035 5000 10000 15000 20000 25000 30000 100 200 300 400 500 600 700 800 900 d(Δm/S)/dt (g.m-2.s-1) Time(s) Temperature ( C) Temperature 2h05 isothermal 4h15 isothermal 6h15 isothermal

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24/07/2017

École des Mines de Saint-Étienne 10

Results

Thermogravimetric analysis, effect of time

0,005 0,01 0,015 0,02 0,025 0,03 0,035 5000 10000 15000 20000 25000 30000 100 200 300 400 500 600 700 800 900 d(Δm/S)/dt (g.m-2.s-1) Time(s) Temperature ( C) Temperature 2h05 isothermal 0,005 0,01 0,015 0,02 0,025 0,03 0,035 5000 10000 15000 20000 25000 30000 100 200 300 400 500 600 700 800 900 d(Δm/S)/dt (g.m-2.s-1) Time(s) Temperature ( C) Temperature 2h05 isothermal 4h15 isothermal 0,005 0,01 0,015 0,02 0,025 0,03 0,035 5000 10000 15000 20000 25000 30000 100 200 300 400 500 600 700 800 900 d(Δm/S)/dt (g.m-2.s-1) Time(s) Temperature ( C) Temperature 2h05 isothermal 4h15 isothermal 6h15 isothermal

Mixed region: protective & non protective Non protective region

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24/07/2017

École des Mines de Saint-Étienne 11

Results

Thermogravimetric analysis, effect of time Protective ZrN Mixed region: two co-existing regions protective & non protective Optical microscopy of a mixed stage sample

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24/07/2017

École des Mines de Saint-Étienne 11

Results

Thermogravimetric analysis, effect of time Protective ZrN Non protective ZrN High temperature

  • xide

Mixed region: two co-existing regions protective & non protective Optical microscopy of a mixed stage sample

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Institut Mines-Télécom École des Mines de Saint-Étienne

Model

Mechanism

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12

Scheme of the degradation process, catalyzed by nitrogen

ZrO2 (dense) α-Zr(O) ZrO2 (porous) high temperature ZrO2 (porous) pre-oxide ZrN N2 (g), O2 (g), H2O (g)

H (2-x)Oi + ZrOx ↔ ZrO2 R.3 Oxidation of metal PBRZrO2/Zr =1,56 → volume increase ZrOx + Ni ↔ ZrN + xOi R.2 Nitridation of metal PBRZrN/Zr =1,03 → no volume change

}

ZrN + O2(g) = ZrO2 + Ni R.1 Oxidation of ZrN PBRZrO2/ZrN= 1,47 ZrN + 2 H2O(g) = ZrO2 + Ni + 2 H2 → Volume increase R.1 R.2 R.3

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  • Does the corrosion proceed in a steady-state?
  • Is the assumption of the rate-determining step

confirmed?

  • What is the influence of oxygen and nitrogen partial

pressures on the kinetic rate and how can it be explained?

École des Mines de Saint-Étienne

Model

Kinetic expression

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13

  • Does the corrosion proceed in a steady-state?
  • Is the assumption of the rate-determining step

confirmed? Assumptions validated thanks to experimental results

  • M. Pijolat and M. Soustelle, Thermochimica Acta, 2008, vol. 478, pp. 34-40

𝑒(Δ𝑛 𝑇 ) 𝑒𝑢 = 𝐶0 × Φ 𝑈, 𝑄 × 𝑇𝑛 𝑢

Φ : areic growth reactivity mol.m-2.s-1 Sm : related to the extent of reaction zone where the rate determining step of growth takes place m2. mol-1 𝐶0 =

𝑜𝑝×𝑁 𝑃2 𝑇

Coefficient of proportionality g.m-2

n0 : number of mole of Zy4 S : total surface aera of the specimen M(O2): molar mass of oxygen Δm : change in mass

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Institut Mines-Télécom 0,005 0,01 0,015 0,02 0,025 0,03 0,035 5000 10000 15000 20000 25000 d(Δm/S)/dt (g.m-2.s-1) Time (s)

Model

Kinetic, reactivity function Φ

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École des Mines de Saint-Étienne 14

𝑒 ∆𝑛 𝑇 𝑒𝑢

𝑏𝑔𝑢𝑓𝑠

𝑒 ∆𝑛 𝑇 𝑒𝑢

𝑐𝑓𝑔𝑝𝑠𝑓

= 𝐶0 × 𝛸(𝑄(1)) × 𝑇𝑛(𝑢) 𝐶0 × 𝛸(𝑄(0)) × 𝑇𝑛(𝑢) = 𝛸 𝑄(1) 𝛸 𝑄(0)

Variations of Φ with oxygen, steam and nitrogen partial pressures→ jumps method

P(0) 8% O2 P(1) 11% O2 P(2) 5% O2 Pressure jump

Variations of Φ divided by F(P(0)) is obtained by scanning a range of given pressures

𝑒(Δ𝑛 𝑇 ) 𝑒𝑢 = 𝐶0 × Φ 𝑈, 𝑄 × 𝑇𝑛 𝑢

Initial pressure 8% O2 – 32% N2 – 5% H2O, 850°C

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0,2 0,4 0,6 0,8 1 1,2 1,4 100 200 300 400 500 600 Φ(PN2)/Φ(P0) = 320 hPa PN2 (hPa) 0,2 0,4 0,6 0,8 1 1,2 1,4 20 40 60 80 100 Φ(PH2O)/Φ(P0) = 50 hPa PH2O (hPa)

0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2 50 100 150 200 250 Φ(PO2)/Φ(P0) = 80 hPa PO2 (hPa)

Model

Kinetic, reactivity function Φ

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École des Mines de Saint-Étienne 15

Jumps method, 850°C Φ varies with P(O2) Φ independent of P(N2) Φ varies with P(H2O)

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0,2 0,4 0,6 0,8 1 1,2 1,4 100 200 300 400 500 600 Φ(PN2)/Φ(P0) = 320 hPa PN2 (hPa) 0,2 0,4 0,6 0,8 1 1,2 1,4 20 40 60 80 100 Φ(PH2O)/Φ(P0) = 50 hPa PH2O (hPa)

0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2 50 100 150 200 250 Φ(PO2)/Φ(P0) = 80 hPa PO2 (hPa)

Model

Kinetic, reactivity function Φ

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École des Mines de Saint-Étienne 15

Jumps method, 850°C Φ varies with P(O2) Φ independent of P(N2) Φ varies with P(H2O) (2-x)Oi + ZrOx ↔ ZrO2 R.3 Oxidation of metal PBRZrO2/Zr =1,56 → volume increase ZrOx + Ni ↔ ZrN + xOi R.2 Nitridation of metal PBRZrN/Zr =1,03 → no volume change

}

ZrN + O2(g) = ZrO2 + Ni R.1 Oxidation of ZrN PBRZrO2/ZrN= 1,47 ZrN + 2 H2O(g) = ZrO2 + Ni + 2 H2 → Volume increase

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Model

Kinetic, reactivity function Φ

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École des Mines de Saint-Étienne 16

Proposition of mechanism Expression of Φ as a function of partial pressures for each elementary step of the growth mechanism

Rate determining step Areic rate of growth F (1) Adsorption

ϕ 1 = k1. p O2 . p(H2O). K2

  • 3. K4. KR2. KR3

x (2−x)

1 + K2. K4. KR2. KR3

x (2−x) 3 . 1 −

p O2 eq p O2 exp

(2) External interface reaction

ϕ 2 = k2O. p O2 + k2H2O. p(H2O) 1 + K1o. p O2 + K1H2O. p(H2O) . K4. KR2. KR3

x (2−x)

1 − p O2 eq p O2 exp + p H2O eq p H2O exp

(4) Internal interface reaction

ϕ 4 = k4. 1 − p O2 eq p O2 exp + p H2O eq p H2O exp

O2 (g) + 2 s ↔ 2 O-s (1) Adsorption H2O(g) + s ↔ H2O-s O-s + VO¨ + 2 e’ ↔ Ox

O + s

(2) External interface reaction Zrx

Zr(ZrN) + Nx N(ZrN) + 2Ox O ↔ ZrO2 + 2 VO¨ + 4 e’ + Ni (4)Internal interface reaction

}

𝑒(Δ𝑛 𝑇 ) 𝑒𝑢 = 𝐶0 × Φ 𝑈, 𝑄 × 𝑇𝑛 𝑢

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Institut Mines-Télécom École des Mines de Saint-Étienne

Model

Kinetic, reactivity function Φ

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17

Φ2 𝑄𝐼2𝑃, 𝑄𝑃2 = 𝑏 × 𝑄 𝑃2 + 𝑐 × 𝑄(𝐼2𝑃) 1 + 𝑑 × 𝑄 𝑃2 + 𝑒 × 𝑄(𝐼2𝑃) Φ modeling for isothermal and isobaric conditions, Φ is constant

  • strong influence of P(O2) and low influence of P(H2O)
  • nature and location of the rate determining step → interface ZrN/Oxide high

temperature

ZrO2 (dense) α-Zr(O) ZrO2 (porous) high temperature ZrO2 (porous) pre-oxide ZrN N2 (g), O2 (g), H2O (g)

H

0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2 50 100 150 200 250 Φ(PO2)/Φ(P0) = 80 hPa PO2 (hPa)

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Model

Kinetic, geometric function Sm

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Φ modeling for isothermal and isobaric conditions, Φ is constant

𝑒(Δ𝑛 𝑇 ) 𝑒𝑢 = 𝐶0 × Φ 𝑈, 𝑄 × 𝑇𝑛 𝑢

Increase of the mass gain rate measured by TGA can be explained by: Sm(t) increase → increase of kinetic rate

0,005 0,01 0,015 0,02 0,025 0,03 0,035 5000 10000 15000 20000 25000 100 200 300 400 500 600 700 800 900 d(Δm/S)/dt (g.m-2.s-1) Time(s) Temperature ( C)

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Institut Mines-Télécom École des Mines de Saint-Étienne

Model

Kinetic, geometric function Sm

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. Before HT oxidation Pre-oxide at 425°C in O2 + H2O, 30 µm After HT oxidation 2h05min at 850°C in O2, N2, H2O Oxidation initiates at sample’s edges and propagates axially

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Conclusion

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École des Mines de Saint-Étienne 20

Kinetic analysis of a complex reactive system in mixed oxygen, steam and nitrogen atmosphere at 850°C Growth reactivity (Φ) modeling

  • Validation of steady state assumption and rate-determining step assumption
  • Variations of Φ with P(O2), P(H2O)
  • Localization and nature of the rate determining step : interfacial reaction

→ oxidation of ZrN precipitates Geometric term (Sm) modeling, work in progress

  • Initiates at sample’s edges and propagates axially

Pre-oxidized After oxidation in air/steam at 850°C

High temperature

  • xidation
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Perspectives

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École des Mines de Saint-Étienne 21

Thesis:

  • Determination of Φ at other temperatures
  • Determination of respective contribution of oxygen/steam thanks to

experiments with 18O/H2

16O

  • Determination of Sm as a function of sample geometry, thickness of

pre-oxide, P(N2), time and creep Project:

  • Derivation of a simplified oxidation law for the severe accident code

ASTEC

  • Scaling coupon to tube
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Thank you for your attention

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