INES-1#101 1

Experimental Studies on Steel Corrosionin Lead-Bismuth with Steam Injection

Koji Hata, Kazuyuki HaraNuclear Development Corporation

Minoru TakahashiResearch Laboratory for Nuclear Reactors

Tokyo Institute of Technology

2

Objectives

BackgroundFeasibility study of Pb-Bi direct contact boiling water reactor (PBWFR) for innovated nuclear reactor energy system.PurposeTo investigate the compatibility of high Cr steel

in the steam injecting Pb-Bi Study items

Effectiveness of Cr contents for corrosion resistance Influence of (PH2/PH2O) ratio in the injecting steam

on corrosion behaviorEffect of temperature on the steel corrosionSelection of more promising Cr steel and

evaluation of its applicability

3

System of the Experimental Apparatus

Pb-Bi Test Sub-systemSteam Supply Sub-system

Pb-Bi drain tank

Pb-Bitest tank

vacuum pump

exhaust gasheader

cooling water

DH meter

gas bubbling

flow meter

pump

filter

pump

waterconditioning

tank

condenser

steamgenerator

Ar gas

H2 gas

level sensorview port

oxygen sensor

chimney

slug filter

injection nozzle

4

Chimney

Test Specimens

Pb-BiCirculation

Pb-Bi Test Tank

Steam Bubbles

Steam Injection Steam Exhaust

Corrosion Test Concept

5

Chemical Composition of Tested Materials (wt.%)

C Si Mn Ni Cr Mo W V Nb0.1 0.1 0.2 0.02 7.7 ~ 1.9 0.2 ~0.1 0.4 0.4 0.1 8.6 1.0 ~ 0.2 0.080.1 0.3 0.5 0.3 8.8 0.3 1.9 0.2 0.07

0.15 0.1 0.5 0.6 10.0 0.5 ~ 0.2 ~0.1 0.3 0.5 0.2 12.0 1.1 1.0 0.3 0.10.1 0.3 0.5 0.3 12.0 0.3 1.9 0.2 0.05

0.01 1.0 0.5 4.5 16.0 ~ ~ ~ 0.20.01 1.4 0.7 ~ 17.7 ~ ~ ~ ~

F82HSTBA28

RECLOY17-5PH

Steel

NF616TMK1

HCM12HCM12A

6

Summary of the Experimental Parameters

400 450 500Ｏ ~ ~Ｏ Ｏ Ｏ

Ｏ ~ ~Ｏ ~ ~

Ｏ : tested, ~ : not tested

ExposurePeriods

Oxygen Potential Relatives

0.25 MPa 500 hours

Temperatures (℃）

5 x 10-6

1 x 10-5

DH

500 ppb1,000 ppb

1 x 10-6

Pressuresin Test TankP H2/P H20

< 3 x 10-7 < 30 ppb100 ppb

P H2P H2O

M H2O＝ (DH ) M H2 M H2O = molecular weight of H2O

M H2 = molecular weight of H2

(DH )＝disolved hydrogen concentrationrelashionship between (P H2/P H2O) and DH

7

Oxygen Potential: Ox Electro-motive Force: Eand Oxygen Concentration: C

Nernst’s equation for electro-motive force

E = ( OREF – OPb-Bi )/nFwhere E: electro-motive force for an electrochemical system

OREF : oxygen potential of reference electrode OPb-Bi : oxygen potential of Pb-Bi

n: atomic valence of oxygen ion, F: Faraday’s constant

Calculation of E for oxygen concentration of C

E = [OREF - △GPb(Bi)-oxide - RTln(C/C0)] / nFwhere E: electro-motive force calculated for oxygen concentration of C

△GPb(Bi)-oxide : Gibb’s free energy of formation for Pb(Bi)-oxideR: gas constant, T: temperatureC : oxygen concentration in Pb-Bi, C0 : oxygen solubility in Pb-Bi

8

Experimental Conditions for E, C, and T

0

100

200

300

400

500

600

250 300 350 400 450 500 550 600

Temperature (℃）

E(m

V）

Fe3O4 formation

(Pb-Bi) oxide formation

oxygen in Pb-Bi(wt.fraction)

1.0E-10

1.0E-11

1.0E-9

1.0E-8

1.0E-7

1.0E-6

Experimental Condition

9

Ｆｅ in steel

before exposure (Wa )

Ｆｅ in steel

O in Pb-Bi

exposure in Pb-Bi

Pb-Bi

Fe

(FeCr)3O4Fe3O4Pb-Bi

Fe

(FeCr)3O4Fe3O4Pb-Bi

after exposure

after exposure

Fe

(FeCr)3O4

Fe3O4into Na

Pb-Bi

Na treatment (Wb)Fe

(FeCr)3O4into

citrate sol.

citrate sol. Treatment (Wc)

Process Flow for the Post-Exposure Treatment

10

Surface of HCM12A by Post-Exposure Treatment

optical microscope

4 mm4 mm 4 mm

before exposure test Na-ethanol treatment citrate teatment

before exposure test Na-ethanol treatment citrate teatment

1,000μm1,000μm 1,000μm

electron microscope

11

Fe

(FeCr)3O4into

citrate sol.

Fe

(FeCr)3O4

Fe3O4into Na

Pb-Bi

Ｆｅ in steel

before exposure (Wa ) citrate sol. Treatment (Wc )Na treatment (Wb )

Fe3O4: defective(porous) structure

(( (FeCr)3O4: sound structure

Weight Changes after Na treatment : (Wb – Wa) after citrate treatment : (Wc – Wa)

12

Weight Changes after Na Treatment (400℃)

-15.0

-10.0

-5.0

0.0

5.0

10.0

Ｆ８２Ｈ

ＳＴＢＡ２８

ＮＦ６１６

ＴＭＫ１

ＨＣＭ１２

ＨＣＭ１２Ａ

１７－４ＰＨ

ＲＥＣＬＯＹ

Symbol of Steel (in the order of Cr content)

Wb－Wa

(mg/

test

pie

ce)

DH < 30 (ppb)

DH = 100 (ppb)

DH = 1,000 (ppb)

13

0

50

100

150

200

250

Ｆ８２Ｈ

ＳＴＢＡ２８

ＮＦ６１６

ＴＭＫ１

ＨＣＭ１２

ＨＣＭ１２Ａ

１７－４ＰＨ

ＲＥＣＬＯＹ

Symbol of Steel (in the order of Cr content)

Wa-

Wc

(mg/

test

pie

ce)

DH = < 30 (ppb)

DH = 100

DH = 1,000

Weight Losses after Citrate Treatment (400℃)

14

0

40

80

120

160

200

Ｆ８２Ｈ

ＳＴＢＡ２８

ＮＦ６１６

ＴＭＫ１

ＨＣＭ１２

ＨＣＭ１２Ａ

１７－４ＰＨ

ＲＥＣＬＯＹ

Symbol of Steel (in the order of Cr content)

Wa-

Wc

(mg/

test

piec

e)400℃

450℃

500℃

Weight Losses after Citrate Treatment (DH=100 ppb)

15

Conclusions & Future Works

Corrosion behaviors for some types of high Cr steel were examined.It was identified that :

Higher Cr content lead more corrosion resistance to Cr steel, and more than 9 % Cr content would be feasible for an application.

DH seemed to be little effective to control corrosion, but would be effective to avoid PbBi-slug formation or its precipitation.

DH should be limited less than 1,000 ppb to lower the amountof corrosion product (Fe-oxide ) released in Pb-Bi.

Corrosion rate increased with temperature, and Cr content effectiveness decreased at temperatures 500oC.

Corrosion rate of 12Cr steel were estimated as a few μm /y at 400oCand evaluated to be promising for a large reactor structure.

Further experiments are in progress to investigate the corrosion behavior of12Cr steel and other advanced materials (refractory metals and ceramics).