1

原子力学会水化学部会の定例会(財)電力中央研究所 狛江地区, 2011.3.7

2

Introduction
423および453Kの高温純水中における鋭敏化ステンレス
鋼のSCC感受性に及ぼす過酸化水素の影響
加古謙司, 新井 拓(㈶電力中央研究所)
永田義昭(中国電力株式会社)
永田暢明, 堂崎浩二(日本原子力発電株式会社)

At plant start-up in BWRhydrogen peroxide andoxide concentration
yincrease and dynamic
distortions occur↓
S
Severecondition
diti forf
structural materials↓
Hydrogen injection
during start-up

Efffective O
Oxygen Co
oncentrattion
O2+1/2・H2O2(ppb)

10 4


10 3

F.P.Ford, 1979
SCC resion of sensitized type 304 SS（SSRT tests）

Normal start-up without H2O2

10 2

10Hydrogen
injection
1350

400
450500Temperature (K)3Introduction
Efffective Oxxygen Co
oncentratiion
O2+1/2・H2O2((ppb)

10 4

10 3

NWC

without H2O2

10 2

HWC
350Purpose
 Effect of hydrogen peroxide on SCC susceptibility
 Effect of hydrogeny g peroxide
pon oxide film
Experiments
 SSRT tests of sensitized type 304 SS
 TEM observation
observation, Laser Raman spectrometry ofoxide film

101

4Purpose and Exeriments

F.P.Ford, 1979
SCC area of sensitized type 304 SS（SSRT tests））400450500
Temperature (K)

550

550

5Experiment

Experiment

Material
Type 304 SS

C0.050

6Si
0.62

Mn
1.00

P
0.027

S0.005

Ni
8.16

Cr
18.25

Water condition

FeBal.

Temp.
T(K)Sensitization; 893 K×24hr, air cooled
Surface;; #600 polishedp

EOC
(ppb)

400

Tests

453

SCC tests

SSRT (plate; gauge 20mm(l)×5mm(w)×2mm(t))

Strain rate

4.2 x 10-7 /sec

423

452720400
47

DO at 293 KDO,
(ppb)

H2O2 att 293 K(ppb)

N b offNuber
specimens

4002545510850100750080332470074444444447Test loop8

Overview of specimen setting
Upper hook

Autoclaveto tensile specimens
Water circulating system
to control oxygen concentrationin water conditioning tank
Injection/sampling system
to inject H2O2 and to sample
water close to SSRT specimenpthrough Teflon lining pipe.
to control H2O2 concentration inthe vicinity of SSRT test
specimens by changing H2O2
concentration in chemical tankand injection flow rate.

Sampling line

SSRT specimen

Injection
jline

Lower hook

H2O2 was injected from the bottom of SSRT specimen
H2O2 was sampled from the middle of SSRT specimen

9Decomposition in sampling and injection line

Results of SSRT tests, EOC=400ppb

Directly connecting injection line to samplingline 99.5%line,
99 5% of H2O2 concentration in chemicaltank was detected in sampled water at 453 K.

Sampling line

Injection
jline

During SSRT testing, 85% of H2O2 in samplingline at 293 K were detected in sampled waterat 453 K.

Lower hook

453K, 4.2x10 -7 /s
Type304
pp
EOC: 400ppb

800

Decomposition of H2O2 in injection andsampling line was very low.

SSRT specimen

1000

Strress（MPa)Upper hook

10600
DO=400ppb

400
DO=40ppb
H2O2=720ppb

2000720~765 ppb H2O2 at 293 K020

⇒ 615~657 ppb H2O2 at 453 K

40Strain (%)

60

80

Specimens tested under H2O2 injection condition were decreased in elongation.

11Tensile properties

12Appearance of fracture surface after SSRT test.
H2O2 injection side
（A）

EOC

H2O2 (453 K) H2O2 (453 K)

( b)
(ppb)

( b)
(ppb)

( b)
(ppb)

40000400

720764736748617657563
642

00.22 %
proofstress(MP )
(MPa)
248
231
237
228
227
228
225
226

Tensilestrength

Elongation

Reduction of area(MPa))(MP580
546
560
571
516
395
412
466(%)
5055525337
161727(%)
6368
71
70
51
26
1548

H2O2 injection reduced TS, EL and R.A.

（B）

500μm
（A）

（B）

50μm

453K, EOC; 400ppb, H2O2 injection
IGSCC fractures were observed.

13

Appearance of specimens after SSRT tests
EOC; 400ppb

14Appearance of specimens after SSRT tests

EOC; 45ppb

453K

Flow
H2O2 injection sideSampling point

H2O2 injection1mm

Optical microscopy

H2O2 injection↓Changed the color of oxide film.

1mm

SEM image

453K, EOC; 400ppb, H2O2 injection
Many SCC cracks were observed on H2O2 injection side.
And counted number of SCC crack

15

Rate of SCC on fracture surface
Number of cracks on the surface

EOC
(ppb)

H2O2(RT)(ppb)

H2O2(453K)(ppb)

40000400

720
764
736
748

617
657
563
642

SCC
No
Observed
NoNNo
Observed
Observed
Observed
Observed

SSRT test results

Number of SCC
Rate of SCC
H2O2 side Another side(%)

03.90022.7
63.7
67 467.4
41.1

SCC cracks were observed on only H2O2 injection side

1600003932
47600000000

Temperature

EOC(K)(ppb)

400453423452720400
47

H2 O 2injection

SCC occurance /specimens
*/4No
Yes
No
Yes
Yes
Yes
Yes
Yes

1/4
4/40/41/42/4
0/4
0/4
0/4

17

SSRT test results
10 418Laser Raman spectrometry
16000

NWC

10 3Blue-Run3皮膜
Brown-Run2皮膜
Fe3O4
Fe2O314000

FeCr2O4
Fe(Metal)

12000

SCC susceptibility((with H2O2)

Intensity, AA.U.

Effecttive oxygen concenttration=O2+1
1/2・H2O2 /ppb

SCC susceptibility region of sensitizedt
type304 SS（SS（withoutith t H2O2）
F.P.Ford, 1979 2)

IGSCCNo SCC

10 2

10000
8000

Oxide
film (withoutH2O2), brown
茶色皮膜（HO 注入無）
2260004000

青色皮膜（HO 注入有）H O ), blue
Oxide
film (with2 22102000

HWC

200200

400

600

800

1000

1200

1400

-11323

373

423
473
523
Temperature, T/K

Wave Number,, cmOxide films are mainly consisted of Fe3O4 (Magnetite)573

No difference between oxide films tested under water condition with or without H2O2

19

TEM observation2)

20

TEM observation

Oxide film
200-350nm

453K、EOC；400ppb、without H2O2OxideO
id filfilm
2 50～200nm
3220

Substrate(type 304 SS)

Substrate(type 304 SS)

453K、EOC；400ppb、H2O2 co-existent condition(b) 40 ppb DO +200nm
200nm(a) 400 ppb DO
720 ppb H2O2
TEM micrographs of cross sections of sensitized type 304 SS tested under theconditions of 400 ppb EOC without H2O2 (a) and with H2O2 (b) at 453 K.
K200 nm

H2O2 injection thins oxide film thickness.
H2O2 injection makes planar surfaces of oxide film.

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22ConclusionThe addition of H2O2 increases the SCC susceptibility ofsensitized type 304 SS at 453 K.
SCC susceptibility was not observed under 400 ppb EOC
condition with and without H2O2 at 423 K.
The addition of H2O2 changes the surface shape of oxide
film in sensitized type 304 SS, from wavy to planar andthins oxide film thickness.

Thanks for your attention !