5.13

Material Performance in Sodium

T. Furukawa and E. Yoshida
Japan Atomic Energy Agency, O-arai, Ibaraki, Japan

ß 2012 Elsevier Ltd. All rights reserved.

5.13.1

Introduction

327

5.13.2
5.13.3
5.13.3.1
5.13.3.2
5.13.4
5.13.4.1
5.13.4.2
5.13.4.3
5.13.4.4
5.13.4.5
5.13.4.6
5.13.4.7
5.13.5
5.13.5.1
5.13.5.2
5.13.5.3

5.13.6
5.13.6.1
5.13.6.2
5.13.7
5.13.7.1
5.13.7.2
References

Material Selection in the Consideration of Application in Sodium
Corrosion Mechanism of Materials in Sodium
Corrosion Produced by the Dissolution of Alloy Elements to Sodium
Corrosion Produced Through Chemical Reaction with the Impurities in Sodium
Corrosion Behavior and Factors Affecting Steel
Immersion Time
Temperature
Dissolved Oxygen
Sodium Velocity
Alloy Elements
Carburization and Decarburization
Corrosion Estimation of FBR Materials
Effect of Sodium on the Mechanical Strength of Steels
Austenitic Stainless Steel
Ferritic Steels
Others (Ni Base Alloys, ODS)
Damage to Steels with Sodium Compounds
Sodium–Water Reaction
Sodium Leak
Tribology
Self-Welding
Frictional Wear


328
328
328
330
331
331
332
332
333
333
333
334
336
336
338
338
338
338
339
339
339
339
340

Abbreviations
EBR-II
FBRs
FFTF
FMS

JAEA
Monju
ODS
PFR
PNC

Experimental Breeder Reactor No. 2 (USA)
Fast breeder reactors
Fast Flux Test Facility (USA)
Ferritic–martensitic stainless steel
Japan Atomic Energy Agency
Japanese Prototype Fast Breeder Reactor
Oxide dispersion-strengthened steel
Prototype Fast Reactor (UK)
Power Reactor and Nuclear Fuel
Development Corporation (present JAEA)

5.13.1 Introduction
Sodium is one of the elements that exhibit the characteristics demanded of coolants for fast breeder
reactors (FBRs). The physical properties of sodium

are shown in Table 1 and see Chapter 2.14, Properties of Liquid Metal Coolants.
Sodium is a solid at room temperature, and the
melting and boiling temperatures are 97.82 and
881.4  C, respectively. Therefore, sodium is in the
liquid phase at FBR operating temperatures without
pressurization. For this reason, it is not necessary to
adopt the proof-pressure design employed in light
water reactors for sodium-cooled FBRs. Moreover,
the thermal conductivity and specific heat of sodium

at 550  C are 0.648 W cmÀ1  CÀ1 and 1.256 J gÀ1  CÀ1,
respectively, and sodium can transfer the heat of the
reactor core to the power generation system efficiently. Furthermore, its insignificant neutronmoderating capability is suitable for the coolant for
the FBR, in which fast neutrons play a major role in the
nuclear reaction.
On the other hand, the weakness of sodium as a
coolant is its reactivity with oxygen and/or water.

327


328
Table 1

Material Performance in Sodium

Physical properties of sodium

Atomic number
Atomic weight
Melting point ( C/K)
Boiling point ( C/K)
Volume increase on melting (%)
Density (g cmÀ3)
Thermal conductivity (W cmÀ1 KÀ1)
Specific heat (J molÀ1 KÀ1)

11
22.9898
97.8/371.0

881.5/1154.7
2.71
0.856 at 400  C
0.821 at 550  C
0.727 at 400  C
0.657 at 550  C
29.40 at 400  C
28.88 at 550  C

Table 2
elements1

Element Solubility equation

Cu
Ag
Au

Mg

Zn

When high-temperature sodium is leaked into the
atmosphere, it reacts with the oxygen and moisture
in the atmosphere, and the by-products of this reaction are known to cause structural damage to the
reactor. Moreover, in the event of a steam generator
tube failure, high-temperature steam blows off into
the sodium, and wastage of the adjoining tubes occurs.

5.13.2 Material Selection in the

Consideration of Application in Sodium
In the process of material selection, it is necessary to
take the environment into consideration by estimating
the mechanical properties and thermal characteristics.
Environments specific to the FBR components
include: (a) contact with the coolant (liquid metallic
sodium), (b) high temperature at which the creep
effects must be taken into account, and (c) neutron
irradiation. In this chapter, an outline of the compatibility of materials with sodium is provided.
The oxides formed on the surface of the material
are easily reduced in high-temperature sodium, resulting in direct contact between the material and sodium.
Under this condition, the dissolution of elements
contained in the material, such as iron, chromium,
and nickel, in sodium and the reverse phenomenon
(deposition) occur on the material surface due to the
difference in chemical potential. The behavior is fundamentally controlled by the solubility of the material
elements in sodium and by the diffusion rate of the
materials. The solubility equation of the various elements in sodium is shown in Table 2.
Among the elements in austenitic stainless steel,
the solubility of nickel is greatest. Therefore, the
phase transformation of austenite to ferrite through
nickel dissolution is observed on the surface in longterm immersion in sodium.
The compatibility of various metals with sodium
reported by Borgstedt and Mathews1 is shown in

Solubility equation of metallic and amphoteric

Cd
Al
Ga

In
U
Pu
Sn
Pb
Bi
Cr
Mo
Mn
Fe
Co
Ni

log Swwpm ¼ 5.450 À 3055/T (K)
log Swwpm ¼ 7.22 À 1479/T (K)
Swt% ¼ À11 þ 0.52 Â
(T(K) À 273.15) À 6 Â 10À4 Â
(T(K) À 273.15)2
Swt% ¼ À0.1414 þ 2.08 Â 10À6
 (T(K) À 273.15) þ 1.248
 10À3  (T(K) À 273.15)2
Swppm ¼ 1.4 þ 0.057 Â
(T(K) À 273.15)
log Swt% ¼ 3.67 À 1209/T (K)
log Swwpm ¼ 1.4 þ 0.057/T (K)
log Swt% ¼ 1.349 À 1010/T (K)
log Swt% ¼ 4.48 À 1552/T (K)
log Swwpm ¼ 4.36 À 6010.7/T (K)
log Swwpm ¼ 8.398 À 10.950/T
(K)

log Swt% ¼ 5.113 À 2299/T (K)
log Swt% ¼ 6.1097 À 2636/T (K)
log Swt% ¼ 2.15 À 2103/T (K)
log Swt% ¼ 5.67 À 4038/T (K)
log Swwpm ¼ 9.35 À 9010/T (K)
log Swwpm ¼ 2.738 À 2200/T (K)
log Swwpm ¼ 3.640 À 2601/T (K)
log Swwpm ¼ 4.720 À 4116/T (K)
log Swwpm ¼ 0.010 À 1493/T (K)
log Swwpm = 2.07 À 1570/T (K)

Temperature
range (K)
623–773
377–806
373–873

373–573
373–600
423–773
375–573
373–573
560–970
560–970
473–673
393–523
398–563
563–923
948–1198
500–720

550–811
658–973
673–973
673–973

Table 3. The data can be used to create an index
for the selection of the material used in sodium.

5.13.3 Corrosion Mechanism of
Materials in Sodium
There are two known mechanisms of sodium corrosion. One is corrosion produced by the dissolution of
alloy elements to sodium, and the other is corrosion
produced through chemical reaction with the impurities in sodium. These two corrosion mechanisms are
described in Sections 5.13.3.1 and 5.13.3.2.
5.13.3.1 Corrosion Produced by the
Dissolution of Alloy Elements to Sodium
In this case, corrosion is dependent on the solubility
in sodium of the elemental composition in the material, temperature, and the rate of solution.
The solution rate Rc is given by the following
formula:
Rc ¼ K ðCs À Ci Þ

½1Š


Material Performance in Sodium

Table 3

329


Compatibility of materials with alkali metals1
Compatible with alkali metal up to ( C)

Material

Mg alloys
Al alloys
Cu alloys
Ag and its alloys
Au and its alloys
Zn coatings
Pb and its alloys
Sn and its alloys
Fe
Low-alloy steels
Ferritic steels
High-Cr steels
Austenitic steels
Ni alloys
Mo alloys
W alloys
Ti alloys
Zr alloys
V alloys
Nb alloys
Ta alloys
Sintered A12O3
Stab. ZrO2/CaO
Stab. ThO2/Y2O3

Glass
UO2
UC

Factors influencing compatibility

Li

Na

K

Rb and Cs

n.c.
n.c.
300
n.c.
n.c.
n.c.
n.c.
n.c.
500
500
500
500
450
400
1000
1000

700
700
700
700
700
350
350
400
n.c.

n.c
350
400
n.c.
n.c.
n.c.
n.c.
n.c.
700
700
700
700
750
600
1000
1000
700
700
700
700

700
500
350
550
250
750
750

300
400
400
n.c.
n.c.
n.c.
n.c.
n.c.
700
700
700
700
750
600
1000
1000
700
700
700
700
700
500

350
550
250

300
450
400
n.c.
n.c.
n.c.
n.c.
n.c.
700
700
700
700
750
600
1000
1000
700
700
700
700
700
500
350
550
250


Metal solubility, oxygen exchange
Metal solubility
Metal solubility
High metal solubility
High metal solubility
High metal solubility
Very high metal solubility
Very high metal solubility
Nonmetallic impurities
Nonmetallic impurities
Nonmetallic impurities
Nonmetallic impurities
Nonmetallic impurities
Flow velocity
Nonmetallic impurities
Nonmetallic impurities
Nonmetallic impurities
Nonmetallic impurities
Nonmetallic impurities
Nonmetallic impurities
Nonmetallic impurities
Thermomechanical action
Intergranular corrosion
Intergranular corrosion
Chemical reaction
Excess of oxygen
Nonmetallic impurities

n.c. ¼ not compatible.


1.0E + 02

1.0E + 00
Ni
Solubility (ppm)

Mn
1.0E − 02

Fe

C
Mo
1.0E − 04
Si
1.0E − 06
Cr
1.0E − 08
1

1.2

1.4
1000/T (K)

1.6

Figure 1 Solubility of alloy elements in sodium.

1.8


where K is the solution rate constant, Cs is the solubility limit in sodium, and Ci is the actual concentration in sodium.
The solution rate constant K is controlled by diffusion. The solubility of the alloy elements of the
steel is shown in Figure 1.1–5 Included in Figure 1
are the major elements of austenitic stainless steels
(type 304SS and 316SS) and the Cr–Mo steels
(2.25Cr–1Mo and Mod. 9Cr–1Mo) which are used as
the structural materials of FBRs. The solubility of each
of the elements in sodium at 550  C is less than a few
parts per million. This means that the compatibility of
the steels with sodium is fundamentally excellent.
In the isothermal sodium condition, the corrosion
of the steels stops when the dissolved elements reach
saturation concentration at the temperature of sodium.
However, in the nonisothermal sodium condition,
corrosion resulting from the difference in activity
between sodium and the material surface occurs continually. This corrosion behavior is called thermal
gradient mass transfer. In the cooling system, the elements in the materials in the high-temperature section


330

Material Performance in Sodium

ΔW (mg cm-2)

Temperature (ЊC)

dissolve as a result of the temperature dependency of
the solubility of the elements in sodium, and the dissolved elements are deposited on the steel surface in

the low-temperature section by the same mechanism.
The results of thermal gradient mass transfer
using a sodium loop made of SUS316, which is equivalent to AISI type 316SS, is shown in Figure 2. The
weight loss caused by the dissolution of the elements
in the steel is measured in the high-temperature
section, and the weight gain caused by the deposit
of the dissolved elements in sodium is observed in the
low-temperature section.
Figure 3 shows the microstructure of the inner
surface of the sodium pipe taken from the flowing
sodium loop operated for 82 000 h. Dissolution of the
elements in the material is observed in the hightemperature section, and precipitation is observed in
the low-temperature section located in the lower
stream.
Generally, selective corrosion occurs at the initial
stage as a result of the dissolution of the elements

600 Sodium flow→
550
500
500
400
+1 390

600
520
470
410

0

–1

-1

Sodium velocity :3 m s
Oxygen level
:9 ppm
Immersion time
5512 h
7141 h
10644 h

Weight loss

-2
-3
0

5

10
15
20
Distance from electro magnetic
pump of sodium loop (m)

25

29


Figure 2 Weight change in SUS316 after corrosion test
in flowing sodium. Reproduced from Maruyama, A.;
Nomura, S.; Kawai, M.; Takani, S.; Ohta, Y.; Atsumo,
H. J. Atomic Energy Soc. Jpn. 1984, 26, 59.

in the steel, and then, the behavior moves to general
corrosion with the progress of time. In the hightemperature section, the dissolution of nickel, chromium, manganese, and silicon to sodium occurs
easily, and molybdenum and iron remain in the material. In the low-temperature section, chromium deposits easily with decreasing temperature.
Carbon transfer in the steel affects the mechanical properties of the FBR structural materials.
Decarburization occurring in the high-temperature
section, in particular, has the potential of degrading
creep strength. The effect of sodium on the mechanical strength is described in Section 5.13.5.
5.13.3.2 Corrosion Produced Through
Chemical Reaction with the Impurities
in Sodium
The most important element in the impurities in
sodium is oxygen. Sodium is the reducing agent,
and its affinity to oxygen is very strong.
The temperature dependence of the oxygen
saturated in sodium is shown in Figure 4. The solubility of oxygen in sodium is significantly higher than
in water. However, the control of impurities in
sodium can be achieved by using the cold trap technique6 based on the theory of the deposit of dissolved
impurities in sodium.
The introduction of oxygen into sodium may
occur during nuclear plant construction, refueling,
the supplementing of the reactor cover gas, the opening of the coolant boundary for maintenance operations, etc. These are the paths for contamination
through oxides adhering to the components and the
impurities in the gas.
The relationship between the standard free
energy of the formation of iron oxides and the temperature is shown in Figure 5. The thermodynamically stable oxide in sodium is sodium oxide, Na2O.

Sodium flow

(a)
525 ЊC, 82 000 h (BD-1)

(b)
575 ЊC, 82 000 h (BD-2)

(c)

(d)
625 ЊC, 82 000 h (BD-3)

420 ЊC, 82 000 h (BD-4)

10 μm

Figure 3 Corrosion of the inner surface of sodium loops made of type 304SS operated for 82 000 h. Reproduced from
Yoshida, E.; Kato, S.; Wada, Y. Liquid Metal Systems; Plenum press: New York, 1995.


Material Performance in Sodium

Dissolved oxygen (ppm)

1.0E + 04

oxidize iron thermodynamically (i.e., iron oxide cannot be formed). The iron is oxidized by the formation
of complex Na–Fe oxides.7
In addition to oxygen, impurities in sodium

include elements in the steel, hydrogen, and nitrogen.
Hydrogen and nitrogen induce changes in the microstructure that lead to the potential degradation of
mechanical properties.

1.0E + 03
1.0E + 02
1.0E + 01

5.13.4 Corrosion Behavior and
Factors Affecting Steel

1.0E + 00
1.0E - 01
1

1.5

2

2.5

3

1000/T (K)
Figure 4 Temperature dependence of saturated oxygen
concentration in sodium.

-300
O2
Na 2


2/3

ΔG0f (KJ mol-1 O2)

-400

Fe 2O 3
O

2Fe

The basic mechanism of the steel corrosion in sodium
is described in Section 5.13.3. In this section, the
corrosion behavior and its effects are described. The
major data are obtained for austenitic stainless steels.
The important factors which influence the corrosion of the steels in sodium are: (1) immersion time,
(2) temperature, (3) dissolved oxygen, (4) sodium
velocity, (5) alloy elements, and (6) carburization and
decarburization. The data on each factor are described
in the following sections.
5.13.4.1

-500

1/2

e 3O 4

a 2O


F

2N
O3

2/3

-600
O4

1/2

Fe
Na 3

O3

e
a 4F

N
2/3

e
a 5F

N

-700

O2

Fe
Na 2

-800
200

331

400

600
800
Temperature (K)

1000

1200

Figure 5 Relationship between ÁG0f and temperature in
oxides consisting of iron and sodium.

Iron, the main element in the steel, is corroded by the
following reaction:
Fe½s;lŠ þ 3Na2 O½s;lŠ ! Na4 FeO3 ½sŠ þ 2Na½s;lŠ
0
0
¼ þ43:8 KJ molÀ1 ; ÁGr298
¼ þ26:1KJ molÀ1

ÁHr298

where [g], [l], and [s] stand for gas, liquid, and solid.
This is an endothermic reaction. However, Gibbs
energy of reaction (ÁGr0 ) becomes negative at 380  C,
and the reaction progresses spontaneously above
that temperature. In addition, Na2O cannot directly

Immersion Time

As mentioned in Section 5.13.3.1, nickel, chromium,
and manganese dissolve easily in sodium. Therefore,
when austenitic stainless steel is immersed in sodium,
the selective corrosion caused by the dissolution of
these elements progresses in the initial stage. This
process is based on the solid diffusion of the elements
in the steel, and is described by Fick’s second law.
Diffusion in sodium is given by the following two
formulas:
dM
dc
¼ ÀD
dt
dx

½2Š

2 pffiffiffiffiffi
Mðt Þ ¼ pffiffiffi Dt ðC0 À Cs Þ
p


½3Š

where M is the diffusion amount, D is the diffusion
coefficient, C0 is the initial concentration, and Cs is
the surface concentration at time (t).
Formula [2] is Fick’s first law and its integration is
given as the total diffusion. Formula [3] is the function given as the approximate formula. From these
formulas, it is understood that the corrosion behavior
at the initial stage observes the parabolic law proportional to the root of time. At the initial process of
the corrosion, the parabolic type behavior caused
by the selective corrosion is dominant. The corrosion
behavior is called start-up corrosion.


332

Material Performance in Sodium

100

400

Weeks et al.9

Steady-state corrosion

Metal loss

Start-up


Temperature (ЊC)
600
500

700

Immersed time, t
Selective loss (Ls) ∝ t1/2
Bulk loss (Lb) ∝ t
Total loss (Ls + Lb)

Corrosion rate (µm year–1)

Bagnall and Jocobs12

10

Menken30

Zebroski10

Kolster11

Thorley and Tyzack8
JAEA

1

Figure 6 Schematic representation of corrosion data for

austenitic stainless steel.

The corrosion behavior of iron, which is the main
element of stainless steel, is general corrosion and the
corrosion progresses as a linear function of time.
Therefore, the corrosion of the dominant factor
changes from start-up corrosion to general corrosion
with the progress of time (Figure 6). The corrosion
behavior that dominates general corrosion is called
steady-state corrosion. The time required for a
change from start-up corrosion to steady-state corrosion is 2000–5000 h, although it is dependent on
conditions such as sodium volume, temperature,
velocity, and dissolved oxygen.
5.13.4.2

Temperature

Temperature dependence of the corrosion rate in
the sodium of austenitic stainless steels is shown in
Figure 7.
The corrosion rate CR is described by the following Arrhenius function:


E
½4Š
CR / exp À
RT
where R is the gas coefficient (8.3145 J molÀ1 KÀ1), E
is apparent activation energy, and T is temperature.
The apparent activation energy E is a function of

temperature. The values are reported as 100–120 kJ
molÀ1 by numerous researchers (Table 4). The
energy is lower than that of the activation energy of
the diffusion of iron, chromium, and nickel, in

Austenitic stainless steel
Oxygen content: 10 ppm
Na velocity: 3.8 m s–1
0.1
0.9

1.1

1.3

1.5

1000/T (K)
Figure 7 Corrosion rate of austenitic stainless steels in
flowing sodium.

stainless steel ($250–300 kJ molÀ1), and it agrees
with the activation energy of solubility in sodium
(Figure 1, Fe: 82.5 kJ molÀ1 and Cr: 104 kJ molÀ1).
In fact, it is understood that the corrosion of stainless
steel is dominated by the dissolution process of
the major elements (iron, chromium, and nickel)
of the steel. The effect of dissolved oxygen on
sodium, which influences the dissolution reaction,
is described in the following section.

5.13.4.3

Dissolved Oxygen

The effect of dissolved oxygen on the corrosion rate
is described by the following formula because the
corrosion process is dominated by the reaction process of oxides.
CR / ½O2 Šn

½5Š

where CR is the corrosion rate, [O2] is the oxygen
concentration, and n is a constant.
The constant n, reported by the researchers, is
listed in Table 5. This result suggests the possibility


Material Performance in Sodium

Table 4
Comparison of apparent activation energy on
corrosion rate
Sodium
temperature
( C)

Activation
energy
(kJ molÀ1)


Reference

Thorley
Weeks
Zebroski
Kolster
Bagnall
Maruyama

450–725
538–705
500–700
650–700
593–723
500–650

73.5
108.8
110.5
114.2
167.4
92–109

[8]
[9]
[10]
[11]
[12]
[13]


Table 5
Comparison of oxidation coefficient on
corrosion rate
Bibliography

O2 content
(ppm)

Coefficient
(n)

Reference

Thorley
Zebroski
Roy
Kolster

5–100
12, 50
5–30
1–8
8–40
2.5–9

1.5
1, 1.56
1.2
0.91
>1

0.8

[8]
[10]
[14]
[11]

Maruyama

Sodium Velocity

It has been observed that the corrosion rate in sodium
increases as sodium velocity increases. However, it is
known that the increase ends when the velocity
reaches a certain limit. It is believed that the limit is
a function of oxygen concentration in sodium and/
or the structure of the sodium loop. According to
Thorley and Tyzack,8 Roy,14 and Kolster,11 the limit
is 3.8, 6–7, and 3 m sÀ1, respectively. It is believed that
the effect of such a sodium velocity is based on the
thickness of the boundary layer between the material
surface and the flowing sodium. In fact, the thickness
of the boundary layer decreases as sodium velocity
increases, and the diffusion of alloy elements via the
boundary layer increases.
5.13.4.5

O2 cont.: 1 ppm
Velocity: 1.48 m s–1
Immersion time: 2930–5254 h

650 ЊC

1.0
600 ЊC

0.1

0

20
30
10
Nickel concentration in steel (mass %)

40

Figure 8 Effect of nickel content in stainless steel on the
corrosion rate.

[13]

that the control of dissolved oxygen may significantly
influence the corrosion behavior.
5.13.4.4

10

Corrosion rate (µm year–1)

Bibliography


333

Alloy Elements

The effect of the alloy elements on corrosion is
examined because long-term corrosion occurs as a
result of thermal gradient mass transfer. The effect of
the chromium and nickel concentration on the steels
is particularly significant. Figure 8 shows the effect

of the nickel content of stainless steel on the corrosion rate. On the other hand, the dependence of the
corrosion rate on elements in the steels is hardly
observed in austenitic stainless steels, such as types
304SS, 316SS, and 321SS, because of the slight difference in chemical composition (Figure 9).
5.13.4.6

Carburization and Decarburization

In monometallic sodium loops, the difference of
the carbon activity, which is the driving force of the
carbon transfer of the material, increases as temperature increases. Therefore, decarburization occurs in
the high-temperature section and carburization
occurs in the low-temperature section. On the other
hand, in bimetallic sodium loops which consist of
austenitic stainless steel and ferritic steel, it is easy
for decarburization to occur in the ferritic steel,
which has a high carbon activity due to the difference
in carbon activity between different materials,
whereas carburization in austenitic stainless steel,

which has low carbon activity, easily occurs at elevated temperature.
Carbon is an important element in maintaining
the superior mechanical strength of steel. Therefore,
the carburization/decarburization behavior of the
steels via sodium is important from the perspective
of mechanical properties.


334

Material Performance in Sodium

750

650

Temperature (ЊC)
550
450
304SS
316SS

Corrosion rate (μm year–1)

10

Fuel
cladding
tube
(FCT)


321SS

~9 ppm O2
~2.5 ppm O2
~9 ppm O2
~2.5 ppm O2
~9 ppm O2
~2.5 ppm O2

1
20 ppm O2
10 ppm O2
5 ppm O2

Sodium velocity
2–4 m s-1
(FCT: 2–4.8 ms-1)
0.1

0.9

2.5 ppm O2

Immersion time
1000–7200 h
1.1

1 ppm O2
1.3

1000/T (K)

1.5

Figure 9 Comparison of corrosion rates of austenitic
stainless steels.

Carbon concentration in sodium (ppm)

100
7
5
3
2
10–1
7
5
3
2

Decarburization
Type316
(0.06 wt% C)

FFTF (566 ЊC)
FFTF (474 ЊC)

Type304 L
(0.025 wt% C)
Data band of the carbon

concentration in
EBR-II primary
cooling system

EBR-II (470 ЊC)

10–2
7
5
3
2
10–3
400

Carburization

500

600
700
Temperature (ЊC)

Figure 10 shows the boundary between carburization and decarburization in monometallic sodium
loops consisting of austenitic stainless steel (single
alloy).15 At a carbon concentration of 0.2 ppm in
sodium, the temperature boundary is $650  C, with
decarburization occurring over that temperature and
carburization occurring below that temperature.
Although the boundary is influenced by the carbon
concentration in sodium (carbon activity), it is necessary to take decarburization and carburization into

consideration to apply austenitic stainless steel when
the temperature is above 550  C, such as fuel cladding tubes.
On the other hand, in bimetallic sodium loops that
consist of ferritic steel and austenitic stainless steel
(two alloys), decarburization and carburization also
occur in the temperature range of the structural
materials <550  C.
The thickness of decarburization of the component (ÁWD ) can be estimated by the following
formula:
pffiffi
ÁWD ¼ K t
½6Š
where K is the decarburization coefficient (g cmÀ2
sÀ1/2) and t is time (s).
The temperature dependence of the decarburization of 2.25Cr–1Mo steel in bimetallic sodium loops
consisting of type 304SS and 2.25Cr–1Mo steel,
which have the same structure as those in FBR
Monju, is shown in Figure 11.
In recent times, the application of high chromium
ferritic steel, which has excellent mechanical strength
at elevated temperatures and superior corrosion
resistance with the coolant, has been used as the
structural material for advanced FBRs.16 The relationship between decarburization and chromium
concentration in the steel is shown in Figure 12.
It is known that the decarburization/carburization
behavior of the ferritic steels is dependent on chromium concentration. The precipitation of chromium
carbide increases as the chromium concentration
increases. In this case, decarburization of the steel
is inhibited because the carbon activity in steel
decreases.


800

Figure 10 Boundary between carburization and
decarburization in monometallic sodium loops consisting of
austenitic stainless steel. Reproduced from Snyder, R. B.
An analysis of carbon transport in the EBR-II and FFTF
primary sodium systems. In Proceedings of the International
Conference on Liquid Metal Technology in Energy
Production, Champion, 1976.

5.13.4.7 Corrosion Estimation of FBR
Materials
The corrosion rate in the sodium of austenitic stainless steel and ferritic steel is very slight (a few
microns per year). Furthermore, since the estimated
corrosion thickness during the operation period is


Material Performance in Sodium

550

Temperature (ЊC)
500
450

400

∗The depth in microns from the surface is indicated
beside each plot by numerals in brackets.


350
0.25

Carbon concentration near the surface∗ (%)

’s
nju
Mo
or

f
ine
dl
de
en
n
sig
de

(15)

(16)

0.15
(10)

(29)

(11)

(16)

0.10

(14)

(11)
(17)

Tube/
pipe

Bar Coupon

2517
5071

0
0

10180
17768
1.1

1.2

1.4
1.3
1000/T (K)


1.5

1.6

Figure 11 Temperature dependency of the
decarburization coefficient of 2.25Cr–1Mo steel in
sodium.

small compared with the thickness of the structures
(permanent components) of FBRs, it is not a critical
point in the reactor design.
For the structural materials of Monju, therefore,
the following corrosion formula was applied for all
materials for the design
103
log10 R ¼ 0:85 þ 1:5log10 Co À 3:9
T þ 273

½7Š

where R is the corrosion rate (mm yearÀ1), Co is the
dissolved oxygen (ppm, 5 Co 25), and T is
the temperature ( C, 400 T 650). This equation
is valid for materials types 304SS, 316SS, 321SS, and
2.25Cr–1Mo steel.
After the construction of Monju, the data for corrosion in sodium for the structural materials for
advanced FBRs were obtained by the Japan Atomic
Energy Agency (JAEA),16,17 and it was confirmed
that the corrosion rate of the materials is also
described by the aforementioned formula. The corrosion formula is expected to be applied to advanced

steels as well.

1

(9)
9Cr–1Mo→

0.05

Specimen

7Cr–1Mo→

Time
(h)

10-10
1.0

(17)
(21)

(6)

5Cr–1Mo→

10

-9


(14)

0.20

2.25Cr–1Mo→

Decarburization coefficient (G cm-2 s-1/2)

mm
co
Re

10-8

Testing conditions
1000 h, 8 ppm O2
1000 h, 50 ppm O2
3000 h, 9 ppm O2

3Cr–1Mo→

10-7

700 650 600

335

2
3
4

5
6
7
8
9
Chromium concentration in steel (mass %)

10

Figure 12 Relationship between decarburization and
chromium concentration in high chromium ferritic steel.
Reproduced from Matsumoto, K.; Ohta, Y.; Kataoka,
T. Nucl. Technol. 1976, 28(3), 452–470.

On the other hand, since the thickness of the fuel
cladding materials is thin, the ratio of the corrosion
thickness to the original thickness is larger than that
of the structural materials. Therefore, it is necessary
that corrosion estimation be performed with greater
precision.
The corrosion formula is proposed for each core
material by JAEA.18–20
Monju core materials (PNC316 [16Cr–14Ni–B–
P–Ti–Nb]), type 316SS)
X ti
CRi
½8Š
CNa ¼
8760
i



104
5
CRi ¼ 4:927Â10 exp À1:647
Oxi
½9Š
Ti þ 273
where CNa is the corrosion thickness (mm), ti is the
operation time (h) at temperature Ti with dissolved
oxygen Oxi, CRi is the corrosion rate (mm yearÀ1) at
sodium temperature Ti with dissolved oxygen Oxi,
Oxi: dissolved oxygen (ppm, Oxi 5), and Ti is the
sodium temperature ( C 400 T 700)
For PNC1520 [15Cr–20Ni–B–P–Ti–Nb]
CNa ¼ ðCR1 þ CR2 Â ti ÞOxi

½10Š


336

Material Performance in Sodium

log10 CR1 ¼ 7:6036 À 6:6021

103
Ti þ 273



log10 CR2 ¼ 1:5172 Â 108 exp À2:4275

½11Š


104
Ti þ 273

½12Š

where CNa is the corrosion thickness (mm), CR1 is the
initial corrosion (mm) at temperature Ti with dissolved oxygen Oxi, CR2 is the steady corrosion rate
(mm hÀ1) at temperature Ti with dissolved oxygen
Oxi, ti is the operation time at temperature Ti with
dissolved oxygen Oxi, Oxi is the dissolved oxygen
(ppm, Oxi 5), and Ti is the sodium temperature
( C, 400 T 650)
For PNC-FMS [11Cr–2W–Mo–Nb–V]
CNa ¼ ðCR1 þ CR2 Â ti ÞOxi

½13Š

103
Ti þ 273

½14Š

log10 CR1 ¼ 9:078 À 8:251



log10 CR2 ¼ 4:1666 Â 104 exp À1:7580

104
Ti þ 273



½15Š

where CNa is the corrosion thickness (mm), CR1 is the
initial corrosion (mm) at temperature Ti with dissolved oxygen Oxi, CR2 is the steady corrosion rate
(mm hÀ1) at temperature Ti with dissolved oxygen
Oxi, ti is the operation time at temperature Ti with
dissolved oxygen Oxi, Oxi is the dissolved oxygen
(ppm, Oxi 5), and Ti is the sodium temperature
( C, 400 T 650).

5.13.5 Effect of Sodium on the
Mechanical Strength of Steels
The effect of sodium on the mechanical strength of
steel is determined by three factors: (a) corrosion and
mass transfer, (b) decarburization and carburization,
and (c) nonoxidation (reducing atmosphere) by
sodium. For creep strength whose dominant factors
are time and temperature, the behavior of the carbon
and minor elements in the steels are important factors. For the fuel cladding materials, which are thin
structures, it is necessary to consider the effect of
metal loss by corrosion. On the other hand, fatigue
strength in sodium is enhanced in a nonoxidizing
environment such as vacuum.

Thus, the effect of sodium on mechanical strength
appears as the synthesis of both the corrosion and
mass transfer of the steel elements. In this section, the
important points concerning the effects of sodium on

the mechanical strength of core materials, such as
fuel cladding and wrapper tubes, and structural materials, such as reactor vessels, main components, and
pipes, are described.
To estimate the sodium environmental effect of
the core materials, the following three points must
be taken into consideration: (a) the thin structure
(about 0.5 mm thickness for fuel cladding tubes),
(b) the high temperature (maximum 650  C), and
(c) the exchangeable components. Regarding (a),
since the ratio of the sodium-effect layer (corrosion
layer) to the thickness of the fuel cladding tubes
becomes large, the stress increment affecting the base
metal is larger than that of the structural materials.
Regarding (b), since carbon transfer (decarburization/
carburization) becomes active, the high-temperature
strength of the core materials changes easily. Regarding (c), on the other hand, it can be advantageous to
allow a design that takes into account the degree of
material deterioration.
The structural materials are thick compared with
the core materials, and the operation temperature is
550  C or less. Therefore, the effect of sodium is
lower than it is on the core materials. However,
since the structural materials make up the permanent
structure, the long-term (30 years of more) structural
integrity of the materials has to be estimated

appropriately.
The FBR structure materials are used at high
temperatures under which creep phenomenon will
occur. Therefore, the plant design requires that creep
effects as well as tensile and fatigue strength properties be taken into account. In particular, in the case of
the fuel cladding tubes, internal pressure creep
resulting from the generation of fission product gas
is one of the main failure modes. In the case of the
structural materials, since cyclic stress occurs during
plant start-up/shut-down and creep stress occurs
during operation, creep fatigue, which is determined
by both the creep and fatigue effects, is likely to be
one of the main failure modes.
5.13.5.1

Austenitic Stainless Steel

The creep rupture test results in sodium for the
austenitic stainless steel type 304SS are shown in
Figure 13. The creep strength in sodium is equivalent
to that in air at 650  C or less, and no effect of sodium
on creep strength is observed. The same behavior is
observed in the creep rupture test of material preimmersed in sodium for 20 000 h and the material cut
from the sodium loops operated for 100 000 h.21


Material Performance in Sodium

5.0
Type 304SS

: In sodium
: In air

3.0
2.0
1.0

30

500 ЊC
550 ЊC

0.5

600 ЊC
10
5
101

650 ЊC
102

103
Time to rupture (h)

104

105

Figure 13 Creep strength of type 304SS in sodium.

Reproduced from Yoshida, E.; Aoki, M.; Kato, S.; Wada, Y.
28th Symposium on High Temperature Strength,
The Society of Materials Science: Japan, 1990.

Transgranular

450 ЊC
3.0
2.0
1.0
0.5
550 ЊC
3.0
2.0
1.0
0.5
650 ЊC

Stress (MPa)

500

2ϫ102
650 ЊC

200

700 ЊC

20

102

Intergranular

103
104
105
Number of cycle to failure (cycles)

5ϫ105

Figure 15 Low-cycle fatigue properties of type 304SS in
sodium. Reproduced from Wada, Y. Genshiryoku-kogyo
1990, 36(3); in Japanese.

100
50

Type of surface crack

Material: SUS304
In air
In sodium

Total strain range (%)

Stress (kg mm-2)

100


337

In air
In sodium
103
104
Time to rupture (h)

105

Figure 14 Creep strength of PNC316 in sodium.
Reproduced from Yoshida, E.; Wada, Y. Creep rupture
properties of austenitic stainless steel in elevated
temperature sodium. High Temperature Strength
Committee of the Society of Materials Science, Japan,
1992.

Furthermore, no effect on creep strength in the carburization environment of a bimetallic sodium system
was observed. However, a slight degradation of creep
ductility was observed in the carburization environment. In this case, micro cracks caused by carburization were also observed in the ternary creep region.22
On the other hand, the strength reduction caused by
the dissolution of the alloy elements, including carbon, in sodium was observed at temperatures greater
than 650  C (Figure 14).
The results of the low-cycle fatigue test in sodium
are shown in Figure 15. In the temperature range of
550  C or less used for the structural materials of
FBRs, the strength in sodium is greater than in air.
This can be explained by the distribution behavior
of surface cracks. Many surface microcracks were
observed on the surface of the specimen tested

in air due to the fact that oxides formed by

high-temperature oxidation in air cause the appearance of fatigue cracks. On the other hand, hardly any
microcracks were observed on the in-sodium specimens because of the effect of nonoxidation (reducing
atmosphere) by sodium. This is the equivalent of
fatigue behavior in a vacuum, and showed excellent
strength in the low-strain range in particular. However, the superiority of the fatigue strength in sodium
decreases as temperature increases, and the fatigue
strength in sodium at 650  C is equivalent to that
in air. It is thought that the strength of the grain
boundary decreases due to the fact that the selective
dissolution of the material elements to sodium via
the grain boundary increases as the temperature
increases.23
The major failure mode of the structural materials
in the FBR is creep-fatigue loading. In this case,
creep damage becomes the dominant factor, and the
nucleation and growth of the creep cavity exacerbates the failure. Therefore, it is thought that the
effect of sodium on the failure mode is negligible.
Moreover, it has been reported that the creep fatigue
strength of type 304SS, which produced accelerative
carburization in sodium, is comparable to its strength
in air.24 From these results, it is concluded that the
effect of sodium on mechanical strength is negligible
for austenitic stainless steels.


338

Material Performance in Sodium


5.13.5.2

Ferritic Steels

The corrosion behavior in the sodium of ferritic steel
is fundamentally the same as that of austenitic stainless steel. However, the carbon content in ferritic
steel is high compared with austenitic stainless steel,
and the steel tends to undergo strength reduction by
decarburization.
Figure 16 shows the creep strength of PNC-FMS
steel, which is planned as the core material for the
advanced Japanese FBRs. At 650  C, the strength in
sodium is lower than that in air, and this tendency
becomes more evident when kept for longer periods
of time. Such strength reduction is associated with
the carbon concentration in steel. Therefore, it is
necessary to give the strength reduction coefficient
for the design of the FBRs and to estimate the
strength reduction in sodium conservatively.

5.13.5.3

Others (Ni Base Alloys, ODS)

Nickel base alloys, which have excellent mechanical
strength at high temperature, are used as the liner for
protection from high-cycle fatigue failure caused by
thermal striping near the coolant surface. The corrosion thickness of the nickel base alloy in sodium is
equivalent to that of austenitic stainless steels. However, its tensile and fatigue strength in sodium at

elevated temperatures are lower than in air because
of the nickel’s dissolution to sodium and the formation of an intermetallic compound by thermal aging
in high temperature.25
Oxide dispersion-strengthened (ODS) ferritic
steel is a promising candidate for the fuel cladding
tubes of advanced FBRs. It was reported that the

ODS steel had excellent creep strength in sodium as
well as in air due to the effect of nano-oxide particles
dispersed in the matrix. On the other hand, it was
reported that the nickel, which is dissolved from the
nickel-containing steels in sodium, penetrated to
ODS steel in flowing sodium at elevated temperatures (Figure 17). To apply the steel simultaneously
with the nickel-containing steels, such as austenitic
stainless steel, it is necessary to carefully estimate the
microstructure change by nickel penetration and its
strength reduction.

5.13.6 Damage to Steels with Sodium
Compounds
5.13.6.1

Sodium–Water Reaction

One of the weak points of the present FBRs is the
steam generator, the main component of the power
generation system. When the steam generator tube is
damaged, high-temperature pressurized steam is
blown into sodium, and the following chemical reactions occur:
Na½s;lŠ þ H2 O½gŠ ! NaOH½s;lŠ þ 1=2H2 ½gŠ ½16Š

0
0
ÁHr298
¼ À183:8KJmolÀ1 ; ÁGr298
¼ À150:9KJmolÀ1

2Na½s;lŠ þ H2 O½gŠ ! Na2 O½s;lŠ þ H2 ½gŠ

½17Š

0
0
¼ À172:8KJmolÀ1 ; ÁGr298
¼ À147:2KJmolÀ1
ÁHr298

where [g], [l], and [s] stand for gas, liquid, and solid.
The environment around the failed tube is heated
to high temperature in the aforementioned chemical

Stress (MPa)

600 ЊC
650 ЊC

100
Material: PNC-FMS
In sodium
In air
50

101

102

103

104

Time (h)
Figure 16 Creep strength of PNC-FMS in sodium.
Reproduced from Ito, T.; Yoshida, E.; Kobayashi, T.;
Kimura, S.; Wada, Y. Materials Design Base Standard
Supplement (Tentative) of High Strength Ferritic/Martensitic
Steel (PNC-FMS) Core Components for LMFBR; Research
report of the Japan Atomic Energy Agency, PNC TN9410
93–045; 1993.

Ni and Cr concentration (mass %)

500
20.0
16.0

Immersed condition
4.5 m s–1, 2604 h

Material: ODS
Temperature: 973 K

12.0

Cr
8.0
4.0
Ni
0.0
0

50
100
150
200
250
Distance from sodium exposed surface (μm)

Figure 17 Typical result of Ni diffusion for the ODS steel in
sodium. Reproduced from Yoshida, E.; Kato, S. J. Nucl.
Mater. 2004, 329–333, pp 1393–1397.


Material Performance in Sodium

reactions. Depending on the condition of failure, the
temperature may exceed 1200  C. Furthermore, the
combination of corrosion by the aforementioned
chemical compounds and erosion by the jet blast
causes damage to the steam generator tubes at a significant rate. This damage behavior is called wastage.
Figure 18 shows an example of wastage test results
from Monju safety analysis. The wastage rate of the
steam generator tubes increases as sodium leak rate
increases.

Furthermore, the progression of wastage may
cause an unstable fracture called a high-temperature
rupture. The phenomenon was observed on the
superheater tubes in the Dounreay’s Prototype Fast
Reactor (PFR) in the UK.
5.13.6.2

2Na½s;lŠ þ 1=2 O2 ½gŠ ! Na2 O½s;lŠ

½FeŠ1:75 ¼ kt

½18Š

0
0
ÁHr298
¼ À414:6KJmolÀ1 ; ÁGr298
¼ À147:2KJmolÀ1

2Na½s;lŠ þ O2 ½gŠ ! Na2 O2 ½s;lŠ

½19Š

0
0
ÁHr298
¼ À510:9KJmolÀ1 ; ÁGr298
¼ À447:5KJmolÀ1

Wastage rate (mm s–1)


100

10-1
2.25 Cr–1Mo steel

10-2

10-3

Although sodium peroxide is a thermodynamically
stable oxide in air (P(O2) = 0.21 atm), sodium oxide
usually exists stably due to the reduction effect of
nonburned sodium. The corrosion reaction occurring
in this case is the same as that caused by chemical
reaction with the oxygen dissolved in sodium. The
corrosion is expressed by the formula shown subsequently. Note that the formula shows the maximum
corrosion in the state where the Na2O that is necessary
for the progress of the corrosion is always supplied.
In air, where an excess of moisture is supplied to
the sodium combustion, the corrosion reaction
known as the molten salt type may occur. The corrosion was caused by the peroxide ion in the molten salt
pool composed of NaOH-containing Na2O and
Na2O2.26

Sodium Leak

When high-temperature sodium is leaked into the
atmosphere, it reacts with oxygen, and sodium oxides
are formed by the following chemical reactions:


Austenitic stainless steel

10−1

100
Leak rate (g s–1)

339

½20Š

k ¼ 2:01Â10À1 expðÀ17 100=RT Þ
where [Fe] is the number of reaction moles (mol cmÀ2),
t is the time (h), R is the gas constant, and T is the
temperature (K).

5.13.7 Tribology
5.13.7.1

Self-Welding

Parts of the components in FBRs that come into
contact and rub are the pad part of the fuel assembly,
the contact part between the fuel cladding tubes and
the wrapping wire, the axle hole of the mechanical
pump, the control rod actuator, and the steam generator tube support. In sodium, the oxides of the component surface are reduced with sodium. Therefore,
it is easy for self-welding and frictional wear to
occur.27 Although frictional wear is also observed in
air, self-welding is peculiar to sodium. Therefore,

hard-facing material, such as Co–Cr base alloy
(e.g., Stellite®) and Ni–Cr base alloy (e.g., Colmonoy), is used for such parts to protect against the
tribological phenomena.
The self-welding phenomenon is based on the
diffusion of the metallic elements that occurs
between the contact surfaces of the material. Therefore, the dominant factors in self-welding are temperature, stress, and time.

101

Figure 18 Relationship between leak rate and wastage
rate. Reproduced from Tanabe, H.; Himeno, Y.
Genshiryoku-kogyo 1988, 34(1), 69–76.

5.13.7.2

Frictional Wear

It is important to maintain sodium at a high level
of purity from the viewpoint of the inhibition of


340

Material Performance in Sodium

Dynamic friction coefficient

1.0

Material: Chromium-carbide (LC-1H)

Temperature: 600 ЊC

0.8

3.
4.
5.
6.

0.6
7.

0.4

0.2

8.
9.

0
100

220
140
180
Cold trap temperature (ЊC)

260

Figure 19 Relationship between oxygen concentration in

sodium and friction characteristics. Reproduced from
Yoshida, E.; Hirakawa, Y. In-Sodium tribological study on
cobalt-free hard-facing materials for contact and sliding
parts of FBR components. In Fourth International
Conference on Liquid Metal Engineering and Technology,
Avignon, France, 1988, Vol. 2.

material corrosion. On the other hand, since the
oxides formed on the surface are reduced, frictional
wear is promoted. When the oxygen concentration of
sodium increases, complex sodium oxides and material elements form on the surface. The oxides function as a lubricant, and frictional wear is reduced. For
example, the relationship between the oxygen concentration in sodium and friction characteristics is
shown in Figure 19.
On the other hand, it is known that there is an
intimate relation between frictional wear and material hardness. Under the same operating conditions,
frictional wear decreases as material hardness
increases. Therefore, to control frictional wear, generally, surface-hardening materials are used for the
components of nuclear plants. Co–Cr base alloy,
Ni–Cr base alloy, and chromium carbide are used as
the surface-hardening materials for FBRs.

References

10.
11.

12.

13.


14.
15.

16.
17.

18.

19.

20.

21.
22.

1.

2.

Borgstedt, H. U.; Mathews, C. K. Applied Chemistry of
the Alkali Metals; Plenum Press: New York, 1987;
ISBN 0–306–42326-X.
Stanaway, W. P.; Thompson, R. Solubility of metals, iron
and manganese in sodium. In Proceedings of the 2nd

23.
24.

International Conference on Liquid Metal Engineering and
Technology, Harwell, Oxford, 1980; p 1854.

Claar, T. D. Reactor Technol. 1970, 13(2), 124.
Stanaway, W. P.; Tompson, R. Liquid Metal Systems;
Prenum Press: New York, 1982; p 421.
Iizawa, K. Nucl. Eng. 1987, 33(11), 62.
Eichelberger, R. L. The Solubility of Oxygen in Liquid
Sodium: A Recommended Expression; Atomics
International: Canoga Park, CA, 1968; AI-AEC-12685.
Furukawa, T.; Yoshida, E.; Aoto, K.; Nagae, Y. The hightemperature chemical reaction between sodium oxide
and carbon steel. In Proceedings of the Symposium on
High Temperature Corrosion and Material Chemistry, The
Electrochemical Society, 98–9, San Diego, CA, 1998;
pp 312–323.
Thorley, A. W.; Tyzack, C. Liquid Alkali Metals; BNES:
London, 1973.
Weeks, J. R.; Klamut, C. J.; Gurinsky, D. H. Alkali Metal
Coolants; H M Stationery Office: London, 1967; E C 1,
pp 3–24.
Zebroski, E. L. Liquid Alkali Metals; BNES: London, 1973;
pp 195–211.
Kolster, R. H. Corrosion transport and deposition of
stainless steel in liquid sodium. In Proceedings of the
International Conference on Liquid Metal Technology in
Energy Production, Champion, PA, 1976; p 368.
Bagnall, C.; Jocobs, D. C. Relationship for corrosion of
Type 316 stainless steel in liquid sodium, 1975; WARDNA-3045–23.
Maruyama, A.; Nomura, S.; Kawai, M.; Takani, S.;
Ohta, Y.; Atsumo, H. J. Atomic Energy Soc. Jpn. 1984,
26, 59.
Roy, P. ASME Publ., 74-PWR-19, 1975.
Snyder, R. B. An analysis of carbon transport in the EBR-II

and FFTF primary sodium systems. In Proceedings of the
International Conference on Liquid Metal Technology in
Energy Production, Champion, 1976.
Ito, T.; Kato, S.; Aoki, M.; Yoshida, E.; Kobayashi, T.;
Wada, Y. J. Nucl. Sci. Technol. 1992, 29(4), 367–377.
Wada, Y.; Yoshida, E.; Kobayashi, T.; Aoto, K.
Development of new materials for LMFBR components –
evaluation on mechanical properties of 316FR steel.
International Conference on Fast Reactors and Related
Fuel Cycles, I, Kyoto, Japan, p 7.2.
‘The Tentative Materials Strength Standard of Advanced
Austenitic Stainless Steel (PNC1520) for FBR’s Core
Components’ Research report of the Japan Atomic
Energy Agency; PNC TN9410 90–051; 1990.
Ito, T.; Yoshida, E.; Kobayashi, T.; Kimura, S.; Wada, Y.
Materials Design Base Standard Supplement (Tentative) of
High Strength Ferritic/Martensitic Steel (PNC-FMS) Core
Components for LMFBR, Decrease in Thickness by
Sodium Corrosion, Strength Reduction Factors by
Decarburization and Fatigue Curves; Research report
of the Japan Atomic Energy Agency, PNC ZN9410
93–045; 1993.
Kaito, T.; Mizuta, S.; Uwaba, T.; Ohtsuka, S.; Ukai, S.
The Tentative Materials Strength Standard of ODS Ferritic
Steel Cladding; Research report of the Japan Atomic
Energy Agency, PNC TN9400 2005–015; 2005.
Yoshida, E.; Kato, S.; Wada, Y. Liquid Metal Systems;
Plenum press: New York, 1995.
Yoshida, E.; Aoki, M.; Kato, S.; Wada, Y. In 28th
Symposium on High Temperature Strength; The Society

of Materials Science: Japan, 1990.
Wada, Y. Genshiryoku-kogyo; 1990, 36(3); in Japanese.
Asayama, T.; Kagawa, H.; Komine, R.; Wada, Y. J. Mech.
Behav. Mater. VI 1991, 2.


Material Performance in Sodium
25. Yoshida, E.; Komine, R.; Ueno, F.; Wada, Y. Liquid Metal
Systems; Plenum press: New York, 1995.
26. Aoto, K. In Proceedings of the Symposium on High
Temperature Corrosion and Materials Chemistry, 98–9,
San Diego, CA, 1998; pp 287–298.
27. Yoshida, E.; Hirakawa, Y. In-Sodium tribological study on
cobalt-free hard facing materials for contact and sliding
parts of FBR components. In Fourth International
Conference on Liquid Metal Engineering and Technology,
Avignon, France, 1988, Vol. 2.

28.

29.

30.

341

Materials-oriented Little Thermodynamic Database
for Personal Computers (MALT-2). The Japan
Society of Calorimetry and Thermal Analysis,
1992.

Weeks, J. R. In Proceedings of Symposium on Chemical
Aspects of Corrosion and Mass Transfer in Liquid Sodium,
1971; pp 207–222.
Menken, G. In 2nd International Conference on Liquid
Metal Technology in Energy Production, XIII-2–3,
Richland, WA, 1980.