State of the art on role of nickel and manganese on radiation embrittlement : safelife 2003 - TASK 1.4 deliverable.
Date: 2011-07-07
Institutions: Institute for Energy and Transport
Subjects: Joint Research Centre, energy research, manganese, nickel, nuclear safety, research report

Institute for Energy

State of the Art on
Role of Nickel and Manganese 
on Radiation Embrittlement

Mn

P

Ni

Cu 

SAFELIFE 2003-TASK 1.4 Deliverable

Edited by L. Debarberis, B. Acosta & F. Sevini

EUR 21304 EN

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European Commission
Directorate General Joint Research Centre (DG JRC)
Institute for Energy
Petten
The Netherlands

Contact:
L. Debarberis

B. Acosta

F. Sevini

http://ie.jrc.cec.eu.int/

http://www.jrc.cec.eu.int/

Tel.: +31 (0) 224 56 5130

E-mail: luigi.debarberis@cec.eu.int

Tel.: +31 (0) 224 56 5435

E-mail: beatriz.acosta-iborra@jrc.nl

Tel.: +31 (0) 224 56 5139

E-Mail: filippo.sevini@cec.eu.int

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ã
State of the Art on 

Role of Nickel and Manganese 
on Radiation Embrittlement  

L. Debarberis 
B. Acosta 
F. Sevini 

SAFELIFE 2003 – Task 1.4 Deliverable 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
SOAR on: 

Role of Nickel and Manganese 
on Radiation Embrittlement  

SAFELIFE 2003 – Task 1.4 Deliverable 

L. Debarberis 
B. Acosta, F. Sevini  

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Index 

Background ......................................................................................................................... 1 

1. VVER-1000 embrittlement trends from surveillance, Tacis and other Russian programmes 
data. ..................................................................................................................................... 2 

2. Research data: model alloys............................................................................................ 5 

3. US data on super-clean alloys ......................................................................................... 8 

4. Other data sources ........................................................................................................... 9 

5. Extended analysis of VVER-1000 surveillance data set showing manganese effect ... 10 

6. PWR materials: Hints on Nickel-Manganese effect ..................................................... 18 

7. ATHENA view.............................................................................................................. 19 

8. Micro-structural/NDT methods additional information ................................................ 20 

9. Conclusions & reccommendations................................................................................ 23 

References ......................................................................................................................... 25 

ANNEX I – Summary of R.Nanstad presentation at high Ni CRP................................... 26 

ANNEX II ATHENA Workshop Relevant presentations................................................. 33 

Figure 1 DBTT shift as a function of fluence for steels with a Ni content of 1.2 wt.% 
2 
Figure 2 DBTT shift as a function of fluence for steels with a Ni content of 1.7 wt.% 
3 
Figure 3 Embrittlement trends for Ni = 1.2 wt %, Ni = 1.7 wt % and Russian guide 
3 
Figure 4 Comparison simplified model and Russian guide trends 
4 
Figure 5 Influence of Ni and P in low and middle Cu model alloys 
6 
Figure 6 DBTT shifts versus Russian Guide chemistry factor 
7 
8 
Figure 7 US “super clean” high Ni steels 
Figure 8 Observed temperature transition shifts as a function of fluence. All analysed data sets
12 
13 
Figure 9 Observed DBTT shifts for Ni=1.7 wt.% and medium Mn content 
13 
Figure 10 Observed DBTT shifts for Ni=1.88 wt.% and high Mn content 
Figure 11 Observed DBTT shifts for Ni=1.76 wt.% and high Mn content 
13 
Figure 12 Transition temperature shifts; measured versus calculated. For all studied RPVs  14 
15 
Figure 13 Transition temperature shifts; measured versus calculated for a sub-set of data 
16 
Figure 14 Average CF versus manganese content 
18 
Figure 15 Effect of nickel on PWR materials embrittlement 
18 
Figure 16 Manganese effect in high Ni PWR materials 
19 
Figure 17 ATHENA view of mechanistic framework 
Figure 18 RSC as function on Ni at two different Cu levels 
20 
Figure 19 RSC as function on Ni, before and after irradiation, initial Cu content  ≈0.1 wt.% or 
21 
Figure 20 RSC as function on Ni, before and after irradiation, initial Cu content = 0.4 wt%  22 
23 
Figure 21 Role of Mn in Ni steels 

lower 

 
 
 
 
 
Acronyms 

AMES: 

Ageing Material European Strategy 

ATHENA:  AMES Thematic Network on Ageing 

CF: 

Chemistry factor 

DBTT: 

Ductile to brittle transition temperature 

DPA: 

EOL: 

HFR: 

Displacement per atom 

End of Life 

High Flux Reactor 

IAEA: 

International Atomic Energy Agency 

JRC: 

LWR 

NDT: 

NPP: 

Joint Research Centre 

Light Water Reactor 

Non-destructive Testing 

Nuclear Power Plant 

ORNL:  Oak Ridge National Laboratory (US) 

PWR: 

Pressurized Water Reactor 

RPV: 

Reactor Pressure Vessel 

RRC-KI:  Russian Research Center “Kurchatov Institute” 

TACIS: 

Technical Assistance to Commonwealth of Independent States 

VVER:  Water Water Power Reactor (Russian type) 

wt.: 

weight 

 
 
 
 
 
 
SOAR on Role of Ni and Mn on radiation embrittlement 

BACKGROUND 

The fact that embrittlement of phosphorus – copper “clean” steels, such are those 
used for the last generation of VVER RPV’s, is enhanced by nickel is very well known 
since several years. Results from surveillance programmes, those obtained in TACIS 
projects,  research  data  and  results  of  model  alloys  programmes  confirm  such 
conclusions up to end of life (EOL) VVER-1000 fluences [1]. 

Only  recently,  the  role  of  manganese  in  embrittling  high  Ni  steels  and  welds  has 
been  identified  clearly.  It  is  observed  that  embrittlement  of  Ni  steel/welds  increases 
dramatically if Mn content is above a certain threshold (≈0.9 wt.%). 

Nickel or nickel-manganese mechanisms on irradiation embrittlement of steels and 
welds is an issue requiring further studies; especially when considering the practical 
relevance  of  the  issue.  In  fact,  several  LWR  vessel  rings/shells  happens  to  be  in  a 
critical range of Ni-Mn contents. 

In  this  state-of-the-art  (SOAR)  report  the  available  information  on  the  issue  is 
collected  and  commented,  and  preliminary  conclusions  and  recommendations  are 
drawn.  

 
 
 
 
 
 
 
 
 
 
 
 
 
 
1. VVER-1000 EMBRITTLEMENT TRENDS FROM SURVEILLANCE, TACIS AND 
OTHER RUSSIAN PROGRAMMES DATA.  

The  data  matrix  used  for  this  study  is  composed  by  selected  VVER-1000 
surveillance data, TACIS results and Russian Research Centre – Kurchatov Institute 
(RRC-KI) results, containing two nickel content levels: 1.2 wt.% and 1.7 wt.%. 

Available  data  on  radiation  embrittlement  with  nickel  content  of  1.2  wt.%  are 
plotted  in  the  Figure  1;  in  which  yellow  squares  represent  RRC-KI’s  research  data, 
open  squares  are  results  from  TACIS  programmes  and  black  squares  come  from 
surveillance data. For comparison the “Russian Trend Curve” given by the PNAE G7-
002-86  code  [2]  for  a  CF  =  20  have  been  also  plotted.  As  can  be  seen  all 
experimental data fall below Guide curve. 

Ni ~ 1.2 wt%

C
°

,
t
f
i

h
s
T
T
B
D

120
100
80
60
40
20
0

ED-3

TAC-2

SS NV-5 Z-2

Guide Curve
CF=20

0

50

100

150

200

Fluence, 1018 n cm-2 (E>0.5 MeV)

Figure 1 DBTT shift as a function of fluence for steels with a Ni content of 1.2 wt.% 

Data on radiation embrittlement for nickel ≈1.7 wt.% and the Guide curve for CF = 
20 can be seen in the Figure 2. All data at fluences below design life are falling below 
Guide curve.  

2

 
 
 
 
 
 
 
 
 
Ni ~ 1.7 wt%

TAC-3

TAC-4

SS SU-1 R-3

Guide Curve
CF=20

C
°

,
t
f
i
h
s
T
T
B
D

160
140
120
100
80
60
40
20
0

0

50

100

150

Fluence, 1018 n cm-2 (E>0.5 MeV)

Figure 2 DBTT shift as a function of fluence for steels with a Ni content of 1.7 wt.% 

A summary of all data together with their respective trends is given in the Figure 3. 
It  can  be  observed  that  trends  are  slightly  different  than  the  Russian  guide  curve; 
showing  for  the  case  of  high  Ni  content  (1.7  wt.%)  higher  DBTT  shifts  than  these 
predicted by the guide. 

C
°

,
t
f
i

h
s
T
T
B
D

160

140

120

100

80

60

40

20

0

0

30

60

150
Fluence, 1018 n cm-2 (E>0.5 MeV)

120

90

TAC-3

TAC-4

SS SU-1 R-3

Ni=1.7 wt%

ED-3

TAC-2

SS NV-5 Z2

Ni=1.2 wt%

CF=20

180

Figure 3 Embrittlement trends for Ni = 1.2 wt %, Ni = 1.7 wt % and Russian guide 

3

 
 
 
 
 
 
 
 
 
 
As  it  is  observed  the  Russian  prediction  curve  given  by  the  PNAE  G7-002-86 
code,  is  not  always  conservative  for  accumulated  fluences  beyond  the  presently 
considered design life fluence for VVER-1000 (5⋅1019 n cm-2). The displayed trend is 
more  complex  than  a  power  function,  and  therefore  more  elaborated  function  is 
required in order to fit the data. As an example a ‘simplified model’ is chosen. 

The ‘simplified model’ is based on the assumption that for low fluences the usual 
1/3  power  applied  to  the  fluence  follows  relatively  well  the  data  points  and  a  linear 
dependence  with  fluence  is  observed  at  higher  fluences.  Simplified  model  and 
Russian guide predictions are summarized in Figure 4: 

C
°

,
t
f
i

h
s
T
T
B
D

160

140

120

100

80

60

40

20

0

high Nickel

Ni=1.7 wt%

Ni=1.2 wt%

CF=20

low Nickel

0

30

60

90

120

150

180

Fluence, 1018 n cm-2 (E>0.5 MeV)

Figure 4 Comparison simplified model and Russian guide trends 

From Figure 4 it is noted that the nickel effect is extremely clear for the data sets: 
embrittlement  increases  up  to  a  certain  level  with  fluence.  During  the  subsequent 
phase, embrittlement saturates or grows very slowly. After that the embrittlement re-
starts to increase faster that in the initial phase (almost linearly with fluence). 

4

 
 
 
 
 
 
 
 
 
 
 
2. RESEARCH DATA: MODEL ALLOYS 

In  order  to  understand  the  influence  of  copper,  phosphorus,  nickel  and  others 
elements on steel embrittlement, RPV model alloys have been studied at JRC-IE. 32 
different model alloys with parametric variation of elements (Ni from 0.004 to ≈2 wt%, 
P from 0.001 to 0.039 wt%, Cu from 0.005 to ≈1 wt%) have been used for the study. 
Such  study  on  model  alloys  reveals  to  be  a  fundamental  tool  to  understand  the 
individual role of each element and synergisms. 

The model alloys have been offered by RRC-KI. As it can be seen in Table 1, the 
adopted model alloy matrix is covering several conditions typical of different reactor 
systems.  These  model  alloys  were  machined  as  miniaturised  Charpy  specimens 
(4×3×27.5 mm). Material in “as received” condition has been tested with a 50 Joule 
Impact hammer at JRC Petten. Afterwards model alloys were irradiated in the HFR of 
Petten  using  the  LYRA  facility.  The  average  temperature  during  the  irradiation  was 
270 °C and the accumulated dose in the samples was 0.0082 DPA (≈ 5.53⋅1022 nm-2, 
E>1 MeV). 

The  testing  of  the  32  sets  of  irradiated  samples  was  carried  out  at  VTT  Finnish 
Research  Laboratories.  The  Charpy  impact  curve,  and  therefore  the  transition 
temperature  and  the  upper  shelf  energy,  have  been  calculated  for  all  the  model 
alloys. Very clear transition temperature shifts are measured, enabling the analysis of 
the results in order to recognize the effect of Cu, Ni and P. 

Table 1 Model alloys Ni, Cu and P contents  

Remarks 

Content levels typical of 
VVER-440 and Magnox 

Content levels typical of western 
PWR 

Content levels typical of 
VVER-1000 
base metal and part of welds 
& some PWR 

Content levels typical of VVER-1000 
part of welds 

Ni 
wt% 

~0.01 

~0.21 

~0.75 

Cu 
wt% 

~0.005 
~0.11 
~0.42 
~1.05 
~0.007 
~0.11 
~0.007 
~0.11 

~0.43 

~0.006 

~1.25 

~0.12 

~0.43 
~0.006 
~0.13 
~0.44 

~2 

P 
wt% 

~0.002, ~0.014, ~0.041 
~0.004, ~0.013, ~0.039 
~0.003, ~0.012, ~0.033 
~0.003, ~0.013, ~0.039 
~0.004 
~0.004, ~0.039 
~0.004 
~0.013, ~0.039 
~0.004 
~0.013 
~0.004 
~0.004 
~0.012 
~0.038 
~0.003, ~0.012 
~0.003 
~0.003, ~0.011, ~0.038 
~0.004, ~0.012, ~0.041 

5

 
 
 
 
 
 
 
The  experimental  results  obtained  are  consistent  with  previous  studies:  for 
increasing levels of content of the key elements the DBTT shifts are increasing, as it 
is described in references [3] and [4].  

•  The  effect  of  nickel  is  always  very  clear  and  some  synergism  with  phosphorus 
and  copper  contents  can  be  observed.  For  each  level  of  nickel  content,  the 
combined effect of copper and phosphorus to increase the transition temperature 
shift is clearly and consistently visible. The influence of Ni for low and middle Cu 
alloys  seems  to  become  even  more  marked  for  Ni  contents  above  ≈1.2  wt.%, 
which  is  in  agreement  with  data  obtained  on  VVER  commercial  steels. 
Phosphorus plays a clear role in further increase DBTT shifts; see Figure 5. 

•  The low phosphorus data sets are showing a clear detrimental effect of nickel in 
the material properties, but after a certain Ni concentration level the DBTT ceases 
to  increase.  These  results  obtained  on  model  alloys  support  the  embrittlement 
models based on the assumption that nickel is influencing steel embrittlement by 
in fact increasing phosphorus effects like diffusion and segregation. 

•  The influence of copper is always clearly observed as a constant increase of the 
DBTT  shifts,  especially  for  the  high  to  very  high  Cu  contents  sets.  The  effect  of 
copper  is  visible  from  a  threshold  level  of  approximately  0,1  wt.%.  This  is  in 
agreement with observations on commercial steels. 

•  No information can be drawn on manganese effect since its content in the model 

alloys was constant, in the order of ≈ 0.5 wt.%. 

HFR Irradiated Model Alloys
Cu 0.1-0.4 wt%

C
°

,
t
f
i

h
s

T
T
B
D

250
200
150
100
50
0
0.000

P 0.003 - 0.037 w t%

"P ~0.001 w t%"

2.000

4.000

Ni, wt%

Figure 5 Influence of Ni and P in low and middle Cu model alloys 

6

 
 
 
 
 
 
Figure  6  shows  the  obtained  shifts  in  DBTT  for  all  the  model  alloys  sets  plotted 
versus the chemistry factor used in the Russian Trend Curve given by the PNAE G7-
002-86 code. 

All data sets

300

250

200

150

100

50

C
D

,

I

T
F
H
S
T
T
B
D

0

0

Very Low Nickel

Medium Nickel

High Nickel

Very High Nickel

Linear (Very Low
Nickel)

Log. (Very High
Nickel)

20

40

60

80

100

800(P+0.07Cu)

Figure 6 DBTT shifts versus Russian Guide chemistry factor 

The  low  nickel  data  shifts  are  very  well  correlated  with  the  chemistry  factor 
(containing  only  Cu  and  P),  which  was  designed  for  VVER  440  type  reactor  steels 
with  low  Ni  content.  The  good  correlation  indicates  that  the  model  alloys  are 
behaving in a very similar manner to commercial steels in the case of low Ni [5]. For 
higher  nickel  levels  (in  the  range  of  VVER-1000)  the  shifts  are  proportionally  larger 
and, as expected, the correlation is not good anymore, clearly indicating the need to 
include the nickel content in the chemistry factor. 

7

 
 
 
 
 
 
 
 
 
 
 
 
 
3. US DATA ON SUPER-CLEAN ALLOYS 

Data obtained in US on a special set of high Ni steels have been presented at the 

ATHENA workshop held in Madrid in 2002, and are summarised in the Annex 1.  

The  above-mentioned  ‘super  clean  steels‘  have  high  nickel  content,  but  are 
practically  phosphorus  free  and  with  Cu  contents  in  the  order  of  100  ppm.  Also 
manganese content is very low, less than the 0.3 wt.%. 

It can be seen in the Figure 7 that this steel are showing, in spite of very high Ni 

contents, a very low sensitivity to radiation damage. 

USA data on 'super clean' high Ni steels
Mn < 0.3 wt%, at 11-18 mdpa

C
°

,
t
f
i

h
s

T
T
B
D

100
80
60
40
20
0

0

1

2

3

4

5

Ni, wt%

Figure 7 US “super clean” high Ni steels 

The  obtained  results  lead  to  the  conclusion  that  nickel  alone  is  not  necessarily  a 
source  of  material  sensitivity  to  embrittlement.  However  these  results  support  the 
assumption that in steels containing higher level of impurities and alloying elements, 
nickel enhances their detrimental effects. 

8

 
 
 
 
 
 
 
 
 
 
4. OTHER DATA SOURCES 

Data  analysis  of  some  specific  VVER-1000  surveillance  results,  research  model 
alloys  and  US  super  clean  alloys  is  shown  in  the  precedent  chapters.  However  to 
carry  out  an  extensive  study  on  the  role  of  elements  like  nickel  and  manganese  in 
material  embrittlement  it  is  required  the  analysis  of  a  wide-range  of  materials  (and 
irradiation conditions) or large databases. 

Important information is available, for example, in: 

• 

IAEA “International database on Nuclear Power Plant life Management” 

•  Results form TACIS projects 

•  Results from PHARE project 

•  US Nuclear Regulatory Commission Reactor Vessel Integrity Database 

Use of the above-mentioned information, as for example surveillance results from 
PWR, VVER-440 and VVER-1000 reactors, will be of great help in the development 
of comprehensive studies on materials embrittlement.  

9

 
 
 
 
 
5. EXTENDED ANALYSIS OF VVER-1000 SURVEILLANCE DATA SET SHOWING 
MANGANESE EFFECT 

Up  to  now  20  surveillance  specimen  sets  of  14  VVER-1000  Reactor  Pressure 
Vessel  (RPV)  have  been  evaluated  in  Russia,  Ukraine  and  Bulgaria  by  different 
testing organizations: 

•  Kurchatov Institute, Russia – (10 RPVs) 

• 

• 

Institute for Nuclear Research, Ukraine – (2 RPVs) 

Institute of Metal Science, Bulgaria – (2 RPVs) 

The  extended  analysis  presented  here  is  based  on  the  testing  results  of  17  sets 
from  the  surveillance  programmes.  The  materials  involved  contain  very  low  and 
homogeneous  levels  of  phosphorus  and  copper  and  a  significant  variation  of  nickel 
and other elements like manganese. 

The observed ductile to brittle transition temperature shifts are showing consistent 

behaviour: 

•  The materials with low nickel content are embrittling at a much lower rate than 

the one predicted by the Russian Guide (using a chemistry factor = 20) 

•  The  Guide  looks  to  be  conservative  also  for  the  higher  nickel  steels  if  the 

content of Manganese is lower than 0.8 wt.%. 

•  The materials embrittling at much higher rates are those with both high nickel 
and manganese contents. The threshold for nickel is evaluated to be at Ni ≈1.2 
wt.% and for manganese at Mn ≈0.8 wt.%. 

Manganese,  together  with  nickel,  seems  to  play  a  key  role  in  radiation 

embrittlement of low Cu and P steels.  

10

 
 
 
 
 
 
5.1 Materials 

The  materials  involved  in  this  analysis  are  given  in  Table  2  together  with  their 
nominal  compositions.  Actual  specific  NPP  material  composition  differs  significantly 
from the nominal, and actual composition is used for this extended analysis. 

A  high  level  of  nickel  is  present  in  both  the  base  metal  and  particularly  the  weld 
material. On the contrary, the contents of P and Cu are very low; so low that these 
two elements do not play significant role in neutron embrittlement. 

Table 2 VVER 1000 Materials 

Material 

Nimax 

Pmax 
% 

Cumax 

CFmax 

Remarks 

15Ch2NMF (AA) 

1.4 

0.010 

0.07 

15Ch2NMF (A) 

1.4 

0.010 

0.17 

08ChGNMTA 

1.3 

0.014 

0.08 

23 

29 

20 

10ChGNMAA 

1.9 

0.014 

0.08 

20 (*) 

All RPVs 
except 3 

3 RPVs 

~20 % RPV 
welds 
~80 % RPV 
welds 

(*) according to actual analysis this value could be up to 34 

Based on the chemistry factor provided by the Russian Guide PNAE, CFmax (see 

Table 2) it is evident that the critical materials are: 

•  Welds 10ChGNMAA and 

•  Base metal 15Ch2NMFA 

which need to be more carefully investigated. 

The  observed  temperature  shifts  for  all  considered  surveillance  sets  have  been 
analysed  as  a  function  of  fluence.  As  expected,  for  such  a  low  level  in  P  and  Cu 
contents (P=0.005-0.010 wt.%, Cu=0.03 - 0.08 wt.%) no significant role of P and Cu 
is observed. 

All  results  together  are  shown  in  Figure  8.  On  the  same  figure,  a  trend  curve 

according to the Russian Guide with CF = 20 is also drawn. 

11

 
 
 
 
 
 
 
 
90

80

70

60

50

40

30

20

10

0

High Ni - High Mn

High Ni - Medium Mn

Low Ni

Guide, CF=20

C
°

,

l

e
u
a
v

t
f
i
h
S

0

10

20

30

fluence value, 1018 n cm-2 (E>0.5 MeV)

Figure 8 Observed temperature transition shifts as a function of fluence. 
All analysed data sets 

Data have been sub-divided into three groups. As can be seen, all steels with low 
nickel  content  embrittle  at  a  much  lower  rate  than  the  predicted  by  the  Russian 
Guide, which in this is case very conservative. It is also conservative for the higher 
nickel steels provided that the content of manganese is low. 

The  steels  embrittling  at  much  higher  rates  are  those  with  both  high  nickel  and 
manganese  contents.  For  this  effect  it  is  found  that  the  threshold  value  for  nickel 
content is Ni≈1.2 wt.%, whereas the threshold for manganese level is ≈0.9 wt.%. 

Other elements could play a role in combination with Ni and Mn; including C, Si, S, 
etc.  The  above-mentioned  observations  are  in  agreement  with  recent  findings.  Mn 
and  Ni  are  elements  that  become  non-randomly  distributed  and  co-segregated  in 
welds with high Ni and low Cu. 

5.2 Examples of the detailed data analysis 

In  Figures  9,  10  and  11,  the  results  for  specific  NPP  steels  containing  Ni  =  1.7, 
1.88 and 1.76 wt.% respectively are given. The data shown in Figure 9 are for steel 
containing low level of manganese, (Mn < 0.8 wt.%); while the data in Figure 10 and 
Figure 11 are for higher Mn contents. 

12

 
 
 
 
 
 
 
 
C
°

,
e
u
l
a
v

t
f
i
h
S

70

60

50

40

30

20

10

0

0

5

NPP data

CF=11

Guide, 
CF=20

35

10

20
fluence value, 1018 n cm-2 (E>0.5 MeV)

30

15

25

Figure 9 Observed DBTT shifts for Ni=1.7 wt.% and medium Mn content 

C
°

,
t
f
i
h
s
d
e
r
u
s
a
e
M

100

90

80

70

60

50

40

30

20

10

0

Surveillance data

CF=30

Guide, CF=20

20
0
fluence value, 1018 n cm-2 (E>0.5 MeV)

10

30

40

Figure 10 Observed DBTT shifts for Ni=1.88 wt.% and high Mn content 

C
°

,
t
f
i
h
s
d
e
r
u
s
a
e
M

120

100

80

60

40

20

0

Surveillance data

CF=34

Guide, CF=20

40

20
0
fluence value, 1018 n cm-2 (E>0.5 MeV)

30

10

Figure 11 Observed DBTT shifts for Ni=1.76 wt.% and high Mn content 

13

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
It is very clear, independently of some uncertainties on the data, that the values for 

each individual material composition are quite consistent: 

•  Most  of  the  values  for  the  same  material  still  follow  the  1/3  power  function  of 

the fluence in spite of some uncertainty in fluence determination itself.  

•  The  differences  in  nickel  and  manganese  contents  can  explain  the  large 

difference in sensitivity to embrittlement.  

•  The  content  of  other  elements,  like  residual  S,  C,  Si  etc,  could  even  explain 

some minor deviations from the general trend.  

The data sets have been studied by using statistical correlation analysis, taking Ni 
and Mn as variables and a 1/3-power dependence on neutron fluence, in the form of:  

DBTT

Shift

(
a
⋅=

Ni

b
⋅+

cMn
+

)

Φ∗

31

(1) 

where a, b and c are fitting coefficients (a= 21.037, b=29.453 and c=-39.191). Ni and 
Mn  are  respectively  the  contents  in  wt.%  of  nickel  and  manganese,  and  Φ  is  the 
accumulated neutron fluence (E>0.5 MeV).  

The results are shown in Figure 12. All data sets are nicely aligned to the diagonal 

of the plot, and most of them fall within a scatter band of just 20 °C.  

C
°

,
t
f
i
h
s
d
e
r
u
s
a
e
M

100

90
80

70
60

50

40
30

20
10

0

0

20

40

60

80

1

00

Calculated shift, °C  

Figure 12 Transition temperature shifts; measured versus calculated. 
For all studied RPVs 

14

 
 
 
 
 
 
 
 
 
 
 
 
The  result  is  impressive  considering  the  various  uncertainties  in  the  analysis; 
scatter  in  fluence  values,  different  data  treatment  between  laboratories,  different 
content  of  elements  like  sulphur  and  carbon  and  different  alloying  elements.  Such 
data,  when  properly  known,  can  be  considered  for  more  advanced  predictive 
correlations.  

Just as example, we considered the content of S in the steel and the results are 
shown in Figure 13 for a sub-set of data. In comparison with the previous regression 
the scatter band is reduced form 25 °C to 15 °C. 

Measured vs Calculated for High Ni - Mn

C
°

,
t
f
i
h
s
d
e
r
u
s
a
e
M

100
90
80
70
60
50
40
30
20
10
0

0

20

40

60

80

10

0

Calculated shift, °C  

Figure 13 Transition temperature shifts; 
measured versus calculated for a sub-set of data 

Looking  back  more  carefully  to  the  results  obtained  with  Eq.1,  we  observe  in 
particular the fact that for such regression required a relatively large negative value 
for  the  parameter  c  in  order  to  give  reasonable  results.  The  logical  explanation  of 
such large negative parameter has to be found on the fact that both Ni and Mn have 
a  relatively  high  threshold  values  for  their  effects.  In  fact,  to  show  this,  we  could 
better re-write Eq.1 as  

DBTTshift

=

[
1a

⋅

(
Mn

−

Mn

threshold

)

+

1b

⋅

(

Ni

−

Ni

threshold

]
)

Φ∗

31

(2) 

15

 
 
 
 
 
 
 
 
 
 
 
The observed average chemistry factor CF for steels with high nickel content has 
also been calculated and is given in Figure 14 as a function of Mn. Clearly values of 
CF higher than 20 (up to 30 and more) are observed for Mn contents higher than ≈ 
0.9 wt.%. 

60

50

40

30

20

10

F
C
e
g
a
r
e
v
A

0

0

Ni between 1.6 to 1.9 wt%

0.5

1

1.5

2

Mn, wt%

Figure 14 Average CF versus manganese content 

16

 
 
 
 
 
 
 
 
5.3 Discussion 

The presented analysis is based on the results of 17 surveillance programmes of 
14  VVER-1000  RPV  tested  in  Russia,  Ukraine  and  Bulgaria.  The  steels  involved 
contain  very  low  quantities  of  phosphorus  and  copper,  but  they  have  a  significant 
variation of nickel and other elements such as manganese. 

Based on the above-mentioned results, a key to understanding VVER-1000 steel 

embrittlement is found in spite of the uncertainties in the surveillance data set: 

a)  Manganese,  and  possibly  other  elements,  in  combination  with  the  nickel  are 

playing a significant role in the embrittlement of low Cu and P steels. 

b)  The  observed  temperature  transition  shifts  exhibit  a  coherent  behaviour:  Steels 
with  low  nickel  content  embrittle  at  a  much  lower  rate  than  the  predicted  by  the 
Russian  PNAE  code  when  a  chemistry  factor  equals  to  20  is  used.  Also  the 
Russian  code  is  conservative  in  the  case  of  steel  with  high  Ni  if  the  content  of 
manganese  is  medium.  On  the  contrary  the  steels  embrittling  at  much  higher 
rates are those with high Ni and high Mn contents at the same time. 

Correlation analysis, considering Ni and Mn and fluence dependence to 1/3 power, 
shows predictive capabilities within 20 °C scatter band in most cases. The influence 
of  other  elements,  for  example  carbon  and  sulphur,  could  also  explain  the  residual 
scatter in the data.  

-  Nickel is contributing to neutron embrittlement. If the content of other impurities is 
relatively low (VVER-1000 last generation steels), Ni is practically controlling the 
rate  of  embrittlement.  It  appears  that  it  acts  indirectly  by  increasing  effects  of 
other  impurities.  Ni  threshold  for  strong  effects  is  estimated  at  ≈  1.2  wt.%  in 
VVER type steels. 

-  Manganese,  as  Ni,  is  contributing  to  neutron  embrittlement.  If  Mn  contents  are 
low in comparison with the Ni contents, then Ni masks the effect. Threshold for 
manganese is estimated at ≈ 0.9 wt.% for VVER-1000 materials. 

Further  study  needs  to  be  done  in  order  to  build  more  precise  predictive 

correlations and update the Russian Guide’s embrittlement trend curve. 

Important  results  are  also  expected  from  the  recently  launched  TACIS  –TAREG 

projects. 

17

 
 
 
 
 
 
 
 
6. PWR MATERIALS: HINTS ON NICKEL-MANGANESE EFFECT 

Studying  the  available  data  of  suitable  PWR  materials  additional  conclusions  on 
embrittlement effect due to Ni and Ni-Mn can also be drawn. The obtained results are 
consistent with the results found on VVER materials as it can be seen for example in 
Figure 15. 

250

200

150

100

50

C
o
,
t
f
i
h
s
T
T
B
D

0

0

PWR

high Ni

low  Ni

2

4

6

8

Fluence, 1019 n cm -2 (E>1 MeV)

Figure 15 Effect of nickel on PWR materials embrittlement 

Higher  Ni  contents  increase  sensitivity  to  radiation.  Indications  that  higher  Mn 
contents further increase such sensitivity are also evident. As it can be seen in Figure 
16  for  high  nickel  materials  with  a  manganese  content  of  about  1.4  wt.  %  the 
embrittlement  trend  is  faster,  resulting  higher  DBTT  shift  at  relative  lower  fluences, 
than for materials with Mn ≈0.7 wt.%. More studies are ongoing to clarify and quantify 
such effects. 

High Ni data

Mn 0.7

Mn 1.4

C
o

,
t
f
i

h
s

T
T
B
D

250

200

150

100

50

0

0

5

10

15

20

Fluence, 1019 n cm-2 (E>1MeV)

Figure 16 Manganese effect in high Ni PWR materials 

18

 
 
 
 
 
 
 
 
 
 
 
 
7. ATHENA VIEW 

The AMES Thematic Network on Ageing (ATHENA) is a Task Force designed to 
carry  out  key  strategic  tasks  identified  by  the  AMES  European  Network  Steering 
Committee  as  being  of  interest  to  the  Plant  Life  Management  of  eastern  PWR  and 
VVER  Nuclear  Power  Plants.  Work-package  5  aims  to  improve  understanding  of 
radiation embrittlement mechanisms and the steel’s response to neutron radiation. 

Six elements of the mechanistic framework for embrittlement have been identified 

as given in the following figure: 

Figure 17 ATHENA view of mechanistic framework 

The  work-package  members  have  discussed;  key  data  were  presented  and/or 
reviewed  and  a  plenary  discussion  complemented  with  the  available  knowledge. 
Significant  interdependencies  exist  between  the  elements  of  the  above  mechanistic 
framework. More information can be found in the ANNEX 2. 

This report includes the ATHENA group’s key conclusions about Ni/Ni-Mn effects. 

19

 
 
 
 
 
 
8. MICRO-STRUCTURAL/NDT METHODS ADDITIONAL INFORMATION 

Not  much  information  from  microstructurel  and/or  non-destructive  evaluation  is 
available  in  EU  to  properly  support  explanation(s)  on  the  role  of  nickel  and 
manganese on irradiation embrittlement. However some research on the field using 
novel non-destructive methods have been carried out. 

At the JRC-IE measurement of thermoelectric voltage using a specially developed 
non-destructive method to assess the degree of embrittlement id regularly performed. 
The  method,  named  STEAM,  is  based  on  the  measurement  of  the  thermoelectric 
voltage generated by the Seebeck and Thomson effects taking place in the material. 
These are described by the so termed Relative Seebeck Coefficient (RSC), which is 
characteristic  of 
its  chemical  composition  and 
microstructural arrangement. 

the  material  and  related 

to 

Relative  Seebeck  Coefficient  (RSC)  measurements  on  the  selected  model  alloys 
(nickel  content  ranging  from  0.7  to  2  wt.%  and  different  copper  concentrations,  see 
§2)  have  been  performed  on  both  as-received  and  HFR  irradiated  specimens.  The 
results, as already shown in several papers [6], are very promising for the scope of 
developing  non-destructive  radiation  embrittlement  monitoring  methods.  They  are 
also very interesting from the point of view of mechanism understanding, in particular 
for the study of copper precipitation kinetics in nickel containing alloys [7]. 

It is observed that for “as received” alloys, before irradiation, a clear dependence 

of the RSC on the Ni content exists for a given Cu content, as shown in Figure 18. 

Alloys with Ni between 0.2 and 2 wt.%

C
o
V
µ

/

,

C
S
R

7.00

6.00

5.00

4.00

3.00

2.00

1.00

0.00

R2 = 0.9843

R2 = 0.911

M-L Cu

H CU

0.000

0.500

1.000

1.500

2.000

2.500

Ni, wt. %

H Cu =~ 0.4 wt%, M-L Cu = ~0.1 wt% 

Figure 18 RSC as function on Ni at two different Cu levels 

20

 
 
 
 
 
 
 
According  to  the  mechanistic  models,  Cu  concentration  in  matrix  is  expected  to 
decrease  during  irradiation,  thus  increasing  the  value  of  the  RSC.  This  is  in  fact 
observed in experimental results obtained by testing the same alloys after irradiation 
in the HFR. The effect is particularly clear for alloys with high initial copper content. 

From  the  obtained  results  it  is  deduced  that  phosphorus  content  does  not 
influence  the  value  of  the  RSC  for  the  irradiated  alloys.  In  fact,  alloys  with  smaller 
amounts  of  copper  (0.1  wt.%  or  less)  are  showing  little  or  no  variation  of  the  RSC 
value  due  to  irradiation  (see  Figure  19)  in  spite  of  relatively  large  DBTT  shifts, 
attributed to P segregation. By mean of measuring the thermoelectric voltage it does 
not seem to be possible to establish the embrittlement contribution due to P. 

Alloys with Ni between 0.7 and 2 wt.%

Fresh

Irradiated

C
o

/

V
µ

,

C
S
R

7.00

6.00

5.00

4.00

3.00

2.00

1.00

0.00

0.000

0.500

1.000

1.500

2.000

2.500

Ni, wt.%

Figure 19 RSC as function on Ni, before and after irradiation, 
initial Cu content  ≈0.1 wt.% or lower 

As it can be seen in Figure 20, the RSC values for the high Cu alloys (≈0.4 wt.%) 
consistently  increase  after  irradiation,  approaching  the  values  of  the  un-irradiated 
alloys  with  ≈0.1  wt.%  Cu.  As  expected,  the  largest  DBTT  shifts  were  found  for  the 
alloys with a high copper content, and on the contrary alloys with smaller amounts of 
copper (0.1 wt.% or less) are showing little or no variation of the RSC value due to 
irradiation. 

It  is  also  noticed  that  larger  variations  of  RSC  for  the  same  copper  content  take 
place for higher Ni contents, as Figure 20 shows, whereas phosphorus content does 
not influence the value of the RSC for the irradiated alloys. 

This  can  be  explained  by  the  fact  that  further  decrease  of  Cu  content  below  a 
certain threshold in concentration does not affect the RSC value significantly. For the 
analysed sets of model alloys such threshold occurs at ≈0.08 wt.% Cu. 

21

 
 
 
 
 
 
 
 
Alloys with Ni between 0.7 and 2 wt.%

R2 = 0.9642

Fresh

Irradiated

R2 = 0.9843

C
o

/

V
µ

,

C
S
R

5.00

4.50

4.00

3.50

3.00

2.50

2.00

1.50

1.00

0.50

0.00

0.000

0.500

1.000

1.500

2.000

2.500

Ni, wt.%

Figure 20 RSC as function on Ni, before and after irradiation, 
initial Cu content = 0.4 wt% 

Above this threshold, for high nickel alloys, the changes in RSC are correlated with 
the  decrease  of  copper  available  in  the  matrix,  hence  following  Cu  precipitation 
effects. 

From the above analyses the main conclusions that can be drawn are: 

•  RSC  measures  radiation  embrittlement  indirectly  by  measuring  the  decrease  of 

Cu available in matrix for precipitation. 

•  Below  a  certain  threshold,  Cu  ≈0.08  %  wt,  RSC  is  not  significantly  changing 

anymore. 

•  RSC  variations  are  larger  for  alloys  containing  ≈2%  Ni;  variations  decrease 

progressively for lower Ni content. 

•  Since the P content does not influence the RSC, it does not seem to be possible 

to measure the embrittlement part due to phosphorus 

As  regards  the  manganese  effect  on  RSC  no  conclusion  can  be  drawn  since  its 
content in the model alloys is constant (≈0.5 wt.%). To identify the influence of Mn on 
the RSC evolution dedicated tests on irradiated VVER materials are on-going. 

Regarding  microstructural  evaluation  some  interesting  data  from  atom  probe 
analysis  performed  in  Oak  Ridge  National  Laboratory  (US)  are  shown  in  Annex  1. 
Atom probe tomography (APT) demonstrates Mn boosting Ni effects. 

22

 
 
 
 
 
 
 
 
 
9. CONCLUSIONS & RECCOMMENDATIONS 

The present study demonstrates that: 

-  Higher nickel content increases sensitivity to radiation 

-  Manganese  further  control  the  “Ni  effect”  enhancing  embrittlement  in  high 

nickel steels 

MnMn
Mn

NiNi
Ni

Cu
Cu

PP
P

Threshold  of embrittlement
Threshold  of embrittlement

Mn made 
Mn made 
me do it!!
me do it!!

MnMn
Mn

NiNiNi
Ni

C
C
u
u

P
P

Figure 21 Role of Mn in Ni steels 

Even  considering  that  in  practice  embrittlement  for  VVER-1000  is  sufficiently 
quantified  for  the  acceptable  limits  for  RPV  operation  in  the  next  decade,  a  more 
precise analysis of the nickel effect is required in order to reduce uncertainties.  

Important  results  on  VVER-1000  are  also  expected  from  the  TACIS  –TAREG 

projects recently launched. 

Such a precise analysis for VVER-1000 surveillance data should be performed in 

order to allow for improved: 

• RPV integrity assessment and assurance of safety margins 

• Residual life estimation 

• Mitigation methods / plant life management strategies 

23

 
 
 
 
 
 
To this end the following steps need to be undertaken: 

1)  Harmonisation  of  the  method  for  transition  temperature  determination  for 
involved testing laboratories (common data-base, training, Round-robin and/or 
Benchmarking exercise) 

2)  More  precise  assessment  of  Ukrainian  &  Bulgarian  testing  results:  e.g. 
Individual fluence value for each specimen; verification of actual fluence rates, 
etc. 

3)  Decrease of data scatter by using re-constitution of broken Charpy specimens 
(based  on  the  experience  acquired  in  TACIS  96  projects  and  AMES  projects 
like RESQUE, etc.) 

4)  Direct  measurement  of  the  irradiation  temperature  of  surveillance  specimens 

and possibly update of the Russian Guide.  

The  case  of  Mn  in  high  Ni  steels  (and  possibly  other  elements;  e.g:  P,  Si)  is 

different. Here more data are needed urgently and R&D should focus on: 

-  The  ‘realistic  welds’  and  ‘model  steels’  projects  as  already  launched  by  the 

JRC in co-operation with the IAEA. 

-  Micro-structural  analysis  of  irradiated  high  Mn-Ni  samples  by  TEM,  atom 

probe etc. 

-  Study of steels with combined contents of Mn and Ni by novel NDT methods 

as positron annihilation, thermoelectric, magnetic Barkhausen. 

-  Use of the VVER-1000 reference steel as monitor material (as JRQ used by 
its 

the 
characterization and storage in co-operation with the IAEA. 

in  CRP-3  and  CRP-4) 

for  which  JRC 

takes  care  of 

IAEA 

-  Development  of  other  ‘reference  steel’  with  both  high  Mn  and  high  Ni 

contents. 

-  Studies  on  feasibility  of  annealing  &  re-embrittlement  of  high  Ni-Mn  steels 

could also be promoted 

-  Modelling actions (physical-mechanistic models, prediction modelling, etc.).  

24

 
 
 
 
 
 
REFERENCES 

Debarberis, L. et al., VVER-1000 embrittlement trends from surveillance, Tacis 

[1] 
and other programmes data: Effect of Nickel at 1.2 and 1.7 wt%, JRC-IE Technical 
Note, European Commission Directorate General JRC, Joint Research Centre, 
Institute for Energy, Petten, The Netherlands, 2003. 

Strength  Analysis  Standards  for  Equipment  and  Piping  at  Nuclear  Power 

[2] 
Plants, Regulatory document PNAE G-7-002-86, Moscow, Russia 1989. 

[3] 
Debarberis, L., Törrönen, K., Sevini, F., Acosta, B., Kryukov, A., Nikolaev, Y. 
and Valo, M., Experimental Studies of Copper, Phosphorus and Nickel effect on RPV 
Model  Alloys  at  Two  Different  Fluences,  6th  International  Conference  on  Materials 
Issues  in  Design,  Manufacturing  and  Operation  of  NPP  Equipment,  St.  Petersburg, 
Russia, 19-23 June 2000. 

[4] 
Debarberis,  L.,  The  effect  of  Nickel,  Phosphorus  and  Copper  in  Irradiation 
Embrittlement of RPV Steel Model Alloys, NATO International Workshop on Reactor 
Pressure Vessel Embrittlement, September 2000, Varna, Bulgaria. 

[5] 
Debarberis,  L.,  Sevini,  F.,  Acosta,  B.,  Kryukov,  A.,  Nikolaev,  Y.  Amaev  A.D., 
Valo, M., Irradiation embrittlement of model alloys and commercial steels: analysis of 
similitude  behaviours,  Int.  Journal  of  Pressure  Vessels  and  Piping  79  (2002),  pp. 
637-642. 

Acosta,  B.,  Sevini,  F.,  Evaluation  of  irradiation  damage  effect  by  applying 
[6] 
electric  properties  based  techniques.  Nuclear  Engineering  and  Design  229,  (2004), 
pp. 165-173. 

[7]  Acosta,  B.,  Debarberis,  L.,  Sevini,  F.,  Kryukov,  A.,  Cu  effects  on  radiation 
embrittlement of Ni-containing complex model alloys and the related potentials of the 
thermoelectric method, NDT&E International 37, (2003), pp. 321-324. 

25

 
 
 
 
 
 
 
 
 
 
ANNEX I – SUMMARY OF R.NANSTAD PRESENTATION AT HIGH NI CRP 

Summary  of  the  presentation:  “Comparison  of  Nickel  Effects  on  Embrittlement 
Mechanisms  in  Prototypic  WWER-1000  and  A533B  Steels”;  Randy  K.  Nanstad, 
Mikhail  A.  Sokolov,  Michael  K.  Miller,  and  G.  Robert  Odette  (UCSB)  -  Metals  and 
Ceramics Division - Oak Ridge National Laboratory - Oak Ridge, Tennessee, USA - 
Presented by Randy K. Nanstad at: International Atomic Energy Agency Coordinated 
Research  Program  Mechanisms  of  Nickel  Content  on  Irradiation  Embrittlement  of 
RPV Steels - Pamporovo, Bulgaria, 2–4 December 2002. 

The  Heavy-Section  Steel  Irradiation  Program  at  ORNL  includes  tasks  to 

investigate nickel effects in RPV steels: 

-  A533B  submerged-arc  weld  (1.20  wt.%  Ni)  with  high  copper  (0.20  wt.%)  -
same as one of the welds in a commercial RPV- to increase sparse database 
on irradiation effects of high-nickel steels.  

-  Charpy  impact  and  0.5TC(T)  specimens  irradiated  to  1.6×1019  n/cm2  (E>1 

MeV) completed. 

-  Charpy impact specimens with target fluence of 3.5×1019 n/cm2 (E>1 MeV) to 

be completed in mid-2003. 

-  A specially fabricated submerged-arc weld (1.23 wt% Ni) with very high copper 
(0.37 wt%) to investigate effect of high embrittlement on shape of the fracture 
toughness master curve. 

-  Charpy  impact,  tensile,  1TC(T)  specimens  irradiated  and  tested;  atom  probe 

tomography completed.  

-  VVER-1000 submerged-arc weld (1.7 wt.% Ni) and forging (1.26 wt.% Ni) for 

mandatory portion of IAEA CRP on nickel effects. 

-  Unirradiated  Charpy  impact  testing  completed,  irradiation  to  2×1019  n/cm2 
(E>1 MeV) [~ 4×1019 n/cm2 (E>0.5 MeV)] to be completed in spring 2003. 

-  Plan to obtain a highly irradiated surveillance weld with high nickel (1.36 wt%) 
and  high  copper  (0.25  wt.%)  from  Palisades  RPV  irradiated  to  fluence  of 
1.8×1020 n/cm2 (E>1 MeV). 

-  Plan  to  irradiate  very  high  nickel  RPV  steels  (e.g.,  3.5  wt.%)  under 
consideration for advanced reactors; similar to steel reported in CRP by U.S. 
Industry Group. 

The KS-01 Weld was irradiated to investigate the relevance of the master curve 
to highly irradiated steel and to examine nickel effects.  

The  microstructure  of  neutron  irradiated  KS-01  test  weld  has  been  characterized 

by atom probe tomography. 

This high copper (0.37%), high manganese (1.84%), high nickel (1.23%) and high 
chromium (0.47%) weld has exhibited a very high sensitivity to neutron irradiation at 
a relatively low fluence of 0.8 x 1019 n/cm2 (E>1 MeV).  

26

 
 
 
 
 
The focus of this atom probe tomography study is to compare the microstructure of 
this  atypical  steel  to  those  of  other  pressure  vessel  steels  and  model  alloys  to 
ascertain the reason for its high sensitivity to embrittlement under neutron irradiation.  

Weld KS-01 exhibited high irradiation sensitivity, after neutron irradiation, this 
weld exhibited:  

•  Charpy T41J shift of 169 K,  

•  Decrease in USE from 124 J to 78 J,  

•  Increase in yield strength from 600 to 826 MPa and 

•  Shift in fracture toughness transition temperature (To) of 160 K. 

•  RG 1.99-2: 162K, EWO: 186K 

)
J
(

E
N
E
Y
G
R
R
E
G
N
E
Y, 

150

125

100

75

50

25

0

KS-01 weld
Irradiated at 288oC
0.84x1019 n/cm2 (E.1MeV)

169
169K
K

124 J
124 J

78 J
78 J

-100

0

100

200

300

TEMPERATURE, oC
TEMPERATURE  (oC)

27

 
 
 
 
 
 
 
 
KS-01 weld

ULTIMAT

YIELD 

YIELD

IRRADIATED 
8 x 1022 n m-2

TE

ULTIMA

0.84x1019 n/cm2 at 288oC

ULTIMAT

ULTIMATE

unirr.

YIELD 

YIELD

UNIRRADIATE

-100

0

100
Temperature  (oC)

200

300

KS-01 weld
0.8x1019n/cm2(E>1MeV)
288oC

KJIc

1T C(T)
0.5T C(T)
PCVN
JIc (JQ) 
MPA data

KJIc

1200

1100

1000

900

800

700

600

500

400

(

)
a
P
M

h
t
g
n
e
r
t
s

T
E
N
SI
L
E 
S
T
R
E
N

s
n
e
T

e

l
i

300

250

200

150

100

50

)

m
√
a
P
M

(

c
J
K
D
E
T
S
U
J
D
A
E
Z
S
T
1

-

I

0
-150

-50

50

150

250

TEMPERATURE  (oC)

Atom  maps  reveal  irradiation-induced  precipitates  enriched  in  Cu,  Mn,  Ni,  P, 
and Si in the KS-01 Weld  

Neutron irradiation produces an extremely high number density: Nv =3x1024 m-3 of 
nanoscale  copper-,  manganese-,  nickel-,  phosphorus-  and  silicon-enriched 
precipitates. 

The  number  density  is  significantly  higher  than  other  RPV  steels  irradiated  to 

similar or higher fluences.  

28

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Cu   Ni Mn S

P Cr N

Each dot is an atom. 
Box is 19 x 19 x 110 nm  
and contains 1.5M ions. 

29

 
 
 
 
FFee

Cu 

Ni Mn Si P

APT Data Analysis of Weld KS-01 Reveals 3-D Nature of Precipitates    

-  The  atoms  that  comprise  each  precipitate  are  identified  with  the  maximum 

separation envelope method.   

- This method is based on the principle that the solute atoms in a solute-enriched 
precipitate are closer together than those in solid solution in the surrounding matrix.   

- The approximately spherical morphology of the precipitates is evident. 

30

 
 
 
 
 
APT Also Revealed Diffuse Phosphorus Clusters in the Irradiated KS-01Weld 

- In addition to the copper-, manganese-, nickel-, phosphorus- and silicon-enriched 

precipitates, some diffuse phosphorus clusters were observed. 

- These phosphorus clusters were approximately 3 nm in extent. 

-  Their  number  density  was  approximately  50  times  lower  than  the  Cu-enriched 

precipitates: Nv = 1 x 1023 m-3. 

- Phosphorus segregation to dislocations was also observed. 

Cu P

5 nm

Irradiation  of  High-Nickel  Weld  KS-01  revealed  High  Radiation  Sensitivity  due 
to High Number Density of Cu-, Mn-, Ni-, P-, and Si-enriched precipitates 

-  KS-01 Weld exhibited very high radiation sensitivity with fracture toughness shift 

of ~ 160°C at 0.8x1019 n/cm2 (>1 MeV). 

-  The  high  copper,  manganese  and  nickel  levels  in  the  KS-01  weld  produces  an 
extremely high number density of Cu-, Mn-, Ni-, P- and Si-enriched precipitates 
during neutron irradiation. 

31

 
 
 
 
 
-  The number density of precipitates is significantly higher than in neutron 

irradiated Fe-Cu and Fe-Cu-Mn model alloys and other pressure vessel steel 
welds irradiated to similar or higher fluences. 

-  The sizes of the precipitates are similar to other neutron irradiated welds. 

-  The high copper, manganese and nickel content of the weld produces a larger 

supersaturation in copper and hence a larger number density of precipitates. 

32

 
 
 
 
 
 
ANNEX II ATHENA WORKSHOP RELEVANT PRESENTATIONS 

Madrid, 18 – 20 September 2002 

33

 
 
 
 
 
 
 
 
 
L. DEBARBERIS (JRC-IE) – SUMMARY 

Mechanistic framework for embrittlement 

DISCUSSION for each item

(LD, AK, FG)

Ni/Ni-Mn
effect

(MB, RC)

Cu/P effect
with/without Ni

(CE, FG, AB, FS)

Dose rate
effects

(FS, MB, CB)

Other
V, Mo, Cr, stress,
cooling rate,  etc.

(CE, MB, RC)

Decrease 
of USE

(CE, CB, RC)

Thermal/Irradiation
(C-Mn Effect, 
Hardening vs
non-hardening,etc.)

Mechanism - Ni effects in ‘clean’ steels and its practical 
relevance
- It is observed that embrittlement of P/Cu ‘clean’ steels, VVER-1000 last 
generation, is enhanced and mainly correlated to Ni content.
Example(s)/evidence
- Research data (RADAMO, etc.), model alloys (KI-JRC-VTT), Collection 
of surveillance data, Tacis results, etc.
Explanation(s) (preliminary)
Ni is contributing to neutron embrittlement. If the content of other 
impurities is very low, Ni is practically controlling the rate of embrittlement.
Threshold is estimated at ~ 1.1 wt% for ‘large’ effects.
Micro-structural/NDT methods additional information
Discussion
Consensus
Discussion
Recommendations
Discussion (probably no further R&D is required, embrittlement in practical 
cases for VVER-1000 is anyhow within acceptable limits, etc.)

34

 
 
 
 
 
 
VVER RPV embrittlement - effect of Nickel at 1.2 and 1.7 wt%
trends from Surveillance, Tacis & other programmes data

High Nickel

Ni=1.7 wt%

Ni=1.2 wt%

Low Nickel

C
°

,
t
f
i
h
s
T
T
B
D

160
140
120
100
80
60
40
20
0

TAC-3

TAC-4

SS SU-1 R-3

Ni=1.7 wt%

ED-3

TAC-2

SS NV-5 Z2

Ni=1.2 wt%

CF=20

30 60

0
Fluence, 10 18 n cm -2 (E>0.5 MeV)

90 120 150 180

C
°

,
s
t
f
i
h
s
d
e
t
a
l
u
c
l
a
C

200
180
160
140
120
100
80
60
40
20
0

Ni~1.7 w t%

Series1

Ni~1.2 w t%

0

100

200

Measured shifts, °C

All data sets

300

250

C
D

200

,

I

T
F
H
S
T
T
B
D

150

100

50

0

Very  Low Nickel

Medium Nickel

High  Nickel

Very  High Nickel

L inear  ( Ver y L ow
Nickel)

L og. (V ery Hig h
Nickel)

0

20

40

60

80

100

800(P+0.07Cu)

CF* = [P + 0,07 Cu] x [Ni ]^a

All data sets

y = 103.13Ln(x) + 456.45
R2 = 0.9227

Low  Ni

Medium Ni

High Ni

Very High Ni

Very Low  Ni

Log. (Very Low  Ni)

C
D

,

I

T
F
H
S
T
T
B
D
d
e
r
u
s
a
e
M

300

250

200

150

100

50

0

300

250

200

150

100

50

0

ALL DATA SETS

+15%

-15%

R2 = 0.8841

0.001

0.01

0.1

1

[P+0.07Cu]*[Ni-0.1]^a+b

0

100

200

300

Calculated DBTT SHIFT, DC

35

C
D

,

I

T
F
H
S
T
T
B
D

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Mechanism - Ni-Mn effects and its practical relevance
- It is observed that embrittlement of Ni steel/welds increases 
dramatically if Mn content is above a certain threshold (~0.9 wt%)
- some VVER-1000 vessel rings/shells in critical Ni-Mn range (possibly 
some older PWR as well)
Example(s)/evidence
- VVER-1000 surveillance data
- IAEA d-base data
Explanation(s) (preliminary)
Mn, as Ni, is contributing to neutron embrittlement. If Mn contents are 
low in comparison with Ni contents, than the effect is masked by Ni. 
(Threshold is estimated at ~ 0.9 wt% for VVER-1000 Ni contents)
Micro-structural/NDT methods additional information
n.m.t.m.k.
Consensus
Discussion
Recommendations
Discussion (needs for further R&D, realistic welds JRC proposal,
IAEA-JRC R-R, etc.)

C
°

,
e
u
l
a
v
t
f
i
h
S

90

80

70

60

50

40

30

20

10

0

F
C
e
g
a
r
e
v
A

0

60

50

40

30

20

10

0

VVER-1000 surveillance

Measured vs Calculated for all NPPs
100

C
°

,
t
f
i
h
s

d
e
r
u
s
a
e
M

90
80

70
60

50
40

30
20

10
0

High Ni - High Mn

High Ni - M Mn

Low Ni

Guide, CF=20

0

20

40

60

80

10

0

Calculated shift, °C  

10

20

30

fluence value, 1018 n cm-2 (E>0.5 MeV)

Ni between 1.6 to 1.9 wt%

C
°

Measured vs Calculated for all NPPs

Shift = (a Ni + b Mn +c) * F^1/3

,
t
f
i
h
s
d
e
r
u
s
a
e
M

100
90
80
70
60
50
40
30
20
10
0

0

20

40

60

80

100

Calculated shift, °C  

Critical value:
Mn, ~0.9 wt%

0

0.5

1
Mn, wt%

1.5

2

36

 
 
 
 
 
 
 
 
 
 
 
 
 
 
A. KRYUKOV (RRC-KI) 

Some new results concerning P, Cu and Mn
influence on VVER materials irradiation

embrittlement

RRC «Kurchatov Institute»
А..Кryukov

ATHENA
Madrid

September 2002

Main influencinig chemical 
elements

VVER-440 - Phosphrus and Copper

VVER-1000 - Nickel ( and Manganese)

37

 
 
 
 
 
 
VVER-440 surveillance data  and prediction 
(∆Tf=800(P+0.07Cu) F 1/3

 BM
 WM

300

250

200

150

100

50

,

C
o
d
e
r
a
u
s
a
e
m

K
T
∆

0

0

50

100

150
∆TK predicted,oC

200

250

300

38

 
 
 
 
 
 
Сu (а)  и Р (b) in VVER-440 irradiated weld

C C

а)

b)

39

 
 
 
 
 
Cu (a) and P (b) in irradiated and annealed 
VVER-440 weld

а)

b)

Cu precipitate in VVER-440 irradiated and
annealed weld

40

 
 
 
 
 
P in VVER-440 irradiated and annealed
weld

Microstructural investigation results
[P.Pareige, O.Zabusov,  M.Miller]

Initial irradiation:

-significant level of Cu and P depletion (up to 0.03-
0.04%) in irradiated weld ferrite matrix
-ultrafine (2-3 nm) intragranular clusters enriched in-
Cu, P, Ni, Mn and Si were observed
-cluster density and Cu content in cluster increases as
the fluence increases
-intragranular P atmospheres were detected in
irradiated materials.

41

 
 
 
 
 
Annealing effect:
-Cu matrix content is still ~0.04%, similar to
irradiated material,
-during annealing Cu clusters dissolve and
growth of Cu precipitates (~5 nm) takes place,
-Cu content in precipitates is 60-100%,
-density of Cu precipitates in annealed
material is low,
-P matrix content is detected 2.3 times higher
then before annealing, like in as unirradiated
material.

CONCLUSION (VVER-440)
1. Good agreement between microstructural and
mechanical testing results
2. During re-irradiation the contribution of Cu is a
minimum
3. P  plays basic role in RPV re-embrittlement
behavior after annealing
4. Re-irradiation of annealed material should not
produce large transition temperature shifts
5. There is a necessity of VVER-440 weld re-
embrittlement assessment model elaboration
6. The benefit – VVER-440/230 RPV lifetime
extension

42

 
 
 
 
 
Ni between 1.6 to 1.9 wt%

F
C
e
g
a
r
e
v
A

60

50

40

30

20

10

0

0

0.5

1

1.5

2

Mn, wt%

Microstructural investigation results

SANS & APT Data
M.Miller, B.Wirst, G.Odette

Моdel alloys  0.8%Cu and 0.8%Cu & 1% Mn:
-Cu- Mn precipitates were observed in 0.8%Cu  & 
1% Mn model alloy
-Precipitate density is much more than in Fe-Cu alloy

Mn increases the precipitate density and decreases their size

43

 
 
 
 
 
 
VVER-1000             
No sinificant role of Cu and P due to low contents
P=0.005-00.010%, Cu=0.03-0.08%

High Ni alone does not always explain different 
observed shifts (Ni>1.55%)  

Mn content looks to be impotent

Mn and Ni are the elements to become non rendomly 
distributed and co-segregated in welds with high Ni 
and low Cu

New programme
Total 12 alloys: 3 fusing (100 kgs each) to 4 ingots each.
From these 25 kgs ingot has to be prepared about 15 kgs of good 
metal to the specimens - ~ 500 mini-Charpy if the thickness for 
rolling about 7 mm

№ 1.1

Ni

0,1

Mn

0,5

0,6

1.2

0,9

1,0

0,5

0,6

1.3

1,7

1,9

0,5

0,6

1.4

2,3

2,5

0,5

0,6

2.1

0,1

1,5

1,6

2.2

0,9

1,0

1,5

1,6

2.3

1,7

1,9

1,5

1,6

2.4

2,3

2,5

1,5

1,6

3.1

1,7

1,9

0,9

1,0

3.2

1,7

1,9

0,9

1,0

3.3

1,7

1,9

0,9

1,0

3.4

1,7

1,9

1,5

1,6

Si

0,35

0,35

0,35

0,35

0,35

0,35

0,35

0,35

0,20

0,35

0,50

0,50

0,45

0,45

0,45

0,45

0,45

0,45

0,45

0,45

0,30

0,45

0,60

0,60

Others:C=0,10-0,12%, Cr=1,7-2,2%, Mo=0,55-0,65%, V=0,1%,

P,S=0,008-0,010%, Cu=0,07-0,08%.

44

 
 
 
 
 
 
F. GILLEMOT (AEKI) 

ATHENA NETWORK
Embrittlement Mechanism
WP5
Mn-Ni effect

JRCJRC--IEIE

IAEA database search
IAEA database search

Advantages
Advantages

Wide range of data
Wide range of data

High quality data
High quality data

Large number of data
Large number of data

Difficulties
Difficulties

Several affecting factor (difficult to find 
Several affecting factor (difficult to find 
examples where everything is the same only the 
examples where everything is the same only the 
Mn content is varied)
NiNi--Mn content is varied)

JRCJRC--IEIE

45

 
 
 
 
 
 
A302B

Code

MAT_ID

C
%

Mn
%

P
%

Si
%

Ni
%

Cr
%

Mo
%

Cu
%

RPV1

A302B

0.09

1.6

0.02 0.49

0.6

0.4 0.20 0.01

RPV4

A302B1

0.19

1.7

0.01 0.14

0.3

0.5 0.16 0.01

RPV5

A302BM 0.08

1.1

0.01 0.20

1.3

0.5 0.24 0.01

JRCJRC--IEIE

ASTM A302B

 RPV1B
 RPV4B
 RPV5B

220

200

180

160

140

120

100

80

60

40

20

0

]

C
o

[
T
∆

0.0

0.5

1.0

JRCJRC--IEIE

2.0

1.5
2.5
3.5
Fluence 1019n/cm2 E>1 MeV

3.0

4.0

4.5

5.0

46

 
 
 
 
 
 
M. BRUMOVSKY (NRI) 

Nuclear Research Institute Řež plc
Nuclear Research Institute Řež plc
Nuclear Research Institute Řež plc

Effect of Ni-Mn

Milan Brumovský

10.3.2004

1

Autor: Brumovský

Nuclear Research Institute Řež plc

Nuclear Research Institute Řež plc

Effect of nickel and manganese on radiation embrittlement 
of 15Kh2NMFA welds 

10.3.2004

2

Autor: Brumovský

47

 
 
 
 
 
 
 
 
 
 
 
Nuclear Research Institute Řež plc

Nuclear Research Institute Řež plc

Effect of nickel on radiation embrittlement and hardening 
of 15Kh2NMF type steel with different impurity contents

10.3.2004

3

Autor: Brumovský

Nuclear Research Institute Řež plc

Nuclear Research Institute Řež plc

Effect of manganese on radiation embrittlement of 15Kh2NMFA type steel

10.3.2004

4

Autor: Brumovský

48

 
 
 
 
 
 
 
 
 
 
 
 
 
European Commission

EUR 21304 EN

State of the Art on Role of Nickel and

Manganese on Radiation Embrittlement

L. Debarberis
B. Acosta
F. Sevini

Luxembourg: Office for official Publications of the European Communities

2004 – 48  pp. – 21 x 29.7 cm

Scientific and Technical Research series

EUR 21304 EN

The mission of the Joint Research Centre is to provide customer-driven scientific and technical support for the
conception,  development,  implementation  and  monitoring  of  European  Union  policies.  As  a  service  of  the
European Commission, the JRC functions as a reference centre of science and technology for the Community.
Close to the policy-making process, it serves the common interest of the Member-States,while being independent
of commercial or national interests.