PREDICTION OF RADIATION EMBRITTLEMENT OF THE

KOZLODUY NPP UNIT 5 REACTOR PRESSURE VESSEL

MATERIALS

NRC “Kurchatov Institute”

D. Erak, D. Zhurko, V. Kochkin

17 June 2016, Varna, Bulgaria

VVER-1000 Reactor Pressure Vessel

The temperature and neutron flux influence during operation

Radiation embrittlement (RE) and temperature ageing (ТA)

of the metal

WELD МETAL DETERMINES LIFETIME of REACTOR PRESSURE VESSEL

welds

С Si Mn Cr Ni Mo P S Cu

BM 0.13-0.18 0.17-0.37 0.3-0.6 1.8-2.3 1.0-1.5 0.5-0.7 0.1-0.12 ≤0.01 ≤0.08

WM 0.06-0.12 0.15-0.45 0.65-1.1 1.4-2.1 1.2-1.9 0.4-0.75 ≤0.01 ≤0.02 ≤0.08

To determine the mechanical properties and fracture toughness parameters of steels

exposed to the operating conditions it is required to test specimens made from the

same material as a reactor pressure vessel and exposed to similar neutron fluence

and the temperature.

a b

Charpy impact specimen (a); tensile specimen (b)

3

Charpy Impact Test Procedure to Determine Ductile to Brittle Transition Temperature

(T) = A + Bth[(T-T0)/C]

f - absorbed energy (J) or

lateral expansion (mm);

T – test temperature (°C);

A, B, C and T0 – fitting parameters

A = (upper shelf level + low shelf level)/2

B = (upper shelf level – low shelf level)/2

Parameters A and B in (2.1) should be related to the upper

and the low shelves of the trend curves and defined as

follows:

kfT

RPV materials properties have

Ductile-Brittle Transition Region

4

Lead factor К=0,5 – 2,0

F < 6,4 1023 neutron/m2

Expose time

T=310-320oC

26 000-200 000 h

≈27 years

RADIATION EMBRITTLEMENT (RE) & THERMAL AGING (TA) of METAL

Most representative data of RPV materials degradation are results

of surveillance specimens (SS) investigations

Surveillance program of VVER-1000 RPVs

SS Location

SS Location

5

WWER-1000/320 surveillance program

RPV material radiation embrittlement is controlled by surveillance program

6 surveillance sets

Each set consist of 5 assemblies

Each assembly contains 14 capsules with surveillance specimens

Surveillance

assembly

RPV

Surveillance assembly design

Each level of

surveillance

assembly contains 6

capsules with 12

Charpy specimens

and 1 capsule with

tensile specimens

Upper

level

Low

level

7

SETS 1L-3L SETS 4L-6L

Lead factor К1,0Lead factor К=1,0-3,0

SS sets of WWER-1000/320 RPVs

Surveillance Specimen Sets WWER-1000/320

Material of the Specimen

Base Weld HAZ

Number

of SS in

one set

Ch T CT Fat Ch T CT Fat CH CT

Type of the set Номер

комп-

лекта

Number of specimens

1К 18 12 15 9 18 12 15 9 18 15 141 Reference

2К 18 12 15 9 18 12 15 9 18 15 141

1Л 24 24 12 18 24 24 12 18 24 12 192

2Л 24 24 12 18 24 24 12 18 24 12 192

3Л 24 24 12 18 24 24 12 18 24 12 192

4Л 12 12 6 - 12 12 6 - 12 6 78

5Л 12 12 6 - 12 12 6 - 12 6 78

Irradiated

6Л 12 12 6 - 12 12 6 - 12 6 78

1М 12 6 6 6 12 6 6 6 12 6 78

2М 12 6 6 6 12 6 6 6 12 6 78

3М 12 6 6 6 12 6 6 6 12 6 78

4М 12 6 6 - 12 6 6 - 12 6 66

5М 12 6 6 - 12 6 6 - 12 6 66

Thermal Ageing

6М 12 6 6 - 12 6 6 - 12 6 66

Total 1332

9

WWER-1000/320The capsules with surveillance specimens are located above the core

baffle in a place with high neutron flux gradient

29

8

Surveillance

10

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

-180 -120 -60 0 60 120 180

angle,deg

Lead

fact

orLead factor obtained by RPV fluence calculation and investigation of different surveillance sets L2 & L4 positions (preliminary estimation)

Upper level

Low level

Lead factor = ФSample/ФRPV wall

11

The reconstitution technique enables to provide the representativeness of the WWER-1000 surveillance programmes

12

The CONDITION: it is necessary to measure fluence in the positions 1/4, 1/2, 3/4

Neutron metrology in RRC KI

evaluation of the fast neutron fluence for

each Charpy type specimen in positions

¼, ½ and ¾ using results of 54Mn

absolute activity measurements;

three-dimensional calculation of neutron

spectrum, taking into consideration

global power history of the core and

effective time of reactor operation at

rated power. Detailed data on geometry

and material of reactor zones are used

in the calculations.

13

Location of neutron dosimeters in surveillance assembly

14

Standard neutron dosimeters set

Aluminium

gasket

Aluminium

capsuleAluminium

plug

Cu dosimeter, Ethreshold =7MeV 63Cu(n,α)60Co T1/2=5.27 years

Fe dosimeter, Ethreshold =3MeV 54Fe(n,p)54Mn, T1/2=312.2 days

Nb dosimeter, Ethreshold=0.5MeV 93mNb(n,n`)93Nb, T1/2=16.1 years

15

BM SS of Kozloduy unit 5 RPV. Collecting of specimens into testing groups

16

0 10 20 30 40 50 60 70 80

0

5

10

15

20

25

30

Группа 2

левая половинка ША

правая половинка ША

центр ША

Флю

енс,

х1

02

2 м

-2

Порядковый номер

Группа 1

0 10 20 30 40 50 60 70 80

0

10

20

30

40

50

60

70

80

90

Группа 3

Группа 2

Группа 1

левая половинка ША

правая половинка ША

центр ША

Флю

енс,

х1

02

2 м

-2

Порядковый номер

Set 3L

Set 2L

WM SS of Kozloduy unit 5 RPV. Collecting of specimens into testing groups

17

0 10 20 30 40 50 60 70 80 90

0

5

10

15

20

25

Группа 2

Группа 1

левая половинка ШВ

правая половинка ШВ

левая половинка ШБ

правая половинка ШБ

центр ШБ

Флю

енс,

х1

02

2 м

-2

Порядковый номер

0 10 20 30 40 50 60 70 80 90

0

10

20

30

40

50

60

70

80левая половинка ШВ

правая половинка ШВ

левая половинка ШБ

правая половинка ШБ

центр ШБ

Флю

енс,

х1

02

2 м

-2

Порядковый номер

Группа 1

Группа 2

Группа 3

Set 2L

Set 3L

Ageing time, h

TF

TK

T

K

Fluence

TT

)(.)(),( tTFTtFT TFк

8.0

0

F

FAT FF

Existing normative approach for prediction of VVER-1000 RPV

weld materials embrittlement (based on data base of SS )

%5,1,18inf NiifCT o

t

),,( SiMnNi

W M

F CCCfA

%5,1,2inf NiifCT o

t

18

OTOT

TTt

t

tth

t

ttbTt exp)(T inf

T

The existing approach allows

-to construct a normative curve for particular vessel

weld based on chemical composition of the material

--to construct an individual embrittlement curve for

particular vessel weld based test results (min 6

experimental points with not than 2 durations of

irradiation)

РД ЭО 1.1.2.09.0789-2012, Положение 1.3.2.01.0061-2009

B. Margolin, V. Nikolayev, E. Yurchenko, Yu/ Nikolayev, D. Erak, A. Nikolayeva /International Journal of Pressure Vessels

and Piping 89 (2012)

45,1BM

FA

SS test results of base and weld metal ofKozloduy Unit 5 RPV

Матер

иалКомплект

Время

выдержки, час

Флюен

с,

1022×м-

2

Тк, °С ∆Тк, °С

ОМ1

Контрольный 0 0 -68 0

1Л 26016 6,9 -60 8

2Л 65208 6,74 -56 12

2Л 65208 20,03 -53 15

3Л 149496 21,28 -59 9

3Л 149496 43,72 -46 22

3Л 149496 60,72 -40 28

МШ

Контрольный 0 0 -47 0

1Л 26016 5,81 -26 21

2Л 65208 5,56 -29 18

2Л 65208 14,53 -16 31

3Л 149496 17,64 -25 22

3Л 149496 31,45 -15 32

3Л 149496 45,33 -9 38

Radiation embrittlement curves for weld metal of KozloduyUnit 5 RPV. (CNi =1.7%, CMn =0.83%)

20

21

Radiation embrittlement curve for base metal of Kozloduy Unit 5 RPV. (CNi =1.15%, CMn =0.46%)

CONCLUSIONS

The representative experimental surveillance specimens

test results for providing forecast of Kozloduy unit 5 RPV

materials radiation embrittlement have been obtain

Development of the irradiation embrittlement curves for

Kozloduy unit 5 RPV materials have been done

Elaborated prognoses allowed to extend Kozloduy unit

5 RPV life time up to 60 years of operation