RUSSIAN RESEARCH CENTERKURCHATOV INSTITUTE
Development of annealing for VVER-1000 reactor vessels
Experimental assessment ofpossibility for performance of restoration anealing
Ya.I. ShtrombakhYa.I. Shtrombakh
The lifetime of VVER reactor vessels mainly depends on irradiation embrittlement of weld joint materials
Generation 1 Generation 2
VVER - 440/230 VVER - 440/213 VVER - 1000
To 0,22%To 0,22%
To 0,048%To 0,048%To 0,027%To 0,027% < 0,012%
< 0,3% 1,2 - 1,9% 1,2 - 1,9%
To 0,22%To 0,22%
< 0,3%
2
< 0,08%
Elements impacting irradiation embrittlement
Performance of restoration annealing at VVER-440 reactor vessels
3
VVER-440VVER-440
Annealing efficiency
Annealing efficiency
Annealing temperatureAnnealing temperature
Rating of VVER-440 units by chemical composition of the weld joints
By TecSpec for weld joints of Rovno NPP-1 0.037%Р
Rovno NPP 1 0.21%Р
4
Cutting of templates for assessment of the real conditions in VVER-440/320 reactor vessels
If Tk 55 0°C: Tk
1010 = 53.5 + 0.94Tk 55 + 2.6210-4 (Tk
55)2 , °C
If Tk 55 0°C: Tk
1010 = 53.5 + 1.00Tk 55 + 1.3710-4 (Tk
55)2 , °C
5×5
10×10
5
VVER-1000 RO MKR raises significantly with increase of Ni concentration
6
Range of Ni concentration
change in the weld joints
Activities necessary for LTE
1.70 - 1.88Monitoring of radiation loads for ensuring of the designed life and ANNEALING for
LTE
1.57 - 1.64Monitoring of radiation loads for ensuring of the designed life additional attestation
for LTE
1.10 - 1.21The designed life is ensuredAdditional attestation for LTE
7
Mechanisms of irradiation embrittlement caused by nano-structure evolution
Radiation-induced precipitates
Brittle intergranular
destruction
Irradiation strengthening Development of intergranular segregations of impurities
IRADIATION EMBRITTLEMENT
Radiation defects
8
Brittle intergranular destruction
0 100 200 300 400 500 600 700 800 900 1000
CuNi
Fe
CrOCr
CMo
P
Ин
тен
сив
но
сть
, у.е
.Кинетическая энергия, эВ
The spectrum of OZ electrons from the intergranular surface of the reactor vessel
destruction (F=6,51023 м-2). The presence of phosphor intergranular segregations is visible
The spectrum of OZ electrons from the intergranular surface of the reactor vessel
destruction (F=6,51023 м-2). The presence of phosphor intergranular segregations is visible
9
Kinetic energy, eVKinetic energy, eV
Intensity, s.u.Intensity, s.u.
Changes of density of the radiation induced segregations in the weld joint of VVER-1000
Ф = 11,6×1023н/м2
N=700-800×1021м-3
Ф = 6,5×1023н/м2
N=300-500×1021м-3
Ф = 3,1×1023н/м2
N=70-90×1021м-3
10
Changes of density in the dislocation loops of VVER-1000 weld joint
Ф = 11,6×1023н/м2
N=400-600×1021м-3
Ф = 6,5×1023н/м2
N=10-20×1021м-3
Ф = 3,1×1023н/м2
N=5-6×1021м-3
11
Radiation induced segregations in the weld joints of
VVER-1000 made of the atoms of Ni, Mn, Si
M.K. Miller, A. Chernobaeva, Y.I. Shtrombakh, M.K. Miller, A. Chernobaeva, Y.I. Shtrombakh, K.K. F. Russell, R.K. Nanstad, D.Y. Erak, O.O. Zabusov., Evolution of F. Russell, R.K. Nanstad, D.Y. Erak, O.O. Zabusov., Evolution of the nanostructure of VVER-1000 RPV materials under neutron the nanostructure of VVER-1000 RPV materials under neutron irradiation and post irradiation annealing., JNM, irradiation and post irradiation annealing., JNM, 20092009
The higher the
segregations density,
The bigger displacement of ТК
12
Dependence of maximum temperature for temper brittleness from nickel concentration in the steel
(duration 100 hrs)
13
Temperature-time diagram of isothermal embrittlement of Cr-Ni-Mo steels
Temperature-time diagram of isothermal embrittlement of Cr-Ni-Mo steels
Displacement of embrittlement temperatureDisplacement of embrittlement temperature
Tem
peratu
reT
emp
erature
Experimental effectiveness justification for the annealing of VVER-1000 reactor vessel weld joints
Material Balakovo NPP, unit 1 Kalinin NPP, unit 1
Composition of elemets, % Ni=1,88Mn=1,1
Ni=1,76Mn=0,98
Fluency during primary receiving of the templates (flux 2-4 ×1014 м-2с-1),
×1022 м-2
32 37
Displacement of the embrittlement temperature after the primary irradiation of the templates, º С
93 90
Annealing mode 565 º С/ 100 hrs, cooling less than 20 º С/hr. to 100 º С; further on with disconnected heaters
Displacement of the embrittlement temperature after the restoration
annealing, º С
4 8
Fluency during the secondary irradiation, ×1022 м-2
50 27 27
Flux during the secondary irradiation, ×1016 м-2с-1
17,0 2,1 2,1
Displacement of the embrittlement temperature after the secondary
accelerated irradiation, º С
44 17 36
14
Change of density in radiation-induced segregations under irradiation in the weld joint VVER-1000
SECONDARY SPEEDED-SECONDARY SPEEDED-UP IRRADIATIONUP IRRADIATIONФ=5,0×1023 н/м2
PRIMARY IRRADIATION
Ф=3,2×1023 н/м2
RESTORATION ANNEALING
15
The velocity of the secondary embrittlement of the VVER-1000 reactor steels after the restoration annealing is significantly slower than during the primary irradiation
16
InitialInitial
Loops
Precipitates
Loops
Precipitates
Primary irradiationPrimary irradiation Secondary irradiationSecondary irradiation
Restoration annealingRestoration annealing
State, fluencyState, fluency
Dose dependences of the density in the radiation-induced structure Dose dependences of the density in the radiation-induced structure elementselements
PrecipitatesPrecipitates Radiation defectsRadiation defects
17
FluencyFluency FluencyFluency
The share of brittle intergranular destruction in the Charpy tests of the main material thermal sets (Ni < 1.2 %) and weld
joints with increased concentrations of Ni (>1.6 %)
18
Weld joint,
Kalinin 2
Weld joint,
Kalinin 2
Main material,
Kalinin 2
Main material,
Kalinin 2
Main material,
Rovno 3
Main material,
Rovno 3
Weld joint,
Rovno 2
Weld joint,
Rovno 2
Duration of thermal treatment, eff. hrs.Duration of thermal treatment, eff. hrs.InitialInitial
Th
e share of in
tergranu
lar destru
ction, %
Th
e share of in
tergranu
lar destru
ction, %
19The share of brittle intergranular destruction, displacements of brittleness temperature and viscosity limits in various
states for the weld joint of Balakovo NPP-1
The share of brittle intergranular destruction
Displacement of brittle temperature
Displacement of viscosity limit
The share of brittle intergranular destruction
Displacement of brittle temperature
Displacement of viscosity limit
InitialInitial
IrradiationIrradiation AnnealingAnnealing AnnealingAnnealing AnnealingAnnealing
The share of brittle intergranular destruction, %
The share of brittle intergranular destruction, %
Annealing 565 C/100 hrs + secondary accelerated
irradiation
Annealing 565 C/100 hrs + secondary accelerated
irradiation
Displacement of brittleness temperature in different states of Balakovo NPP-1 reactor vessel steels
20
Weld jointWeld jointWeld jointWeld joint
Main materialMain material
InitialInitial IrradiationIrradiation IrradiationIrradiation IrradiationIrradiation IrradiationIrradiation IrradiationIrradiation IrradiationIrradiation
+ annealing+ annealing + annealing+ annealing + annealing+ annealing + annealing+ annealing + annealing+ annealing
+ irradiation+ irradiation + irradiation+ irradiation
Comparison of primary and secondary irradiation embrittlement in the materials of Balakovo NPP unit
1 reactor vessel
Main metalMain metal Weld jointWeld joint
21
1. Consideration of temperature ageing effect1. Consideration of temperature ageing effect 1. Consideration of flux effect
2. Consideration of temperature ageing effect
1. Consideration of flux effect
2. Consideration of temperature ageing effect
22Comparison of the primary and secondary radiation embrittlement in the weld joint at Balakovo NPP, unit 1
0 20 40 60 80 1000
20
40
60
80
100
120
После отжига 565°С/100ч
Повторное РО
- модель го
ризонтального сдвига
Сварной шов ВВЭР-1000
TF ,
°C
Флюенс, 1022 нейтрон/м2 (E>0.5МэВ)
Перви
чное РО
После отжига 565°С/30ч
VVER-1000 weld jointVVER-1000 weld joint
FluencyFluency Neutron, m2Neutron, m2
Primary irradiation
embrittlement
Primary irradiation
embrittlement
Secondary irradiation
embrittlement
Secondary irradiation
embrittlement
After annealing 565
0C/30 hrs
After annealing 565
0C/30 hrs
After annealing 565
0C/100 hrs
After annealing 565
0C/100 hrs
Computed diagram of temperature distribution along the VVER-1000 reactor vessel in the process of the restoration annealing
(stationary task)
2323
24
The irradiation embrittlement of the vessel steels caused by radiation strengthening due to radiation induced changes of its nano-structure, as well as formation of intergranular and boundary-granular phosphor segregations.
It is demonstrated that the velocity of radiation embrittlement in weld joints of VVER-1000 reactors is higher the one of main VVER-1000 materials.
The maximum of temperature intervals for phenomenon of temper brittleness is raising along with increase of nickel concentration in the steel, which required to increase the restoration annealing temperature for weld joints of VVER-1000 with increased nickel concentration.
The parameters of time and temperature for restoration annealing of VVER-1000 weld joints with increased nickel concentration are identified.
The restoration of features and structure of steels in VVER-1000 reactor vessels after restoration annealing is demonstrated.
It is identified that the velocity of the embrittlement after the annealing under the speeded-up irradiation is lower than during the primary irradiation.
It is shown the presence of «flux effect» during the speeded-up irradiation after the restoration annealing.
The flowchart of temperature distributions along the VVER reactor vessel within the scope of the stationary task is computed for the restoration annealing process.
ConclusionsConclusions