corrosion of structural materials and electrochemistry in...
TRANSCRIPT
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.0
Corrosion of Structural Materials and Electrochemistry in High Temperature Water
of Nuclear Power Systems
Shunsuke Uchida Institute of Applied Energy
17th International Workshop on Nuclear Safety & Simulation Technology (IWNSST17)
Kyoto, Japan, January 21-22, 2014
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.1
1. Background 2. Objectives 3. Optimal water chemistry 4. Theoretical approaches towards quantifying interaction of materials and water 4.1 Electrochemistry 4.2 Electrochemical corrosion potential 5. Flow-accelerated Corrosion 6. Water radiolysis 7. Future subjects 8. Conclusions 9. Acknowledgements 10. References
Table of Contents
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.2
1. Background
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.3 World list of nuclear power plants Countries*1 total PWR, VVER PHWR BWR GCR, AGR LWGR LMFBR USA 104 69 35 France 59 58 1 Japan 55 (49*3) 24 31 (25*3) Russia 31 13 17 1 South Korea 20 16 4 UK 19 1 18 Canada 18 18 Germany 17 11 6 India 17 15 2 Ukraine 15 15 China 11 9 2 Sweden 10 3 7 Spain 8 6 2 Belgium 7 7 Taiwan 6 2 4 Czech 6 6 Slovakia 5 5 Switzerland 5 3 2 Total*2 439 260 43 93 18 23 2 Share (%) (59) (10) (21) (4) (5) (0.5) *1: more than 5 plants Others: Finland, Hungary: 4 plants, Bulgaria, Argentina, Brazil, Mexico, Pakistan, South Africa: 2 plants, Romania, Armenia, Lithuania, Netherlands, Slovenia: 1 plant *2: 380GWe *3: after March 11 accident Version 2008 Ref.1
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.4 Major accidents and incidents at nuclear facilities Plant (reactor type) Date Causes Environmental effects Three Mile Island-2 (PWR) Mar. 1979 LOCA <1mSv Chernobyl (LGR) Apr. 1986 RIA 31 people died 16 k person Sv Surry-2 (PWR) Dec. 1986 FAC* 4 people died Fukushima Daini-3 (BWR) Jan. 1989 vibration none Mihama-2 (PWR) Feb. 1991 CF none Monju (LMFBR) Dec. 1995 parts defect none (Na leakage ) JCO (conversion Sep. 1999 critical 2 people died facility) accident 130 residents received radiation dose Hamaoka-1 (BWR) Nov. 2001 H2 explosion none Mihama-3 (PWR) Aug. 2004 FAC* 5 people died Fukushima (BWR) Mar. 2011 earthquake radioactivity release: Daiichi 1-4 + tsunami 600 PBq evacuee: 160,000 *: related to material LOCA: loss of coolant accident RIA: reactivity initiated accident FAC: flow assisted corrosion CF: corrosion fatigue Ref.2
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.5 Major problems related to structural materials in NPPs
problem reactor troubled location countermeasures type FAC PWR feed water piping material exchange water chemistry improvement BWR feed water piping water chemistry improvement heater drain piping material exchange SCC BWR primary piping material exchange, stress improvement water chemistry improvement PWSCC PWR core internals material exchange, water chemistry improvement Fuel cladding PWR fuel material improvement corrosion BWR material improvement SG tubing defects PWR SG water chemistry improvement material exchange
Ref.2
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.6
2. Objectives
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.7
1. Roles of materials, water and their interaction on plant safety and reliability are confirmed.
2. Optimal water chemistry control required for satisfying multi-problems related to interaction of materials and water is introduced. 3. Theoretical approaches as well as empirical ones required for quantifying the interaction of materials and water and for establishing suitable countermeasures for those problems are introduced. Electrochemistry is one of key issues to determine corrosion related problems. 4. As examples of application of theoretical electrochemistry procedures, a prediction
model for flow-accelerated corrosion (FAC) and prediction models for water radiolysis are introduced.
5. As future subjects of the theoretical models related to electrochemistry and water
radiolysis, verification and validation evaluation procedures are introduced and standardization of the procedures are introduced.
Objectives
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.8
3. Optimal water chemistry
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.9
BWR primary cooling water
radwaste system recirculation system main steam/ feed water systems
radioactive contamination
occupational exposure
pre-filter demineralizer
spent resin liquid waste (back wash, regeneration)
radwaste source volume
fuel integrity
structural material integrity
major roles: energy transporting medium neutron moderating medium
under line: items concerning adverse effects
PWR primary and secondary cooling water
fuel integrity occupational exposure
structural material integrity
major roles: energy transport medium neutron moderating medium
primary cooling system secondary cooling system
Major roles and adverse effects of cooling water of nuclear power plants
Ref.3
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.10 Optimal water chemistry control (BWR and PWR)
Establishing 4 targets
iron, nickel & cobalt control
Fewer environmental impacts
Improving reliability of cladding materials
Reducing radwaste sources Minimizing radioactive effluent
Reducing occupational exposure (radioactive contamination)
Improving reliability of structural materials
radiolysis control pH & hydrogen control
Higher safety and higher reliability
nickel alloy
zirconium alloy
stainless steel
a) PWR (primary system)
zirconium alloy
stainless steel
carbon steel
b) BWR
Major materials in primary system Their wetted surface
Ref.2
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.11 Interaction between structural materials and cooling water
composition (impurities crystal structure local stress
temperature pH conductivity oxidant
materials water
release of metallic ions
growth of oxide film
oxide film
barrier for diffusion of oxidant and metallic ion
Ref.4
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.12
4. Theoretical approaches towards quantifying interactions of materials and water
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.13 Comparison of corrosion behaviors and features of major materials
Materials Carbon steel Stainless steel Zirconium alloy (nickel alloy) Corrosion rate high medium low (relatively) Oxide film magnetite/hematite Cr rich nickel ferrite zirconium oxide Application piping of secondary piping and component fuel cladding system of primary system Problems FAC IGSCC, PWSCC clad thinning radioactivity accumulation Effects of strong medium weak electrochemistry
Corrosion rates / corrosion effects should be predicted based on theoretical tools for preparing for suitable countermeasures
Ref.4
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.14 Major parameters of major corrosion induced phenomena
temperature. pH, [O2]
mass transfer due to
flow turbulence
Cr content
material factors
environmental factors
flow dynamics factors
Flow accelerated corrosion(FAC)
sensitization at heat affected zone
radiolytic species,
[O2],[H2O2]
residual stress at heat affected
zone
material factors
environmental factors
stress factors
Intergranular stress corrosion cracking (IGSCC) Zircaloy corrosion
compression due to
lattice constant
material factors
environmental factors
stress factors
radiolytic species,
[O2],[H2O2] Ref.4
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.15
4.1 Electrochemistry
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.16 Electrochemistry Basic reaction between metal and aqueous solution
Corrosion mechanism depends on electrochemistry. Mass and charge balances between metal surface and aqueous solution. Electrode reactions => Corrosion rate Electrode potential => Electrochemical corrosion potential (ECP) Electrolysis Radiolysis Hydrogen generation reaction
2H+ + 2e- → H2
H+ e-
H2
Oxygen generation reaction 2H2O → O2 + 4H+
+ 4e- O2,H+
e- H2O
H2O
O2,H+ e-
Oxygen reduction reaction O2 + 4H+ + 4e- → 2H2O
Metal dissolution reaction Fe → Fe2+ + 2e-
Fe Fe2+ e-
Oxide film formation reaction 2Fe+3H2O → Fe2O3+6H++6e-
H+
H2O
e-
Fe Fe2O3
Ref.5
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.17 Schematic diagram of charge balance at surface
pote
ntia
l (ar
bitr
arily
scal
e)
-1.0
-0.5
0
0.5
current density (arbitrarily scale)
10-4 100 10-1 10-3 10-2
Fe Fe2+ + e- total anodic current
with oxide film
without oxide film
total cathdic current O2 + e- O2
-
high [O2]
low [O2]
hydrogen generation
potential
H
L
b) Static charge balance
boundary layer
metal bulk
O2
H+ H2O e-
N2H4
H+
M+ e-
e-
diffusion
anodic current
cathodic current
oxide film
a) Cathodic and anodic reactions
H2
anodic reaction
cathodic reaction
Ref.6
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.18
4.2 Electrochemical corrosion potential
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.19 Coupled electrochemistry/oxide layer growth model for ECP evaluation
Sub-model electrochemistry model oxide layer growth model (static model) (dynamic model) Input temperature, [O2] , pH, km, temperature mass transfer coefficient (hm) anodic/cathodic current densities oxide film thickness, ECP oxide properties Output anodic/cathodic current densities oxide film thickness ECP properties (Fe2O3/Fe3O4 ratio)
coupling calculation
Ref.7
release
mass transfer
hematite particles
magnetite particles
dissolution adsorption
oxidation
flow
δ outer layer (hematite particles)
inner layer (magnetite particles)
base metal
boundary layer
bulk water
pote
ntia
l (a.
u.)
current density (a..u)
cathodic current
anodic current
oxide filn effects
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.20 Cathodic reaction. H2O2 + e- = OH + OH- O2 + e- = O2
- O2 + 2H2O +2e- = 2O2
- + 2H2 2H+ + 2e- = H2 (hydrogen generation at low potential) Current density due to the cathodic reaction is expressed by Eq. (1) Ic = fc (φ) Xs (1) fc (φ) = zc F kc
e exp(-αczcF(φ-φc0)/RT) (2)
[O2] at the metal surface is determined by its diffusion from the bulk to the surface. Da
B(Xb-XB)/δΒ = Ic/zc/F (3) Da
o(XB-Xs)/δο = Ic/zc/F (4) The current density due to the cathodic reaction is expressed by Eq. (5). Ic= fc (φ)Xb/{1+ fc (φ)/zc/F (δo/Da
o+δB/DaB}} (5)
Anodic reactions M = Mz+ + ze- Current density due to the metal release is expressed by Eq. (6). Ia = fa (φ) (Csol-Cs) (6) fa (φ) = za F ke
a exp(+αazaF(φ-φa0)/RT) (7)
The cation concentration at the metal surface is determined by its diffusion. Dc
o(Cs –CB)/δο = Ia/za/F-β(Csol-Cs) -βXs = fa (φ) (Csol-Cs)/za/F-βXs (8) Dc
B(CB -Cb)/δΒ = Ia/za/F= fa (φ) (Csol-Cs)/za/F-βXs (9) The current density due to the anodic reaction is expressed by Eq. (10). Ia = fa (φ) [Csol -{Cb+fa (φ)Csol /za/F(δο/Dc
o+δΒ/DcB)}/{1+(fa (φ)/za/F+β)(δο/Da
o+δΒ/DaB)}] (10)
Numerical expression for cathodic and anodic reactions
Ref.14
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.21 Ferrous ion release rate from base metal dM/dt= -Ia/za/F (12) dCB/dtδB=Ia/za/F -δmCBSmCmδB
2 -δhCBShChδB2 -kgCB/Csolfb(CB)δB -km(CB-Cb)δ
+ζmTm +ζhTh (13) dCp
B/dt δB = kgCB/Csolfb(CB)/Wm δB -kdCpB -k(Cp
B-Cpb) δB (14)
dTim/dt =Φ-ζmTi
m for Tim<Ti
m* (15) =0 for Ti
m>Tim* (16)
Φ = ΦOX(φSS)+ ΦHPO([H2O2])+ ΦΗ (17) ΦOX(φSS) = ΦOX*( φSS - φH)1/2/Tb
m for φSS > φ H (18)
= 0 for φSS < φ H (19)
ΦHPO([H2O2]) = ΦHPO*( [H2O2])/Tim (20)
Φ H = ΦH*/Tim (21)
dCm/dt τb = kdCpBδB - (χ+km)Cm δB (22)
dTm/dt=δmCBSmCmδB 2+kdCp
BWmδB -(ζm+χ+km)Tm for Tim>Ti
m* (23) dTm/dt=δmCBSmCmδB
2+kdCpBWmδB -(ζm +χ+km)Tm+Φ for Ti
m<Tim* (24)
The transfer ratio from magnetite to hematite χ=χOX +χHPO (25) χOX = χOX* (φSS - φ H)1/2 for φSS > φ H
(26) = 0 for φSS < φ H
(27) χHPO = χHPO*([H2O2]) (28) dCh/dt δB =χCm δB -khChδB (29) dTh/dt= χTm +δhCBShCh δB
2 -(ζh +kh)Th (30)
Numerical expression for oxide film growth
Ref.14
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.22
decreasing potential
101
100
10-1
10-2
10-3
10-4 -1.0 -0.5 0 0.5 1.0
potential (V-SHE)
curr
ent d
ensi
ty (
A/m
2 )
increasing potential
dV/dt=1 V/s
dV/dt=0.01 V/s
dV/dt=100 V/s
a) Potential increasing rate dependence
101
100
10-1
10-2
10-3
10-4 -1.0 -0.5 0 0.5 1.0
potential (V-SHE) cu
rren
t den
sity
(A
/m2 )
increasing potential
decreasing potential
mass transfer coeff., km= 0.01 m/s
km= 0.002 m/s
km= 0.001 m/s
b) Mass transfer coefficient dependence
Calculated anodic polarization responses
Ref.2
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.23 Temperature dependent Co release rate from stainless steel
10-1
10-2
10-3
10-4
coba
lt re
leas
e ra
te (
g/m
2 /mon
th)
20 50 100 200 500 1000 5000 exposure time (h)
200ºC 250ºC
170ºC 270ºC
240ºC
150ºC
temperature decrease 250℃ 240℃
Temperature dependence of corrosion rate When temperature decrease from 250 ºC to 240 ºC, corrosion rate decrease due to protective oxide film
developed under 250 ºC water
Ref.8
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.24
5. Flow-accelerated Corrosion
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.25 Condensate water piping rupture at Mihama-3 NNP
Accident (Aug. 9, 2004) Rupture of condensate water piping
of secondary system (A)
5 person injured to death
Causes Flow assisted corrosion of carbon steel piping
Environmental effect: Non
HP turbine
SG
deareter
ruptured HP
heater
LP heater
feed water pump
moisture re-heater
LP turbine
condenser condensate
water pump
condensate polisher
water chemistry AVT: NH3 + N2H4 pH: 8.8-9.3
[O2]:<10ppb
bent piping orifice
flange ruptured hanger
upstream (A)
upstream (B)
2.5 m 1.5 m 4.0 m
1.9 m 1.5 m 3.4 m
0.45 m
Possible countermeasures · thermal hydraulic improvement · material improvement · water chemistry improvement
Ref.9
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.26 Evaluation and inspection steps for wall thinning
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
1D CFD code
1D O2-hydrazine reaction code
3D CFD code
Wall thinning calculation code
1D wall thinning calculation
Total evaluation [planning for preventive maintenance, analysis of plant system safety]
Periodic wall thinning measurement
Continuous wall thinning measurement
Evaluation of residual wall thickness
Selection of measuring point based on JSME code
Selection of measurement location for wall thinning
Improvement of 3D FAC code
Improvement of FAC codes
Corrosion (chemical) analysis Measurement and inspection Flow dynamics analysis System analysis
Ref.10
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.27 Evaluation code system for FAC Calculation Flow pattern [O2], [Fe2+] Wall thinning rate and ECP targets (anodic/cathodic (oxide film current density) formation) Input Reactor Reactor [O2] , T, pH, km, icorr, parameters: parameters: geometries, T, flow velocity (v), oxide film ECP heat flux (Q), surface/volume rate, thickness, temperature (T) mixing rate properties Computer 1D CFD N2H4-O2 reaction Static model Dynamic model programs 2-3D k-ε CFD code (Electro- (Oxide layer 3D LES -chemistry) growth) Output T, v distributions [O2] and [Fe2+] icorr, ECP oxide film along distributions wall thinning rate thickness flow path along flow path properties (Fe2O3/Fe3O4 ratio)
coupling calculation
Ref.7
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.28 Relationship between corrosion rate and ECP po
tent
ial (
arbi
trar
ily sc
ale)
-1.0
-0.5
0
0.5
current density (arbitrarily scale)
10-4 100 10-1 10-3 10-2
Fe Fe2+ + e- total anodic current
with oxide film without
oxide film
oxidation of hydrazine
total cathdic current O2 + e- O2
-
high [O2]
low [O2]
hydrogen generation
potential
H
L
Protective oxide film mitigates further corrosion with increasing ECP
Increasing ECP mitigates further corrosion with increasing [O2]
Ref.7
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.29
10-5 10-4 10-3 10-2 10-1
mass transfer coefficient (m/s)
pH: 7.3
pH: 9.2
101
100
10-1
10-2
10-3 W
all t
hinn
ing
rate
(a.
u)
condensate water heater
main condenser
feed water heater
steam generator
demineralizer
deaerator
①*
② ⑫ ⑤
⑥ ⑦ ⑧
⑨
⑩ ⑪
⑬ ⑭
⑮
⑯
③ ④
Application of FAC code to PWR secondary cooling system
3D computational fluid dynamics code
Mass transfer coefficient at pipe inner surface
Wall thinning rate
3D FAC code
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.30 Time margin and hazard scale of pipe rupture
time margin relative effects
0 20 40 60 80
100 120 140
location
time
mar
gin
for
rupt
ure
(y)
0
0.2
0.4
0.6
0.8
1.0 re
lativ
e ha
zard
scal
e (-)
① ② ③ ④ ⑤ ⑥ ⑦ ⑧ ⑨ ⑩ ⑪ ⑫ ⑬ ⑭ ⑮ ⑯
Time margin and hazard scale according to location
Relationship of time margin and hazard scale
0
0.2
0.4
0.6
0.8
1.0
0 10 20 30 40 time margin for rupture (y)
rela
tive
haza
rd sc
ale
(-)
primary location for inspection and maintenance
15
14 13 12
11
10 9
8
7 6 5 4 3
2
16
1
Ref.10
condensate water heater
main condenser
feed water heater
steam generator
demineralizer
deaerator
①*
② ⑫ ⑤
⑥ ⑦ ⑧
⑨
⑩ ⑪
⑬ ⑭
⑮
⑯
③ ④ Thinning rate evaluation
+ Effects evaluation
For risk evaluation
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.31
6. Water radiolysis
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.32
0 20
200 50
[O2]eff (ppb)
HWC [H2]eff : 50 ppb NWC
Maps of distribution of [O2]eff in RPV (Effects of hydrogen injection on suppression of [O2])
Ref.12
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.33 Theoretical determination of corrosive conditions of BWRs based on water radiolysis model
steam flow
water flow
feed water
recirculation water
release of gaseous species steam
H2, O2
reactor core water radiolysis
2H2O→ H2 + H2O2
sampled water to determine oxidant concentrations
cooled down
upper plenum
2H2O2→ 2H2O + O2
decomposition of hydrogen peroxide
down comer lower plenum
2H2 + O2→ 2 H2O H2 + H2O2→ 2 H2O
recombination reactions
Ref.12
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.34 Effects of H2 injection in BWR plants
b) Calculated for plants
0 20 40 60 80 100 [H2]RW (ppb)
[O2]eff [O2]
102
101
100
[O2] e
ff (p
pb)
[O2]eff= [O2]+1/2 [H2O2]: effective oxygen concentration [H2]RW :[H2] in the reactor water
0
50
100
150
200
250
0
1
2
3
4
5
6
0 20 40 60 80 100
mai
n st
eam
line
dos
e ra
te
[O
2] eff
(ppb
)
[H2]RW (ppb)
ECP
(V-S
HE)
-0.6
-0.4
-0.2
0
0.2
0.4
optimal [H2]RW MSDR
limit [O2]eff target
MS dose rate
[O2]eff
ECP NMCA ECP
a) Measured in plants
Ref.12
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.35 ECP evaluation procedures
Evaluation of lifetime of major component
ECP calculation code
(AESJ standard - proposed) Crack grow calculation code
ECP
Water radiolysis code
Fluid dynamics parameters
Reactor parameters (flow velocity, equivalent diameter, radiation energy deposition)
(JSME standard) Plant materials Residual stress
Concentrations of radiolytic species
b) Hydrogen water chemistry
100 101 102
10-5
10-6
10-7
10-8
10-9 crac
k gr
owth
rate
(m
m/s
)
stress intensity factor, K (MPa m1/2)
austenitic stainless steel
low carbon containing austenitic
stainless steel
conductivity: <0.2µS/cm ECP: <-100mV-SHE
a) Normal water chemistry
10-5
10-6
10-7
10-8
10-9 100 101 102
crac
k gr
owth
rate
(m
m/s
)
stress intensity factor, K (MPa m1/2)
austenitic stainless steel
low carbon containing austenitic stainless
steel
conductivity: <0.2µS/cm ECP: >150mV-SHE
Ref.13
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.36 Crack growth rate as a function of ECP
NWC: normal water chemistry (without hydrogen injection) HWC: hydrogen water chemistry (with hydrogen injection)
measured calculated
-600 -400 -200 0 200 400
10-5
10-6
10-7
10-8
10-9
ECP (mV-SHE)
crac
k gr
owth
rat
e (m
m/s
) Type 304 stainless steel (25mm CT specimen) furnace sensitized: 15C/cm2
water temperature: 288 C constant load: Kin/(in)1/2
Conductivity (mS/cm) :
0.3 0.2 0.1
HWC NWC
Decreasing ECP mitigates IGSCC occurrence and propagation with decreasing [O2]
Ref.16
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.37 Effects of hydrogen on PWSCC crack initiation and crack growth rate
Ni/N
iO li
ne 25
20
15
10
5
0
tube diameter 3/4 inches 7/8 inches
Nml-H2/kg-H2O (at 330 C) cr
ack
initi
atio
n tim
e (k
h)
0 5 10 15 20 25 30 35
b) Crack initiation time
0 50 100 150 [H2] (Ncm3/kg)
crac
k gr
owth
rat
e(m
ills/
day)
NiO Ni metal
2.0
1.0
0
X-750, 360C, 49 MPam1/2
a) Crack growth rate
Refs.2, 17 and 18
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.38 High Temperature G-values
molecules, atoms /100ev absorption
e-
H H+
H2
H2O2
HO2
OH OH-
species
3.50 0.90 3.50 0.60 0.55 0.00 4.50 0.00
γ rays
0.60 0.50 0.60 1.50 1.14 0.04 1.70 0.00
neutrons PWR(305ºC)
0.152 0.199 1.974 0.152 1.104 0.300 1.191 0.000
α rays
3.565 0.927 0.612 3.565 0.542 0.000 4.632 0.000
γ rays
0.662 0.453 1.278 0.662 0.836 0.050 1.849 0.000
neutrons BWR(285ºC)
Water radiolysis codes for BWR have been well developed and applied, while those for PWR have just developed with different G value sets
Ref.19
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.39
7. Future subjects
IWNSST17, Kyoto, Japan, Jan. 21-22, 2014 S. Uchida
No.40 Calculated results of PWR radiolysis model Comparison with INCA loop experiments
Standard procedures to authorize the computer simulation codes have been based on the verification and validation (V&V) method.
The verification and validation (V&V) processes for the FAC simulation code and the corrosive condition calculation code were done in conformity with the ASME “Guide for Verification and Validation in Computational Solid Mechanics.” The definitions of V&V are as follows: 1. code verification: addressing errors in the software 2. calculation verification: estimating numerical errors due to under resolved discrete representations of the mathematical model 3. validation: assessing the degree to which the computational model is an accurate representation of the physics being modeled, based on comparison between numerical simulations and relevant experimental data (predictive capability of the model).
Ref.20
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0
10
20
30
40
50
0 10 20 30 40 50 calculated (mm)
mea
sure
d (m
m) -20%
+20%
Bend (condensate water line: 146ºC)
Bend (feed water line: 222ºC)
T-junctions (drum: 190ºC)
T-junctions (pipe : 190ºC)
Ref.6
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0.2
0
-0.2
-0.4
-0.6
-0.6 -0.4 -0.2 0 0.2 measured ECP (V- SHE)
calc
ulat
ed E
CP
(V- S
HE
)
+0.05V
-0.05V
: BWR4 : BWR5
Comparison of the calculated results with the measured Validation of corrosive condition calculation code based on Residual thickness
Ref.13
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8. Conclusion
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8. Conclusions 1. Optimal water chemistry control has been established to satisfy multi-problems related to interaction of materials and water is introduced. 2. Theoretical approaches as well as empirical ones have been established to quantify the interaction of materials and water and to establish suitable countermeasures for those problems. 3. Electrochemistry procedures have been successfully applied to determine corrosion related problems. 4. As examples of application of theoretical electrochemistry procedures, a prediction model for FAC and prediction models for water radiolysis are introduced. 5. As future subjects of the theoretical models related to corrosion problems, standardization of the codes should be established based on V&V evaluation procedures
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9. ACKNOWLEDGEMENT
The author expresses his thanks to the members of the Institute of Applied Energy for their enthusiastic discussion and contribution to develop the FAC code.
He also expresses his thanks to the members of the HWC Standard Working Group of
the Standard Committee of the AESJ for enthusiastically discussing on the standard draft and Prof. Seiichi Koshizuka for his helpful guidance on V&V evaluation..
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10. References (1)
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Thank you for your kind attention.