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Modelling Coolant Radiolysis in Nuclear Reactors

Digby D. Macdonald1 and George R. Engelhardt2

1. Department of Nuclear Engineering

University of California at Berkeley

Berkeley, CA 94720

2.OLI Systems, Inc.

240 Cedar Knolls Road, Suite 301

Cedar Knolls, NJ 07927 USA

OBJECTIVES

• Review the challenges in modeling radiolysis phenomena in water-cooled nuclear reactors.

• Briefly review some of our previous work on modeling BWRs and PWRs.

• Describe process for modeling multi-loop reactor cooling systems.

• Define a metric for the “degree of suppression of radiolysis” in terms of the concentrations of oxidizing and reducing radiolysis products.

• Present some preliminary radiolysis modeling results for ITER-like environmental conditions.

• We ultimately seek to calculate the concentrations of radiolysis products (H2, O2, H2O2, H, OH, etc) and the ECP at closely-spaced points around the entire PHTS of fission and fusion reactors as a function of reactor operating conditions.

D. D. Macdonald and M. Urquidi-Macdonald. "The Electrochemistry of Nuclear Reactor Coolant Circuits," Encyclopedia of Electrochemistry, A.J. Bard and M. Stratmann eds. Vol 5 Electrochemical Engineering, Edited by Digby D. Macdonald and Patrik Schmuki, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, pp. 665-720, (2007).

Previous Work in Modeling PCC Radiolysis in Water-Cooled Nuclear

Reactors

• Early work (prior to 1995) by Burns, Ishigure, Ibe, Ruiz, Christensen, Lukashenko, Pastina, Baldacchino, Bartels, and Elliot, to name a few of the more prominent researchers, modelled the radiolysis of coolant water in the primary coolant circuits (PCC) of water-cooled nuclear fission reactors, with the objective of calculating the concentrations of radiolysis products that micht pose a risk of enhanced corrosion.

• Electrochemical principles were generally foreign to the nuclear industry and the role of electrochemistry in the initiation and propagation of corrosion damage was not recognized. Also, it was not appreciated that the radiolysis products (O2, H2O2, H2, OH, H, HO2

-, etc) are electroactive species and hence can participate in corrosion ractions.

• Extension of coolant radiolysis models to incorporate electrochemical principles (e.g., calculation of the Electrochemical Corrosion Potential –”ECP”) was first reported by Macdonald and Urquidid-Macdonald and later by Macdonald and his co-workers, including Yeh, Motta, Engelhardt, Betuch, Kim, and Balachov (post 1993).

• These workers later incorporated the deterministic Coupled Environment Fracture Model (CEFM), such that the crack growth rate (CGR) and the integrated damage (crack length) could be accurately predicted at “state points” with a fuel cycle (post 1995).

• Later (post 1998), Macdonald and Balachov developed as series of codes for predicting IGSCC damage in stainless steels (ALERT, REMAIN) over multiple operational (fuel) cycles of BWRs

• In 2000, Macdonald and Urquidi-Macdonald developed PWR_ECP, which was the first code to estimated ECP in the PCC of a PWR. This code was expanded in 2005 by Macdonald and Kim (FOCUS) to model multiple fuel cycles of a PWR or a BWR and to estimate CGR in not only sensitized stainless steels, but also in mill-annealed Alloys 600 and 690.

Algorithm for Our Previous Work on Modeling Primary Coolant in Fission Reactors

T-H Data Velocity, Temp.

& Steam Quality

Initial Conditions

& Plant Data

Dose Rate Neutron

& Gamma

Corrosion Potential

Species Concentrations

Crack Growth Rate

Water Radiolysis

Radiolytic Effects

Chemical Reactions

Fluid Convection

Corrosion Evolutionary

Path

Integrated

Damage

I. Balachov, G. R. Engelhardt and D. D. Macdonald. “Deterministic Prediction of Damage in Boiling Water Reactors Due to Stress Corrosion Cracking”. Proc. Symp. Crit. Factors Localized Corros., (1999). Electrochemical Society, Pennington, N.J., 1998.

Boiling Water (Fission) Reactors

• Second most prevalent reactor type after PWRs.

• Direct steam cycle, no heat exchanger (steam generator).

• Boiling in-core at 288 oC, 1000 psia pressure.

• Carry-over of volatile radiolysis products (H2, O2, NH3) from the water phase to the steam phase in-core.

• Widely employs low-level suppression of radiolysis using 0.3 to 1.0 ppm of H2 added to the feedwater.

• Success of radiolysis suppression measured originally in terms of recirculation [O2], but now in terms of ECP (Electrochemical Corrosion Potential).

I. Balachov and D. D. Macdonald. “Enhancing the Operation of Boiling Water Reactors by Deterministic Simulation”, Proc. Water Chemistry ‘98, 1998 JAIF Int. Conf. Water Chem. Nucl. Power Plants, Kashiwazaki, Japan, Oct. 13-16 (1998).

Radiolysis of Water

~

111

~

100100100

)100100

(

FEACGEACGEACG

FN

G

N

GR

L

l

llllK

k

n

k

n

k

n

k

n

kJ

j

jjjj

V

nn

i

V

iy

i

Source Term

Primary Radiation Dose

Activated

Corrosion

Products

T. K. Yeh, D. D. Macdonald, and A. T. Motta. “Modeling Water Chemistry, Electrochemical Corrosion Potential and Crack Growth Rate in the Boiling Water Reactor Heat Transport Circuits-Part I: The DAMAGE-PREDICTOR Algorithm”. Nucl. Sci. Eng., 121, 468-482 (1995).

12

34

5

6

7

8

9

10

Steam Separator

Feedwater

Main Steam Line

Recirculation Pump

Figure 18. Schematic of the primary

coolant circuit of a BWR having external

pumps. The regions are identified as:

(1) Core Channels;

(2) Core Bypass;

(3) Upper Plenum;

(4) Mixing Plenum;

(5) Upper Down-comer;

(6) Lower Downcomer;

(7) Recirculation System;

(8) Jet Pump;

(9) Bottom of Lower Plenum;

(10) Top of lower plenum.

Schematic of Primary Coolant Circuit of a BWR.

T. K. Yeh, D. D. Macdonald, and A. T. Motta. “Modeling Water Chemistry, Electrochemical Corrosion Potential and Crack Growth Rate in the Boiling Water Reactor Heat Transport Circuits-Part I: The DAMAGE-PREDICTOR Algorithm”. Nucl. Sci. Eng., 121, 468-482 (1995).

Component 1 Component 2

Component 3 Component 4

Component 5

Component 6

Component 10

Component 7

Component 8

Core Channel Core Bypass

Upper Plenum Mixing Plenum

Upper Downcomer

Lower Downcomer

Recirculation

System

Jet Pump

Top Lower Plenum

f f

To Steam Line

f

f

Feedwater

f

f

f

Liquid

Steam

f

f

f

: Fraction of Mass Flow into Core Channel

: Fraction of Mass Flow out of the Circuit or

: Fraction of Mass Flow from Upper Downcomer into Jet Pump

Rat ion of Feedwater Mass Flow to Total Mass Flow

Component 9

Bottom Lower Plenum

Primary Coolant Flow

Diagram for a BWR.


Table 2. Extended list of reactions considered in the water

Radiolysis Model. The rate constants refer to a temperature of

25 oC. The kinetic data are taken principally from Burns and

Moore[4].

No. Rate Constant Activation Energy Chemical Reaction (l/mol-sec) (kcal/Mol) 1 1.6E+1 3.0E0 e- + H2O = H + OH- 2 2.4E+10 3.0E0 e- + H+ = H 3 2.4E+10 3.0E0 e- + OH = OH- 4 1.3E+10 3.0E0 e- + H2O2 = OH + OH- 5 1.0E+10 3.0E0 H + H = H2 6 2.0E+10 3.0E0 e- + HO2 = HO2

- 7 1.9E+10 3.0E0 e- + O2 = O2

- 8 5.0E+9 3.0E0 2e- + 2H2O = 2OH- + H2 9 4.5E+9 3.0E0 OH + OH = H2O2 10 1.2E+10 3.0E0 OH + HO2 = H2O + O2 11 1.2E+10 3.0E0 OH + O2

- = OH- + O2 12 2.0E+7 3.0E0 OH- + H = e- + H2O 13 4.5E+8 3.0E0 e- + H + H2O = OH- + H2

9

14 6.3E+7 3.0E0 e- + HO2- + H2O = OH + 2OH-

15 1.44E+11 3.0E0 H+ + OH- = H2O 16 2.6E-5 3.0E0 H2O = H+ + OH- 17 2.0E+10 3.0E0 H + OH = H2O 18 3.4E+7 4.6E0 OH + H2 = H + H2O 19 2.70E+7 3.4E0 OH + H2O2 = H2O + HO2 20 4.4E+7 4.5E0 H + H2O2 = OH + H2O 21 1.9E+10 3.0E0 H + O2 = HO2 22 8.0E+5 3.0E0 HO2 = O2

- + H+ 23 5.0E+10 3.0E0 O2

- + H+ = HO2 24 2.7E+6 4.5E0 2HO2 = H2O2 + O2 25 1.7E+7 4.5E0 2O2

- + 2H2O = H2O2 +O2+ 2OH- 26 2.0E+10 3.0E0 H + HO2 = H2O2 27 2.0E+10 3.0E0 H + O2

- = HO2-

28 1.3E+8 4.5E0 e- + O2- + H2O = HO2

- + OH- 29 1.8E+8 4.5E0 OH- + H2O2 = HO2

- + H2O 30 1.9973E-6 14.8E0 2H2O2 = 2H2O + O2 31 1.04E-4 3.0E0 H + H2O = H2 + OH 32 1.02E+4 3.0E0 H2O + HO2

- = H2O2 + OH- 33 1.5E+7 4.5E0 HO2 + O2

- = O2 + HO2-

34 7.7E-4 7.3E0 H2O2 = 2OH

10

W. G. Burns and P. B. Moore, Radiation Effects, 30, 233 (1976). J. Elliot, “Rate Constants and G-Values for the Simulation of the Radiolysis of Light Water over the Range 0 – 300 oC”, AECL-11073, COC – 94 -167 (1994).

Specie Primary G-Values (# species formed / 100 eV of energy absorbed)

Specie No. Gama Neutron Specie

1 2.66E0 0.37E0 e-

2 0.55E0 0.36E0 H

3 2.67E0 0.46E0 OH

4 0.72E0 1.00E0 H2O2

5 0.00E0 0.17E0 HO2

6 0.00E0 0.00E0 HO2-

7 0.00E0 0.00E0 O2

8 0.00E0 0.00E0 O2-

12 0.45E0 1.20E0 H2

13 0.10E0 0.00E0 OH-

14 2.76E0 0.37E0 H+

11

W. G. Burns and P. B. Moore, Radiation Effects, 30, 233 (1976). J. Elliot, “Rate Constants and G-Values for the Simulation of the Radiolysis of Light Water over the Range 0 – 300 oC”, AECL-11073, COC – 94 -167 (1994).

Radiolysis of Water in the Heat

Transport Circuit

• Balance of Species: LOSS + GAIN = 0 • Radiolytic Yield

• Chemical Kinetics (Reactants & Products)

• Boiling (Liquid and Gas Exchange)

• Convection

0.)dVCmC(mdV]dx

)d(uC[

]dVCkCCCk[rdVF)100N

G

100N

G(

gfii

gii

i

N

1s

N

1sssii

N

1mmssm

V

nni

V

ggi

~

12

Need to solve 14 stiff differential equations for

each location in the primary coolant circuit.


Electrochemical Corrosion Potential (ECP)

• R/O Reactions at Metal/Solution Interface

•

• Charge and Mass Transfer

• Conservation of Charge: Net Current is Zero

• Mixed Potential, ECP

H 2H 2e

O 4H 4e 2H O

H O 2H 2e 2H O

2+ -

2+ -

2

2 2+ -

2

ie e

1

i

1

ie

1

ie

R/O

(E E )/b (E E )/b

0,R/O i,f

(E E )/b

i,r

(E E )/b

R/Oe

a R/Oe

c

R/Oe

a R/Oe

c

i (E) i (E) 0R/O,jj 1

n

corr

13


ECP Calculated/Measured (Liebstadt) Recirculation

Feedwater Hydrogen Concentration (ppm)

0.0 0.5 1.0 1.5 2.0

EC

P (

mV

)

-500

-400

-300

-200

-100

0

100

200

300

Measured (accuracy = 50 mV)

Calculated (accuracy = 40 mV)


Oxygen Concentration (Liebstadt) NWC HWC (0.5 ppm H2)

[H2]FW = 0.0 ppm

Flow Path Distance from Core Inlet (cm)

0 1000 2000 3000 4000 5000 6000 7000

Oxygen C

oncentr

ation (

ppm

)

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Normal Calibration

High LP [O2] Calibration

CC : Core ChannelCB : Core BypassUP : Upper PlenumMP : Mixing PlenumUD : Upper DowncomerLD : Lower DowncomerRS : Recirculation SystemJP : Jet PumpBLP : Bottom Lower PlenumTLP : Top Lower Plenum

CCCB

UP MPUD

LDRS

JP BLP TLP

[H2]FW = 0.50 ppm


0 1000 2000 3000 4000 5000 6000 7000

Oxygen C

oncentr

ation (

ppm

)

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Normal Calibration



CC

CB

UP MP

UD

LD

RS

JP BLPTLP

15

D. D. Macdonald, and I. Balachov, “On the Determination of Bottom Drain Oxygen in Boiling Water Reactors”, Nuclear Technology, 120, 86-93 (1997).

H2O2 Concentration (Liebstadt) NWC HWC (0.5 ppm H2)

[H2]FW = 0.0 ppm


0 1000 2000 3000 4000 5000 6000 7000

Hydro

gen P

ero

xid

e C

oncentr

ation (

ppm

)

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Normal Calibration



CC

CB

UP

MP

UD LDRS JP

BLP TLP

[H2]FW = 0.50 ppm


0 1000 2000 3000 4000 5000 6000 7000

Hydro

gen P

ero

xid

e C

oncentr

ation (

ppm

)

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Normal Calibration



CC

CB

UP

MP

UDLD

RS JP BLP TLP

16


H2 Concentration (Liebstadt) NWC HWC (0.5 ppm H2)

[H2]FW = 0.0 ppm


0 1000 2000 3000 4000 5000 6000 7000

Hyd

roge

n C

on

cen

tra

tio

n (

pp

m)

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Normal Calibration



CC

CB

UP MPUD

LDRS

JP BLPTLP

[H2]FW = 0.50 ppm


0 1000 2000 3000 4000 5000 6000 7000

Hyd

roge

n C

on

cen

tra

tio

n (

pp

m)

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Normal Calibration



CC

CB

UP MPUD LD

RSJP BLP TLP

17


ECP in Liebstadt

Figure 21. Predicted corrosion potential (ECP) vs. flow path distance from the bottom of the core for 0 and 1.2 ppm of hydrogen added to the feedwater of the Leibstadt BWR 19. The locations correspond to those given in Figure 19.

18

D. D. Macdonald, Iouri Balachov, and George Engelhardt, “Deterministic Prediction of Localized Corrosion Damage in Power Plant Coolant Circuits”, Power Plant Chemistry, 1(1), 9–16 (1999).

Figure 36. Schematic of a PWR primary coolant circuit.

Schematic of a PWR Primary Coolant System

Figure 37. Schematic of a PWR reactor vessel showing the various internal components.

T = 290 oC – 330 oC P = 150 b (2250 psia)

Core Channel Dose Rate γ-Photon Neutron Particles

3 x 105rad/s 6 x 105rad/s 3 x 105rad/s

Coolant Mass Flow Rate

18,000kg/s

Figure 38. pH control strategies affected by adjusting the lithium concentration as the boron is

consumed during fuel burn-up. The trajectory that is commonly employed over a typical fuel cycle

is represented by the hatched path, with the lithium concentration being controlled by ion

exchange.

Chemistry Control in the PHTS Over a Fuel Cycle in a

PWR.


Comparison of ECP values throughout the RCS loop (using Alloy 600)

Time (months)

0 2 4 6 8 10 12

EC

P (

mV

SH

E)

-900

-850

-800

-750

-700

-650

-600

Boro

n C

oncentr

atio

n (

ppm

)

0

500

1000

1500

2000

2500

pH

5.8

6.0

6.2

6.4

6.6

6.8

7.0

7.2

7.4

7.6

ECP at Bottom of Core

ECP at Top of Core

ECP at Hot Leg

ECP at U-tube Hotside

ECP at U-tube Coldside

ECP at Cold Leg

Boron Concentration

pH at Bottom of Core

pH at Top of Core

Sensitivity Study

H.-S. Kim and D. D. Macdonald, “Specification of PWR Primary Coolant Chemistry”, to be published.

Coordinated Chemistry

Coordinated Chemistry

Time (months)

0 2 4 6 8 10 12

CB (

pp

m)

500

1000

1500

2000

2500

pH

6.0

6.2

6.4

6.6

6.8

7.0

EC

P (

mV

SH

E)

-900

-880

-860

-840

-820

-800

CL

i (p

pm

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

CB

pH

ECP

CLi

-835mVSHE

PWSCC od Alloy 600 predicted and found, because ECP is more negative

than -835 mVshe

.


Adjusted Chemistry Modified Chemistry

Time (months)

0 2 4 6 8 10 12

CB (

pp

m)

500

1000

1500

2000

2500

pH

6.0

6.2

6.4

6.6

6.8

7.0

EC

P (

mV

SH

E)

-900

-880

-860

-840

-820

-800

CL

i (p

pm

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

CB

pH

ECP

CLi-835mVSHE

PWSCC od Alloy 600 not predicted and not found, because

ECP is more positive than -835 mVshe

.


Fusion Reactors

• Following the success of JET (Joint European Torus) in the UK, which demonstrated controlled thermonuclear fusion: 3T1 + 2D1 4He2 + 1n0 (14 MeV vs 4.8 MeV for fission neutrons) by exceeding the Lawson Energy Balance (Q = energy out/energy in), a multi-national effort, is developing an experimental fusion reactor in Cadarache, France to demonstrate that a sufficiently high Q may be obtained for fusion power to be commercially feasible (Q > 10).

• Fusion reactors will also incorporate “on-board” tritium generation via the nuclear reaction: 1n0 + 6Li3 3T1 + 4He2 using an aqueous 6LiOH blanket.

• Important differences between the experimental fusion and operating fission reactors (BWRs and PWRs) include: (a) Lower operating temperature (< 200 oC vs 288 oC – 320 oC); (b) Higher LET radiation; (c) More complicated PHTS; (d) Not designed to produce power, just to demonstrate the fission concept.

ITER Preliminary Calculations

• Used code that was originally developed for describing radiolysis in Zircaloy crevices in the cores of Westinghouse PWRs.

• Assumed dose rates of 1.0e20 eV/cm3, 3.0e21 eV/cm3, 3.0e21 eV/cm3 for n, γ, and α radiation. These values are not considered to be very representative of ITER.

• G-values taken from PWR_ECP that was developed to model a Framatome (AREVA) PWR in France. The G values are traceable to the work of John Elliot at CRNL of AECL and are probably the best set that currently exists.

• Reaction model taken from PWR_ECP. This code calculates the electrochemical corrosion potential (ECP) around a PWR PHTS.

• Defined suppression of radiolysis metric as: O/R = sum of the concentrations of oxidizing species (H2O2, O2, OH)/sum of the concentrations of reducing species (H2, H, O2

-). This would be best done by calculating the ECP for each structural material, but this was not included in the SoW.

High LET component of the radiation (fast 1n0, 14.1 MeV). Primary radiolytic yields depend on the Linear Energy Transfer (LET) value, which is a measure of how much energy is absorbed by the medium per unit length of travel (eV/nm).

Figure 14: (a) G-values for 𝑒𝑎𝑞

− (filled squares), H (filled triangles) and H2 (filled and open diamonds) as

a function of LET. (b) G-values for OH (filled and open squares, H2O2 (filled and open diamonds) and

HO2 (filled triangle) (filled squares), as a function of LET. Data from Elliot and McCracken

a

b

A. J. Elliot and D. R. McCracken, “Effect of temperature on O- reactions and equilibria: A pulse radiolysis study”, Radiat. Phys. Chem., 33, 69 – 74 (1989).

Water radiolysis

– No Added

Hydrogen T = 120

0C , G

n = 0.8

W/cm3, G

g= 0.2 W/cm

3,

[O2]in

= 10 ppb, [H2]in

= 0

Time, s

1e-8 1e-7 1e-6 1e-5 1e-4 1e-3 1e-2 1e-1 1e+0 1e+1

Co

nce

ntr

atio

n,

M

1e-13

1e-12

1e-11

1e-10

1e-9

1e-8

1e-7

1e-6

1e-5

1e-4

1e-3

1e-2

H2

OH-

e-

H+

OH

H2O

2

H

HO2

HO2

-

O2

O2

-G. R. Engelhardt and D. D. Macdonald, to be published.

Water Radiolysis –

Added Hydrogen

T = 120 0C , G

n = 0.8 W/cm

3, G

g= 0.2

W/cm3, [O

2]in

= 10 ppb, [H2]in

= 25 cc/kg

STP

Time, s

1e-8 1e-7 1e-6 1e-5 1e-4 1e-3 1e-2 1e-1 1e+0 1e+1

Concentr

ation

, M

1e-13

1e-12

1e-11

1e-10

1e-9

1e-8

1e-7

1e-6

1e-5

1e-4

1e-3

1e-2

H2

OH-

e-

H+

OH

H2O

2

H

HO2

HO2

-

O2

O2

-

G. R. Engelhardt and D. D. Macdonald, to be published.

Extent of radiolysis suppression in acidic B(OH)3 solution (1000 ppm B, open symbols) and basic LiOH

(10-4 m, filled symbols) as a function of added hydrogen to the system.

G. R. Engelhardt and D. D. Macdonald, to be published.

Figure 17. Comparison of calculated electrochemical potentials

for Type 304 and 316 SS with experimental data obtained in

hydrogenated solutions and deoxygenated solutions.

Figure 26: Variation of ECP of stainless steel in the ITER

PHTS as a function of periodic plasma burning of 400 s. After

Wikman et.al.

S. Wikman, A. Molander, J. Oijerholm, J. Eskhult, and O. Tomblom, “Recent developments and Quantification of Materials for the European Contribution to ITER”, ITR P1-53

Mathematical Considerations

)C,...,C,t,x(Rx

C)t(V

t

CNi

ii1

It is assumed that the velocity V(t) as a function of t is known.

Temperature, pressure, and radiation dose are known as functions of

x and t. In this case, the source terms can be calculated as functions

of x, t, and all concentrations, Ci(x,t).

t

dttVxxtu0

')'(),(

),...,,,')'(( 1

0

N

t

ii CCtdttVuR

t

C

By introducing new variable

we reduce the problem to the solution of the system of ordinary

differential equations

which was solved by using Rosenbrock method with adaptive step control.

Mass balance equation for i-th species:

Basic element for describing

complicated system

Each element is characterized by the following set of parameters:

L - length of the element

V – averaged hydrodynamic velocity

T - temperature

Γn – neutron absorption rate

Γγ – gamma absorption rate

Γα – alpha absorption rate

Dh – hydraulic diameter

It is assumed that basic elements are sufficiently short (L is sufficiently small) that V,

T, Γn, Γγ, Γα and Dh can be considered to be constant within these elements.

V Dh

L

Ck,in Ck,out

Computer code was developed

Input data:

Ck,in, k = 1, 2,…,K Output data:

Ck,out, k = 1, 2,…,K

IBED PHTS Perspective View Complicated system can be considered as parallel and series combination of basic elements

Reactions of copper ions with water radiolysis products.

Copper is the most important impurity.

CueCu aq

2

OHOHCuOHHOCu 22

2

22

OHOHCuOHCu 2

22

22

2 OHCuHOCu

HCuHCu 222 2

2

2

2

2 OCuOCu

HCuHCu2

OLI Software!!!

IBED PHTS Chemistry

Parameterster

Copper and Iron limits can

be changed. The decision on

the use of hydrogen for

chemistry/radiolysis control

is pending.

Parameter IBED PHTS

Conductivity @ 25 0C, mS/cm <= 0.2

pH @ 25 0C 7.0 – 9.0

Sodium, ppb <= 5

Hydrogen, ppb <= 350

Catalyzed Hydrazine, ppb <= 30

Ammonia, ppb <= 10000

Oxygen, ppb <= 10

ORP @ 25 0C, mV (-400) – (-100)

Iron, ppb <= 10

Copper, ppb <= 10

Chloride, ppb <= 5

Concentrations of copper ions as

functions of the tube length at [H2]in

= 0

Tube Lenght / M

0.01 0.1 1 10

Concentr

ation / M

1e-12

1e-11

1e-10

1e-9

1e-8

1e-7

1e-6

Cu2+

Cu+

T = 120 0C

n = 0.8 W/cm3

= 0.2 W/cm3

V = 10 m/s

[Cu2+]in = 10 ppb

Copper exists mainly in the form of Cu2+.

Concentrations of copper ions

as functions of the tube length

at [H2]in

= 25 cc/kg STP

T = 120 0C

n = 0.8 W/cm3

= 0.2 W/cm3

V = 10 m/s

[Cu2+]in = 10 ppb

At large tube length copper exists mainly in the form of Cu+.

Tube Lenght / M

0.01 0.1 1 10

Concentr

ation / M

1e-10

1e-9

1e-8

1e-7

1e-6

Cu2+

Cu+

Polarization curves for carbon steel corrosion in

1.4x10-7

M CuCl2 + 1.3x10

-5 M NaOH at T =100

0C

pH = 9 at T = 25 0C

Cu(II) reduction and water reduction are the leading cathodic

reactions and may drive anodic corrosion reactions.

Summary

• Complicated ITER system can be subdivided into parallel and series

combination of basic elements. Within each elements physical parameters:

velocity, temperature, radiation rates, etc.) are considered to be constant.

Computer code was developed for calculating concentration of all species

at output of this element if concentration of these species at input is known.

• It was taken into account interactions of radiolysis products with certain

impurities, which the reactor water coolant can contain.

• Thus for the most important impurity - copper it was shown that copper

exists mainly in the form of Cu2+ at the absence (small concentration) of

hydrogen in the system. In this case the reaction Cu2+ Cu+ + e- can

be one of the leading cathodic reactions in the system and accordingly can

substantially increase corrosion potential.

• It was shown that at the addition of hydrogen to the water coolant copper

exists mainly in the form of Cu+ and reaction of copper(II) reduction does

not take play substantial role. Accordingly the addition of hydrogen for

chemistry/radiolysis control is recommended.

Acknowledgements

• The authors gratefully acknowledge the support of

this work by the Oak Ridge National Laboratory

under Contract UT–Battelle # 4000146085.

• We also acknowledge helpful discussions with Dr.

David Bartels of the University of Notre Dame on

radiolysis of water issues.

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