Transcript LWR oxide model for improved understanding of activity

LWR oxide model for improved
understanding of activity build-up and
corrosion phenomena (LWROXI), 2004-2006
Kinetics of the growth and restructuring of the oxide layer on stainless
steel in a light water reactor coolant
Martin Bojinov, Petri Kinnunen
VTT Industrial Systems
SAFIR-puoliväliseminaari 20.-21.1.2005
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
What the project is about?
Co olant wate r
60Co
H 2O
I
De pos ite d o ute r
oxide laye r
Inne r oxide layer
II
III
Fe2+
Bas e me tal
Modelling approaches for steps I-III were separately
developed in the former FINNUS research program
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
What the project is about?
The goals of the project are
• to develop a predictive model for activity build-up in nuclear power
plants
• to increase the understanding and develop a phenomenological
model of the oxide film build-up and break-down, controlling the
stress corrosion cracking.
• This work is performed in co-operation with ALARA Engineering
(Sweden) and Advanced Nuclear Technology (ANT, Sweden), who have
long experience of BWR type water chemistries in Sweden and Finland.
• The work is funded by VYR, Statens kärnkraftinspektion (SKI, Sweden)
and Statens strålskyddsinstitut (SSI, Sweden)
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Tasks of the project (1/3)
Stage I. State-of-the-art and refinement of the model for oxide films in LWRs (2004).
1. Literature review of oxide growth and restructuring
2. Description of the current state of the model for oxide films on stainless
steels and nickel base alloys in LWRs.
3. Refinement of the model for oxide films on stainless steels and nickel base
alloys in LWRs.
Results presented in:
Characterisation and modelling of oxide films on stainless steels and nickel alloys in light
water reactors (Bojinov, Martin; Kinnunen, Petri; Lundgren, Klas; Wikmark, Gunnar, 2004,
VTT Industrial Systems, Espoo. 142 s. Research report No. BTUO : 73-041285
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Tasks of the project (2/3)
Stage II. Further development and quantification of the Mixed-Conduction Model (2005).
4. Further development and quantification of the surface complexation / deposition
model at the oxide / coolant interface.
• To experimentally produce high temperature data to be used in estimating
surface complexation constants for adsorption reactions of different cations.
This data is needed in establishing a foundation for item 7. Equipment
produced in SAFIR/INTELI -project in 2004.
5. Further development and quantification of the Mixed-Conduction Model for the
inner compact layer of the oxide film.
• The information obtained during 2004 on the compact film and that
obtained in item 4 will be combined in order to cover all the possible paths
for transport and incorporation of minor species in the oxide. This
information is needed for item 7.
6. Critical analysis and evaluation of LWR data on water chemistry and activity
build-up to be used in integrating the modelling approach to real process
conditions.
• This information is needed for item 7.
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Tasks of the project (3/3)
Stage III. Benchmarking and development of an integrated model (2006).
7. Benchmarking by comparison of plant data and model predictions.
• The benchmarking will be made on basis of the previous performed plant
data analysis, and the parallel performed development of an integrated
activity build-up model, i.e. in an iterative process. )
8. Development of an integrated activity build-up model.
Development of an integrated activity build-up model includes the data,
insights and sub-models gained in steps 1 to 6. The integrated model will
be used to predict a few typical scenarios planned for already operating or
new BWR or PWR plants, in order to demonstrate and establish the
applicability of the model.
9. Reporting.
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VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Oxidation of stainless steels in high temperature electrolytes
k4

k2 V O
VO
H2O
H+
CrIII
Crm
Vm
Fe
Steel
CrIIICr
Cr
k1
k1i
e-
OO
V ´´´
Cr
V ´´´
Cr
Fe i
Fe i
Ni i
Ni i
Barrier
inner layer
k3
6+
Craq
k3i
kr
2+
Fe y+
,Ni
aq
aq
Precipitated
outer layer
Electrolyte
sMFE = RT / [F2 (32Di)1/2 cion(L)(1-a)]
cion(L) = (k1i / k3i ) exp(-2KL) + k1i /(2KDi) + 2.25 (k3 / k1)
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