What the project is about?

1. 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

2. What the project is about? Modelling approaches for steps I-III were separately developed in the former FINNUS research program SAFIR-puoliväliseminaari 20.-21.1.2005

3. 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) SAFIR-puoliväliseminaari 20.-21.1.2005

4. 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 SAFIR-puoliväliseminaari 20.-21.1.2005

5. 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. SAFIR-puoliväliseminaari 20.-21.1.2005

6. 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. SAFIR-puoliväliseminaari 20.-21.1.2005

7. sMFE = RT / [F2 (32Di)1/2 cion(L)(1-a)] cion(L) = (k1i / k3i ) exp(-2KL) + k1i /(2KDi) + 2.25 (k3 / k1) Oxidation of stainless steels in high temperature electrolytes SAFIR-puoliväliseminaari 20.-21.1.2005