La atribución de la guarda y custodia de los hijos tras ruptura convivencial de los progenitores De acuerdo con el objeto del presente trabajo,

The co-operation between VTT and OECD Halden Reactor Project has resulted in the development of a prototype of an in-core Pd reference electrode which can be used for several years in in-core locations for corrosion potential measurements. This is a significant step in performing in-line water chemistry monitoring in in-core locations of boiling water reactors since the life time and accuracy of the commercially available sensors is limited to less than one fuel

cycle. Long term in-core and calibration runs will be performed at Halden test

reactor during the years 1999−2000. Improvements in the in-line monitoring

technology due to these new high temperature sensors allow for an improved analysis and narrow range control of “true” operational environments.

6. Conclusions

The main conclusions from this subproject dealing with oxide films in high temperature aqueous environments are:

• Installation of a TrendChem high-temperature water chemistry monitoring

system at Loviisa plant has enabled the establishment of correlations between the applied water chemistry, oxide film properties and the extent of activity incorporation on primary circuit material surfaces.

• The development of a thin-layer electrode arrangement has made it possible

to conduct versatile electrochemical measurements in simulated power plant coolants, even in poorly conductive BWR coolants.

• The combination of results obtained using the developed electrochemical and

new surface analytical techniques together with mechanistic modelling has facilitated the clarification of the mechanisms of phenomena related to activity build-up on primary coolant surfaces and to different types of corrosion.

The studies focused so far mainly on grown-on oxide films need to to be extended to cover also the deposited layer of the oxide film. This is how the transport of species through the whole oxide film can be modelled and the impact of transport properties on activity incorporation and corrosion rate can be estimated. Investigations in carefully controlled simulated conditions need to be continuously supported by plant experiments in order to guarantee the relevance of the experiments. This can be best accomplished if the developed techniques are installed and can be tested in Finnish nuclear power plants.

7. Acknowledgements

The reported work was part of the Finnish Research Programme on the Structural Integrity of Nuclear Power Plants 1995 - 1998, subproject RAVA5 on Material Degradation in Reactor Environment. This subproject was not included in the original RATU2 plans, but increased interest in behaviour of oxide films and activity pickup gave reason to launch this RAVA5 subproject starting in 1997. The work for Chapter 2 was completed in 1997 - 1998, Chapter 3 in 1997, Chapter 4 in 1998 and Chapter 5 in 1997 - 1998.

Co-operation with Seija Suksi and Juhani Hinttala from the Radiation and Nuclear Safety Authority (STUK), Thomas Buddas, Magnus Halin, Kimmo Tompuri and Ossi Hietanen from IVO and Anneli Reinvall, Erkki Muttilainen and Olli-Pekka Luhta from TVO, together with many other colleagues is gratefully acknowledged. The work was coordinated to the co-operation with the OECD Halden Reactor Project, Norway.

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