Keywords: concrete damage, concrete creep, nuclear power plant containment, coupled problem.

Many EU countries have the problem of the increasing consumption of electrical energy. In addition to that, there are many power plants either coal or nuclear at the end of their projected service life. Usually, the prolongation of service life of coal power plants is not supported with respect to the living environment. In the case of nuclear power plants, the situation is different because it seems that the production of energy in nuclear power plants will be relatively cheap, sources of atomic fuel are located in relatively stable countries and the problem with nuclear waste can be solved. That is why the actual operating nuclear power plants are considered for prolongation of their service life.

Our department was invited to analyse the nuclear power plant in Temelín with a focus on the life prolongation of the plant. One of the key points was the prediction of security of concrete containments. The simulation should capture a period about thirty years with possible extension up to fifty years and one of the requirements was that the results of the analysis should be in good agreement with measurements of strains at the reinforcement. The reinforcement of the containment is organised at all principal directions i.e. there are vertical, radial and side reinforcement. Under these conditions, the model used has to be in three dimensions in order to capture strains in the reinforcement.

The given containment consists of a prestressed concrete cylindrical structure which is also affected by temperature changes caused by the operating nuclear reactor. The moisture problem was not assumed with respect to the age of the concrete analysed. From the material point of view, concrete exhibits very complex behaviour and it is necessary to use several material models to capture major phenomena. In the performed analyses, creep, ageing and damage effects have been taken into account. The paper also describes the coupling of these models together and describes used damage models. More details about creep modelling and modelling of prestressing can be found in Krejcí [1].

The coupled thermo-mechanical analysis had to be performed with respect to these assumptions. In addition to that, the geometry and stress state in the containment have the required three-dimensional geometric model. Generally, the coupled problems have high computing demands especially in the case of three-dimensional problems and this led to modelling only a typical section of the containment but in three dimensions and with significant detail.

The results from the analyses performed have been compared with measured strains in the reinforcement. There is also a comparison of results obtained with the use of different damage models (scalar isotropic damage model, anisotropic damage model and orthotropic damage model).

1

T. Krejcí, T. Koudelka, J. Šejnoha, "Computer Simulation of Concrete Structures subject to Cyclic Temperature Loading", in B.H.V. Topping, L.F. Costa Neves, R.C. Barros, (Editors), "Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, 2009. doi:10.4203/ccp.91.131

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £140 +P&P)