The Swedish nuclear reactors are enclosed by a prestressed concrete containment. To prevent corrosion, the ducts in several containments have been grouted. When using this system, problems arise in monitoring the prestress losses. When the nuclear power plant Olkiluoto was built in Finland in the mid-1970s, several prestressed concrete beams were constructed. Five of these beams were recently tested in order to determine the prestress losses. The prestress losses have also been calculated using different models for predicting creep and shrinkage of the concrete and the relaxation in the tendons. This paper presents the results from both the tests and the models. The measured prestress losses were quite high, ranging from 37% to 61%. The most accurate of the prediction models was model B3, which was in good agreement with the measured prestress losses. Explanations forthe scatter in the measured results and the difference between the results obtained from the prediction models and the tests are proposed in this paper.
