Restraint forces of HTR-concrete during heat-up to 300 deg C

In course of the research and development of the prestressed concrete vessel for the HTR-500 high temperature reactor, the comprehensive analyses concerning the technology and the thermomechanical behavior of concrete have been carried out. The tests were initiated by Hochtemperatur-Reaktorbau GmbH, and executed by the Institut fuer Baustoffe, Massivbau und Brandschutz. Some of the results of the previous studies concerning the creep and strength at service or accident temperature up to 600 deg C have already been published. However up to now, there is no established concept at hand to estimate the restraint stress with sufficient accuracy. Accordingly, restraint test was necessary to gather the required reliable data for the elaboration and confinement of a constitutive model. The restraint test which is reported in this paper is strongly related to the real conditions in PCRVs as far as the initial mechanical stress and heating rate are concerned. Only two limit states of the moisture regimes were able to be included in the test program: free evaporation of water and complete prevention of water evaporation. The experiment and the results are reported. (K.I.)