Preliminary operating experiences with the AVR at an average hot-gas temperature of 9500C

The two-loop system with a high temperature reactor, which is operated by the Arbeitsgemeinschaft Versuchsreaktor (AVR) GmbH and which was built by the BBC/Krupp consortium (today HRB), has been in operation for more than seven years. In that time more than 635 x 106kWhr have been produced and more that 6.5 x 105 spherical fuel elements have been circulated under operation. The fully integrated design, and above all the ceramic gas duct, permit very high gas temperatures although no high alloyed, heat resistant steels were used in the reactor. In February 1974 the average hot-gas temperature at the outlet of the core could thus be increased from its original design value of 8500C to 9500C. Peak temperatures of above 500C are thereby confined to a small region between the middle of the core and the beginning of the steam generator. Carbon protects the steel structures against high temperatures. Unplanned interruptions and reductions of operation due to the increase of the hot-gas temperature have not occurred so far. Some thermocouples in the hot-gas region failed. All other components functioned satisfactorily and, one year after the increase in the hot-gas temperature, there are no misgivings as to their future functioning. These satisfactory but short operating experiences at 9500C will have to be supplemented in the next few years by experiences over a longer period. (Auth.)