The startup of the Dodewaard natural circulation BWR - experiences

During the recent two startups of the Dodewaard natural circulation boiling water reactor various parameters have been measured and recorded. The measurements during the first one (February 1992 startup after refuelling - the beginning of cycle 23) have been more extensive covering items like the recirculation flow, incore steam velocity, downcomer pressure difference, downcomer subcooling and reactor thermo hydraulic stability. Due to the extensive set of measurements this startup was prolonged. In order to give an impression of a normal startup time schedule, data from a normal startup (June 1992) are also presented in this paper, together with a brief description of the Dodewaard reactor and its startup procedure. The results of the particular measurements have shown a very early recirculation flow onset already during the low power operation and no indications of reactor instability whatsoever have been observed. (author)