| Abstract: | An advanced startup procedure for the PIUS-type reactor has been developed. The procedure is related to the way to isolate the primary loops from the borated reactor pool by establishing stable hot/cold water interfaces in the so-called density lock sections. The procedure starts with accumulating preheated water in the high points of the steam-generator-side legs. Then, by restarting the reactor coolant pumps, the primary loops can be isolated from the pool as the primary loops reaches a uniformly higher temperature than the pool water. The additional components required for this procedure are only a low-pressure grade heater and a pump of small capacities. Since the isolation is achieved with the density locks left open, the core shutdown and cooling capabilities by means of the natural circulation of borated water are maintained in case of any abnormal events during startup. The feasibility and the predictability of this procedure were investigated by running an experiment in a scaled single-loop facility and conducting an analysis using a one-dimensional model. Both in the experiment and in the analysis. the primary loop was successfully isolated from the pool. |
