Maximum allowable power levels in HANARO fuel channels

HANARO is a light-water-cooled and heavy-water-reflected research reactor designed and operated at a full power of 30 MWth. The compact core is composed of 23 hexagonal and 16 circular flow channels. Each hexagonal flow channel, formed by a hexagonal flow tube, is loaded with a hexagonal fuel bundle which has 36 fuel elements. The circular flow channel formed by a circular flow tube is loaded with a circular fuel bundle which has 18 fuel elements. In the thermalhydraulic design of the HANARO, the design limit values for the three design parameters were determined using the statistical thermal design method. The design basis is that for the normal operation and the operational occurrences, the physical phenomena like as CHF (Critical Heat Flux) or ONB(Onset of Nucleate Boiling) would not occur with the 95% of probability and the 95% confidence level as illustrated in Figure 1. In this paper, the maximum power levels satisfying the design limits were obtained and the safe operational ranges were made for the four different fuel channels