Study on the natural circulation characteristics of the integral type reactor for vertical and inclined conditions

To investigate the thermal-hydraulic characteristics during natural circulation in an integral type marine reactor, basic single-phase natural circulation experiments were performed using scaled test facilities of the Syslem-integrated Modular Advanced Reactor (SMART), and the RETRAN-03ʹINT code was developed. For both vertical and inclined conditions, the flow distribution through eight steam generator cassettes and thermal mixing in downcomer regions were observed. It was found that feedwater isolation does not enhance the asymmetric temperature distribution at the outlets of the steam generator cassettes. For inclined conditions, the results show typical flow characteristics according to the inclination angles. Flow rates in ascending steam generator cassettes increase by the increase in the thermal driving head, and consequently the outlet temperatures increase. Analytical and experimental results showed good agreements and it was concluded that RETRAN-03/INT is sufficiently capable of analyzing three-dimensional phenomena in an integral type reactor.