Experimental investigations on the heat transfer characteristics in a natural circulation loop for an integral type reactor

The natural circulation characteristics in the primary loop of an integral type reactor were experimentally investigated during various operational conditions by using the VISTA facility. The test matrices included the natural circulation characterization tests and operational transient tests. The heat transfer characteristics in a natural circulation loop for an integral type reactor were experimentally investigated by using the VISTA facility and steady-state natural circulation tests were performed by changing the core power and feed water flow rate simultaneously. The initial core power and feed water flow rate were 25%. During a natural circulation operation both the core power and feed water flow rate were changed from 20% to 50%. The experimental data were compared with the predictions from existing correlations of Duffey et al. [1] and Vijayan et al. [2]. It was shown that Duffey et al.'s correlation [1] for a two-phase natural circulation predicted the experimental data very accurately. Also four operational transient tests were performed for the cases of feed water increase, feed water decrease, power decrease and power increase. The thermal-hydraulic parameters of core power, flow rate, pressure and fluid temperatures in the primary system, feed water flow rate, pressure and fluid temperatures in the secondary system were investigated. They showed a symmetric behavior between their increases and decreases and a quick stabilization behavior of major thermal-hydraulic parameters including the natural circulation flow rate in the primary loop.