Abstract
In the envisioned high-power density core plant, the degradation of stability is concerned that is attributed to the shortening of rod heat conduction time constant upon the dense fuel grid and the increment of pressure drop caused by the wall friction. To confirm the influence of such degradation on the fuel soundness, the bundle geometry critical power test was held under flow-power oscillation condition which envisages the unstable phenomenon occurring under in the flow transient event. This paper describes the analysis results of the cited test with sub-channel code NASCA, and the discussion of the mechanism of boiling transition under flow-power oscillating condition.
