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Abstract

The results of a 1% cold leg break transient (ISP18) performed in the LOBI facility of JRC Ispra led to the conclusion, that for a long time period stratified flow conditions are prevailing in the loop components between the high pressure injection position and the position of the break, and that, at the same time, the water flow via the downcomer to the core is sufficiently high for avoiding overheating of the fuel rod simulators. Computer simulations of the experiment with LWR system codes (CATHARE, DRUFAN, RELAP, etc.) show a strong dependence of the computational results from the correlation used for nd describing condensation heat transfer under stratified flow conditions. Taking account of the uncertainty of the existing correlations with respect to separate effect experiments, quite unrealistic computational results may be produced concerning the flow through the core and the related fuel rod temperatures. In view of this unsatisfactory situation available separate effect experiments are reexamined to provide a better understanding of the related phenomena. The paper illustrates the difficulty to obtain better correlations based on local flow conditions than the presently existing ones. This is due especially to the fact that the situation considered corresponds to a spatial initial value problem, which, in principle, cannot develop towards a steady state situation.

Additional information

Authors: EIFLER W JRC ISPRA ESTAB. (ITALY), JRC ISPRA ESTAB. (ITALY)
Bibliographic Reference: 1987 EUROPEAN TWO PHASE FLOW GROUP MEETING, TRONDHEIM (NORWAY), JUNE 1-4, 1987 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 33414 ORA
Availability: Can be ordered online
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