A theoretical model for the single-phase natural circulation flow rate and its assessment against the ATLAS test data

A theoretical model for the single-phase natural circulation flow rate has been derived on the assumption of the quasi-steady state flow. The unique feature of this model is that it is just a simple function of the heat source power rate and the system flow resistance number with a power of one third, enabling it very convenient for use and application. The derived model has also been assessed against available single-phase NC flow test data from the ATLAS facility, an integral effect test facility with respect to the APR1400. The test data used for the assessment include those from the SBO-01 test, a kind of (Station Blackout) scenario test, and those from the FLB-EC-01R test, a FLB (Feedwater Line Break) test. Different from conventional treatment where the power and mass pair is plot, the NC flow rate transient is correlated with the proposed model by a single constant flow resistance number Nr. The predicted NC flow rate with the proposed model agree very well with the test data, inferring that the change of the NC flow rate with time can be well correlated with the proposed model by a single constant flow resistance number Nr. In addition, the flow resistance number was also varied to see its effect on the NC flow rate.