Analysis on special two-phase flow instabilities at full power natural circulation reactor condition

Abstract The experiments were performed on the test loop HRTL-5, which simulates the geometry and system design of the 5 MW nuclear heating reactor. In a wide range of inlet sub-cooling various flow instabilities were observed at p = 0.1 MPa and p = 1.5 MPa. Because of the different geometry design and operating conditions between the heating reactors and the boiling water reactors, the flow behavior presents great difference. Analysis shows: (1) under heating reactor conditions, sub-cooled boiling, condensation and void flashing are the fundamental thermodynamic processes; (2) sub-cooled boiling, condensation, void flashing and the compressibility of the steam space play an important role in the flow instabilities of the natural circulation system; (3) sub-cooled boiling instability, flashing instability, and flow excursion are the special instabilities at nuclear heating reactor conditions.