29th Symposium on Fusion Technology (SOFT 2016)

P2.200 Effective water cooling of very hot surfaces during the LOCA accident

Sep 6, 2016, 2:20 PM

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 200

Poster J. Power Plants Safety and Environment, Socio-Economics and Technology Transfer P2 Poster session

Speaker

Jan Stepanek (Department of Energy Engineering)

Description

The first wall, blanket and divertor targets provide a physical boundary for the plasma influence and have to be intensively cooled during the operation in case of the high power fusion reactor. In the case of the LOCA accident, the released fusion power can be stopped very quickly, but the final plasma disruption may load the non-cooled components, and a large amount of heat accumulated in the component material needs an emergency cooling. Moreover, the decay heat power in the range of a few percent of the fusion power can destroy components, if not emergency cooled. Heat transfer during cooling of very hot surfaces with subcooled liquid is still not fully explored area. When water meets a hot surface, a thin steam layer is presented between the coolant and cooled surface. Heat removal can be successful only when water rewets the surface. The place where water rewets the surface is called the quench front. In the paper, the quench front propagation along the cooled geometry highly influenced by initial wall temperature, coolant flow rate and by heat accumulated in the cooled components. Understanding the phenomenon of rewetting of hot surfaces is crucial for reactor safety. The study is focused on the quench front propagation in the annular channel with initial wall temperatures within range 250 – 800°C and coolant flow rates from 100 kg/m²2s up to 1200 kg/m²2s. Also, the influence of heat capacity of the cooled wall is investigated. For this purpose, an experimental loop with a variable hydraulic circuit including the test section with a length of 1.7 m has been built, and results of the experimental research are presented.