Study on the cooling performance of sea salt solution during reflood heat transfer in a long vertical tube

Following the March 2011 earthquake, the nuclear power plants in Japan were affected, and emergency systems were activated. The earthquake caused a tsunami, which hit the east coast of Japan, and caused a loss of all on-site and off-site power at the Fukushima Daiichi, leaving it without any emergency power. In this situation, freshwater and seawater were used by helicopter, fire truck, and concrete pump truck to remove heat. To investigate the effect of 35‰ sea salt solution on reflood heat transfer in a long vertical tube (1600 mm in the heating length), quenching experiments were conducted. We have observed a more enhanced cooling performance in the case of the sea salt solution reflood. Consequently, the cooling performance is enhanced more than nearly 10 s for sea salt solution. The enhancing cause of the cooling performance after the quenching experiments using the sea salt solution were investigated through the macroscopic observation, scanning electron microscopy (SEM), contact angles and SEM-energy dispersive X-ray spectroscopy (EDS) of the inner surface of the test section. The cause of the cooling performance enhancement for the sea salt solution is not related to the enhanced wettability of the liquid film on the heater surface due to the deposition of sea salts but the top quenching by earlier condensation of vapor during sea salt solution reflood.