Direct contact condensation of steam bubbles in a boiling water reactor suppression pool has long been studied utilizing video recording of experiments.The use of video recording enables observation of the behaviour of the bubble surface area and can assist in validation of computational fluid dynamics models.A direct contact condensation experiment of the suppression pool test facility PPOOLEX was recorded using high-speed cameras. The recorded video material was used for development of a pattern recognition and data analysis algorithm. 300 fps video of 48 s duration was cut into frames with a resolution of 768 px × 768 px. The side profile of the bubbles was identified and the volumes and surface areas of the bubbles were evaluated using a voxel-based method.The purpose of the algorithm was to determine the shape and size of steam bubbles during their formation, expansion, collapse and re-formation.The most probabilistic chugging frequencies were estimated. The bubble

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Direct contact condensation (DCC) phenomena in boiling water reactor (BWR) pressure suppression pool systems need to be understood to properly assess the performance of the pool as a heat sink and as a safety critical structure.Condensation oscillations in the form of chugging are challenging to predict by computational fluid dynamics (CFD) methods but safety relevant because of associated high dynamic loads on in-pool structures and the pool itself. Re-

The transition-metal dichalcogenide tantalum disulphide (1T -TaS 2 ) hosts a commensurate charge density wave (CCDW) at temperatures below 165 K where it also becomes insulating. The low temperature CCDW phase can be driven into a metastable "mosaic" phase by means of either laser or voltage pulses, which shows a large density of CDW domain walls as well as a closing of the electronic band gap. The exact origins of this pulse-induced metallic mosaic are not yet fully understood. Here, using scanning tunneling microscopy and spectroscopy (STM/STS), we observe the occurrence of such a metallic mosaic phase on the surface of TaS 2 without prior pulse excitation over continuous areas larger than 100 × 100 nm 2 and macroscopic areas on the millimeter scale. We attribute the appearance of the mosaic phase to the presence of surface defects which cause the formation of the characteristic dense domain wall network. Based on our STM measurements, we further argue how the appearance of the metallic behavior in the mosaic phase could be explained by local stacking differences of the top layer. Thus we provide a potential avenue to explain the origin of the pulse-induced mosaic phase.