The good news is it's not smoke. It's steam.
Have you ever wondered what those large, strangely shaped concrete towers at a nuclear power plant are? Often, they are shown belching massive columns of steam. These towers are called "hyperboloid cooling towers." This article seeks to understand the purpose of these towers and why they have such a distinctive shape.
In the heat cycle for a nuclear power plant, an ultimate heat reservoir is required. These cooling towers take hot water from the nuclear reactor's condenser system and circulate it through a cold air draft found at the bottom of the building along the inlet plenum. Once it has passed through the inlet plenum heat exchanger, the relatively cool water is sent through a chemical treatment system and returned to the nuclear reactor plant condensers for use.
The cooling tower's unique shape promotes the required cold air draft. As the structure curves inward, a more laminar flow characteristic is created. While the wide base allows for improved evaporation, the wide top forces the warm, moist air to achieve a more turbulent flow. This creates a negative pressure system at the bottom of the cooling tower, which is the motive force behind the initial cold air draft. By acting this way, the efficiency of the cooling tower is significantly increased.
Photo Credit: Owen Cliffe