Cooling of the spent stream of the turbine exhaust is accomplished in a component known as the main stream surface condenser. Coolant is pumped from a body of water through the condenser via the “cooling water system”. The circulating water is physically isolated fom the stream path so that the cooling water will not diminish the purity of the stream and water in the primary cycle. The circulating water flows through the interiors if thin wall condenser tubes that make up the tube bundle, while spent steam from the turbine exhaust passes donwward and around the outside of the tubes, exchanging its latent heat with the cooling water inside the tubes. The resulting condensate collects in the “hot well” beneath the tube bundle.