WEI Xinyu, ZHANG Kun, DANG Yuqin, XIONG Xiaowei, CHE Shuwei
The characteristics of thermal discharges and their ecological impacts for 18 American nuclear power plant (NPP) sites in coastal regions (31 units) were analyzed. It was found that, for the designs of thermal discharge systems, most American NPPs use offshore discharge systems which also increase the flow velocities at the discharge points. Other NPPs' thermal discharge systems are designed in accordance with local conditions, such as using buffer pool to decrease water temperatures before discharges, designing three weirs to create mixing of the thermal discharges with air; arranging thermal discharge points upstream from withdrawal points; when necessary, using closed-cycle cooling systems. The adverse impacts of thermal discharges on aquatic organisms are small for most American NPPs in coastal regions. As the Chinese NPPs' site has more units, the larger amounts of heated water were discharged into the receiving water, and the adverse impacts of thermal discharges on aquatic organisms may be more obvious. Chinese NPPs have following main problems in the designs of thermal discharge systems:the near shore discharge systems don't have mixing promotion measures; landscape optimization in the design of discharge canals is not considered enough; In order to meet the requirements of the coastal functional areas, some NPPs set up diversion facilities which hinder the heat dissipations. Therefore, we need to make guidelines for thermal discharge evaluations, optimize the designs and constructions of NPPs thermal discharge systems, and minimize the possible adverse effects of thermal discharges on aquatic organisms.
