美国滨海核电厂温排水及生态影响分析和启示

Analysis and enlightenment from Thermal discharges and their ecological impacts of American nuclear power plants in coastal regions

分析了美国滨海18个核电厂(31台核电机组)温排水系统的设计特点及其对水生生物的影响。结果表明,在排水系统设计上,美国滨海厂址考虑了减小温排水对水生生物影响的措施,大部分厂址采用离岸排放,提高排水流速,有些则因地制宜采用缓冲池、设计三级堰、或者将排水口布置在取水口的上游,必要时使用闭式循环冷却水系统等。美国大部分滨海厂址温排水对水生生物的影响较小。中国核电厂机组数量较多,温排水量较大,应重视对水生生物可能产生的不利影响。在排水系统上,中国核电厂存在的主要问题有:近岸排放缺乏促进掺混的考虑,明渠排放对景观优化的考虑不够,有些电厂为了满足近岸海域环境功能区要求而设置的导流设施有碍于温排水的扩散等问题。应研究制定中国核电厂温排水影响评价导则,优化核电厂温排水排水系统的设计和建造,尽可能降低温排水对水生生物可能产生的不利影响。

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.