Power Uprate Effect on Thermal Effluent of Nuclear Power Plants in Taiwan

Abstract

Power uprate is presently being considered by several nuclear power plant (NPP) utilities as a promising way to increase the power generation efficiency of existent power plants with or without increasing nuclear fuel consumption since 1970s. In general there are three types of power uprate: measurement uncertainty recapture power uprate (MURPU, <2%), stretch power uprate (SPU, 2 to 7 %), and extended power uprate (EPU, 7 to 20%) (US NRC, 2011 a). Thorough evaluations of existing plant equipments and environmental impact must be assessed before a final decision and an optimal selection of power uprate are made. Upon a power uprate, the power density and thermal release of a nuclear reactor would increase instantly, followed by the impact due to the waste heat from the thermal effluent to the environment. In Taiwan, two BWR NPPs and one PWR NPP were scheduled for MURPU. These NPPs are all located at the seacoast and using marine water as the coolant due to that fact that there is no rivers can supply enough light water near the site of the NPP in Taiwan. The marine water temperature is high during summer time due to the fact that Taiwan’s weather is marine tropical. According to the Effluent Standards of Taiwan’s Environmental Law: for effluents discharged directly into marine waters, the temperature at the discharge point shall not exceed 42°C; and the temperature difference should not exceed 4°C for surface water at 500 meters from the discharge point. Hence, the effect from the waste heat is always a very crucial issue to the power uprate of NPPs in Taiwan. Currently the three operating NPPs of Taiwan are all owned by the Taiwan Power Company (TPC). There are two reactor units setup at each NPP. The technology chosen for the reactors is General Electric (GE) BWR for Chinshan Nuclear Power Plant (NPP1) and Kuosheng Nuclear Power Plant (NPP2), and Westinghouse PWR for Maanshan Nuclear Power Plant (NPP3). Moreover, Lungmen Nuclear Power Plant (NPP4), which is GE ABWR and will to be the largest NPP in Taiwan, is still under construction at present. Fig. 1 shows the locations of NPPs in Taiwan. As can be seen, NPP1 and NPP2 are located in the most northern part of Taiwan in which is a subtropical zone, whereas NPP3 is located in the most southern part of Taiwan where is a tropical zone. They are all located next to the seacoast and using marine water as the coolant due to the fact that there is no any big rivers can