Power generation efficiency improvement through auxiliary system modifications

Thermal performance analyses have been performed for some proposed modifications in the Three Mile Island Nuclear Power Plant auxiliary systems, including: 1) auxiliary-condenser circulating-water (ACCW) flow reduction; 2) ACCW discharge diversion to the main condenser; and 3) feedwater heater drain recycling. Analysis shows that the secondary-system thermal efficiency can be improved by reducing circulating-water (CW) flow to the auxiliary condensers at high CW temperatures. This improvement decreases as CW temperature decreases. No benefit can be obtained from ACCW flow reduction at low CW temperatures. It is also shown that electricity output can be increased by diverting ACCW discharge to the main condenser instead of directly to cooling towers as in the current practice. This increase, though also varying with CW temperature, is consistently positive within the considered CW temperature range. For feedwater heater drain recycling, thermal efficiency improvement is significant for the two lowest-pressure stages.