/ Using specially designed temperature profiling equipment, two surveys were conducted during thermal backwashing operations at Pilgrim Nuclear Power Station to determine the spatial and temporal extent of temperature rises above ambient. Thermal backwashing is a process where biofouling is combated by a heat treatment procedure. Backwashing formed a thermal plume about 5-to 6-ft thick (1.5-to 1.8-m) in front of the intake screenwall. Maximum observed surface temperatures were 101.0~ (38.3~ representing a rise (AT) of about 43.4~ (24.1~ above ambient. The frontal zone of the plume spread gradually seaward at about 0.2 kn. Its outer edge became thinner and rapidly cooled, presumably by advection and turbulent diffusion associated with currents from the reverse pumping and local changes from dissipation to the atmosphere. Along the intake shoreline, the plume was often less than 1 ft (0.3 m) thick. Most of the hot water was dissipated within several hundred feet of the intake with ~Ts of about 10.0 to 15.0~ (5.6 to 8.3~ above ambient. Under the influence of 15 mph southwesterly winds during the second survey, some warmed water was apparently carried beyond the outer breakwaters into Cape Cod Bay. These surveys provided real-time data indicating that the backwashing operation caused a relatively thin thermal plume, which spread rapidly from the intake out across the study area and along the seaward breakwater. Within a few hours these backwash thermal plumes were completely dissipated.The electric utility industry places emphasis on improving the efficiency of electrical generation. One area that is receiving significant attention is the control of biofouling within operating condensers. Biofouling, which occurs on the water side of operating condensers, contributes to the decrease in circulating (cooling) water flow rate and decreases the heat transfer efficiency of the condenser. These problems lead to an overall decrease in operating efficiency of the entire energy production system.Biofouling is a process which goes through various stages. There are two major types of biofouling: macrofouling (associated wiih setting and growth of shellfish within the condenser tubes) and microfouling (associated with the growth ofa bio-film). Cooling water flowing past the tube surface represents a nearly endless supply of a large variety of seed organisms (for example, mussel larvae), nutrients, and constituents for the growth process. The entire biofouling process is quite complex and involves physical, chemical, and biological reactions.The control of biofouling is quite site-specific. At Pilgrim Station, biofouling control is based upon the use of chlorine and thermal backwashes. The efficiency of chemical use is typically low because of the short residence time and the tendency toward secondary chemical
The Pilgrim Nuclear Power Station (PNPS) License Renewal Application (LRA) was submitted to the NRC in January 2006. As a part of the LRA submittal, Entergy committed to manage the aging effects of the reactor coolant environment on fatigue usage during the extended period of operation. As a part of PNPS’s aging management strategy, fatigue analysis was performed for 60-years of operation including EAF. This document provides some background information on the PNPS fatigue analysis, a summary of related information contained in the LRA submitted for NRC review and the specific actions taken to address the LRA commitments. A previous paper (PVP2010-25329) was prepared to provide an example of efforts expended to demonstrate long-term acceptability for license renewal where additional margins are required for PNPS Nuclear Power Station. The intent was to educate the reader on the efforts involved, the vast array of input that is needed and the possible hurdles that may be encountered for the validation and re-evaluation of Class 1 component fatigue for license renewal. The previous PVP paper discussed the foundation aspects necessary to prepare a refined fatigue evaluation with environmental affects for the plant. These include plant history, B31.1 piping analyses, environmental considerations, transient history, design specification and refined nozzle evaluations. The present paper discusses the importance of laying the appropriate foundation in the context of the final results that were obtained. It provides additional background information and actions taken to address the license renewal commitments and summarizes detailed results.
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