News Cleanliness Program Improved Condenser Performance Nine Mile Point gained 20 MW of capacity and saved $1 million. Clarion Energy Content Directors 12.1.2009 Share Nine Mile Point gained 20 MW of capacity and saved $1 million. By Daniel Cicero, Nalco, Gerald Munyan, Constellation Energy, and Scott Reich, Nalco Nine Mile Point Nuclear Station is located on Lake Ontario in Scriba, N.Y., just outside Oswego. The plant operates two boiling water reactors (BWRs), generating about 1,700 MW. Nine Mile Point is a once-through, parallel flow condenser with two water boxes. The unit draws cooling water from Lake Ontario, which varies from about 35 F to approximately 75 F, as shown in Figure 1. Click here to enlarge image In the cooler months when lake temperatures are at their lowest, condenser fouling impact is low. As lake temperatures rise, the impact of existing fouling increases. Biological activity also increases during the summer months. As shown in Figure 2, the condenser fouling factor varies throughout the year in response to changing temperatures. Click here to enlarge image The impact of condenser fouling was greatest during the even years, the second year of each two-year refueling cycle. This, coupled with high temperatures during the summer months, resulted in condenser back pressures and discharge temperatures approaching, respectively, their manufacturer and state-mandated limits. Click here to enlarge image Figure 3 shows the output curves for the years prior to the de-silting of Unit 1’s condenser. In the second week of June 2006, Unit 1’s condenser was cleaned to avoid problems caused by excessive back pressures predicted for August. Following the cleaning, periodic chemical treatments were started. Their frequency increased over time. Cleaning, in conjunction with chemical injection, improved plant performance for the remainder of the cycle. This improvement in generation continued through the first half of the cycle started in 2007. In 2008, the cycle started to repeat and back pressure curves predicted that operations would again face challenges during high lake temperature months. The Solution The efficacy of a cleaning program was proven, but holding on to gains from any cleaning required follow-on maintenance. A team formed to address the issue developed an online condenser cleaning program designed to restore condenser performance by removing the maximum amount of fouling deposits in the shortest period of time. A maintenance dispersant program would “hold the gains.” Organic material and microbial deposits bind inorganic material like silt, iron oxides and other solids into amorphous, insulating deposits. High-level halogenation (using bleach) oxidized the microbial deposits and made the cleaning environment more alkaline. The bleach was followed up with bromine, which improved microbial kill and penetrated the deposits. A bio-detergent was added to disperse and flush the deposits from the system. Following the chemical cleaning, total residual halogen (TRO) was reduced using sodium bisulfite to meet the plant’s discharge requirements. Holding the gains achieved by the chemical cleaning required new technology. Nalco’s 3D Trasar technology combines an inert, fluorescent signal with a fluorescent functionality attached to a polymer backbone—a chemical “tag” that reacts to stress on the dispersant polymer—to deliver dispersion and deposit control. Measured using a multi-channel fluorometer, the inert material acts as a benchmark; a measure of total polymer present. The chemical tag, measured by a different channel in the fluorometer, registers the amount of active polymer present. Comparing the concentrations of inert and active polymer—and the rates at which they change—delivers dispersant control based on the amount of dispersant needed at any given time. Results were dramatic. (See Figure 4, p. 22.) Lake temperatures increased in 2008 as expected and also as expected, condenser cleanliness declined. Click here to enlarge image In June 2008 when the new treatment program was initiated, instead of condenser cleanliness continuing to decline as the lake temperature increased, cleanliness factors increased, clearly demonstrating the efficacy of the program. The financial implications were also dramatic. During the first two days of treatment—during the hottest part of the year, when electricity demand (and prices) are highest—the plant saw an increase of 16 MW in generating capability. Over the next week, this improvement increased to 20 MW. After 60 days using the new treatment program, the plant realized an economic recovery of approximately $1.05 million. Authors: Daniel Cicero is the industry development manager in Nalco’s power group. Since joining the company in 1991, he has worked in a number of sales, product management and new product development roles. Gerald Munyan is a thermal performance engineer at Nine Mile Point, Constellation Energy. He has been with Constellation for nine years and before that, with the Department of the Navy for 15 years. Scott Reich is an executive account manager in Nalco’s power group. Since joining the company in 1987, he has worked in a number of sales and management roles across the U.S. He is a graduate of Illinois State University with a B.S. in industrial engineering. 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