Power Plant Cooling Water Systems Research Articles

Evaluation of a Primary Treatment Unit for the Cooling Water of a Nuclear Power Plant

It is essential to have an effective treatment program and control methodology for a nuclear power plant cooling water system. As the accumulationand growth of cooling water deposits reduce the overall heat transfer coefficient and have an adverse effect on the operation of equipments,plant availability, production, and maintenance cost. The study aims at evaluationof using a primary treatment unit debris filter as a controllingof fouling formation, in a nuclear power plant located in coastal area. Selecting Sedi kerir, and Sidi Abdelrahman cooling water channel for the proposed nuclear power plant. Samples of the two selected sites had been taken and some physicochemical and biological parameters were analyzed such as (pH, total alkalinity, total dissolved solids, suspended solids, temperature and total count of microalgae). A mathematical model has been used also in order to help in evaluation of the suggested pretreatmentunit. The results has showed that sea water temperature used at the two selected sites (Sidi kerir, and Sidi Abdelrahman below 1250F that mean low fouling factor, also the measured physicochemical and biologicalparameter concentrations at the proposed two selected sites increase the probability of fouling formation at these sites. As a using of suggested debris filter pretreatment unit for cooling water at the two selected sites, will help in decreasing the probability of fouling formation at these site.

Impingement of marine organisms in a tropical atomic power plant cooling water system

A one-year impingement monitoring was conducted at Madras Atomic Power Station (MAPS), Kalpakkam, southeastern coast of India and identified a total of 67 species of marine organisms in the cooling water system. Estimates of total annual impingement contributed about 1.47×106 individuals and 142.5t of biomass. Jellyfish contributed about 6.8×105 individuals and 135.6t of biomass. Crabs, shrimps and fish were the most vulnerable organisms contributing about 4.29×105 individuals, 1.39×105 individuals and 2.16×105 individuals respectively. Commercially important species namely Trichiurus lepturus, Sardinella longiceps and Portunus pelagicus were found to be impinged 1.88% and 0.29% by number and weight of the total biomass respectively. Out of ~327 fish species recorded at Kalpakkam, only about 9.4% of species were impinged at MAPS. Multispecies impingement at MAPS poses the problem of finding the best mitigation options for tropical conditions.

Multi-Layer Electrodes for Electrochemical Antifouling

One of key issues in navigation and marine technology is the biofouling of underwater surfaces. Ten thousand of Cargo vessels as well as smaller motorboats, yachts and even offshore installations are affected. Biofouling involves the biological settlement of organisms and its continuous growth forming complex layers of centimetre thickness. This process severely increases of docking periods, corrosion, roughness and mass. For ship hulls, this leads to a huge hydrodynamic drag and, thus, higher fuel consumption at a constant speed [1]. Different seas and oceanas have their unique biotopes demanding specialised requirements of protective coatings. Since the prohibition of tin-organic coatings in 2003 an environmentally friendly as well as universally effective coating for antifouling has not been found yet. Even state-of-the-art copper and biocidal containing varnishes have fallen into disrepute as they contain bioaccumulating substances [2-5]. However, the biocidal-free, electrochemical antifouling technology can be applied regardless for the specific naval environment. Therefore, this is a promising approach for coating protection of ships that pass many seas. The antifouling effect of this concept is based on electrochemically generated redox stresses by pole changing of the electrodes in controlled sequence of intervals which also leads to changes of the pH between 2 and 12 at the surface. Additionally, the antimicrobial effect of anodically generated chlorine, and thereby hypochlorite, is under discussion [6-8]. This technological approach requires large electrodes with a very homogenous electrically conductive coating. In this study, polyurea coatings become electrically conductive resulting in conductivities between 0.1 and 160 mS cm-1 by homogeneous admixing of graphite flakes. This opens up a way to large area electrodes which can be deposited by rolling and brushing. Smoothly grinded surfaces of the conductive lacquers are investigated by scanning electrochemical microscopy (SECM) in the feedback mode in an 0.1 M KCl electrolyte with 2 mM K3[Fe(CN)6] as mediator. The distribution of the current at tip of an ultramicroelectrode of Pt over the coated working electrode allows imaging of the topographic distribution of conductivity and electrolysis with resolution at the micrometer scale. In the substrate-generator/tip-collector (SG/TC) modus is shown, that the anodic oxidation of chloride to chlorine also at potentials E = 1.3 V in 1 M KCl at pH = 8 is accompanied by the anodic oxidation of hydroxide ions. Therefore, besides the inherent pH stress, both, chlorine species and reactive oxygen species, preferably hydroxyl radical and hydrogen peroxides, cause a disinfecting redox stress suppressing settlement and growth of marine organisms. Imaging of the painted working electrode by scanning electrochemical microscopy give detailed information about the corrosion at their surface both at polymer matrix and dispersed graphite particles. Based on paintable large-area electrodes sea water electrolysis takes place at low current densities between 0.05 and 0.2 mA cm-2and generates a pH- and redox stress at the surface. Adjusting the ratio of conductivities between an outer and an inner layer of the painted electrodes a homogeneous distribution of the current density can be achieved also at large area electrodes. These conductive graphite composite coatings based on polyurea show an outstanding electrochemical stability with extremely low swelling in sea water. The coatings are painted on steel plates pre-coated by an isolating primer and the test plates keep almost free of any settlement of marine organisms over 16 month, e.g. barnacles and mussel among others. Abbott, A.; Abel, P. D.; Arnold, D. W.; Milne, A. Sci Total Environ 2000, 258, p. 5.Tolosa, I.; Readman, J. W.; Blaevoet, A.; Ghilini, S.; Bartocci, J.; Horvat, M. Mar Pollut Bull 1996, 32, p. 335.Thomas, K. V.; Fileman, T. W.; Readman, J. W.; Waldock, M. J. Mar Pollut Bull 2001, 42, p. 677.Connelly, D. P.; Readman, J. W.; Knap, A. H.; Davies, J. Mar Pollut Bull 2001, 42, p. 409.Biselli, S.; Bester, K.; Huhnerfuss, H.; Fent, K. Mar Pollut Bull 2000, 40, p. 233.Nakasono, S.; Burgess, J. G.; Takahashi, K.; Koike, M.; Murayama, C.; Nakamura, S.; Matsunaga, T. Appl Environ Microb 1993, 59, p. 3757.Satpathy, K. K.; Mohanty, A. K. Biofouling and its Control in Seawater Cooled Power Plant Cooling Water System - A Review; Sciyo, 2010 S. 191.Stoodley, P.; deBeer, D.; LappinScott, H. M. Antimicrob Agents Ch 1997, 41, S. 1876.

Chlorine dioxide as an alternative antifouling biocide for cooling water systems: Toxicity to larval barnacle Amphibalanus reticulatus (Utinomi)

Chlorine dioxide (ClO2) is seen as an effective alternative to chlorine, which is widely used as an antifouling biocide. However, data on its efficacy against marine macrofoulants is scanty. In this study, acute toxicity of ClO2 to larval forms of the fouling barnacle Amphibalanus reticulatus was investigated. ClO2 treatment at 0.1mg/L for 20min elicited 45–63% reduction in naupliar metamorphosis, 70% inhibition of cyprid settlement and 80% inhibition of metamorphosis to juveniles. Increase in concentration to 0.2mg/L did not result in any significant difference in the settlement inhibition or metamorphosis. Treatment with 0.2mg/L of ClO2 elicited substantial reduction in the settlement of barnacle larvae compared to control. The study indicates the possibility of using ClO2 as an alternative antifouling biocide in power plant cooling water systems. However, more work needs to be done on the environmental effects of such switchover, which we are currently undertaking.

Chlorination-induced genotoxicity in the mussel Perna viridis: assessment by single cell gel electrophoresis (comet) assay

Mussels are important fouling organisms in the cooling water systems of coastal power plants. Continuous low-dose chlorination (CLDC) is being practiced as an effective method to control mussel biofouling in power plant cooling water systems. CLDC effectively controls mussel fouling by discouraging larval settlement rather than by killing the larvae or adults. Mussels are an integral part of the natural benthic community in the receiving water body where the coolant water is discharged. Hence, from a toxicological point of view, they can serve as both target and non-target organisms. Previous researchers have indicated that chlorine residual, rather than elevated temperature, can be the major stress factor in the effluents released from coastal power plants. However, very little data are available on the sub-lethal effects of low level chlorination on representative benthic fauna. In this study, we used native and transplanted mussels (Perna viridis) to study lethal and sub-lethal effects of chlorination in the cooling water circuit of an operating power plant. Experiments involving comet assay suggested that CLDC can cause DNA damage in treated mussels. However, activation of DNA repair appeared to get initiated after the accrued damage reached a threshold. The results indicate that, at chlorine residual levels observed at the discharge point, exposure to chlorinated effluents is unlikely to cause significant genetic damage to mussels in the recipient water body.

Evaluation of inhibitors and biocides on the corrosion, scaling and biofouling control of carbon steel and copper–nickel alloys in a power plant cooling water system

Corrosion, scaling and biofouling are three problems in the power plant cooling system. In this paper, the influence of inhibitors and biocides on control of these problems for mild steel and copper–nickel alloys in a power plant cooling water system was investigated. The results showed that alone sodium hypochlorite (NaClO) in the presence of 1-Hydroxyethylidene-1,1-Diphosphonate (HEDP), maleic anhydride homopolymer (HPMA), 2-phosphonobutane-l,2,4-tricarboxylic acid (PBTC) as scaling inhibitors, and ZnSO4, 2-Mercaptobenzothiazole (MBT) as corrosion inhibitors was not effectively reduced corrosion, scaling and biofouling. In the presence of Alkyl Dimethyl Banzil Ammonium Chloride, one of the Quaternary Ammonium Compounds (QACs), the inhibition efficiency was increased. The effects of inhibitors on carbon steel copper–nickel were studied through electrochemical and weight loss measurement.

Application of multiphase modelling for vortex occurrence in vertical pump intake - a review

Vortex formation within pump intake is one of common problems faced for power plant cooling water system. This phenomenon, categorised as surface and sub-surface vortices, can lead to several operational problems and increased maintenance costs. Physical model study was recommended from published guidelines but proved to be time and resource consuming. Hence, the use of Computational Fluid Dynamics (CFD) is an attractive alternative in managing the problem. At the early stage, flow analysis was conducted using single phase simulation and found to find good agreement with the observation from physical model study. With the development of computers, multiphase simulation found further enhancement in obtaining accurate results for representing air entrainment and sub-surface vortices which were earlier not well predicted from the single phase simulation.The purpose of this paper is to describe the application of multiphase modelling with CFD analysis for investigating vortex formation for a vertically inverted pump intake. In applying multiphase modelling, there ought to be a balance between the acceptable usage for computational time and resources and the degree of accuracy and realism in the results as expected from the analysis.

Corrosion Control when Using Passively Treated Abandoned Mine Drainage as Alternative Makeup Water for Cooling Systems

Passively treated abandoned mine drainage (AMD) is a promising alternative to fresh water as power plant cooling water system makeup water in mining regions where such water is abundant. Passive treatment and reuse of AMD can avoid the contamination of surface water caused by discharge of abandoned mine water, which typically is acidic and contains high concentrations of metals, especially iron. The purpose of this study was to evaluate the feasibility of reusing passively treated AMD in cooling systems with respect to corrosion control through laboratory experiments and pilot-scale field testing. The results showed that, with the addition of the inhibitor mixture orthophosphate and tolyltriazole, mild steel and copper corrosion rates were reduced to acceptable levels (< 0.127 mm/y and < 0.0076 mm/y, respectively). Aluminum had pitting corrosion problems in every condition tested, while cupronickel showed that, even in the absence of any inhibitor and in the presence of the biocide monochloramine, its corrosion rate was still very low (0.018 mm/y).

Corrosion Control When Using Secondary Treated Municipal Wastewater as Alternative Makeup Water for Cooling Tower Systems

Secondary treated municipal wastewater is a promising alternative to fresh water as power plant cooling water system makeup water, especially in arid regions. Laboratory and field testing was conducted in this study to evaluate the corrosiveness of secondary treated municipal wastewater for various metals and metal alloys in cooling systems. Different corrosion control strategies were evaluated based on varied chemical treatment. Orthophosphate, which is abundant in secondary treated municipal wastewater, contributed to more than 80% precipitative removal of phosphorous-based corrosion inhibitors. Tolyltriazole worked effectively to reduce corrosion of copper (greater than 95% inhibition effectiveness). The corrosion rate of mild steel in the presence of free chlorine 1 mg/L (as Cl2) was approximately 50% higher than in the presence of monochloramine 1 mg/L (as Cl2), indicating that monochloramine is a less corrosive biocide than free chlorine. The scaling layers observed on the metal alloys contributed to corrosion inhibition, which could be seen by comparing the mild steel 21-day average corrosion rate with the last 5-day average corrosion rate, the latter being approximately 50% lower than the former.

Effect of Tolyltriazole on the Corrosion Protection of Copper against Ammonia and Disinfectants in Cooling Systems

Tolyltriazole (TTA) has been widely used as a corrosion inhibitor for copper and copper alloy heat exchanger components in power plant cooling water systems. In this work the effectiveness of TTA protection in the presence of free chlorine, monochloramine, and ammonia was studied, in the context of using secondary treated municipal wastewater as cooling water. Results indicated that the corrosiveness of ammonia becomes negligible in the presence of TTA. Also, monochloramine represents a better disinfection agent in terms of copper corrosion protection by TTA than free chlorine. The packing density, film thickness, and number of layers of TTA adsorbed on the Cu surface were estimated from measurements and compared with estimates from other studies. It was found that copper can work as a catalyst for free chlorine to degrade TTA and that the surface packing density, film thickness, and number of layers increased in the presence of monochloramine.

Delaware Bay salt marsh restoration: Mitigation for a power plant cooling water system in New Jersey, USA

In 1994 Public Service Electric and Gas of New Jersey (PSE&G), now Public Service Enterprise Group (PSEG), proposed and implemented a program to offset egg, larvae and fish losses at the cooling water intake at Salem Generating Station. The program included wetland habitat restoration, fish ladder installation, new cooling water intake technology, and a biological monitoring program. The wetland habitat restoration was the core component and the most controversial aspect of the program. It addressed two types of habitats: diked salt hay farms and wetlands dominated by Phragmites australis. The wetland restoration program used ecological engineering principles to restore approximately 4550 ha. It also protected upland buffers and other lands for a total of over 8700 ha. Eight fish ladders were installed to allow anadromous river herring to return to previously blocked spawning habitat. PSEG also implemented operational changes, installed advanced cooling water intake technology to reduce losses of invertebrates and early life stages of fish, and conducted studies of behavioral deterrents. The biological monitoring program continues to assess the abundance and distribution of juvenile coastal migratory fish species while they are in the Delaware River Estuary; it also monitors use of wetlands by fish and invertebrates.

Development of an artificial neural network-based software for prediction of power plant canal water discharge temperature

Power plant cooling water systems that interact with nearby effluents are complex non-linear, large-time-delay systems. A neural network-based software tool was developed for prediction of the canal water discharge temperature at a coal-fired power plant as a function of plant operating parameters and local weather conditions, including tide information. The plant has four units totaling an installed capacity of 1550MW and its water thermal discharge is environmentally regulated. In the summer months, when the price of electricity is very profitable and the risk of exceeding the canal temperature limit is greater, the tradeoff between maximum generation and environmental compliance violations is financially significant. The software is a predictive tool to assist in scheduling load generation among the plant's four units without exceeding a thermal discharge limit of 95^oF. Back propagation neural network architectures were trained using plant operating data with an 'off-set' component. The artificial intelligence models produced reasonable trends for year-round prediction and different operational scenarios. Comparison of measured and predicted canal temperatures indicated an accuracy of less than 0.3^oF over the range between 90 and 95^oF. The software tool was developed as an Object Linking and Embedding (OLE) for Process Control (OPC) client, with real-time communication and interface with the plant Distributed Control System (DCS).

Lethal and sub-lethal effects of chlorination on green mussel Perna viridis in the context of biofouling control in a power plant cooling water system

Continuous chlorination is a widely followed cooling water treatment practice used in the power industry to combat biofouling. The green mussel Perna viridis is one of the dominant fouling organisms (>70%) in the Madras Atomic Power Station. Mortality pattern as well as physiological responses such as oxygen consumption, filtration rate, byssus thread production and faecal matter production of three different size groups of this mussel were studied at different chlorination concentrations. At 0.7 mg l −1 residual chlorine, 3–4 cm size mussels showed 100% mortality in 553.3 h while 8–9 cm size group mussels died within 588 h. At a relatively high level of residual chlorine (9.1 mg l −1), 100% mortality in 3–4 cm and 8–9 cm size groups took 94 and 114 h, respectively. All physiological activities studied showed a progressive reduction as chlorine residuals were increased from 0 to 0.55 mg l −1 . The data indicated that the green mussel can sense a residual chlorine level as low as < 0.15 mg l −1 and complete valve closure occurs only at 0.55 mg l −1. The paper also shows that the sub-lethal physiological responses are better indices than lethal responses in planning chlorination strategies.

Forty years of successful corrosion protection for power plant cooling water systems

Forty years of successful corrosion protection for power plant cooling water systems

The Viability of pH Measurements in Supercritical Aqueous Systems

The measurement of pH of aqueous systems at high temperature is becoming increasingly important because of the need to monitor the chemistry of nuclear power plant cooling water systems and the cycle chemistry of fossil‐fueled power reactors. We have previously shown that the yttria‐stabilized zirconia pH sensor can be used for accurate pH measurements of aqueous systems up to 320°C. This paper describes the viability of pH measurement of aqueous systems up to and above the critical temperature of water.