Cooling Water Intake Research Articles

Key environmental parameters and numerical prediction model of jellyfish bloom in Qingchuan Bay Nuclear Power Plant, China

In recent years, there has been a notable increase in cooling water intake blockage caused by marine organism blooms at coastal nuclear power plants worldwide, resulting in shutdowns of nuclear power plants and large economic losses. A sizable portion of these incidents were caused by blooms from jellyfish, a planktonic invertebrate with a unique growth pattern. Suitable external conditions are conducive to the rapid growth of jellyfish, and blooms can occur within a few days. In order to better predict jellyfish bloom and enable nuclear power plants to prepare for it in advance, this study explores the numerical relationship between jellyfish biomass and environmental parameters. A series of time windows (evaluation intervals) were defined and constructed by a time-series recursive approach, which solved the problem of poor correlation between jellyfish biomass and environmental parameters at non-bloom points. The optimal time window length D = 10 was obtained, and the key environmental parameters affecting jellyfish biomass were screened as sea surface temperature, salinity, voltage value, dissolved oxygen, and chlorophyll. According to the ADF and KPSS tests, the key parameters have no significant time dependence, which ensures the stability and reliability of the subsequent predictions. The jellyfish bloom prediction model was derived by calculating the score F through the recursive Principal Component Analysis of the key environmental parameter in the time interval preceding the prediction point. The sudden change moments of score F correspond well to the jellyfish bloom moments, and the sudden change moments are all advanced for a period of time compared to the bloom time, which can provide valuable time for the nuclear power plant to organize manpower to deal with the blockage. Finally, a maximum score F threshold model was proposed to be coupled with the jellyfish bloom prediction model to provide a more robust basis for early warning of jellyfish at nuclear power plants.

Experimental investigation of material properties of GFRP pipe for numerical simulation of novel nuclear power plant cooling water intake system

The cooling systems of nuclear power plants are typically made of reinforced concrete water intake structures and special steel pipes, making them large, important structures that necessitate very expensive special productions. In the scope of this research, an innovative design for 4-meter diameter GFRP composite pipes used in nuclear power plant cooling systems was developed using the circular wrapping method. The composite GFRP pipe used in the study has a substantial embedment depth. For this reason, an innovative design was created using unique stiffening rings, and the impact of these rings on the overall behavior was investigated. The nonlinear numerical analysis model of the nuclear power station cooling system, which consists of three pipes with a diameter of 4 m, was then created with ANSYS finite element software using the determined material models, and the results were interpreted. As a result of the study, a composite GFRP pipe design that can be used as a cooling system in significant structures like nuclear power plants has been developed.

ASSESSMENT OF COASTAL DAMAGE FOR THE COOLING WATER INTAKE STRUCTURE OF A COAL-FIRED POWER PLANT

Last October 2020, a strong tropical cyclone with international name Molave (local name: Quinta) caused widespread damage to agricultural and infrastructure sectors in the Philippines. Among those affected is a coalfired power plant located within the vicinity of Tayabas Bay. The velocity cap at the head of the cooling water intake structure of the power plant was found washed ashore in the morning of October 26, 2020 (PH time) after the onslaught of Typhoon Molave. Underwater site investigations post-typhoon revealed that the walls and other components of the intake structure were damaged as well. The intake structure head was initially built at seabed depths of 9m below Mean Tide Level (MTL), while the velocity cap was topped at 6m below MTL. This paper presents the forensic analysis and coastal damage assessment methodology carried out to identify the nearshore hydrodynamic conditions during the passage of potentially critical typhoons throughout the useful life of the intake structure (2017 to 2020).

Tsunami waveform forecasting at cooling water intakes of nuclear reactors with deep learning model

The Fukushima nuclear disaster highlights the importance of accurate and fast predictions of tsunami hazard to critical coastal infrastructure to devise mitigation strategies in both long-term and real-time events. Recently, deep learning models allowed us to make accurate and rapid forecasts on high dimensional, non-linear, and non-stationary time series data such as that associated with tsunami waveforms. Thus, this study uses a one-dimensional convolutional neural network (CNN) model to predict waveforms at cooling water intakes of nuclear power plant at Uljin in South Korea. The site is particularly vulnerable to tsunamis originating from the west coast of Japan. Data for the CNN model are generated by numerical simulation of 1107 cases of tsunami propagation initiating from fault locations. The time series data for waveforms were predicted at 13 virtual gauges located in the nearshore region of the study area, 10 of which were classified as observation points and 3 gauges situated at the cooling water intakes were categorized as target locations. The performance assessment of the model's forecasts showed excellent results with rapid predictions. The study highlights two main points: (i) deep learning models can be based on sparse waveform in situ data (such as that recorded by deep-ocean assessment and reporting of tsunamis or any locally operating monitoring stations for ocean waves) or numerically simulated data at only a few points along the dominant wave propagation direction, and (ii) deep learning models are fully capable of accurate and fast predictions of complex geo-hazards that prompt rapid emergency response to coordinate mitigation efforts.

Digital holography for real-time non-invasive monitoring of larval fish at power plant intakes

Effective evaluation of technological and operational approaches to reduce entrainment of marine organisms at cooling water intake structures (CWIS) requires accurate organism-sensing systems. Current detection methods lead to large temporal data gaps, require tedious manual analysis, and are fatal to organisms. Here, we describe integrating deep learning with a non-lethal, non-intrusive imaging method—digital holography—to rapidly detect fish larvae. Laboratory experiments demonstrated that the instrument could successfully image fish larvae at flow rates exceeding ranges seen in CWIS. Holograms of two fish larvae species, in the presence of bubbles and detritus, were collected to build a large database for training a lightweight convolutional neural network. The model achieves 97% extraction accuracy in quantifying larvae, and distinguishing them from other particles, including detritus and bubbles, when applied to a dataset of manually classified images, exceeding previous metrics for non-lethal, accurate, and real-time detection. These results demonstrate the potential of in situ holographic imaging for monitoring endangered larval fish species at power plant intake structures, and for high-fidelity, real-time applications in monitoring aquatic ichthyoplankton.

The Ohio River Ecological Research Program (ORERP): History and Accomplishments

The Ohio River Ecological Research Program (ORERP), sponsored by multiple power plants along the river's main stem, was in existence for 50 years. Its goals were to collect fish community data to evaluate possible impacts to Ohio River fish communities because of either power plant discharges (i.e., thermal effects) or cooling water intakes. Studies by the ORERP have shown that thermal avoidance of discharge areas often occurs during the summer, but this avoidance is temporary and reversible, and long‐term disruptions of the fish communities have not been detected. Impingement studies conducted at 13 plants from 2005 to 2007 showed that impingement was highly episodic and dominated by clupeids and Freshwater Drum Aplodinotus grunniens. Impinged fish were mainly (>90%) young of the year; as a result, impingement numbers strongly reflected year‐class strength. Entrainment of ichthyoplankton was conducted under the ORERP at seven plants in 2015 and 2016. Annual entrainment estimates ranged from 43 million to 3.5 billion (i.e., 3.5 × 109) ichthyoplankton depending on the plant. The principal benefit of this collaborative effort was that these data allowed the sponsoring facilities and others to access an extensive database upon which fact‐based regulatory, resource management, and plant operating decisions could be based. Most importantly, the ORERP is a collaborative model for private and public organizations to collect, share, and analyze data and make resource management decisions for a large, multi‐use aquatic resource.

Cooling water intake system safety analysis based on impingement probability

Invasion or aggregation of marine organisms in cooling water intake systems (CWIS) has gradually become an important problem affecting the safety of nuclear power plants with environmental and climate changes. In this study, a 3-dimensional numerical model (TELEMAC-3D) was used to determine the impingement probability in a typical nuclear power plant with a once-through cooling system, and the effect on CWIS safety. The factors controlling impingement probability were also analyzed. Results show that (1) impingement probability decreased rapidly with an increase in distance from the CWIS. In addition, the distance of the impingement effect of a nuclear power plant with six units was mainly within 1 km of the CWIS. (2) Impingement probability increased with water withdrawal, and as distance to the CWIS increased, the increase in probability increased. (3) Generally, an increase in tide strength led to a decrease impingement probability. (4) Near the CWIS, the impingement probabilities of areas upstream or downstream of the CWIS along the tidal flow direction were much higher than those not in those areas. (5) An increase in water depth significantly reduced impingement probability. When the water depth of the CWIS increased from 5 m to 15 m, impingement probability was reduced up to 30%. Based on the above findings, the following suggestions were made to minimize the impingement effects on CWIS safety: first, the CWIS of coastal nuclear power plants should be set in an area with low aquatic biomass, strong tides, deep water, and few surface species within the range of 1 km, and second, the amount of cooling water withdrawal or velocity should be reduced as much as possible.

Biofouling characteristics in Xinghua Bay of Fujian, China

Biofouling is one of the main factors affecting the efficiency and safety of cooling water systems in coastal nuclear power plants. Understanding the population dynamics, succession rules and cumulative effects of major fouling organisms is the basis for targeted prevention and control. A 1-year simulated concrete panel test was conducted from December 2020 to November 2021 in Xinghua Bay, China. A total of 78 species of fouling organisms were recorded by combining the monthly, seasonal, semiannual, annual and monthly cumulative panels, and the community composition was dominated by nearshore warm-water species, making for a typical subtropical inner bay-type community. The fouling organisms had a peak attachment period from June to October. Significantly more attachment was observed during summer (from June to August) than during the other three seasons. The attachment amount in the second half-year (from June to November) was much higher than that in the first half-year (from December to May). The attachment thickness, density, and biomass of the bottom summer panels reached 20 cm, 105,150 ind./m2, and 19,274.50 g/m2, respectively, while those of the bottom annual panels were 40 cm, 27,300 ind./m2, and 17,762.50 g/m2, respectively. The dominant fouling organisms with calcified shells mainly included Amphibalanus reticulatus and Pernaviridis. These species had high attachment amounts,could accumulate attachments for a long time, and even might cause secondary blockage, making them the most detrimental to the safety of a cooling system. Moreover,the seasonal upward growth of hydroids and bryozoans can also significantly reduce the efficiency of cooling water intake. We suggest that targeted prevention and control should be carried out according to the larval attachment period of different dominant groups of fouling organisms during June-October, which can greatly improve the prevention and control efficiency. Strengthening the research on the biological cycle phenomenon of the main species and their main environmental impact factors, and establishing a scientific and effective early-warning model are the governance direction of formulating and implementing scientific pollution prevention and control in the future.

Public willingness to pay for eradicating a harmful marine organism: the case of Aurelia aurita in South Korea.

Aurelia aurita (AA), a legally registered harmful marine organism in South Korea, is damaging marine human leisure activities, local residents’ tourism income, fisheries, and cooling water intake at power plants. The government is therefore seeking to eradicate AA by removing AA-attached larvae (polyps). This article looks into the public willingness to pay (WTP) for the eradication, utilizing a contingent valuation. For the sake of eliciting the WTP response, the one-and-one-half-bounded (OB) model was adopted. For comparison, the single-bounded (SB) model, which uses only the response to the first question in the OB model, was also applied. A spike model with a considerable plausibility that could explicitly deal with zero WTP responses was employed. Consequently, the estimation results of the SB model were used for further policy analysis. The household average WTP was estimated as KRW 3,911 (USD 3.49) per year, securing statistical significance. The national value was KRW 80.46 billion (USD 71.71 million) per annum. This figure can be interpreted as public value of the AA eradication project and used as essential basic data to evaluate the economic feasibility of implementing the project. Some factors such as income and education level significantly positively affected the intention of paying a suggested bid.

An integrated environmental risk assessment framework for coal-fired power plants: A fuzzy logic approach.

This study quantifies the environmental risk of a coal-fired thermal power plant during operation by using environmental monitoring data, site surveys, and documented evidence. The following criteria are assessed: emissions (CO, SO2 , NOx , PM10 ), impact on aquatic ecosystem (fish protection at cooling water intake and cooling water discharge temperature), and waste management (fly ash and bottom ash). Fuzzy sets were defined for each criterion, taking environmental regulatory context as an expert judgment. A survey was conducted with multiple stakeholders to determine the relative importance of risk factors. The survey results showed that the most concerned risks are SO2 and NOx emissions. The proposed method estimates the risk of each environmental criterion separately and then accumulates them into an environmental risk index (ERI). Accordingly, we assessed the Catalagzi coal-fired power plant, which has been in operation on the Black Sea coast in northwestern Turkey. For this case study, the ERI resulted in a value of 0.78 (on a scale of 0-1), showing high environmental risk to the facility. Moreover, the applicability of the proposed framework was tested in several existing coal-fired power plants using simultaneous measurements. All studied coal-fired power plants in Turkey have unacceptable pollutants (PM10 , SO2 , and NOx ) concentration levels indicating high health risk potential. The application of the integrated environmental risk assessment framework showed that new environmental regulations are needed in Turkey to specify more strict emission limits and to monitor CO2 , fine particulate matter emissions, cooling water discharge, and fish protection at cooling water intake.

발전플랜트 냉각수 계통 취수시스템의 해양생물 및 해저퇴적물 유입에 대한 수치해석 사례연구

Coal thermal power plants traditionally require huge volumes of water to condense steam from the turbine exhaust. Coastal power plants may simply run a large amount of seawater through condensers in a single pass and discharge it back into the sea. However, marine organisms and submarine sediment could enter the cooling water intakes of such once-through systems. In this case study, CFD analysis for the impact of inflow of marine organisms and submarine sediment in a seawater intake system of a power plant was performed. The hydraulic model test method was followed. An objective numerical analysis model for practical impact evaluation was derived by selecting target marine organisms and sediments based on results of investigating surrounding marine environment. This technical paper investigated common challenges and solutions such as the protection of a seawater intake system from jellyfish, possibilities of a safe cooling water intake, coping with large sand quantities, and optimization of pump stations.

Effect of Intermittent Traveling Water Screen Operation on Fish Survival

AbstractThe U.S. Environmental Protection Agency’s final rule for complying with section 316(b) of the Clean Water Act states that cooling water intakes withdrawing >7.6 million liters per day must use one of seven alternatives to reduce fish impingement mortality. Fish‐friendly traveling water screens (TWSs) are expected to be frequently utilized because of relative ease of retrofit. The final rule requires “continuous or near continuous screen rotation” to facilitate recovery of collected fish as soon as practical. However, intermittent TWS operation could be advantageous for operators because reductions in screen system operating time will extend equipment life and reduce operating costs. A laboratory evaluation was conducted with Golden Shiner Notemigonus crysoleucas, Bluegill Lepomis macrochirus, Largemouth Bass Micropterus salmoides, and Common Carp Cyprinus carpio (42–106 mm TL) to determine whether intermittent rotation would optimize TWS operation and maintain biological performance. A preliminary evaluation was conducted with three approach velocities (0.30, 0.45, and 0.60 m/s) at four stationary screen durations (2, 4, 6, 12 h) in small test flumes to select parameters for a larger‐scale evaluation. The full‐scale evaluation tested two approach velocities (0.30 and 0.45 m/s) at two stationary durations (2 and 4 h at 0.45 m/s; 6 and 12 h at 0.30 m/s) and continuous screen operation. Fish avoided impingement at 0.30 m/s, and approach velocity was the primary determinant of survival probability, with increased velocity leading to increased mortality. Severe injuries occurred more frequently during stationary screen trials than with continuous operation; over 50% of fish had >40% scale loss at 0.45 m/s for stationary trials. The results indicate that continuous rotation is optimal for fish survival at approach velocities between 0.30 and 0.45 m/s. However, intermittent operation at average approach velocities of 0.30 m/s or less may be acceptable for fishes with equal or greater swimming ability than those tested in this study.

Seaweed ingress of cooling water intakes with predictions for Torness power station

Seaweed ingress into the cooling water intakes of nuclear power stations has caused several disruptions to electricity supply. Seaweed is transported by tidal and wave-induced currents after dislodgement from the sea bed following stormy conditions but ingress will be shown to be not only determined by wave conditions. An integrated model system has been developed to predict such ingress and applied at the Torness power station in Scotland where the mass of seaweed recovered was measured for some ingress cases. Prior to each case, seaweed is assumed initially to be distributed in areas surveyed within the surrounding coastal domain with a mass per unit area based on local measurements. Criteria for dislodgement are based on near-bed velocity. Six cases where the mass of ingress was measured and two cases with no ingress have been modelled and predicted by adjusting a dislodgement factor (a multiplier on the threshold velocity) within a relatively narrow range.

Agent-based modelling of juvenile eel migration via selective tidal stream transport

Recruitment of temperate eel species Anguilla anguilla, A. rostrata &A. japonica has declined over the last few decades due to human activities, such as overfishing and construction of migratory barriers (e.g. dams, weirs and sluices) and hazardous energy infrastructure (e.g. turbines, intakes and outfalls). Numerical models, substantiated with data from field and laboratory studies, can potentially predict and quantify the relative impacts of such activities, thereby assisting in the sustainable management of eel populations. Here, we present an agent-based model (ABM) of juvenile eel migration up estuaries. The model includes relevant eel behaviours and environmental conditions that, according to the literature, influence upstream migration. Crucially, by assessing the local salinity gradient and relative flow direction, the modelled eels (agents) self-determine whether the tide is flooding or ebbing and orientate themselves for navigation, with no top-down instructions. This allows the agents to decide which particular behaviour to undertake as part of Selective Tidal Stream Transport (STST). The developed ABM is coupled to a hydrodynamic model of the Thames Estuary and the results substantiated by comparison against eel trap data. Combinations of the various STST behaviours are systematically tested and the influence they have on up-estuary migration is assessed in terms of relative energy expenditure. The parameterised model is then used predictively at Milford Haven Waterway to investigate potential impacts on the juvenile eel population due to entrainment in a power plant cooling water intake and outfall. Results from the Thames model case study indicate that including bed anchoring behaviour is essential for achieving a good comparison with the eel trap data and the choice of salinity detection threshold is also important. If daylight avoidance (diel) behaviour is not included, the most energy efficient migration is achieved using just two STST behaviours (ebb tide bed anchoring and upward migration during flood). With diel behaviour included, energy expenditure is greater, but some efficiency is regained by including all of the STST behaviours. For the Milford Haven case study, the model predicted a juvenile eel intake and outfall entrainment rate of 2.0% and 4.7%, respectively. It is concluded that the ABM is a valuable tool for assessing potential impacts on the recruitment of eels (extendable to other species) and could be used to assist in site-selection and low impact design of energy infrastructure in tidal environments.

Why cylindrical screens in the Columbia River (USA) entrain few fish

Cooling-water intakes often entrain large numbers of larval and juvenile fish, leading to questions why a water intake on the Columbia River, USA, with axial flow, cylindrical screens on a T-screen structure entrained very few (four fish in 4,007 x 103 m3 of water sampled over four years). This is despite being downstream of spawning areas for Chinook salmon Oncorhynchus tshawytscha releasing up to 56 million pre-smolts and having screens consisting of porous plate with 9.5-mm-diameter pores capable of passing salmon fry and other small fish (poor physical exclusion). Multiple publications of experiments and observations in hydraulics and biology are used to help explain the low entrainment, concluding that effects of the screening structure rather than the actual screen are most important. Primary mechanisms appear to be: (1) bow-wave-like hydraulics at the structure’s nose cone that deflect small fish away from the screen’s pores, and (2) fish detection and avoidance of pressure and velocity changes upstream of the structure that aid deflection. These combined hydraulic and biological-behavior effects of the structure would cause salmon fry and other small fish to bypass the screened portion of the intake. At the screens, (3) high ratio of sweeping flow to approach and through-screen velocities likely further prevents entrainment. Although site- and design-dependent, this analysis may be useful for evaluating or planning other screen installations and focusing regulatory attention on hydraulics of the structure as well as the screen.

Analysis on Critical Factors of Marine Organism Impacts on Water Intake Safety at Nuclear Power Plants

Abstract The safety of cooling water intake in nuclear power plants (NPPs) has gradually become an important factor affecting the safety of NPPs. Marine flora and fauna outbreaks are one of the main types affecting the safety of cooling water intake in NPPs, and the driving mechanism is more complicated and difficult to predict. This paper mainly analyzes the main types and typical cases of marine organisms that cause cooling water intake blockage in NPPs, and analyzes the key factors such as hydrodynamic conditions, timing of organism's outbreak, characteristics of species, and design of the screen systems. The results show that strong hydrodynamic conditions or strong tides caused by special meteorological conditions are important factors. Considering the time of organism's outbreak, spring and summer (May–August, may change slightly according to different latitude) is key period because of the reproduction and growth of most marine organisms, according to the growth law of marine organisms. In terms of biological characteristics, it is sensible to focus on those species with fast growth, strong reproductive capacity, short life cycle, weak swimming ability, and cluster distribution. As to the design of screen systems, the blockage mainly occurs in revolving filter screens. The grid spacing of normal mechanical grille is too large to block the small marine organisms. It is necessary to add trash interception nets according to the type and size of the marine species. Finally, a case is used to confirm the factors needed to pay more attention.

Membrane Capacitive Deionization for Cooling Water Intake Reduction in Thermal Power Plants: Lab to Pilot Scale Evaluation

Cooling of thermal power stations requires large amounts of surface water and contributes to the increasing pressure on water resources. Water use efficiency of recirculating cooling towers (CT) is often kept low to prevent scaling. Partial desalination of CT feed water with membrane capacitive deionization (MDCI) can improve water quality but also results in additional water loss. A response surface methodology is presented in which optimal process conditions of the MCDI-CT system are determined in view of water use efficiency and cost. Maximal water use efficiency at minimal cost is found for high adsorption current (2.5 A) and short adsorption time (900 s). Estimated cost for MCDI to realize maximal MCDI-CT water use efficiency is relatively high (2.0–3.1 € m−3evap), which limits applicability to plants facing high intake water costs or water uptake limitations. MCDI-CT pilot tests show that water use efficiency strongly depends on CT operational pH. To allow comparison among pilot test runs, simulation software is used to recalculate CaCO3 scaling and acid dosage for equal operational pH. Comparison at equal pH shows that MCDI technology allows a clear reduction of CT water consumption (74%–80%) and acid dosage (63%–80%) at pH 8.5.

ОПТИМИЗАЦИЯ ТЕМПЕРАТУР ДВУХКОНТУРНОЙ ЗАМКНУТОЙ СИСТЕМЫ ОХЛАЖДЕНИЯ СУДОВОЙ ЭНЕРГЕТИЧЕСКОЙ УСТАНОВКИ

The issues of creating environmentally friendly highly reliable closed-loop cooling systems are considered in the paper. The achievement of these qualities is ensured by the rejection of cooling water intake. The analysis of various coolants of the power installation requiring cooling is carried out. It is shown that for the cooling of a number of coolants it is advisable to create double-circuit cooling systems. This requires the introduction of an additional heat exchanger and the separation of the temperature head between the cooled coolant and seawater. The authors suggest an approach that makes it possible to distribute this temperature head between the circuits optimally. This procedure involves comparing various heat exchangers based on their reduced area. A nomogram is presented to determine the optimal value of the temperature head.

Quantifying Restoration Offsets at a Nuclear Power Plant in Canada

In Canada, the Fisheries Act requires all water takers to avoid, mitigate and offset fish losses. To satisfy the act’s requirements, operators of power plants are required to undertake habitat restoration projects to compensate for fish impinged and entrained at cooling water intake structures. Scaling the quantity of restoration needed, and measuring whether adequate compensation has been achieved, requires a metric that expresses the losses and gains in comparable units. Development of such a metric is especially difficult in the case of power plants, because the losses often consist of a mix of species and life stages that are very different from those produced by technically feasible restoration projects. This paper documents the method that has been developed for quantifying offsets for impingement and entrainment at the Bruce Generating Stations on the eastern shore of Lake Huron, and demonstrates how the method is being used to estimate the offset to be provided by removal of a dam on the nearby Saugeen River.

Cooling Water Intake Regulated Through Clean Water Act Section 316(b): A Critical Issue

Section 316(b) protects the aquatic ecology of the nation's waters. In May 2014, the Environmental Protection Agency (EPA) issued the final rule under Section 316(b) of the Clean Water Act. It outlined the regulations and standards for the design and operation of cooling water intake structures.