Drawing No. EH–PG–006 // Power Generation & Grid
Reviewed August 2026
Calculate a complete power-plant water balance for nuclear, coal, combined-cycle, CSP or other steam-electric plants. Estimate cooling-water makeup, withdrawal and consumption, cooling-tower evaporation and blowdown, demineralized-water demand, service and sanitary use, treatment losses, wastewater reuse and liquid discharge.
The calculator closes a zero-storage-change water balance around the plant. Cooling is derived from the plant heat balance; the steam cycle uses a separate high-purity makeup balance; auxiliary and sanitary uses are split into consumed and recoverable wastewater; treatment recovery creates reject streams; and a wastewater-reuse loop can displace external cooling makeup.
See a worked 300 MWe BWR SMR water-use example based on public GE Vernova Hitachi design data and TVA/NRC Clinch River licensing information, with unpublished flow quantities clearly identified as engineering estimates.
Use a real 1,052 MWe hard-coal plant and its published 2,300 m³/h Dortmund-Ems Canal water permit to explore cooling-tower makeup, FGD/process water, demineralized-water demand and industrial wastewater.
The heat-balance method assumes Qin = Pnet/η and assigns an editable fraction of the rejected heat to the main condenser/cooling system. Fossil and CCGT profiles use lower default cooling shares because more heat leaves through stacks and other paths.
For a BWR, “cycle purge” is a generic balance term rather than steam-generator blowdown. For PWR/fossil plants it can represent steam-generator or boiler blowdown. Enter site-specific values whenever available.
Recovered product is assumed suitable for cooling-tower makeup and displaces external cooling makeup first. The model iterates because cooling pretreatment reject itself can feed the reuse system.
This is a concentration-ratio screen only. It does not calculate saturation indices, corrosion rates, microbiology, inhibitor chemistry, acid feed, side-stream treatment or materials compatibility.
| Thermal input | — |
| Total rejected heat | — |
| Main cooling heat load | — |
| Cooling circulation / intake | — |
| Evaporation | — |
| Drift | — |
| Blowdown | — |
| Tower gross makeup | — |
| Recovered water credited to cooling | — |
| External treated cooling makeup | — |
| Stream | Flow | Annual |
|---|
| Constituent | Makeup | Recirculating estimate |
|---|---|---|
| TDS | — | — |
| Hardness as CaCO₃ | — | — |
| Silica as SiO₂ | — | — |
| Chloride | — | — |
mass balance · energy balance · dissolved solids
For a plant represented by net electrical output P and net thermal efficiency η, the model estimates thermal input and total rejected heat:
An editable fraction is assigned to the main cooling system because not all rejected heat necessarily reaches the condenser. This matters particularly for fossil and combined-cycle plants, where stack losses can be significant.
Cooling-water flow follows the sensible heat balance:
The calculator uses ρ ≈ 1000 kg/m³ and cp ≈ 4.186 kJ/(kg·K), appropriate for preliminary water-balance work. For once-through cooling, this is essentially the withdrawal flow; for a wet tower it is the recirculating flow, not the makeup flow.
Evaporation is estimated from the fraction of wet-tower heat transferred as latent heat:
The model uses hfg ≈ 2400 kJ/kg as a screening value at cooling-tower temperatures. IAEA describes wet-tower heat transfer as occurring by convection and mainly evaporation; actual evaporation changes with weather, tower design and approach.
Evaporation leaves dissolved salts behind. For target cycles of concentration C, the dissolved-solids balance gives:
where B is blowdown, D drift and L other liquid losses from the recirculating system. If drift plus other liquid losses already purge more dissolved solids than the target requires, blowdown is set to zero and the model reports the lower physically achievable cycles.
Withdrawal is water removed from an external source. Consumption is water not returned as liquid to the source system, mainly evaporation and other losses. A once-through plant can therefore have very high withdrawal but relatively low consumption; a wet-tower plant withdraws much less but consumes more by evaporation.
This distinction is central in IAEA water-management guidance and is why the calculator reports both metrics separately.
For a treatment train with overall product recovery R:
Eligible cooling blowdown, demineralizer reject and plant wastewater are then sent to a reuse plant. Recovered product is credited to cooling-tower makeup. Because cooling pretreatment reject changes when reuse displaces external makeup, the model solves the loop iteratively.
why one water specification does not fit the whole plant
| Use | Typical quality philosophy | Important parameters | Engineering note |
|---|---|---|---|
| Cooling-tower makeup | Raw, clarified, filtered, softened, reclaimed or membrane-treated water may be acceptable depending on tower metallurgy and chemistry program. | Hardness, alkalinity, silica, chloride, sulfate, TDS/conductivity, suspended solids, organics, nutrients and microbiology. | Quality determines allowable cycles of concentration. IAEA notes hardness, silica and other minerals as key limits; DOE/EPA recommend maximizing cycles only within chemistry constraints. |
| Once-through / service water | Often screened and filtered raw fresh water or seawater; chemistry treatment is site- and materials-specific. | Suspended solids, debris, biological fouling, salinity/chloride, temperature and corrosion potential. | Very high withdrawal can coexist with low consumptive use. Thermal and chemical discharge requirements are permit-specific. |
| Boiler / steam-generator makeup | High-purity demineralized water, commonly produced through membrane and ion-exchange/EDI treatment. | Conductivity, sodium, chloride, sulfate, silica, dissolved oxygen, iron/copper transport and chemistry-control additives. | Required purity depends strongly on pressure, metallurgy and the plant chemistry program. NRC describes PWR secondary water as demineralized water with pH/oxygen control and impurity monitoring. |
| Nuclear primary / safety inventories | Demineralized high-purity water with reactor-specific chemical and radiological controls; boron/lithium or other chemistry may apply by reactor design. | Conductivity, ionic impurities, dissolved gases, pH-control species and radionuclide/chemistry requirements. | IAEA examples show demineralized water for many LWR reactor auxiliary, component-cooling, feedwater, spent-fuel and emergency inventories. This calculator does not size safety inventory. |
| Closed component cooling | Usually high-quality demineralized or specially treated closed-loop water with corrosion-control chemistry. | Conductivity, chloride, pH, oxygen, inhibitor concentration and corrosion products. | Closed systems need low make-up but high chemistry control because leakage or poor chemistry can damage heat exchangers and components. |
| Potable / sanitary | Must meet applicable national drinking-water requirements; WHO guidance provides an international risk-management framework. | Microbial safety, regulated chemicals, radiological quality, taste/odour and operational disinfectant control. | Do not use industrial-process acceptance criteria as a substitute for drinking-water requirements. |
| Reclaimed water for cooling | Tertiary municipal effluent or treated plant wastewater can be a useful cooling makeup source if compatible with the tower treatment program. | TDS, hardness, chloride, nutrients, ammonia, organics, suspended solids and microbiology. | DOE specifically identifies high-quality municipal wastewater effluent and compatible process effluent as potential alternate cooling-tower makeup sources. |
| Wastewater discharge | Quality is governed by the receiving environment and discharge permit, not by a universal plant value. | Temperature, pH, TSS, TDS, metals, treatment chemicals, nutrients and source-specific contaminants. | In the U.S., steam-electric discharges are regulated through 40 CFR Part 423/NPDES; other jurisdictions have their own permitting frameworks. |
what the calculator can and cannot prove
public primary / authoritative sources
Default presets in this calculator are illustrative starting points assembled for model demonstration; they are not asserted as vendor design data for any specific plant. Replace them with project values before using results in engineering studies.
continue the plant-water analysis
Include the inputs, plant type and assumptions used.