Reactor thermal output.
Net capacity to grid; GE also lists ~316 MWe gross.
Lifetime capacity-factor target.
Main cooling heat load at the baseline 95% allocation.
What the TVA/NRC material does—and does not—give us
The NRC confirms TVA’s single-unit Clinch River Nuclear Unit 1 construction-permit application is for the BWRX-300, with a nominal 300 MWe electrical output and 870 MWt thermal rating. The NRC project page links TVA’s PSAR Revision 1 (submitted 29 April 2026), the Final Safety Evaluation Report (25 June 2026), and the Final Supplemental EIS (6 April 2026). Public BWRX design material describes the CWS architecture and cooling options, but the readily accessible sources do not provide a finalized TVA-specific normal-operation circulating-water flow, tower makeup rate or cycles of concentration. Those quantities below are therefore calculated estimates, not quoted TVA numbers. NRC Clinch River application page ↗
Estimated cooling-water assumptions
editable screening basisGE’s public description says the reference site uses mechanical-draft cooling towers, while hybrid, dry and once-through options are also possible. TVA’s earlier Clinch River ESP environmental basis likewise used mechanical-draft evaporative cooling. The exact CRN-1 tower design values remain site-specific.
Estimated auxiliary water
non-cooling usesThe ~150 staff basis is published by GE for a single unit. The water-use rates and high-purity makeup quantities are EngineerHub estimates; replace them with project data when available.
Reuse & annualization
optional sensitivityBaseline reuse is intentionally zero because a current TVA-specific wastewater-recovery design basis has not been verified. Raising this value shows the effect of recycling compatible blowdown/treatment wastewater to tower makeup.
Baseline water balance
normal full-power estimateCooling-system breakdown
mechanical-draft wet-tower case| Total heat not delivered to grid | — |
| Estimated heat to main CWS | — |
| Cooling-water circulation | — |
| Tower evaporation | — |
| Drift | — |
| Blowdown | — |
| Gross tower makeup | — |
| Cooling pretreatment raw feed | — |
Detailed plant balance
estimated flow streams| Stream | m³/h | m³/day |
|---|
Cycles-of-concentration sensitivity
all other assumptions held constant| Cycles | Tower makeup m³/h | Withdrawal m³/h | Discharge m³/h |
|---|
Increasing cycles reduces blowdown and withdrawal, but chemistry—not arithmetic—sets the practical maximum. Hardness, silica, chloride, sulfate, microbiology and materials all matter.
Once-through alternative
comparison only| Assumed condenser range | 12 °C |
| Estimated intake | — |
| Withdrawal intensity | — |
| Illustrative 0.1% consumptive loss | — |
GE states the BWRX-300 can use once-through cooling where an adequately sized water body is available. This comparison is not the selected TVA Clinch River design basis.
Published design basis vs EngineerHub assumptions
traceability matters more than false precision
| Parameter | Value used | Status | Basis |
|---|---|---|---|
| Reactor thermal output | 870 MWt | Published | GE Vernova Hitachi BWRX-300 General Description; NRC Federal Register notice for TVA CRN-1. |
| Net electrical output | 300 MWe | Published | GE lists ~300 MWe net to grid; NRC describes nominal 300 MWe. |
| Gross electrical output | ~316 MWe | Published | GE comparison table; useful context for approximate house load. |
| Lifetime capacity factor | 95% target | Published | GE BWRX-300 parameter table. |
| Single-unit O&M staffing | ~150 total | Published | GE BWRX-300 parameter table. |
| Cooling configuration | Mechanical-draft wet tower baseline | Site/design choice | GE reference site uses mechanical-draft towers; older TVA Clinch River ESP environmental analysis also used mechanical-draft evaporative cooling. Current CRN-1 detailed tower sizing is not asserted here. |
| Main CWS heat load | 95% of 570 MW balance = 541.5 MW | Estimate | Transparent allocation of total 870−300 MW plant heat not delivered to grid. Remaining 5% represents heat rejected elsewhere. |
| Cooling range | 10 °C | Estimate | Representative condenser/tower screening assumption; site-specific optimization required. |
| Evaporative heat fraction | 85% | Estimate | Screening assumption to separate latent and sensible tower heat rejection. |
| Cycles of concentration | 4.0 | Estimate | Representative fresh-water tower basis; actual cycles depend on source-water chemistry and treatment. |
| Drift | 0.005% circulation | Estimate | Low-drift modern tower screening value; vendor guarantee required. |
| High-purity water product | 7 m³/h | Estimate | Order-of-magnitude normal-operation allowance for cycle losses, cleanup, closed-loop makeup and laboratory/chemistry uses; not a safety inventory. |
Water quality in a BWRX-300 plant
different systems need different water
Circulating water / tower makeup
Quality objective: control scaling, corrosion, fouling and biology while maximizing cycles. Track hardness/alkalinity, silica, chloride, sulfate, TDS/conductivity, suspended solids, organics and microbiology. Raw river water may require clarification/filtration, softening, membranes or chemical conditioning depending on site chemistry.
Plant Cooling Water (PCW)
Published BWRX description: PCW is a closed system that provides a barrier between plant components and the CWS. GE states that during normal operation the PCW uses pure demineralized water with no chemicals added, with chemical addition capability if needed for water-quality control.
Condensate / feedwater
Very high purity: the BWRX-300 uses full-flow condensate filtration and mixed-bed demineralization to remove corrosion products and dissolved impurities, including those introduced by condenser in-leakage. Direct-cycle BWR chemistry makes condenser integrity and impurity control especially important.
ICS and fuel-pool inventories
Controlled demineralized inventories: the isolation-condenser pool cleanup and fuel-pool cooling/cleanup systems include demineralization/filtration functions to maintain prescribed water quality. Their required safety inventories are not sized by this calculator.
Potable / sanitary
Drinking-water quality: staff potable supply must meet applicable drinking-water requirements. It should remain segregated from industrial process systems except through approved protected interfaces.
Blowdown / liquid discharge
Permit-specific: cooling-tower blowdown can contain concentrated source-water minerals and treatment chemicals. Discharge temperature, pH, TDS, metals, biocides and other parameters are governed by site permits and receiving-water requirements; there is no universal BWRX discharge specification.
Calculation method
screening equations behind the estimate
1. Heat balance
The published 870 MWt reactor output and approximately 300 MWe net output imply about 570 MW not exported as electricity at full load.
The baseline assigns 95% of this to the main circulating-water heat sink: 541.5 MW. This is an EngineerHub assumption, not a published TVA CWS duty.
2. Circulating-water flow
For a specified temperature rise, the model uses liquid-water sensible heat:
with ρ ≈ 1000 kg/m³ and cp ≈ 4.186 kJ/kg·K. At the baseline 10 °C (18 °F) range, circulation is about 46,600 m³/h (12.9 m³/s), or about 205,000 gpm.
3. Tower evaporation
Evaporation is tied to latent heat rather than an arbitrary fraction of circulation:
with hfg ≈ 2400 kJ/kg for screening. The editable latent fraction represents the share of tower heat rejection accomplished by evaporation.
4. Blowdown and cycles
At steady state, a simple dissolved-solids balance gives:
where C is cycles of concentration and D is drift. Gross tower makeup equals evaporation + drift + blowdown.
5. Withdrawal, consumption, discharge
Withdrawal is external water entering the plant. Consumption is water not returned as liquid, dominated here by evaporation. Discharge is liquid leaving the plant boundary. Internal reuse is not counted as a new external source.
6. What PSAR review changes
The TVA PSAR is essential for safety and plant-system design, but public licensing materials do not automatically provide every commercial heat-balance or water-treatment design flow. Once TVA/GVH publish site-specific CWS duty, tower cells, basin data, makeup/blowdown rates or treatment recoveries, those values should replace the yellow “Estimate” inputs here.
Compare another plant-water case
published permit vs design-based estimate
References
primary sources first
Reference status checked 21 August 2026. Where a project-specific value is not publicly verified, the calculator labels it as an estimate rather than implying it comes from TVA, NRC or GE Vernova Hitachi.