📈 Interactive Thermodynamic Cycle Diagrams
These three interactive tools plot the thermodynamic states of nuclear reactor cycles on classic thermodynamic diagrams. Any combination of reactors can be displayed simultaneously — select one or more cycles from the list and click Load Selected Cycles. Hovering over a point shows its label and coordinates. The saturation curve can be toggled on or off. Plotly’s built-in tools allow zoom, pan, and export to PNG.
How to read these diagrams in context: the reactor fact sheets and flowsheets show how each cycle is constructed. The exergy balances show where the losses occur. These diagrams show how the thermodynamic states distribute relative to the saturation curve — which turbine stages operate in wet steam, how much superheat is available, and how the feedwater heating chain raises feedwater temperature before the steam generator.
Temperature–Entropy Diagram (T-S)
The T-S diagram is the most direct representation of cycle quality. The area enclosed by the cycle is proportional to net work. Irreversibilities appear as deviations from ideal isentropic processes. The WCR family clusters compactly in the lower region; high-temperature cycles (SCWR, AGR, HTR-PM) extend upward.
💡 For better zoom control and full-screen viewing, open the T-S diagram directly.
Enthalpy–Pressure Diagram (h-P)
The h-P diagram shows the full pressure range on a logarithmic scale — the pressure architecture of each cycle and turbine extraction levels. The supercritical SCWR (~250 bar) sits clearly above the saturation dome. The NuScale US460 condenser at 0.038 bar is visible at the extreme bottom.
💡 For better zoom control and full-screen viewing, open the h-P diagram directly.
Mollier Diagram (h-S)
The Mollier (enthalpy–entropy) diagram is the standard tool for turbine engineers. The slope of the expansion lines indicates the isentropic efficiency of each turbine stage. The position relative to the saturation curve shows steam quality throughout the expansion — including the wet steam region of the NuScale US460 that explains the high Turbine 4 irreversibilities discussed in the exergy balance analysis.
💡 For better zoom control and full-screen viewing, open the Mollier diagram directly.
Available Cycles
French PWR family — EPR Flamanville
| Cycle ID | Description |
|---|---|
Flamanville_R_100% simplified WCR model | Flamanville 100 % — simplified WCR model (Nuscle) |
Flamanville_R_90% simplified WCR model | Flamanville 90 % — simplified WCR model (Nuscle) |
Flamanville_R_70% simplified WCR model | Flamanville 70 % — simplified WCR model (Nuscle) |
Flamanville_R_50% simplified WCR model | Flamanville 50 % — simplified WCR model (Nuscle) |
Flamanville_R_30% simplified WCR model | Flamanville 30 % — simplified WCR model (Nuscle) |
Flamanville 100% R ASN security report | Flamanville 100 % — ASN safety report data |
Flamanville 90% R ASN security report | Flamanville 90 % — ASN safety report data |
Flamanville 70% R ASN security report | Flamanville 70 % — ASN safety report data |
Flamanville 50% R ASN security report | Flamanville 50 % — ASN safety report data |
Flamanville 30% R ASN security report | Flamanville 30 % — ASN safety report data |
N4 French PWR | N4 French PWR |
N4 French PWR detailed cycle | N4 French PWR — detailed cycle |
CP0 French PWR | CP0 French PWR |
CP2 French PWR | CP2 French PWR |
Gas-cooled reactors
| Cycle ID | Description |
|---|---|
Hartlepoole AGR Cycle | AGR Hartlepool |
TornessExtr | AGR Torness |
HTR-PM Shidao Bay | HTR-PM — Shidao Bay operating data |
Water-cooled reactors (WCR)
| Cycle ID | Description |
|---|---|
VVER K-1000-60/1500-2 | VVER-1000 (K-1000-60/1500-2) |
VVER_70 | VVER-70 |
RBMK_K-1000-65-3000 | RBMK-1000 (K-1000-65-3000) |
Candu | CANDU Pickering |
ABWR | ABWR |
NuScale SMR | NuScale SMR |
Fast and advanced reactors
| Cycle ID | Description |
|---|---|
Superphenix French SFR | Superphénix (SFR) |
Canadian SCWR | Canadian SCWR |
“Simplified WCR model” = Nuscle model. See the Nuscle section for an explanation of the differences between Nuscle simplified models and detailed Thermoptim models, and how to interpret them.
Particularly Instructive Comparisons
A few combinations that reveal thermodynamic contrasts clearly:
Load pattern sensitivity (Flamanville EPR): load Flamanville_R_30% simplified WCR model through Flamanville_R_100% simplified WCR model together — the five operating points trace a family of cycles that shrink toward the lower left as power decreases. The feedwater heating line progressively shortens.
Two generations of VVER: VVER_70 + VVER K-1000-60/1500-2 — saturated steam + separator vs. superheated steam + MSR. The contrast in steam conditions at HP turbine inlet is immediately visible on the Mollier diagram.
Gas-cooled vs. water-cooled: Hartlepoole AGR Cycle + N4 French PWR — the AGR cycle extends to 541 °C / 170 bar, far above the EPR. On the T-S diagram the temperature difference between the two families is striking.
SMR at low power: NuScale SMR — the most compact cycle in the collection. On the Mollier diagram, the LP expansion clearly crosses into the wet steam region.
Simplified vs. detailed (EPR): Flamanville_R_100% simplified WCR model + N4 French PWR detailed cycle — the Nuscle simplified model vs. the full detailed N4 cycle. On the T-S diagram, the feedwater heating steps are more numerous and smaller in the detailed model.
Reading the Three Diagrams Together
The three diagrams are most informative when used in sequence:
- T-S → identifies temperature conditions and regenerative heating extent
- h-P → reveals the pressure architecture and extraction points
- h-S (Mollier) → evaluates turbine stage quality and wet steam extent
For each reactor, the detailed exergy balance quantifies the irreversibilities that these diagrams make geometrically visible.
Thermodynamic cycle data: Thermoptim project files. Diagrams generated with Plotly. Models for AGR Hartlepool, Torness, HTR-PM Shidao Bay, VVER-70, and the full Flamanville load range are available exclusively on this companion website.