Condenser

Condenser

Patch notes: V 2.2.24.191

We tweaked the way this system works to fix some bugs and make it more realistic. It's not a huge change, but there are now a few important things you'll need to keep an eye on that didn’t matter before.

💧 What’s the Condenser For?

The condenser is in charge of turning steam back into water so it can go back into the system. Without it, the reactor would just keep pumping out steam with nowhere to go.

🌡️ Why It Needs to Be Under Vacuum

To condense steam, the pressure inside the condenser has to stay very low — ideally around 0.1 BAR. At that low pressure, water boils (and condenses) at a much lower temperature. This makes it easier for steam to turn back into liquid water.

If the pressure is too high or the temperature gets too hot, condensation stops. The steam just builds up, and that’s not good for the system.

In a PWR setup, the steam jet ejector by itself creates a partial vacuum in the condenser, but its suction is limited by available steam pressure and flow. The vacuum pump amplifies the ejector’s effect, pulling a deeper vacuum much faster. That’s why—during reactor startup—you run the pump at maximum power: it helps the condenser reach the target 0.1 bar (or lower) as quickly as possible. Once the plant is up and running, you can reduce the pump to minimum power to maintain vacuum with lower energy (and steam) consumption.

⚠️ Turbines and the Vacuum

The condenser's vacuum isn’t just for show — it’s essential for the turbines, too.

When steam leaves the reactor, it pushes the turbine blades and gives you power. But for that to work well, the steam needs somewhere to go after — and that “somewhere” is the condenser.

🌀 Why the Vacuum Matters

A good vacuum creates a pressure drop between the turbine and the condenser. This pressure difference is what pulls the steam through the turbine faster and harder, giving you more efficiency and power output.

Without that vacuum:

  • The pressure behind the turbine rises

  • The steam flow slows down

  • The turbine has to fight backpressure, which it’s not built for

💥 What Happens Without Vacuum?

Running the turbine without proper vacuum can lead to serious problems:

  • Low performance: Steam doesn’t move fast enough, so the turbine produces less or no power.

  • Overheating or mechanical stress: The turbine blades are under strain they weren’t designed for.

  • System imbalance: Pressure builds up in places it shouldn’t.

Keeping the vacuum system active at all times is important because—even if the condenser already sits at 0.1 bar—small leaks or gas diffusion will slowly raise its pressure. If the ejector and pump stop, non-condensable gases build up, condenser efficiency drops, and turbine performance suffers. By leaving the vacuum train online (even at low power), you prevent pressure spikes, sustain proper condensation, and protect the reactor’s thermal cycle.

In real reactors, this is a big deal — and in Nucleares, it means trouble for your setup.

🌀 Vacuum Circuit Valves

The valves allow precise control over steam and gas flow through the vacuum system—enabling safe startup, stable operation, and protection against overpressure, cavitation, and loss of mass in the condenser.

1. Suction Intake Valve

Controls the link between the retention tank and the vacuum pump. When open, it allows the vacuum pump to draw steam and non-condensable gases from the retention tank. When closed, it isolates the retention tank from the pump, preventing any suction.

2. Retention Tank Vent Valve

Regulates the release of non-condensable gases to the atmosphere from the retention tank. If the retention tank’s internal pressure becomes too high, opening this valve vents accumulated gases in a controlled manner. If left closed while the tank is full, backpressure builds up and can block the ejector’s discharge.

3. Condensate Return Valve

Allows condensed motive steam (and any after-ejector condensate) to return to the main condenser. When open, it routes condensed fluid back into the condenser so the water can re-enter the cycle. When closed, it stops that return flow, which can cause liquid levels or pressures to shift incorrectly in the condenser.

4. Startup Motive Steam Inlet Valve

Controls the flow of steam coming directly from the evaporators during plant startup. In startup mode, this valve sends hot steam from the evaporators straight into the ejector to establish vacuum in the condenser without sending steam through the turbine. Closing it prevents evaporator steam from reaching the ejector.

5. Operational Motive Steam Inlet Valve

Regulates the steam extracted from the turbines (low-pressure side) that feeds the ejector during normal operation. Once the plant is up and running, opening this valve delivers a portion of the turbine’s exhaust steam to the ejector. Closing it cuts off turbine steam to the ejector, which forces the vacuum system to switch back to startup steam or stop altogether.

6. Condenser Suction Valve

Acts as an isolation point for vacuum draw between the condenser and the vacuum train (ejector and pump). Opening this valve connects the condenser to the vacuum line so air and vapor can be extracted. Closing it blocks suction from the condenser, so neither the ejector nor the pump can pull gas out of it.