The Reactor Cooling panel might be the most demanding of all the panels, and it requires the constant attention of the operator. This panel essentially supervises the flow in the main cooling circuit. The system consists of three main elements:
- Hotwell - this is where condensed steam gathers after passing through the turbine
- Deaerator - this device is used to remove air from the water condensate (cooling panel manages the water level of deaerator while this device has its own panel for steam and pressure management)
- Reactor - this is water level in the reactor/steam separator system. It is crucial to maintain water level in the reactor as if it drops, the core would melt. Should anything happen, always fill the reactor with water, this is the most important thing!
The typical level for all the devices is 0 meters, with a minimum of -5 meters and a maximum of +5 meters (the deaerator is scaled in decimetres). When the maximum level is reached, water will be automatically drained from the system, leading to a temporary increase in radioactivity within a compartment. A low level in the Hotwell or Deaerator can damage the device (though this is not currently simulated). However, a level below -5 meters in the reactor will trigger emergency pumps and an automatic SCRAM. The operator is responsible for supervising 2 feedwater pumps and 2 condensate pumps. Feedwater pumps operate similarly to circulation pumps, while condensate pumps do not have separate valves; instead, they share one valve with a variable flow setting. Flows of up to 50% can be maintained with a single pump, but when there is a higher flow demand, the other pump must be switched on.
The water flows from top to bottom the following way: Reactor --> Turbine --> Hotwell --> Condensate Pumps --> Deaerator --> Feedwater Pumps --> Reactor
The main operating principle of the panel is 'what goes in must come out.' Therefore, the primary goal is to maintain identical flows throughout the system.
Steam flow indicates the amount of steam generated by the reactor and condensed in the condenser. The panel operator has no direct control over this parameter, as it is regulated by the turbine operator. To maintain consistent water levels, the operator should set the outflow from the Hotwell and the Deaerator to the same value. However, if there is an imbalance in water levels within the system, these values may differ. For instance, if the Hotwell level is significantly above 0 and the Deaerator level is negative, it is evident that the Condenser pumps should be set to a higher flow rate than the Feed Water pumps to balance the system. Ultimately, the goal is to ensure that all flows are maintained at a similar level.
There is also a water makeup valve used to introduce water into the system from the Condensate Storage Tank (CST). Excess water can be drained from hotwell into the CST using the drain valve. Under normal operating conditions, this feature is rarely needed. However, if we lose water due to draining or steam venting, it becomes necessary to replenish the system. When the makeup pump adds water to the Hotwell, it raises its level, so be prepared to increase the flow of the Condensate pump accordingly. In Unit #2 there are two selectable CST tanks and the hotwell control valve works a bit differently. It doesn't drain water from hotwell directly but it takes some hotwell water outflow, therefore it works only along with the Condensate Pumps. There is also a Makeup Pump apart from Makeup Valve but it should only be used when there is not vacuum in the condenser.
On the panel, there are three small levers for preheaters. All three of them should be turned on to heat the feedwater. You may notice that they consume some live steam, but in reality, they generate more steam than is used by the preheaters, increasing overall efficiency. The feedwater temperature is also provided and depends on factors such as steam temperature, available pressure, the number of preheaters in operation, and the Deaerator temperature. Next to the preheaters, there are two small levers for polishers that demineralize water. One of them should always be on during operations. In Unit 2 Polisher operation are more complex, please refer to the Polishers entry of the manual.
Main Cooling Control panel is also equipped with automatic cooling control. Three setpoints can be defined for Hotwell, Deaerator and Reactor levels and once engaged it will try to maintain the levels with pumps that are available (enabled and powered). Automatic Control will also use Hotwell Makeup and Drain valves.