Thermal Balance | Steam-Water Flow Balance

Thermal Balance | Steam-Water Flow Balance

Patch notes: V 2.2.21.172

Refers to the balance between the steam generated in the steam generator and the steam exiting the system. This equilibrium ensures that the steam produced aligns with the water returning from the condenser, sustaining a consistent and efficient cycle.

Steam Generated: It is the steam generation factor of the evaporator, used to compare with the steam outlet and coolant inlet factors to determine internal equilibrium. 

The amount of steam generated is directly proportional to the reactor's power output. To increase the steam generation, one of the following actions must be taken:

• Increase Reactor Power: Boosting the reactor's power raises the heat transferred to the coolant, which in turn increases the rate of steam production.
  
  
• Increase Circulation Pump Speed: Increasing the speed of the circulation pump enhances the flow rate of the coolant through the reactor core. This results in more efficient heat transfer and subsequently higher steam generation.

Adjustments to reactor power or pump speed must be made gradually and with careful monitoring to maintain operational safety and efficiency. Overloading the system can lead to overheating or an imbalance in the steam-water flow cycle, potentially compromising the reactor's stability.

Steam Outlet: It is the steam propulsion factor toward the turbines, used to compare with the steam generated and coolant inlet factors to determine internal equilibrium.

The amount of steam discharged from the evaporator is directly influenced by two key factors:

• Internal Pressure: Higher internal pressure increases the driving force that pushes the steam through the system, thereby raising the amount of steam expelled.
  
  
• Opening of the Main Steam Control Valves: The degree to which the Main Steam Control Valves are open determines the flow rate of steam leaving the evaporator. Wider valve openings allow for greater steam discharge.
  
  How to increase the amount of steam expelled:
  
  
• Increase the internal pressure within the evaporator by adjusting operational parameters, such as reactor power or heat input.
  
  
• Ensure that the Main Steam Control Valves are opened to the appropriate degree to handle the desired flow rate.
  
  Increasing pressure must be carefully managed to prevent system instability or over-pressurization, which could trigger safety mechanisms such as the pressure relief valve.Valve adjustments should be gradual and monitored in real time to avoid abrupt changes in the steam-water balance.

Coolant Inlet: It is the coolant return factor from the condenser, used to compare with the steam generated and steam outlet factors to determine internal equilibrium. If the factor is very low or zero, check whether there is sufficient power in the circulation pump or if the evaporator pressure is too high, preventing coolant return.

The amount of coolant returning to the evaporator is influenced by two primary factors:

• Internal Pressure of the Evaporator: Higher internal pressure can reduce the pressure differential between the evaporator and the condenser, making it more difficult for coolant to return efficiently.
  
  
• Circulation Pump Speed of the Condenser: Faster pump speeds increase the flow rate of coolant back into the evaporator, facilitating a more robust return cycle.
  
  
  How to increase the volume of coolant returning to the evaporator:
  
  Increase the speed of the condenser circulation pumps to boost the coolant flow rate.
  
  
  
  Reduce the internal pressure of the evaporator if it is excessively high and restricting coolant reentry. Adjusting operational parameters or venting excess steam may help achieve this.
  
  
  Maintaining an optimal balance between pressure and pump speed is critical to ensuring efficient coolant return and stable system operation. Excessively high internal pressure not only impedes coolant return but also increases the risk of triggering safety systems such as the pressure relief valve. Adjustments should be performed gradually and under careful monitoring to avoid introducing system instabilities.

Important: Maintaining this balance is essential for the safe and efficient operation of the reactor. However, in situations where the pressure inside the steam generator is very high, the water may not return in sufficient quantities due to the reduced pressure difference between the condenser and the generator. This imbalance can lead to a reduction in reactor efficiency and even jeopardize its operation if not properly controlled.

The balance gauges provide a quick understanding of whether the current equilibrium situation will cause the evaporator to empty or become overpressurized. 

If the needle moves to the left, it means the evaporator is receiving more water than it can evaporate or expel, leading to an increase in the coolant level inside the evaporator. Conversely, 

If the needle moves to the right, the evaporator is generating more steam than it can recover, resulting in a decrease in its coolant volume.

The reactor's control system continuously monitors these variables and adjusts operational conditions to ensure that water and steam flow remain balanced, minimizing risks and optimizing energy generation.