Chemistry module

Chemical Module

Patch notes: V 0.2.18.141

The in-game chemistry module has been enabled. Although it is disabled by default, it can be activated manually for new games. In any case, using it is not mandatory, so if you are not interested in this topic, you can stop reading this entry and continue playing as usual (just ignore the new building and the chemical treatments console in the control room).

If you are interested in understanding what it is and how it works, below you will find all the information.

First and foremost, the chemistry module is not compatible with any previous savegame. If you want to play with a progress prior to this version, the chemistry module must be disabled.

If you save progress created with the Chemistry Module enabled, you will not be able to play with that progress if you later disable the Chemistry Module.

If I can continue operating the reactor as usual, what is the chemical module for?

Boron is used in pressurized water nuclear reactors as an additional method for controlling reactivity. While it's possible to operate a reactor solely with control rods, the use of boron offers several advantages:

Increased control precision: Boron can be injected into the reactor circuit in small amounts to finely adjust the core reactivity. This allows for more precise control of reactor power and a faster response to changes in operating conditions.

Corrosion reduction: Boron can also help reduce corrosion in certain parts of the reactor, as it can form a protective layer on metal surfaces.
Reactor stability: Controlled addition of boron can help maintain reactor stability during changes in load or operating conditions. This can be especially important during power transitions, reactor startup, or shutdown.
Reduced dependence on control rods: By using boron in conjunction with control rods, reliance solely on control rods to manage reactor reactivity can be reduced. This can increase operational flexibility and reactor safety.

Nuclear Reactor Startup and Equilibrium Process

Upon initiating fission within the pressurized water reactor, various types of nuclear isotopes are generated. For this simulator, only two will be considered: iodine-135 and xenon-135.

The presence of xenon-135 can decrease the reactor's reactivity, requiring compensation by the reactor operator to maintain the desired power level. The amount of xenon-135 formed depends on factors such as reactor power and fuel loading. Xenon-135 has a half-life of 9 hours before it decays.

The reactor is considered to reach equilibrium approximately after 14 hours of operation, when the production of xenon-135 and the decay of iodine-135 balance each other. This equilibrium may vary depending on the specific reactor conditions. It is essential to keep operation within normal operating parameters to avoid drastic changes in power and ensure safe and efficient reactor operation.

Production of Iodine-135: During the initial operation, iodine-135 is produced in proportion to the fission rate and the reactor's efficiency in capturing fission neutrons.

During the initial operation phase of the reactor, nuclear fission produces iodine-135 in proportion to the fission rate and the reactor's efficiency in capturing fission neutrons. It is important to note that changes in reactor power can influence the production of iodine-135 due to variations in the fission rate.

Iodine-135 isotope has a half-life of 6 hours, after which it decays and transforms into xenon-135. During the initial decay, the reactor may experience an increase in power due to the production of xenon-135. Although xenon-135 is a more efficient neutron absorber than iodine-135, its production is not proportional to the amount of iodine-135 decayed.

Summarized and structured explanation in steps:

Decay of Iodine-135: After 6 hours, iodine-135 decays and forms xenon-135.
Initial Power Increase: The initial decay may cause a power increase due to the production of xenon-135.
Formation of Xenon-135: Xenon-135 is a more efficient neutron absorber than iodine-135, but its production is not proportional to the amount of iodine-135 decayed.
Reactivity Reduction: Accumulation of xenon-135 can reduce the reactor's reactivity, necessitating adjustments in operation to maintain desired power levels.
Achieving Equilibrium: After approximately 14 hours of operation, the production of xenon-135 and the decay of iodine-135 reach equilibrium.
Continuous Operation: It's important to maintain operation within normal operating parameters to ensure safe and efficient reactor operation.

Variations in power during reactor operation

During normal reactor operation, it is important to consider the transient behavior of xenon-135, especially during power variations. Any variation in power (increase or decrease) of a nuclear reactor in operation produces a temporary behavior of xenon-135 for a period that will depend on the magnitude of such variation.

Additionally, it is important to consider the role of iodine-135 in the generation of xenon-135. Iodine-135 is a direct fission product and a precursor to xenon-135. When nuclear fission occurs, iodine-135 is generated, which then decays via beta decay to form xenon-135. Therefore, the levels of iodine-135 directly affect the subsequent production of xenon-135 in the reactor.

Any change in the fission rate (and hence the production of iodine-135) due to power variations will affect the amount of xenon-135 generated after a certain delay time, as the iodine-135 must first decay. This delay in the generation of xenon-135 is another important factor to consider during reactor power transients.

In the game simulation, these variations are set at 5 minutes for each significant power change.

Simulations and behaviors of the current version:

Iodine generation according to the power of the reactor.
Temporary increased Iodine generation during power peaks.
Reduction of Iodine generation due to Boron presence and reaction.
Indirect generation of Xenon by degradation of Iodine.
Reduction of Xenon generation due to high temperatures.
Reduction of Xenon generation due to Boron presence and reaction.
Degradation of Xenon by lifetime.
Degradation of Xenon due to power increase (Xenon Burnout).
Life time of Iodine within the game before degrading into Xenon: 6 hours.
Xenon life time in-game before completely degrading: 9 hours.
The possibility of cleaning residual Xenon and Iodine was added to the Core maintenance tasks, to avoid the waiting time required for its natural degradation.

Advantages of using Boric Acid vs Control Rods

In pressurized water reactors (PWRs), boric acid is used in the primary coolant as an additional method for controlling the reactor's reactivity, alongside the control rods. Both the use of boric acid and control rods have advantages and disadvantages.

Advantages of using boric acid:

Distributed reactivity control: Boric acid is uniformly distributed in the primary coolant, providing more uniform reactivity control throughout the reactor core.
Ability to compensate for large reactivity changes: Boric acid can compensate for large reactivity changes, such as xenon poisoning during reactor startups and shutdowns.
Backup for control rods: Boric acid provides a redundant reactivity control system, backing up the control rods in case of failure.
Operational flexibility: Adjusting the boric acid concentration allows for more precise reactivity control and greater flexibility during operational maneuvers.

Disadvantages of using boric acid:

Corrosion: Boric acid can cause corrosion in the primary cooling system components if not properly controlled.
Need for purification systems: Coolant purification systems are required to adjust and control the boric acid concentration.
Impact on reactor efficiency: A high concentration of boric acid can reduce reactor efficiency by absorbing neutrons.

Advantages of using control rods alone:

Simpler system: No need for boric acid purification and control systems.
Less corrosion: Without boric acid, the risk of corrosion in components is reduced.

Disadvantages of using control rods alone:

Limited compensation capacity: Control rods have a limited capacity to compensate for large reactivity changes, such as xenon poisoning.
Less operational flexibility: Adjusting reactivity with control rods alone may be less precise and flexible during operational maneuvers.

Indicators and controls in the game

Fission Product Xenon Activity

Radioactive activity of the xenon isotopes that are fission products from the nuclear fission of fuel in the reactor. The fission rate occurring in the reactor and the production of fission products. As the Xenon generation increases, the indicator will move to the red zone.

Xenon Concentration Monitor

Measures the actual concentration levels of xenon isotopes, present in the reactor coolant and off-gas systems. Indicates the amount of Xenon inside the core in relation to the total capacity. Too high a value could indicate rector poisoning.

One crucial aspect of xenon concentration is its effect on reactor operation, particularly its potential to cause reactor poisoning. Xenon is a strong neutron absorber, meaning it readily captures neutrons, which are crucial for sustaining the chain reaction within the reactor core. When xenon concentration increases, can absorb a significant portion of the neutrons, leading to a decrease in reactor power output. This buildup can occur because xenon is continuously being produced by fission reactions, while its decay is slower due to its short half-life.

If the xenon concentration becomes too high, it can lead to reactor shutdown or instability. This phenomenon is known as xenon transients. During transient conditions, such as changes in reactor power level or reactor startup from shutdown, the xenon concentration can change rapidly, impacting reactor reactivity and stability.

Dissolved Gamma Iodine Activity

Measures the radioactive gamma activity of iodine isotopes dissolved in the reactor coolant and primary coolant system. These iodine isotopes are fission products generated during the nuclear fission process in the reactor core.

Iodine Concentration Monitor

Measures the actual concentration levels of iodine isotopes present in the reactor coolant or off-gas systems. Specifically quantifies the amount or concentration of these iodine atoms in the various systems

Control Panel | Chemical Treatments

Within the control panel located in the control room, you will find the following elements:

Boric Acid Dosing Pump: This pump indicates the amount of boric acid to be supplied. The unit is grams per minute, based on the concentration of the acid. Note that boric acid is a liquid, therefore, there must be space within the primary circuit to add the necessary amount of liquid to reach the required grams.

Boric Acid Filtration Pump: This pump redirects the coolant from the primary circuit to an ion exchange column to extract boron. Note that the extraction of boron from the coolant does not reduce the total volume, as it is a filtration process.

"Ion Exchange Capacity" Indicator: This indicator allows you to monitor the current status of the ion exchange columns and their absorption capacity. The ion exchange columns require maintenance to function properly. If they accumulate too much boron, they will lose their absorption capacity. To clean the ion exchange columns, you must use sodium hydroxide.

The valves connecting the primary circuit to the chemical treatment building are manual, therefore, to add boron, filter the added boron, or clean the ion exchange columns, you will need to adjust them manually.

Coolant pH Level: This indicator provides information on the pH level of the primary circuit coolant. pH plays a crucial role in determining the absorption capacity of boron within the coolant. The optimal operating range for pH falls between 7 and 9. If the pH deviates from this range and becomes excessively acidic, it can lead to increased corrosion of the pipes and other components within the system.

The presence of corrosion within the primary circuit pipes deteriorates their structural integrity over time. This deterioration occurs due to the gradual wearing away of the metal surfaces, leading to thinning and weakening of the pipes. As corrosion progresses, it can compromise the functionality of hydraulic valves and circulation pumps connected to the primary circuit.

Corrosion may cause valve components to become stuck or malfunction, hindering their ability to control the flow of coolant effectively. Similarly, corrosion-related damage to circulation pumps can reduce their efficiency and reliability, potentially impeding the proper circulation of coolant throughout the reactor system.