Pressurized Water Reactor

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A three-dimensional, fully modular reactor.

## Description

A Pressurized water reactor (PWR for short) is a fully modular type of nuclear reactor, much like the RBMK, but modular in three dimensions instead of two. The PWR operates much like the RBMK, but with two loops instead of one; one for the coolant, and the second for water.

## Construction

A PWR reactor is made up of the following pieces:

* PWR Fuel Rod
* PWR Control Rod
* PWR Coolant Channel
* PWR Heat Exchanger
* PWR Neutron Source
* PWR Neutron Reflector
* PWR Pressure Vessel
* PWR Access Port
* PWR Controller

### To begin building your PWR:

1. Create a pressure vessel bottom out of the respective block. There are no size requirements, but smaller reactors are generally recommended. The base of the PWR should look vaguely circular or ovaloid.
	* Note that, upon construction, the corners / rims of a pressure vessel will not be used, as perpendicular "wall" segments only require to be connected diagonally.
2. Add fuel rods. As PWR designs are *usually* taller than they are wide, it is recommended to stack these vertically.
	* For optimal performance, fuel rods should be installed in a grid pattern.
3. Add control rods. While self explanatory, control rods allow the user to control the fission rate of the reactor.
	* Control rods should always be adjacent to fuel rods.
4. Add heat exchangers. Heat exchangers transfer *Core heat* into *Hull heat* in order to allow for the reactor to be cooled.
	* The position of heat exchangers generally does not matter.
5. Add coolant channels. Coolant channels transfer *Hull heat* to the *coolant of choice* in order to cool down the *hull.*
	* The position of coolant channels does not matter.
6. Add neutron sources. Neutron sources are required for PWR operation and add a permanent 20 *flux* to the reactor.
	* The position of neutron sources does not matter.
7. (Optionally) Add neutron reflectors. Neutron reflectors increase the reactivity, and subsequently *flux,* of the fuel.
	* Neutron reflectors should be placed on the same grid as fuel rods.
	* **Neutron reflectors act as PWR pressure vessel blocks. Building them inside of the reactor is ill-advised.**
8. Add access ports. Access ports are required for the cycling of coolant. Access ports automatically adopt the fluid type of the connected pipe.
	* A minimum of two access ports are required, one for the coolant, and a second one for the heated version of the coolant.
	* **Access ports** **act as PWR pressure vessel blocks. Building them inside of the reactor is ill-advised.**
9. Add a PWR controller. The PWR controller is required for the finalization of construction, and operation of the reactor.
	* **The PWR controller acts as a PWR pressure vessel block. Building it inside of the reactor is ill-advised.**
10. To finish construction, interact with the PWR controller. Any and all issues with the construction will be highlighted in red, with the issue above the highlight.

## User interface

The UI of a PWR is opened via interacting with the PWR controller. The UI elements are explained in order from left to right, top to bottom.

The coolant bars indicate the amount and type of coolant that currently resides inside of the reactor. A fluid identifier for a fluid with the **[PWR Coolant]** tag can be used to change the type of coolant. **Changing the coolant while the reactor is online will void all of the coolant currently located inside of the reactor.**

The queued fuel and current fuel located inside of the reactor, alongside their amount, is represented on top of the middle panel.

A depletion meter for the next fuel rod is represented below the fuel queue, which fills up as the fuel rod gets depleted.

A control rod screen is shown below the depletion meter. Interacting and changing the number from 0 to 100 changes the position of the fuel rods. **The rod position is "reversed", meaning that "0" means "100% inserted", while "100" means "0% inserted".**

A dim red (or bright orange) circle represents the *master warning*, which indicates that the reactor is dangerously hot, and will change it's state depending on either of the heat gauges.

The two gauges indicate *Core heat* and *Hull heat* respectively. Hovering over either of the gauges shows the current amount of TU of the subsequent elements. **Any PWR has a hard cap of 10,000,000 TU, which, when crossed by any gauge, causes a meltdown (without a blowout).**

A *flux* screen is located below the heat gauges. It indicates the current reactivity of the fuel inside of the reactor, which changes with rod insertion.

## Operation

### Fuels

The PWR accepts PWR fuel rods that are not hot or depleted. The amount of fuel one can put into the reactor depends on the amount of fuel rod blocks installed during construction. Fuel rods cannot be mixed, as the PWR only accepts one kind of fuel at a time.

During operation, indicated by a geiger counter sound, fuel rods get depleted and generate heat. The speed of depletion, alongside heat depends on the amount of flux generated. Depleted rods get automatically removed from the fuel queue and deposited into the respective slot as their heated version.

### Heating and coolant

The PWR accepts coolant with the respective **[PWR Coolant]** tag. TU are transferred from the **Hull heat** to the **coolant.** Different coolants have different thermal capacities and efficiencies, which correspond to how fast the hull heat can be transferred from the hull to the coolant. The coolant pool depends on the amount of PWR Coolant Channels installed during construction.

During operation, an amount of TU based off of the coolant heat capacity is transferred from the hull to the coolant, which turns the coolant into it's heated version. For example, the hull reaches 400 TU, and 1mb of liquid sodium takes the 400 TU onto itself, removing itself from the regular coolant pool, and adding 1mb of hot liquid sodium into the hot coolant pool.

In order to cycle the coolant, A Heat Exchanging Heater is required. The heat exchanger is typically used in combination with a Boiler in order to heat up water and power a turbine.