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## WHAT IS IT?

Nuclear reactor is a machine that produces heat using the nuclear fission. A nuclear reactor is the part responsible to generate steam in a nuclear power plant analogue with a power boiler which can burn oil, gas or other fuel to produce heat and steam. The steam produced in the reactor is used in one or more steam turbine that convert the mechanical energy in electrical energy. One of the benefits of this method over other power generation is that there are no emissions when compared with fossil burning boilers and there are no necessity to flood big areas such as in hydroelectric. Clear disadvantages are the high impact in case of accident, as the famous catastrophes of Chernobyl and Fukushima. Other challenge of this technology is that the part of the nuclear waste needs long time to decay the radioactivity to a level that is not dangerous for the life and environment. In this project I want to show how this technology works using an Agent Based Model to explain the process of a chain reaction, what are the elements used to control it and how can we improve the controllability of this process, using a Proportional Integral Derivative Controller (PID).

## HOW IT WORKS

The whole process is based in a chain reaction. The process starts when a neutron is released, then the neutron has a constant speed and when it hits a fuel, it releases other neutrons and release also energy. The control rods are placed inside of the reactor to absorb the free neutrons and keep the reaction under control, avoiding that the numbers of neutrons and energy increases to a point where the reactor was not designed, this in real life would lead to an emergency shutdown.
When the control mode is in manual, the operator can define how many rods he wants and insert or retract rods according with the generated energy, in this case the challenge is to reduce the difference between the desired power generation and the real generation. It is quite difficult for the operator to control it well because the constant time of this process is quite short and it can have high variability.
With the control in automatic mode, the operator does not need to control the rods, it is controlled automatically by the PID controller. The PID uses the feedback from the energy generation to define how many rods need to be inserted or retracted.

## HOW TO USE IT

In order to use the model you can define the amount of fuel, it has a range from 5 to 50.
THe first button to press is the setup, it will create all the fuel. Release-neutron must be pressed inorder to release at least one neutron which will initialize the whole chain reation.
We have two option to control the reaction:
Press the rods-in-manual to start the simulation in manual mode. You should define the manual-gain, when the add-rods or remove-rods button is pressed, the rods are inserted or removed in the amount of the manual-gain
Press hte rods-in-auto to start the simulation in auto mode. You should define all the control parameters, such as control-gain, control-integral and control-derivative.
Set-point is a variable that is valid for both operation mode and is the set point of the energy generation.
The water flow can be increased in order to reduce the speed of the reaction or reduced to let the neutron mode faster inside the reactor
An online value in the interface help you to control how the reactor is operating.

## THINGS TO NOTICE

See how the energy generation variability changes in manual mode and in automatic mode.

## THINGS TO TRY

You can try to change the control-gain, the control-integral and the control-derivative and observe how each parameter has an impact in the process stability and in the average error between setpoint and real value

## EXTENDING THE MODEL

There are other components that have an impact in the reaction that can be implemented in the future, e.g. better modelling of the cooling water, it could help in the fidelity of the model. the implementation of a turnine could be also interesting because of a addition of a dead time in the process that would make the process control more challenging for a PID controller

## NETLOGO FEATURES

## RELATED MODELS

There are two model in Netlogo that show how a reactor works. one is the Reactor Top DOwn and the second is the Reactor X-Section

## CREDITS AND REFERENCES