Nuclear Reactor Simulation Game

CoreSim Version 1.0

CoreSim Version 1.0 User's Guide

CoreSim is intended to make the physics of nuclear reactors accessible to my friend T. C. MITS (the common man in the street). It's simple, really.

A single neutron causes a uranium nucleus to split (fission).
The fission releases energy that heats up water that turns to steam that drives a turbine that generates electricity.
Each fission also releases several "fast" neutrons.
Unfortunately, fast neutrons aren't very good at splitting. However, if they can be slowed down by bumping into water molecules (thus "moderating" their speed), they become much better splitters. This is why the water in a reactor is referred to as the "moderator." Water is also referred to as the "coolant" because it carries away the heat and prevents the fuel rods from becoming too hot.
What happens to all the fast neutrons that are released during fission? There are several possibilities:

some get absorbed by non-fissile nuclei inside the fuel rods
some get absorbed in the moderator, primarily by colliding with boron atoms (Boron is an excellent neutron absorber. It is added to the water to soak up excess neutrons to help control the rate of fission.)
some leak out of the core and are absorbed somewhere outside the reactor
some get slowed down, then find their way back into fuel rods, where they split other uranium nuclei, which release more fast neutrons, and so the cycle continues.

The goal of reactor design is to create a system in which the rate of heat generation can be

easily controlled, and
maintained at a fairly constant rate for a long period of time.

And this will be your mission, too! That's right, you get to play the role of reactor operator. Your task is to keep the reactor running for as long as possible. How will you accomplish this? Well, you'll have two sets of controls, referred to as "Probability Controls" and "Engineering Controls." You'll also have some monitors to show you how well the core is performing.

Probability Controls

These controls allow you to change various probabilities that affect the rate of fission in the core. They let you "play God" by giving you control over physical properties of nuclei and neutrons that, in reality, there is no way to control.

Fission Capture Control

This slider lets you vary the probability that a neutron inside a fuel rod will cause a fission. If you set this parameter too low, very few neutrons will cause fissions, and the neutron population will die out very quickly. If you set it too high, virtually all neutrons that find their way into fuel rods will cause fissions, the neutron population and power level will soar, and the core will promptly melt.

Absorption in Fuel Control

This slider lets you vary the probability that a neutron inside a fuel rod will be absorbed without causing a fission. If you set this parameter too high, virtually all neutrons that find their way into fuel rods will be absorbed without causing new fissions, so the neutron population and power level will plummet.

Absorption in Moderator Control

This slider lets you vary the probability that a neutron will be absorbed in the moderator. If you set this parameter too high, virtually all neutrons will be absorbed in the water, so the neutron population and power level will plummet.

Slowed Down in Moderator Control

This slider lets you vary the effectiveness of the moderator in slowing neutrons to their most effective speed for causing new fissions. If you set it too high, virtually all neutrons will be slowed to their optimum speed, and when they find their way into fuel rods they will be very effective at causing fissions, so the neutron population and power level will soar, and the core will promptly melt.

Engineering Controls

These controls allow you to change three core parameters that reactor operators can actually control.

Boron Concentration Control

This slider which lets you vary the boron concentration in the moderator. If you set this parameter too low, very few neutrons will be absorbed in the moderator, increasing the probability that they will find their way back into fuel rods and cause fissions. If you set this parameter too high, virtually all neutrons will be absorbed in the moderator, and both the neutron population and power level will plummet.

Control Rod Insertion Control

This slider which lets you raise and lower the control rods (which, unfortunately, are not shown - that's still on my "To Do" list). Increasing the insertion value causes more neutrons to be absorbed and lowers the power level.

Control Rod Worth Control

This slider was originally intended to let you control how well the control rods soak up neutrons, but this same effect is caused by varying the insertion, so you can just ignore this control.

Animation Controls
Start Animation Toggle Button

This toggle button starts and pauses the animation.

Show Cumulative Burnup / Show Fuel Rod Power Toggle Button

This toggle button switches between two modes of coloring the fuel rods:

"Show Fuel Rod Power" mode (default) colors all rods in a color that corresponds to the current power level. The "Fuel Rod Power Scale" color map relates colors to power levels.
"Show Cumulative Burnup" mode shows you how many fissions have occurred in each individual fuel rod. The "Cumulative Burnup Scale" color map relates colors to relative "burnup," a term which indicates how many of a rod's fissile uranium nuclei have undergone fission.

This control is enabled only when the animation is running.

Prepare For New Run Button

This "reset" button is used at the end of a run to generate a new set of 100 randomly-positioned neutrons in preparation for the next run.
To make the next run last longer, you may need to adjust the parameters before hitting the "Start Animation" button.

Core Monitors
Neutron Population Strip Chart (located on the upper right hand side of the core)

This chart lets you dynamically monitor two parameters, the neutron population (solid red line that extends to the bottom of the graph) and a parameter called the "multiplication factor" (squiggly black line that hovers around the 100% mark). A population of 500 neutrons corresponds to normal full power. The core can operate above this level, but if the neutron population exceeds 600 (20% above full power), the core melts and the run ends automatically.

Neutron Loss Strip Chart (located on the lower right hand side of the core)

This strip chart shows you what is happening to the neutrons that disappear. It consists of 3 sections.

The bottom (magenta-colored) section shows you the percentage of the total neutrons lost that leaked out through the containment wall (which is also colored magenta).
The middle (cyan / light blue) section shows you the percentage of the total neutrons lost that were absorbed in the moderator.
The top (black) section shows you the percentage of the total neutrons lost that were absorbed in the fuel rods.

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