Simulators / APES Unit 6 / Topic 6.6

Reactor Control Room

Hold a nuclear chain reaction steady with control rods, watch radioactive waste decay one half-life at a time, then weigh nuclear power against coal, natural gas, wind, and solar. Free, with no login.

Your shift

Each neutron has a chance to split a nucleus. Every fission releases 2 new neutrons. Keep fissions per round between 8 and 14 for 12 rounds, and avoid a SCRAM (more than 60 neutrons in the next round).

Control rods inserted 50%

Demonstrations

Inside the core

1. Run the reactor

Critical: power steady

2. Read the log

Round	Neutrons	Rods in	k setting	Fissions	New neutrons	In band?
No rounds yet. Press Next round.

3. Test the rods

What does k mean?

k is the average number of new fissions caused by each fission. If k is above 1, power grows. If k is below 1, power falls. If k is 1, the reaction is steady. This test runs 400 rounds of 50 neutrons at each rod setting and measures k.

1. Watch the decay

2. Scale it up

How long does waste stay dangerous?

The table uses the isotope and starting mass you chose. Amounts are expected values.

Half-lives	Time passed	Percent left	Grams left

Spent fuelHot and radioactive. Pools cool it first, then dry casks hold it on site.

MiningUranium mining leaves piles of tailings.

Waste heatA 1,000 MW (electric) plant that is one third efficient releases about 2,000 MW of waste heat to cooling water or air. That is thermal pollution.

1. Compare emissions

2. Weigh the trade-offs

Every source has a benefit and a cost

Source	g CO2e per kWh	Million tonnes CO2e per year	Main benefit	Main cost

Data: IPCC Fifth Assessment Report, Working Group III, Annex III (2014). Lifecycle median values, rounded. They include building the plant and supplying fuel, not only the smokestack.

Exit check

Three AP-style questions

Take it to class

Hold the Line

The simulator shows the ideas. Hold the Line is the hands-on classroom activity for Topic 6.6, with a print version and a digital version. It is part of the full APES Unit 6 on TpT.

Control-rod dice

Groups run a chain reaction with dice and keep power in a target band, so students feel why control rods matter.

Penny half-life

Groups flip pennies to model decay and compare their data with the expected curve.

Evidence cards

Students decide how to replace a retiring coal plant and defend the choice with a claim, evidence, and reasoning.

Get the free simulator and student sheet on TpT See APES Unit 6 on TpT

About the model: illustrative, not a real reactor. In the control room each neutron has a fixed chance of causing a fission and every fission releases exactly 2 neutrons. Real reactors have moderators, coolant, delayed neutrons, and many layers of safety systems. The decay lab uses small samples so randomness is visible. Emission values are rounded published medians.