Nuclear Reactor Simulator is more of a simulation than a game. Published by Rainbow magazine in the April, 1983 issue, it combined an Extended BASIC program with some machine language subroutines into a simulation where you try and keep your nuclear reactor running smoothly. You have to keep the temperature set correctly, and manipulate the cooling, etc. to do so.
The program was especially commissioned by Rainbow magazine to kick off their first annual Simulation writing contest. One of the authors, Chris Latham, was already a famous Coco software author by this time (he wrote Donkey King, and later, Sailor Man).
Title: Nuclear Reactor Simulator
Author: Chris Latham and John Erickson
Publisher: Rainbow magazine
Released: April 1983
Requires: Color Computer 1,2,3, 32K RAM Extended BASIC, tape or disk.