Here is the full list of all 17 Rainbow Reactor achievements.
Complete the 1st shift
Make a Quadruple Reaction
Complete the 2nd shift
Complete the 3rd shift
Complete the 4th shift
Complete the 5th shift
Complete the 6th shift
Complete the 7th shift
Complete the 8th shift
Complete the 9th shift
Make a Quintuple Reaction
Make a Sextuple Reaction
Make a Septuple Reaction
Score Over 9000
Reach Max Multiplier
Mix a brown C-Ball
Get the highest Reward at the end of a shift