You are the engineering duty officer getting your submarine, the uss greenville, ready to put to sea. when nuclear material in the reactor is fissioning at an increasing rate, this is known as a:

Super-critical mass

Explanation:

This term refers to the mass, in which the amount of fission processes per unit of time increases to the point, where some intrinsic feedback mechanism causes the reactor to reach an equilibrium point at a high temperature or power, that is, It becomes critical again, or it is destroyed due to the amount of processes.

diagram is missing, but i will try to explain your doubt.

answer:

amplitude is the maximum displacement or distance moved on a point of a vibrating body or wave measured from its equilibrium position.it is equal to half the length of vibration path.