The Mud Monster

Mud is a 1956 British movie that is all about the Mud. A huge, sentient, radioactive mass of mud feeds on radioactive elements and grows significantly every time it encounters some. It's nightly forays are in search of food and it causes death and destruction along its path. The scientist has to figure out a way to defeat the monster before it can reach a nuclear power plant and grow large enough to take over the world.