This was a hardcover book I read in the early 1970's.
The hero was falsely convicted of a crime, and was sentenced to life in prison at hard labor. He resists and is knocked unconscious. As he is taken to prison, the guards carry him past a pallet of power cartridges. These are cylinders about the size of a D-cell battery, containing potent atomic fuel encased in a metal called "intertite" (I'm not sure of the spelling) to contain the radiation. Our hero surreptitiously steals a cartridge under the noses of the guards and hides it on his person.
The prison is an underground mine about a mile below the surface. The mine is dome shaped, with the upper part of the dome far too high for the prisoners to reach. This is the location of the only entrance/exit to the mine, with a chamber containing armed guards. The prisoners are dropped from here to the floor of the mine.
The prisoners labor in the mine to extract intertite. If they mine enough that day, the guards will give them food and water. Otherwise the prisoners starve.
Our hero hordes intertite, and uses it to form a crude rocket engine. When it is finished, he take his stolen power cartridge, scratches the base, then inserts it into the engine. The atomic fuel blast with the might of atomic power (which can only be contained by intertite), and our hero clings to the rocket, rides up to the guard post, overpowers the guards, and escapes.
Does this sound familiar?