Fusion cell is a battery like device that utilized Fusion technology.
The fusion cell is an array of charged rods containing massive amount of electro-chemical energy, attached to a regulator that allows to manage and stabilize a controlled fusion reaction.
A fusion cell needs to be recharged when the reaction reached the point that the creates molecules cannot be fused again. The proper disposable of those highly radioactive materials is paramount since these materials can be used in the creation of new fusion cells via a nuclear reactor.
In plain words the materials generated during fusion can be used to fuel the nuclear reactor that will generate more fussion materials. The whole process of disposal and reuse generates emmense amounts of radiation which are extremely hard to control making it a powerful but dangerous power generation technique.