Accumulator

(1) a storage cell which accumulates electrical energy in chemical form, i.e. a battery. The term ‘accumulator’ is used especially of lead-acid batteries such as those used in automobiles.

(2) A reservoir of cooling water used in certain emergency core- cooling systems for nuclear reactors. The water is held under pressure in the accumulator and would automatically flow into the reactor core to cool it if there were a loss-of-coolant accident.