Separation system and separation method

A separation system comprising a plurality of separation devices connected in series to separate deuterium from a fluid comprising at least light hydrogen and deuterium,

• wherein each of the plurality of separation devices comprises an electrolyte membrane having an electrolyte;
• wherein, of both sides of the electrolyte membrane, an anode catalyst layer and an anode flow passage are provided in this order on a first surface, and a cathode catalyst layer and a cathode flow passage are provided in this order on a second surface;
• wherein a first inflow passage through which a first fluid that is a gas comprising at least light hydrogen and deuterium flows into the anode flow passage, and a first outflow passage through which a second fluid that is a gas having a lower deuterium content than that of the first fluid flows out from the anode flow passage are connected to the anode flow passage;
• wherein a second inflow passage through which a third fluid flows into the cathode flow passage and a second outflow passage through which a fourth fluid comprising at least light water and heavy water flows out from the cathode flow passage are connected to the cathode flow passage;
• and
• wherein, among the plurality of separation devices, a separation device provided at the most upstream side is a first separation device in which a gas comprising at least water vapor flows into the cathode flow passage as the third fluid, and third fluid that has passed through the cathode flow passage and deuterium that has moved from the anode catalyst layer into the cathode catalyst layer are discharged as the fourth fluid from the cathode flow passage.