A spent nuclear fuel pool emergency cooling system comprising: an evaporator heat exchanger having an internal fluid path that extends in a generally planar direction, the evaporator heat exchanger being supported substantially vertically from a wall of a spent fuel pool; a supply of a cryogenic fluid fluidly connected to the internal fluid path; a cryogenic storage vessel for storing the supply of the cryogenic fluid; and a passively actuated valve for preventing the flow of the cryogenic fluid from the cryogenic storage vessel to the internal fluid path until the evaporator heat exchanger is substantially in the position wherein the second side portion of the evaporator heat exchanger is laterally spaced by a preselected extent from the wall of the spent fuel pool, characterized by a hinged support connecting a first side portion of the evaporator heat exchanger to the wall of the spent fuel pool, the hinged support configured to rotate the evaporator heat exchanger away from the wall and outward into a coolant within the spent fuel pool with a second side portion of the evaporator heat exchanger, which is opposed from the first side portion, laterally spaced from the wall of the spent fuel pool; and a fusible link actuator that connects the wall and the second side portion of the evaporator heat exchanger to maintain the heat exchanger in the substantially vertical position, the fusible link being responsive to a preselected change in an element of an environment of the spent fuel pool, to a pre-established level, to transfer the evaporator heat exchanger to the position wherein the second side portion of the evaporator heat exchanger is laterally spaced from the wall of the spent fuel pool. an evaporator heat exchanger having an internal fluid path that extends in a generally planar direction, the evaporator heat exchanger being supported substantially vertically from a wall of a spent fuel pool; a supply of a cryogenic fluid fluidly connected to the internal fluid path; a cryogenic storage vessel for storing the supply of the cryogenic fluid; and a passively actuated valve for preventing the flow of the cryogenic fluid from the cryogenic storage vessel to the internal fluid path until the evaporator heat exchanger is substantially in the position wherein the second side portion of the evaporator heat exchanger is laterally spaced by a preselected extent from the wall of the spent fuel pool, characterized by a hinged support connecting a first side portion of the evaporator heat exchanger to the wall of the spent fuel pool, the hinged support configured to rotate the evaporator heat exchanger away from the wall and outward into a coolant within the spent fuel pool with a second side portion of the evaporator heat exchanger, which is opposed from the first side portion, laterally spaced from the wall of the spent fuel pool; and a fusible link actuator that connects the wall and the second side portion of the evaporator heat exchanger to maintain the heat exchanger in the substantially vertical position, the fusible link being responsive to a preselected change in an element of an environment of the spent fuel pool, to a pre-established level, to transfer the evaporator heat exchanger to the position wherein the second side portion of the evaporator heat exchanger is laterally spaced from the wall of the spent fuel pool.