A system includes a nuclear reactor pressure vessel comprising a heat exchange wall. An interior of the vessel contains nuclear fuel which heats a primary fluid. A primary fluid circuit extends vertically within the wall. The primary fluid circulates in a loop that includes the interior and the primary fluid circuit in the wall. A secondary fluid circuit also extends vertically within the wall, and is fluidly isolated from the primary fluid circuit. A secondary fluid circulates in a loop that includes a power generating system and the secondary fluid circuit in the wall. The wall acts as a heat exchanger in which thermal energy is transferred to the wall from primary fluid flowing through the primary fluid circuit, and then is transferred from the wall to secondary fluid flowing through the secondary fluid circuit.

One variation of a system includes a pressure vessel: formed of a set of structural layers arranged in a column; defining a primary internal volume within the column; defining a set of infrastructure receptacles containing a heat exchanger and a pump and arranged above the primary internal volume within the column; defining a primary coolant circuit extending between the primary internal volume and the set of infrastructure receptacles within the column; and defining a secondary coolant circuit extending within the wall and adjacent and fluidly isolated from the primary coolant circuit. The system also includes: a nuclear fuel arranged within the primary internal volume; a primary coolant circulating between the nuclear fuel and the primary coolant circuit; and a secondary coolant circulating between the secondary coolant circuit and an external power generation system. The heat exchanger is configured to transfer thermal energy from the primary coolant to the secondary coolant.

One variation of a system includes a pressure vessel: including a wall; defining a primary working fluid circuit extending vertically within the wall; defining a secondary working fluid circuit extending vertically within the wall and fluidly isolated from the primary working fluid circuit; and configured to store a nuclear fuel, a primary working fluid, and a secondary working fluid. The wall of the pressure vessel: defines a heat exchanger configured to transfer thermal energy from the primary working fluid flowing through the primary working fluid circuit into the secondary working fluid flowing through the secondary working fluid circuit; and defines a radiation shield configured to attenuate radiation emitted by the nuclear fuel.