Liquid metal cooled nuclear reactor incorporating a fully passive decay heat removal (dhr) system with a modular cold source

A liquid metal cooled fast neutron nuclear reactor, comprising:

• a primary vessel, filled with a liquid metal as heat transfer fluid of the primary circuit of the reactor;
• a vessel pit arranged around the primary vessel defining a space between vessels;
• a closure slab for confining the liquid metal inside the primary vessel;
• a removal system for removing at least some of nominal heat and decay heat of the reactor simultaneously, the system comprising at least:
• a closed circuit filled with a heat transfer liquid comprising:
• an array of a plurality of U-shaped pipes, arranged in the space between vessels, being distributed about the primary vessel and each extending along the primary vessel with a bottom of the U shapes facing a bottom of the latter,
• a first cold collector, connected to one of branches of the U, referred to as cold branch, of each of the pipes in the array, the cold collector being arranged on an outside above the closure slab,
• a first hot collector, connected another one of the branches of the U, referred to as hot branch, of each of the pipes in the array, the first hot collector being arranged on the outside above the closure slab,
• a plurality of monotube exchangers, one end of which is connected to the first cold collector and the other end of which is connected to the first hot collector,
• the circuit being configured such that the heat transfer liquid flows therein by natural convection and remains in a liquid state both during nominal operation of the nuclear reactor and during shutdown operation of the nuclear reactor releasing decay heat;
• a cold source comprising at least one modular reservoir arranged at a distance from the primary vessel and above the closure slab, the reservoir comprising a second cold collector, connected to the first cold collector, a second hot collector, connected to the first hot collector arranged above the second cold collector and connected to the latter via the plurality of monotube exchangers, a plurality of modules arranged in at least one row of boxes, each module containing a phase change material of solid-liquid type confined in a casing and being arranged so as to be cooled by one of the plurality of monotube exchangers, and a support structure supporting at least the second hot collector and the boxes, the PCM present in each module being designed, during exchange with the liquid metal circulating in the monotube exchanger, to be in a solid state during nominal operation of the nuclear reactor and to transition to the liquid state in an accident condition of the nuclear reactor in which decay heat is released.