A loop sodium reactor with a cold resting bottom vessel

The cold bottom design is here applied to loop sodium reactors. In known loop reactors, with complex arrangements of pipes connected to vessels, the primary sodium area is extended, with corresponding aggression risks, but exchangers and pumps may be repaired independently. Here the following features are selected: 1) External vessels for exchangers, sodium pumps and steam generators, containing less heavy components, may rest on dry skirts; 2) Sodium is introduced from the bottom in the diagrid, using U-shaped pipes; 3) The core vessel wall is protected against thermal transients by a static sodium layer; 4) The hot sodium exits radially from the core vessel upper part to the exchanger vessels; 5) Secondary circuits may use a gas instead of sodium and be driven by gas turbines; 6) Lined, leak monitored cooled concrete vaults surrounds the vessels; 7) Argon ascends in the spaces between the wall and the liner from the bottom to the top space of the reactor. In known designs, nitrogen volumes surround the reactor vessel and argon circuits; 8) In these cylindrical spaces, insulation screens could slide for an emergency natural cooling to the liners; 9) A general concrete caisson contains the reactor, exchangers vessels and connecting pipes, and possibly steam generators. For safety against aggressions, this caisson is built below the soil level, without sodium pipes or tanks above the soil. For compactness, a large use of pipe bellows is proposed; 10) At the end of the reactor life, concrete and metallic structures below the soil level may be left in place. Then the advantages of the cold resting bottom vessel are maintained in the loop design and the complexity of known pipe systems is reduced. Calculations are annexed on connection stresses. If a robust and economical design is selected, as here attempted, sodium cooled fast reactors are the easier way to satisfy the energy needs in the world without undue recourse to fossil fuels. (author)