Molten metal fuel buffer in fission reactor and method of manufacture

A fission reactor, comprising:

• a plurality of heat generating sources, wherein each of the heat generating sources includes a fissionable nuclear fuel composition;
• a plurality of primary coolant volumes through which a primary coolant is flowable during operation of the fission reactor;
• a cladding encasing each of the plurality of heat generating sources;
• and
• a molten metal,
• wherein, for each of the plurality of heat generating sources:
• the cladding has a first side oriented toward the heat generating source,
• the cladding has a second side including a first portion oriented toward a first primary coolant volume and a second portion oriented toward a second primary coolant volume, and
• the molten metal is in thermal transfer contact with the heat generating source and the first side of the cladding, and
• wherein, in a cross-section perpendicular to a longitudinal axis of the fission reactor, the cladding encasing each of the plurality of heat generating sources has a shape of a cross-section of a hyperboloid of one sheet.