Nuclear power generator, fuel cartridges, and cooling tubes for nuclear power generator, and related methods

A nuclear fuel cartridge comprising:

• a fuel matrix formed by a neutron moderating material block, the fuel matrix comprising:
• a plurality of fuel channels formed in the neutron moderating material block, each fuel channel configured for receiving a nuclear fuel element;
• and
• a plurality of cooling channels formed in the neutron moderating material block;
• a first header disposed on a first side of the fuel matrix;
• a second header disposed on a second side of the fuel matrix opposite to the first side;
• a plurality of cooling tubes disposed within the cooling channels, the cooling tubes configured to contain a working fluid, each of the plurality of cooling tubes passing through each corresponding cooling channel, each cooling tube having a first end connected to the first header and a second end connected to the second header;
• and
• a pressure vessel defining an interior space for sealingly containing the fuel matrix, the interior space being filled with a filler medium,
• wherein the filler medium fills a non-fuel volume within each fuel channel between the nuclear fuel element and an inner surface of the neutron moderating material block that forms the fuel channel to separate the nuclear fuel element from the neutron moderating material block.