Standing wave nuclear fission reactor and methods

A nuclear fission reactor core of a nuclear fission reactor, the nuclear fission reactor core comprising:

• a central core region and a peripheral core region located radially outward from the central core region;
• a first plurality of nuclear fuel assemblies in the central core region, the first plurality of nuclear fuel assemblies containing fissile nuclear fuel material;
• a second plurality of nuclear fuel assemblies in the central core region, the second plurality of nuclear fuel assemblies containing fertile fuel and/or fissile fuel bred up from fertile fuel in the nuclear fission reactor material;
• a third plurality of nuclear fuel assemblies in the peripheral core region, the third plurality of nuclear fuel assemblies containing fertile nuclear fuel material;
• means for absorbing neutrons in the peripheral core region;
• means for breeding the fertile nuclear fuel material into fissile fuel;
• and
• means for shuffling at least one of the first plurality of nuclear fuel assemblies and at least one of the second and/or third plurality of nuclear fuel assemblies to establish a standing wave of fissioning fissile nuclear fuel material in the central core region.