Nuclear fuel elements may include: a fuel zone including fuel particles disposed in parallel layers in a matrix including graphite powder; and a shell comprising graphite and surrounding the fuel zone. The fuel particles may include fissile particles, burnable poison particles, breeder particles, or a combination thereof. The fuel zone may include a central region and a peripheral region surrounding the central region, and a fuel particle density of the peripheral region may be greater than a fuel particle density of the central region.