Abstract
Herndon proposed a nuclear fission reactor at the center of the Earth to explain changes in the geomagnetic field and the 3 He/ 4 He ratios observed from deep mantle sources. This study investigated the neutronic properties of the planetary-scale reactor by performing rigorous depletion simulations over geologic time by using a modified TRITON sequence in SCALE6. We also conducted analytical calculations of the rates of change of various actinides in the reactor core to identify the primary mechanisms involved in the nuclear system as a function of the operating time. The sound agreement between analytical and TRITON calculations on the predicted variations of the amounts of important actinides revealed that (1) the hypothetical nuclear georeactor is a fast-spectrum converter reactor burning only 235 U; (2) the efficiency of fuel conversion approaches 0.9, and can be sustained for billions of years based on the cycle of 238 U/ 239 Pu/ 235 U, rather than of 238 U/ 239 Pu or 232 Th/ 233 U; and (3) under appropriate conditions, the georeactor can operate at a constant power of 3 TW for up to 6.5 billion years.