[Paper Review] Background for Terrestrial Antineutrino Investigations: Radionuclide Distribution, Georeactor Fission Events, and Boundary Conditions on Fission Power Production

J. Marvin Herndon, D. Edgerley|ArXiv.org|Jan 24, 2005

Neutrino Physics Research21 references20 citations

TL;DR

This paper proposes a georeactor model in which uranium and thorium in the Earth's core sustain self-sustaining fission chain reactions, estimating a maximum fission power of 30 terawatts. Based on analogies with the Abee enstatite chondrite, it predicts radionuclide distributions—K-40 in the lower mantle, U-235 and U-238 primarily in the core, and Th in core floaters at the core-mantle boundary—while showing thorium cannot fuel the georeactor.

ABSTRACT

Estimated masses of fissioning and non-fissioning radioactive elements and their respective distributions within the Earth are presented, based upon the fundamental identity of the components of the interior 82% of the Earth, the endo-Earth, with corresponding components of the Abee enstatite chondrite meteorite. Within limits of existing data, the following generalizations concerning the endo-Earth radionuclides can be made: (1) Most of the K-40 may be expected to exist in combination with oxygen in the silicates of the lower mantle, perhaps being confined to the upper region of the lower mantle where it transitions to the upper mantle; (2) Uranium may be expected to exist at the center of the Earth where it may undergo self-sustaining nuclear fission chain reactions, but there is a possibility that some non-fissioning uranium may be found scattered diffusely within the core floaters which are composed of CaS and MgS; and, (3) Thorium may be expected to occur within the core floaters at the core-mantle boundary, although its presence as well at the center of the Earth cannot be ruled out. Results of nuclear georeactor numerical simulations show: (1) The maximum constant nuclear fission power level is 30 terawatts; (2) U-235 comprises 76 percent of present-day georeactor fission, U-238 comprises 23 percent; and, (3) Thorium can neither be fuel nor converted into fuel for the georeactor.

Motivation & Objective

• To establish a geophysical and nuclear basis for terrestrial antineutrino emissions by modeling the distribution of radionuclides in Earth's interior.
• To investigate the feasibility of self-sustaining nuclear fission chain reactions in the Earth's core, proposing a georeactor hypothesis.
• To determine boundary conditions and power limits for fission in the georeactor using analogs from meteorite composition.
• To clarify the roles of K-40, U, and Th in the georeactor, especially their spatial distribution and fission potential.

Proposed method

• Uses the Abee enstatite chondrite as a compositional analog for the Earth's endo-Earth (82% of Earth's mass), assuming similar radionuclide distributions.
• Applies nuclear georeactor numerical simulations to estimate fission power levels and fuel consumption rates.
• Analyzes the partitioning of K-40, U, and Th between silicate mantle, core floaters (CaS, MgS), and core regions based on geochemical affinity.
• Uses mass balance and phase equilibrium principles to infer where fissionable isotopes like U-235 and U-238 are likely concentrated.
• Evaluates the role of thorium in the georeactor by assessing its potential to act as fuel or fertile material.
• Corrects and validates simulation outputs using revised data for table values and units in multiple revisions.

Experimental results

Research questions

• RQ1 What is the likely distribution of K-40, uranium, and thorium within the Earth's interior based on chondritic composition analogs?
• RQ2 Can self-sustaining nuclear fission chain reactions occur in the Earth's core, and if so, what is the maximum sustainable fission power?
• RQ3 What is the relative contribution of U-235 and U-238 to georeactor fission power under current conditions?
• RQ4 Can thorium serve as a fuel or fertile material in the georeactor, or is it inert in this context?
• RQ5 What are the boundary conditions that constrain fission power production in a planetary-scale georeactor?

Key findings

• The maximum constant nuclear fission power level in the georeactor is estimated at 30 terawatts.
• U-235 contributes 76% to current georeactor fission, while U-238 contributes 23%.
• Thorium cannot be used as fuel or converted into fuel for the georeactor under the model's assumptions.
• Most K-40 is predicted to reside in the silicate lower mantle, possibly concentrated in the upper region near the transition to the upper mantle.
• Uranium is likely concentrated at the Earth's center, where self-sustaining fission chain reactions may occur.
• Thorium may be present in core floaters at the core-mantle boundary, but its presence at the center cannot be ruled out.