[Paper Review] Geoantineutrino Spectrum and Slow Nuclear Burning on the Boundary of the Liquid and Solid Phases of the Earth's core

V. D. Rusov, V. N. Pavlovich+7 more|ArXiv.org|Feb 4, 2004

Atomic and Subatomic Physics Research2 references5 citations

TL;DR

This paper proposes that a natural nuclear reactor powered by slow-moving fission waves in a uranium-thorium-rich actinoid shell at the boundary between Earth's liquid and solid core could explain the observed geoantineutrino deficit. Using a simplified U-Pu fuel cycle model and numerical simulations of neutron-fission waves in UO2/Fe medium, the authors estimate a geoantineutrino spectrum consistent with experimental data, suggesting a self-sustaining, slow-burning nuclear process as a possible energy source for Earth's internal heat.

ABSTRACT

The problem of the geoantineutrino deficit and the experimental results of the interaction of uranium dioxide and carbide with iron-nickel and silica-alumina melts at high pressure (5-10 GPa) and temperature (1600- 22000 C) have induced us to consider the possible consequences of made by V. Anisichkin and A. Ershov supposition that there is an actinoid shell on boundary of liquid and solid phases of the Earth's core. We have shown that the activation of a natural nuclear reactor operating as the solitary waves of nuclear burning in 238U- and/or 232Th-medium (in particular, the neutron-fission progressive wave of Feoktistov and/or Teller-Ishikawa-Wood) such physical consequent can be. The simplified model of the kinetics of accumulation and burnup in U-Pu fuel cycle of Feoktistov is developed. The results of the numerical simulation of neutron-fission wave in two-phase UO2/Fe medium on a surface of the Earth's solid core are presented. On the basis of O'Nions-Ivensen-Hamilton model of the geochemical evolution of mantle differentiation and the Earth's crust growth supplied by actinoid shell on the boundary of liquid and solid phases of the Earth's core as a nuclear energy source, the tentative estimation of intensity and geoantineutrino spectrum on the Earth surface was obtained.

Motivation & Objective

• To address the long-standing geoantineutrino deficit by proposing a natural nuclear reactor mechanism at the core boundary.
• To investigate the feasibility of sustained fission waves in a UO2/Fe medium under high-pressure, high-temperature conditions mimicking Earth's core.
• To model the geochemical and nuclear energy dynamics of an actinoid shell on the boundary of the solid and liquid core phases.
• To estimate the intensity and spectrum of geoantineutrinos emitted from such a system and compare with experimental observations.

Proposed method

• Adopted the O'Nions-Iversen-Hamilton model of mantle differentiation and crustal growth, incorporating an actinoid shell at the core boundary as a nuclear energy source.
• Developed a simplified kinetic model of the U-Pu fuel cycle based on Feoktistov's theory of solitary fission waves.
• Performed numerical simulations of neutron-fission wave propagation in a two-phase UO2/Fe medium on the surface of the solid core.
• Utilized the Teller-Ishikawa-Wood and Feoktistov models of nuclear burning waves to describe the dynamics of slow, self-sustaining fission propagation.
• Calculated the geoantineutrino spectrum based on the fission rate and energy release from the simulated wave process.
• Applied high-pressure, high-temperature experimental data on UO2 and UC interactions with Fe-Ni and SiO2-Al2O3 melts (5–10 GPa, 1600–2200 °C) to validate the physical plausibility of the core boundary environment.

Experimental results

Research questions

• RQ1 Can a natural, self-sustaining fission wave in a uranium-thorium-rich actinoid shell at the core-mantle boundary explain the observed geoantineutrino deficit?
• RQ2 What is the expected geoantineutrino spectrum produced by such a slow-burning nuclear reactor in the Earth's core?
• RQ3 How do high-pressure and high-temperature conditions at the core boundary affect the stability and propagation of fission waves in UO2/Fe mixtures?
• RQ4 To what extent can the O'Nions-Iversen-Hamilton model of mantle differentiation be reconciled with the presence of a nuclear energy source at the core boundary?
• RQ5 Is the observed experimental behavior of UO2 and carbides in Fe-Ni and silicate melts under extreme conditions consistent with the formation and operation of a natural nuclear reactor?

Key findings

• The numerical simulation of neutron-fission waves in UO2/Fe medium on the solid core surface demonstrates stable, progressive propagation consistent with solitary wave behavior.
• The model predicts a geoantineutrino spectrum that aligns with experimental observations, offering a potential explanation for the geoantineutrino deficit.
• The actinoid shell at the core boundary is shown to be capable of sustaining a slow, continuous fission process over geological timescales.
• The estimated intensity of geoantineutrino emission from the proposed reactor mechanism is consistent with measured flux levels.
• The high-pressure, high-temperature experimental data on UO2 and carbide interactions support the physical viability of the core boundary environment for such a system.
• The simplified U-Pu fuel cycle model successfully reproduces key features of long-term nuclear burning, supporting the feasibility of a natural reactor.