Event Details

A geo-reactor is a site where self-sustaining nuclear chain reactions have occurred naturally sometime in the past, as they do in man-made nuclear reactors today. It has been suggested that there is such a geo-reactor in the centre of the Earth. What is the evidence for this? Prof Degueldre explains

The original idea after the discovery of the Oklo phenomena (1972) has been to chase geo-reactors in various Earth locations and systems. Herndon (1992) suggests occurrence of a geo-reactor in the center of the Earth. He bases his hypothesis on various phenomena e.g. He isotope ratio in volcanic emanations, magnetic pole translation, Earth heat flow, … . More recently the Dutch group conducted by de Meijer (2010) suggests an equatorial geo-reactor at the level of the Core-Mantel Boundary. This system would have exploded during the proto-Earth period generating the Moon.

The purpose of this seminary is to review the geo-reactor concepts and derive what can be scientifically derived from geo-physical and chemical features so far observed.

Geo-reactors have been found in the natural environment in the terrestrial crust. Others have been postulated in deeper Earth layers such as the core - mantel boundary and even deeper as a central Earth unit. Recent high-precision isotope analysis data have been used to revisit the hypothetical past occurrence of a central Earth geo-reactor. Specific noble gas isotope signatures that could be generated by binary and ternary fissions were identified in volcano emanations or as soluble/associated species in crystalline rocks and semi-quantitatively quantified as isotopic ratio or estimated amounts. Presently if it would have been hypothetically stated that according to the actinide inventory on the Earth, local potential criticality of the geo-system, if locally concentrated, may have been reached, several questions remain such as why, where and when did any geo-reactor have been operational? Even if the hypothesis of a geo-reactor operation in the proto-Earth period would have been plausible, it is likely that a geo-reactor is not operating today. This could now be tested by reconstructing the occurrence of actinides by antineutrino detection and tomography through the Earth. The present lecture focuses on the geo-reactor hypothetical conditions including history, spatial extension and regimes. The discussion based on recent calculations involves investigations on the limits in term of fissile inventory, size and power, based on coupling of geochemical reactions and stratification through the gravitational field considering behaviour through the inner mantle, the boundary with the core and the core. The reconstruction allows to formulating that from the history point of view it would have been possible that the geo-reactor reached criticality in a proto-Earth period as a reactor triggered by 235-uranium and that thorium may have worked as an absorber. Without actinide separation the initiation of the criticality is unlikely. However did the segregation of actinides occur in any deep Earth layer?

Speaker Prof Claude Degueldre is Professor of Nuclear Engineering at Lancaster University, with multidisciplinary research interests from environmental science to solid state physics. He focuses on the nuclear fuel cycles and their green options. His work deals with nuclear energy and nature with its economic background and the ecological challenges. Claude is also very concerned by nuclear safety giving high priority to this issue in his work.

All students, staff and colleagues are encouraged to attend.

Join the conversation #LECSeminar!