Geophysical research: article

A.V. Legavko
D.A. Legavko
Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
Journal: Geophysical research
Tome: 23
Number: 3
Year: 2022
Pages: 35-47
UDK: 550.8.056
Full text
Keywords: gamma-ray logging, prompt fission neutron logging, pulsed neutron-neutron logging, infiltration uranium deposits, underground leaching
Аnnotation: The article deals with issues of software and technical support of prompt fission neutron logging for direct measurement of uranium content in ores of infiltration deposits. Infiltration (sandstone) type uranium deposits are located in watered, weakly lithified or non-consolidated sands and exploited using underground leaching technology. A distinctive feature of deposits of this type is the variability of radioactive equilibrium coefficient between uranium and its radioactive decay products. Uranium itself is not a source of gamma-ray energy. The most part of gamma radiation is generated by daughter isotopes, mainly radium and its decay products. Gamma logging makes it possible to measure only the integral level of gamma radiation of rocks and is an indirect method that can significantly underestimate or overestimate the uranium content under conditions of radioactive disequilibrium. Prompt fission neutron logging is one of the modifications of the impulse neutron-neutron logging methods and that can overcome the problem of natural or technogenic radioactive disequilibrium. The method is based on the registration of prompt neutrons arising from the fission of uranium atomic nuclei by thermal neutrons, which are formed in the medium as a result of the deceleration of the high energy neutrons injected into this medium by pulse neutron generator. Ratio of generated prompt neutrons to thermal neutrons is proportional to uranium content in rocks, which makes it possible to directly determine the uranium content regardless of radioactive equilibrium state. The article provides a historical development review of domestic software and hardware complexes for prompt fission neutron logging implementation with a brief analysis of their advantages and disadvantages. Special attention is paid to the latest Russian hardware and methodological complex AMC KND-M AINK-49 (AINK-49). In order to improve the overall reliability of the complex, measurement accuracy, usability and industrial logging efficiency, a new alternative software for logging on prompt fission neutron method and a scheme for restructuring the AINK-49 complex using an UGI logging recorder are proposed.