Feasibility of UXO detection via pulsed neutron–neutron logging

Köhli, Markus; Schmoldt, Jan-Philipp

doi:10.1016/j.apradiso.2022.110403

Cited by 5 publications

(4 citation statements)

References 21 publications

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“…Although a standard soil chemistry was used to derive the transfer functions, the observed neutron ratios match the dynamics and ranges of predicted neutron ratios from in situ reference sensors, indicating the suitability and applicability of the d-CRNS approach as well as the equations derived at this site. A different soil chemistry may only introduce an overall damping of the measured intensity (Köhli and Schmoldt, 2022). Nonetheless, the conclusions are limited by the single site chosen for this study.…”

Section: Feasibility Assessmentmentioning

confidence: 96%

A change in perspective: downhole cosmic-ray neutron sensing for the estimation of soil moisture

Rasche,

Weimar,

Schrön

et al. 2023

Hydrol. Earth Syst. Sci.

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Abstract. Above-ground cosmic-ray neutron sensing (CRNS) allows for the non-invasive estimation of the field-scale soil moisture content in the upper decimetres of the soil. However, large parts of the deeper vadose zone remain outside of its observational window. Retrieving soil moisture information from these deeper layers requires extrapolation, modelling or other methods, all of which come with methodological challenges. Against this background, we investigate CRNS for downhole soil moisture measurements in deeper layers of the vadose zone. To render calibration with in situ soil moisture measurements unnecessary, we rescaled neutron intensities observed below the terrain surface with intensities measured above a waterbody. An experimental set-up with a CRNS sensor deployed at different depths of up to 10 m below the surface in a groundwater observation well combined with particle transport simulations revealed the response of downhole thermal neutron intensities to changes in the soil moisture content at the depth of the downhole neutron detector as well as in the layers above it. The simulation results suggest that the sensitive measurement radius of several decimetres, which depends on soil moisture and soil bulk density, exceeds that of a standard active neutron probe (which is only about 30 cm). We derived transfer functions to estimate downhole neutron signals from soil moisture information, and we describe approaches for using these transfer functions in an inverse way to derive soil moisture from the observed neutron signals. The in situ neutron and soil moisture observations confirm the applicability of these functions and prove the concept of passive downhole soil moisture estimation, even at larger depths, using cosmic-ray neutron sensing.

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Section: Feasibility Assessmentmentioning

confidence: 96%

A change in perspective: downhole cosmic-ray neutron sensing for the estimation of soil moisture

Rasche,

Weimar,

Schrön

et al. 2023

Hydrol. Earth Syst. Sci.

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“…The model also supported theoretical considerations by about the influence of train wagons, rail tracks and shielding material on a CRNS detector in moving trains, which then have been confirmed by experiments. Köhli and Schmoldt (2022) investigated the possibilities of detecting unexploded ordnance using the pulsed neutron-neutron technique with the operation mode "URANOS Downhole".…”

Section: Previous Studies Using Uranosmentioning

confidence: 99%

“…As an alternative for the growing user community of cosmic-ray neutron sensing, we developed the Monte Carlo code URANOS (Ultra Rapid Adaptable Neutron-Only Simulation), which was specifically tailored to address open and recurring questions of the CRNS community (Köhli et al, 2015;Schrön et al, 2017;Köhli et al, 2018b;Li et al, 2019;Schattan et al, 2019;Weimar et al, 2020;Köhli et al, 2021;Badiee et al, 2021;Jakobi et al, 2021;Francke et al, 2022). As the model has evolved, it has been proven to be useful for neutron spin echo detectors as in other research fields as well (Köhli et al, 2016(Köhli et al, , 2018aKöhli and Schmoldt, 2022). URANOS is computationally very efficient as it only accounts for the most relevant neutron interaction processes, namely elastic collisions, inelastic collisions, absorption and evaporation.…”

Section: Introductionmentioning

confidence: 99%

URANOS v1.0 – the Ultra Rapid Adaptable Neutron-Only Simulation for Environmental Research

Köhli

Schrön²,

Zacharias³

et al. 2023

Geosci. Model Dev.

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Abstract. The understanding of neutron transport by Monte Carlo simulations led to major advancements towards precise interpretation of measurements. URANOS (Ultra Rapid Neutron-Only Simulation) is a free software package which has been developed in the last few years in cooperation with particle physics and environmental sciences, specifically for the purposes of cosmic-ray neutron sensing (CRNS). Its versatile user interface and input/output scheme tailored for CRNS applications offers hydrologists straightforward access to model individual scenarios and to directly perform advanced neutron transport calculations. The geometry can be modeled layer-wise, whereas in each layer a voxel geometry is extruded using a two-dimensional map from pixel images representing predefined materials and allowing for the construction of objects on the basis of pixel graphics without a three-dimensional editor. It furthermore features predefined cosmic-ray neutron spectra and detector configurations and also allows for a replication of important site characteristics of study areas – from a small pond to the catchment scale. The simulation thereby gives precise answers to questions like from which location do neutrons originate? How do they propagate to the sensor? What is the neutron's response to certain environmental changes? In recent years, URANOS has been successfully employed by a number of studies, for example, to calculate the cosmic-ray neutron footprint, signals in complex geometries like mobile applications on roads, urban environments and snow patterns.

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“…The tracer method [23] is divided into particle tracers, thermal tracers and radioactive tracers [24], [25]. Radioactive tracer is divided into the radioactive isotope tracer method and the pulsed neutron-oxygen activation method [26], [27]. The disadvantage of the radioactive isotope tracer method is that the use of radioactive sources does not meet the safety and environmental protection requirements.…”

Section: Introductionmentioning

confidence: 99%

New Measurement Method of Oil-Water Two-Phase Flow with High Water Holdup and Low Rate by Phase State Regulation

Han,

Chen,

Liu

et al. 2023

Measurement Science Review

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Flow rate and holdup are two essential parameters to describe oil-water two-phase flow. The distribution of oil-water two-phase flow in the pipeline is very uneven, and there is a significant slippage between the phases. This makes it difficult to measure these two flow parameters. In this paper, a new measurement method of flow rate and holdup based on phase state regulation is proposed. The oil-water two-phase flow is adjusted to oil or water single-phase flow according to the time sequence by the phase state regulation, and the oil-water phase interface is measured with a conductance sensor. A wavelet transform based phase inflection point detection model is proposed to detect the oil-water phase change point. The experimental results show that the maximum measurement error of the flow rate of water is 3.73%, the maximum measurement error of the flow rate of oil is 3.68%, and the flow rate measurement repeatability is 0.0002. The accuracy of the measurement holdup is better than 3.23%, and the repeatability of the measurement holdup is 0.0003. The prototype designed based on this method has two advantages. One is that it is small in size, the other is that it does not depend on the accuracy of the sensor. Therefore, it can be widely used in oilfield ground measurement.

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Feasibility of UXO detection via pulsed neutron–neutron logging

Cited by 5 publications

References 21 publications

A change in perspective: downhole cosmic-ray neutron sensing for the estimation of soil moisture

A change in perspective: downhole cosmic-ray neutron sensing for the estimation of soil moisture

URANOS v1.0 – the Ultra Rapid Adaptable Neutron-Only Simulation for Environmental Research

New Measurement Method of Oil-Water Two-Phase Flow with High Water Holdup and Low Rate by Phase State Regulation

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