Measurements of the emanation of 37Ar and 39Ar from irradiated rocks and powders

Environmental gas tracers allow inferring groundwater travel times and mixing ratios. Their concentrations are commonly interpreted with simplified and indirect approaches that are conceptually at odds with the high degree of complexity found in natural systems. However, the information content of the tracers can potentially be fully explored through the explicit simulation of an advection-dispersion transport equation, for example using integrated surface-subsurface hydrological models (ISSHMs). These integrated models can be used to explicitly simulate environmental tracers in complex environments. ISSHMs are usually variably saturated flow models. However, these models do not explicitly simulate gas partitioning with the aqueous phase, restricting explicit simulation of gas tracers to fully saturated conditions or to tracers with very low solubilities. We propose a mathematical formulation for the production of environmental gas tracers that are emanated in the subsurface. The production is scaled according to gas/water partitioning and water saturation, which is already computed by the model. Therefore, ISSHMs can now be used to their full potential to explicitly simulate tracer concentrations under variably saturated and dynamic conditions. The new formulation has been successfully verified against reference simulations provided with a multi-phase flow and transport model. In addition, explicit simulation of 222Rn and 37Ar groundwater concentrations in a synthetic alluvial river-groundwater system was demonstrated, for the first time, with an ISSHM.

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“…where, ǫ (-) is the emanation factor, which was determined by irradiation experiments (Johnson et al, 2021;Musy et al, 2022).…”

Section: Ar Productionmentioning

confidence: 99%

Explicit simulation of environmental gas tracers with integrated surface and subsurface hydrological models

et al. 2022

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“…Past measurements of atmospheric 37 Ar identi ed frequent nuclear testing as a major source, but dramatic reductions in the frequency of nuclear tests have allowed the background levels to decline (Currie & Lindstrom, 1975). The recent characterization of the background has focused on subsurface 37 Ar concentrations from the natural production of 37 Ar through cosmic-ray interactions with calcium in soil (Johnson et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Quantifying the Potential of Argon Detection Capabilities for Nuclear Explosion Monitoring

Adhikari,

Gordon,

Shah

et al. 2023

Preprint

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Current noble gas detection systems for nuclear explosion monitoring are based on the detection of four radioxenon isotopes – Xe-131m, -133, -133m and − 135. The data provided by radioxenon detection could be enhanced by other radionuclide signatures such as Ar-37. Activation of Ca-40 in rock by neutrons produces Ar-37, and monitoring for this additional nuclide could help distinguish detections of nuclear explosions from background sources, such as medical isotope production. This work studies the capabilities of a hypothetical argon detection network. A 10 kt explosion was modeled using MCNP and SCALE to determine the inventory of Ar-37 created in a representative granite rock layer, assuming either 0.1, 1, or 10% of the total inventory was released. The Ar-37 inventory was combined with atmospheric transport data from HYSPLIT compiled in a previous study, along with the detection limits of standard Ar-37 detection systems, to determine how many hypothetical monitoring stations would detect Ar-37 from an explosion. This method was repeated for 365 HYSPLIT data sets to create a year’s worth of hypothetical explosions, releases, and detections. The study quantified the average number of detections per release, the number of stations detecting Ar-37, and the possibility of detecting Ar-37 in coincidence with xenon.

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Hydrogeochronology: Resetting the timestamp for subsurface groundwaters

Warr

Smith

Lollar

2023

Geochimica et Cosmochimica Acta

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Measurements of the emanation of 37Ar and 39Ar from irradiated rocks and powders

Cited by 6 publications

References 19 publications

Explicit simulation of environmental gas tracers with integrated surface and subsurface hydrological models

Explicit simulation of environmental gas tracers with integrated surface and subsurface hydrological models

Quantifying the Potential of Argon Detection Capabilities for Nuclear Explosion Monitoring

Hydrogeochronology: Resetting the timestamp for subsurface groundwaters

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