Abstract
Detecting radionuclide gas seepage from clandestine underground nuclear tests is central to nonproliferation explosion monitoring research. Yet, early-time (<6 day) gas transport driven by the explosive pressure wave remains poorly constrained due to scarcity of field data. We simulate multi-phase gas transport in the vadose zone using pre-shot data from a recent chemical explosion in P-Tunnel at the Nevada National Security Site, USA. Despite using a simplified 2D-radial model, predictions of tracer arrival matched observations within one order-of-magnitude. Our results show how transient blast forcing rapidly mobilizes gases from the cavity into surrounding rock – critical for optimizing sensor placement and test planning. This unique integration of field data and modeling represents a significant improvement in our ability to predict gas migration from underground explosions. More broadly, it offers insights into the coupled dynamics of pressure waves and contaminant transport in the vadose zone, with implications for monitoring and hazard assessment.
Data availability
Data for this research are not publicly available until after Feb 9, 2026, following an embargo on the public release of the data from the sponsoring government organization. After this date, data will be made available via public repository. For reproducibility, experimental data used in the analysis will be included as individual text files in the Supporting Information for editor/reviewer purposes. Description of HE byproducts data are described in “HE Byproducts Metadata User Guide_02062023.pdf”. The HE byproducts tracer data files are uploaded separately for each borehole (e.g., “HEdata_GS1.csv”). Description of the xenon data is described in “README_PE1A_Radioxenon_Concentration.txt”. The xenon tracer data file is uploaded as “XeData.csv”. The experimental data will be uploaded either as Supporting Information or as a repository before publication, depending on sponsor approval.
References
Kalinowski, M. B. et al. Discrimination of nuclear explosions against civilian sources based on atmospheric xenon isotopic activity ratios. Pure Appl. Geophys. 167, 517–539 (2010).
Sun, Y. & Carrigan, C. R. Modeling noble gas transport and detection for the comprehensive nuclear-test-ban treaty. Pure Appl. Geophys. 171, 735–750 (2014).
Auer, L. H., Rosenberg, N. D., Birdsell, K. H. & Whitney, E. M. The effects of barometric pumping on contaminant transport. J. Contam. Hydrol. 24, 145–166 (1996).
Neeper, D. A. Harmonic analysis of flow in open boreholes due to barometric pressure cycles. J. Contam. Hydrol. 60, 135–162 (2003).
Neeper, D. A. & Stauffer, P. H. Transport by oscillatory flow in soils with rate-limited mass transfer: 1. Theory. Vadose Zone J. 11, 1–14 (2012).
Nilson, R. H., Peterson, E. W., Lie, K. H., Burkhard, N. R. & Hearst, J. R. Atmospheric pumping: A mechanism causing vertical transport of contaminated gases through fractured permeable media. J. Geophys. Res. Solid Earth 96, 933–948 (1991).
Harp, D. R. et al. Immobile pore-water storage enhancement and retardation of gas transport in fractured rock. Transp. Porous Media. https://doi.org/10.1007/s11242-018-1072-8 (2018).
Harp, D. R., Ortiz, J. P. & Stauffer, P. H. Identification of dominant gas transport frequencies during barometric pumping of fractured rock. Sci. Rep. 9, 9537 (2019).
Avendaño, S. T., Harp, D. R., Kurwadkar, S., Ortiz, J. P. & Stauffer, P. H. Continental-scale geographic trends in barometric-pumping efficiency potential: A North American case study. Geophys. Res. Lett. 48, 1–10 (2021).
Myers, S. C. et al. A Multi-Physics Experiment for Low-Yield Nuclear Explosion Monitoring. https://www.osti.gov/biblio/2345984https://doi.org/10.2172/2345984 (2024).
Lucero, D. D. et al. Permeability scaling relationships of volcanic tuff from core to field scale measurements. Sci. Rep. https://doi.org/10.1038/s41598-025-96835-5 (2025).
Zyvoloski, G. A. Stauffer, P. H. Implementation of High Temperature and Pressure Fluid Property Interpolation Tables. https://www.osti.gov/biblio/2426532https://doi.org/10.2172/2426532 (2024).
United States. Dept. of Energy. Nevada Operations Office. United States Nuclear Tests: July 1945 Through September 1992. (2000).
Wessel, P. et al. The generic mapping tools version 6. Geochem. Geophys. Geosystems 20, 5556–5564 (2019).
Sawyer, D. A. et al. Episodic caldera volcanism in the Miocene southwestern Nevada volcanic field: Revised stratigraphic framework, 40Ar/39Ar geochronology, and implications for magmatism and extension. GSA Bull. 106, 1304–1318 (1994).
Prothro, L., Drellack Jr., Sigmund Mercadante, J. A Hydrostratigraphic System for Modeling Groundwater Flow and Radionuclide Migration at the Corrective Action Unit Scale, Nevada Test Site and Surrounding Areas, Clark, Lincoln, and Nye Counties, Nevada. DOE/NV/25946--630, 950486 http://www.osti.gov/servlets/purl/950486/https://doi.org/10.2172/950486 (2009).
Prothro, L. Geologic Framework Model for the Underground Nuclear Explosions Signatures Experiment P Tunnel Testbed, Aqueduct Mesa, Nevada National Security Site. https://www.osti.gov/biblio/1495705https://doi.org/10.2172/1495705 (2018).
Fritz, B. G., Peterson, J. A., Munley, W. O. & Boukhalfa, H. Description of the Gas Sampling and Circulation System for the LYNM PE1-A Experiment. https://www.osti.gov/biblio/2475191https://doi.org/10.2172/2475191 (2024).
Bodmer, M. et al. LYNM PE1 Pre-Experiment A Site Characterization Report. SAND--2024-07522, 2429935 https://www.osti.gov/servlets/purl/2429935/https://doi.org/10.2172/2429935 (2024).
Wilson, J. et al. PE1 Site Characterization: Data Documentation on Geologic and Hydrologic Lab Testing. SAND--2024-07526, 2429952 https://www.osti.gov/servlets/purl/2429952/https://doi.org/10.2172/2429952 (2024).
Zyvoloski, G. A., Robinson, B. A., Dash, Z. V. Trease, L. L. Models and Methods Summary for the FEHM Application. 74 (1999).
Zyvoloski, G. A., Robinson, B. A., Dash, Z. V., Chu, S. Miller, T. A. FEHM: Finite Element Heat and Mass Transfer Code. [Software] GitHub (2017).
Zyvoloski, G. A. et al. Software users manual (UM) for the FEHM application version 3.1-3X. (2021).
Bourret, S. M., Kwicklis, E. M., Miller, T. A. & Stauffer, P. H. Evaluating the importance of barometric pumping for subsurface gas transport near an underground nuclear test site. Vadose Zone J. 18, 1–17 (2019).
Bourret, S. M., Kwicklis, E. M., Harp, D. R., Ortiz, J. P. & Stauffer, P. H. Beyond Barnwell: Applying lessons learned from the Barnwell site to other historic underground nuclear tests at Pahute Mesa to understand radioactive gas-seepage observations. J. Environ. Radioact. 222, 1–14 (2020).
Jordan, A. B. et al. Uncertainty in prediction of radionuclide gas migration from underground nuclear explosions. Vadose Zone J. 13, 1–13 (2014).
Jordan, A. B., Stauffer, P. H., Knight, E. E., Rougier, E. & Anderson, D. N. [SI] radionuclide gas transport through nuclear explosion-generated fracture networks. Nat. Sci. Rep. 5, 1–10 (2015).
Neeper, D. A. & Stauffer, P. H. Transport by oscillatory flow in soils with rate-limited mass transfer: 2. Field Experiment. Vadose Zone J. 11, 1–12 (2012).
Ortiz, J. P., Neil, C. W., Rajaram, H., Boukhalfa, H. & Stauffer, P. H. Preferential adsorption of noble gases in zeolitic tuff with variable saturation: A modeling study of counter-intuitive diffusive-adsorptive behavior. J. Environ. Radioact. 282, 107608 (2025).
LaGriT. Los Alamos Grid Toolbox. Los Alamos National Laboratory (2013).
Heath, J. E., Kuhlman, K. L., Broome, S. T., Wilson, J. E. & Malama, B. Heterogeneous multiphase flow properties of volcanic rocks and implications for noble gas transport from underground nuclear explosions. Vadose Zone J. 20, e20123 (2021).
Sander, R. Compilation of Henry’s law constants (version 4.0) for water as solvent. Atmos. Chem. Phys. 15, 4399–4981 (2015).
Knight, E. E., Rougier, E., Lei, Z. Munjiza, A. Hybrid Optimization Software Suite. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States) (2014).
Rougier, E., Knight, E. E. Swanson, E. Source Simulations and Code-Coupling and Damage. (2023).
Knight, E. E., Rougier, E. Swanson, E. PE1A 2D Axisymmetric H7R Model Results. (2023).
Hyun, Y. et al. Theoretical interpretation of a pronounced permeability scale effect in unsaturated fractured tuff. Water Resour. Res. 38, 1092 (2002).
Tidwell, V. C. & Wilson, J. L. Upscaling experiments conducted on a block of volcanic tuff: Results for a bimodal permeability distribution. Water Resour. Res. 35, 3375–3387 (1999).
Illman, W. A. Strong field evidence of directional permeability scale effect in fractured rock. J. Hydrol. 319, 227–236 (2006).
Vesselinov, V. V., Neuman, S. P. & Illman, W. A. Three-dimensional numerical inversion of pneumatic cross-hole tests in unsaturated fractured tuff: 1. Methodology and borehole effects. Water Resour. Res. 37, 3001–3017 (2001).
Vesselinov, V. V., Neuman, S. P. & Illman, W. A. Three-dimensional numerical inversion of pneumatic cross-hole tests in unsaturated fractured tuff: 2. Equivalent parameters, high-resolution stochastic imaging and scale effects. Water Resour. Res. 37, 3019–3041 (2001).
Freyberg, D. L. A natural gradient experiment on solute transport in a sand aquifer: 2. Spatial moments and the advection and dispersion of nonreactive tracers. Water Resour. Res. 22, 2031–2046 (1986).
Gelhar, L. W., Welty, C. & Rehfeldt, K. R. A critical review of data on field-scale dispersion in aquifers. Water Resour. Res. 28, 1955–1974 (1992).
Gelhar, L. W. & Axness, C. L. Three-dimensional stochastic analysis of macrodispersion in aquifers. Water Resour. Res. 19, 161–180 (1983).
Herr, M., Schäfer, G. & Spitz, K. Experimental studies of mass transport in porous media with local heterogeneities. J. Contam. Hydrol. 4, 127–137 (1989).
Hess, K. M., Wolf, S. H. & Celia, M. A. Large-scale natural gradient tracer test in sand and gravel, Cape Cod, Massachusetts: 3. Hydraulic conductivity variability and calculated macrodispersivities. Water Resour. Res. 28, 2011–2027 (1992).
Mackay, D. M., Freyberg, D. L., Roberts, P. V. & Cherry, J. A. A natural gradient experiment on solute transport in a sand aquifer: 1. Approach and Overview of Plume Movement. Water Resour. Res. 22, 2017–2029 (1986).
Wilson, J. L. & Gelhar, L. W. Analysis of longitudinal dispersion in unsaturated flow: 1. The analytical method. Water Resour. Res. 17, 122–130 (1981).
Feldman, J. et al. Effects of natural zeolites on field-scale geologic noble gas transport. J. Environ. Radioact. 220–221, 106279 (2020).
Greathouse, J. A., Paul, M. J., Xu, G. & Powell, M. D. Molecular dynamics simulation of pore-size effects on gas adsorption kinetics in zeolites. Clays Clay Miner. 71, 54–73 (2023).
Neil, C. W. et al. Gas diffusion through variably-water-saturated zeolitic tuff: Implications for transport following a subsurface nuclear event. J. Environ. Radioact. 250, 106905 (2022).
Paul, M. & Feldman, J. Measuring gas transport and sorption in large intact geologic specimens via the piezometric method. Transp. Porous Media 139, 1–20 (2021).
Xu, G., Paul, M. J., Yoon, H., Hearne, G. Greathouse, J. A. Measuring Multicomponent Adsorption of Tracer Gases on Natural Zeolites. https://www.osti.gov/biblio/2432207https://doi.org/10.2172/2432207 (2023).
Neil, C. W. et al. Explosive byproduct gas transport through sorptive geomedia. Transp. Porous Media 152, 80 (2025).
Neil, C. W., Swager, K. C., Bourret, S. M., Ortiz, J. P. & Stauffer, P. H. Rethinking porosity-based diffusivity estimates for sorptive gas transport at variable temperatures. Environ. Sci. Technol. https://doi.org/10.1021/acs.est.4c04048 (2024).
Paul, M. J. Transport and Sorption of Noble Gases in Porous Geological Media. The University of Texas at Austin, (2017).
Paul, M. J. et al. Xenon adsorption on geological media and implications for radionuclide signatures. J. Environ. Radioact. 187, 65–72 (2018).
Powell, M. D., Paul, M. J., Xu, G., Greathouse, J. A. & Broome, S. T. Quantifying fission gas adsorption onto natural clinoptilolite in the presence of environmental air and water. J. Environ. Radioact. 287, 107709 (2025).
Chu, S. et al. lanl/FEHM: FEHM version 3.6.2. Zenodo 10.5281/zenodo.13992016 (2024).
Acknowledgments
This Low Yield Nuclear Monitoring (LYNM) research was funded by the National Nuclear Security Administration, Defense Nuclear Nonproliferation Research and Development (NNSA DNN R&D) by grant number LA21-V-LYNM-Containment-NDD2Fe. This manuscript has been authored with number LA-UR-25-24961 by Triad National Security under Contract with the U.S. Department of Energy, contract no. 89233218CNA000001. The authors acknowledge important interdisciplinary collaboration with scientists and engineers from LANL, LLNL, NNSS, PNNL, and SNL. The authors would like to thank the PE1-A Project Leadership, Site Construction & Field Coordination, Site Characterization, Data Collection, Subsurface Gas Transport, Cavity, and Confinement teams for provision of data used in this paper. See Appendix A for a complete list of contributors.
Funding
This Low Yield Nuclear Monitoring (LYNM) research was funded by the National Nuclear Security Administration, Defense Nuclear Nonproliferation Research and Development (NNSA DNN R&D) by grant number LA21-V-LYNM-Containment-NDD2Fe.
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Hydrologic field and laboratory experiments were performed by B.G.F., J.E.H., M.A.B., K.L.K., H.B., S.O., S.E., B.L.R. R.C.C. and PE1 Experimental Team. Conceptualization of the flow and transport study was designed by J.P.O, D.D.L., P.H.S, and S.M.B. Numerical models were designed by J.P.O, D.D.L., and P.H.S. J.P.O. wrote the main manuscript text. Data interpretation, writing and editing of the manuscript was performed by J.P.O, D.D.L., D.G.F., K.L.K., S.M.B., P.H.S., C.W.N., H.B., and B.G.F. Geomechanics calculations of pore crush were performed by E.R. and E.K. Implementation of the high-pressure and -temperature fluid property tables in FEHM was performed by G.A.Z.
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Ortiz, J.P., Lucero, D.D., Rougier, E. et al. Predicting multiphase flow and tracer transport for an underground chemical explosive test. Sci Rep (2026). https://doi.org/10.1038/s41598-026-35868-w
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DOI: https://doi.org/10.1038/s41598-026-35868-w
