Title: Hydromechanical characterization of gas transport amidst uncertainty for underground nuclear explosion detection

Abstract

Given the challenge of definitively discriminating between chemical and nuclear explosions using seismic methods alone, surface detection of signature noble gas radioisotopes is considered a positive identification of underground nuclear explosions (UNEs). However, the migration of signature radionuclide gases between the nuclear cavity and surface is not well understood because complex processes are involved, including the generation of complex fracture networks, reactivation of natural fractures and faults, and thermo-hydro-mechanical-chemical (THMC) coupling of radionuclide gas transport in the subsurface. In this study, we provide an experimental investigation of hydro-mechanical (HM) coupling among gas flow, stress states, rock deformation, and rock damage using a unique multi-physics triaxial direct shear rock testing system. The testing system also features redundant gas pressure and flow rate measurements, well suited for parameter uncertainty quantification. Using porous tuff and tight granite samples that are relevant to historic UNE tests, we measured the Biot effective stress coefficient, rock matrix gas permeability, and fracture gas permeability at a range of pore pressure and stress conditions. The Biot effective stress coefficient varies from 0.69 to 1 for the tuff, whose porosity averages 35.3% ± 0.7%, while this coefficient varies from 0.51 to 0.78 for the tight granite (porosity <1%, perhapsmore » an underestimate). Matrix gas permeability is strongly correlated to effective stress for the granite, but not for the porous tuff. Our experiments reveal the following key engineering implications on transport of radionuclide gases post a UNE event: (1) The porous tuff shows apparent fracture dilation or compression upon stress changes, which does not necessarily change the gas permeability; (2) The granite fracture permeability shows strong stress sensitivity and is positively related to shear displacement; and (3) Hydromechanical coupling among stress states, rock damage, and gas flow appears to be stronger in tight granite than in porous tuff.« less

Authors:

Li, Wenfeng; Neil, Chelsea W. ;

• Search DOE PAGES for author "Neil, Chelsea W."
• Search DOE PAGES for ORCID "0000-0002-7679-157X"

Carey, J. William ;

• Search DOE PAGES for author "Carey, J. William"
• Search DOE PAGES for ORCID "0000-0001-8488-2925"

Meng, Meng; Frash, Luke P. ;

• Search DOE PAGES for author "Frash, Luke P."
• Search DOE PAGES for ORCID "0000-0002-5424-4698"

Stauffer, Philip H.

Publication Date:

Fri Dec 01 00:00:00 EST 2023

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

2246978

Alternate Identifier(s):

OSTI ID: 2281508

Report Number(s):

LA-UR-23-24703
Journal ID: ISSN 1674-7755; S1674775523003232; PII: S1674775523003232

Grant/Contract Number:  

20220019DR; 89233218CNA000001

Resource Type:

Published Article

Journal Name:

Journal of Rock Mechanics and Geotechnical Engineering

Additional Journal Information:

Journal Name: Journal of Rock Mechanics and Geotechnical Engineering; Journal ID: ISSN 1674-7755

Publisher:

Elsevier

Country of Publication:

China

Language:

English

Subject:

underground nuclear explosion uncertainty quantification; radionuclide transport; biot effective stress coefficient; fracture permeability; matrix permeability