A PHYSICS-BASED APPROACH TO DISCRIMINATE LOW-YIELD NUCLEAR EVENTS: THE SOURCE PHYSICS EXPERIMENT (SPE)

Discriminating low-yield nuclear explosions is one of the current challenges in the field of monitoring and verification. Work is currently underway in Nevada to address this challenge by conducting a series of experiments using a physics-based approach. This has been accomplished by using a collaborative, multifaceted, multi-disciplinary approach that includes a range of activities, from characterizing the shallow subsurface to acquiring new explosion data, as part of the Source Physics Experiment (SPE). The goal of the SPE is to understand the transition of seismic energy from the near field to the far field; to understand the development of S-waves in explosives sources; and to understand how anisotropy controls seismic energy transmission and partitioning. To fully explore these issues, the SPE series includes tests in both simple and complex geology cases. The current series is being conducted in a highly fractured granite body. This location was chosen, in part, because it was the location of previous nuclear tests in the same rock body and because generally the geology has been well characterized. In addition to historic data, high-resolution seismic data, cross-hole tomography, core samples, LIDAR, hyperspectral, and fracture mapping data have been acquired to further characterize and detect changes after each of the shot across the test bed. The complex geology series includes 7 planned shots using conventional explosives in the same shot hole surrounded by diagnostics to measure yield, acceleration and seismic waveforms. This allows for the use of a single test bed in the granite instead of multiple test beds to obtain the same results. The shots are planned at various depths to obtain a Green’s function, scaled depth-of-burial data, nominal depth-of-burial data and damage-zone data. Three shots have been executed to date and the fourth is planned for Aug 2013 as a 220 lb (100 kg) TNT equiv. shot at a depth of 315 ft (96 m). Over 400 data channels have been recorded on the first series of shots with high fidelity. Ultimately, the results from this project will provide the next advances in the science of monitoring to enable a physics-based predicative capability. This work was done by NSTec, LLC, and LANL under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy. DOE/NV/25946—1834.