Carrigan Charles R, Sun Yunwei, Hunter Steven L, Ruddle David G, Simpson Matthew D, Obi Curtis M, Huckins-Gang Heather E, Prothro Lance B, Townsend Margaret J
Lawrence Livermore National Laboratory, Livermore, California, USA.
Mission Support and Test Services, LLC, Las Vegas, Nevada, USA.
Sci Rep. 2020 Jan 29;10(1):1437. doi: 10.1038/s41598-020-58445-1.
Understanding the nature of gas transport from an underground nuclear explosion (UNE) is required for evaluating the ability to detect and interpret either on-site or atmospheric signatures of noble gas radionuclides resulting from the event. We performed a pressure and chemical tracer monitoring experiment at the site of an underground nuclear test that occurred in a tunnel in Nevada to evaluate the possible modes of gas transport to the surface. The site represents a very well-contained, low gas-permeability end member for past UNEs at the Nevada National Security Site. However, there is very strong evidence that gases detected at the surface during a period of low atmospheric pressure resulted from fractures of extremely small aperture that are essentially invisible. Our analyses also suggest that gases would have easily migrated to the top of the high-permeability collapse zone following the detonation minimizing the final distance required for migration along these narrow fractures to the surface. This indicates that on-site detection of gases emanating from such low-permeability sites is feasible while standoff detection of atmospheric plumes may also be possible at local distances for sufficiently high fracture densities. Finally, our results show that gas leakage into the atmosphere also occurred directly from the tunnel portal and should be monitored in future tunnel gas sampling experiments for the purpose of better understanding relative contributions to detection of radioxenon releases via both fracture network and tunnel transport.
为了评估探测和解释地下核爆炸（UNE）产生的惰性气体放射性核素现场或大气特征的能力，需要了解地下核爆炸中气体传输的性质。我们在内华达州一条隧道内发生的一次地下核试验现场进行了压力和化学示踪剂监测实验，以评估气体传输到地表的可能方式。该场地代表了内华达国家安全站点过去地下核爆炸中一个封闭性很好、气体渗透率很低的终端情况。然而，有非常有力的证据表明，在低气压期间在地表检测到的气体是由基本上不可见的极小孔径裂缝产生的。我们的分析还表明，爆炸后气体很容易迁移到高渗透率坍塌区的顶部，从而将沿这些狭窄裂缝迁移到地表所需的最终距离减至最小。这表明，现场检测来自这种低渗透率场地的气体是可行的，而对于足够高的裂缝密度，在局部距离上对大气羽流进行远距离检测也可能实现。最后，我们的结果表明，气体也直接从隧道入口泄漏到大气中，在未来的隧道气体采样实验中应进行监测，以便更好地了解通过裂缝网络和隧道传输对放射性氙释放检测的相对贡献。
