Randy R. Kirkham

Noble gas migration experiment to support the detection of underground nuclear explosions

A Noble Gas Migration Experiment injected 127Xe, 37Ar, and sulfur hexafluoride into a former underground nuclear explosion shot cavity. These tracer gases were allowed to migrate from the cavity to near-surface and surface sampling locations and were detected in soil gas samples collected using various on-site inspection sampling approaches. Based on this experiment we came to the following conclusions: (1) SF6 was enriched in all of the samples relative to both 37Ar and 127Xe. (2) There were no significant differences in the 127Xe to 37Ar ratio in the samples relative to the ratio injected into the cavity. (3) The migratory behavior of the chemical and radiotracers did not fit typical diffusion modeling scenarios.

Measuring Concentrations of Particulate 140La in the Air.

AbstractAir sampling systems were deployed to measure the concentration of radioactive material in the air during the Full-Scale Radiological Dispersal Device Field Trials. The air samplers were positioned 100–600 m downwind of the release point. The filters were collected immediately and analyzed in a field laboratory. Quantities for total activity collected on the air filters are reported along with additional information to compute the average or integrated air concentrations.

Measurement of Fukushima aerosol debris in Sequim and Richland, WA and Ketchikan, AK

Aerosol collections were initiated at several locations by Pacific Northwest National Laboratory (PNNL) shortly after the Great East Japan earthquake of May 2011. Aerosol samples were transferred to laboratory high-resolution gamma spectrometers for analysis. Similar to treaty monitoring stations operating across the Northern hemisphere, iodine and other isotopes which could be volatilized at high temperature were detected. Though these locations are not far apart, they have significant variations with respect to water, mountain-range placement, and local topography. Variation in computed source terms will be shown to bound the variability of this approach to source estimation.

Using Atmospheric Dispersion Theory to Inform the Design of a Short-lived Radioactive Particle Release Experiment.

AbstractAtmospheric dispersion theory can be used to predict ground deposition of particulates downwind of a radionuclide release. This paper uses standard formulations found in Gaussian plume models to inform the design of an experimental release of short-lived radioactive particles into the atmosphere. Specifically, a source depletion algorithm is used to determine the optimum particle size and release height that maximizes the near-field deposition while minimizing both the required source activity and the fraction of activity lost to long-distance transport. The purpose of the release is to provide a realistic deposition pattern that might be observed downwind of a small-scale vent from an underground nuclear explosion. The deposition field will be used, in part, to study several techniques of gamma radiation survey and spectrometry that could be used by an On-Site Inspection team investigating such an event.

PRex: An Experiment to Investigate Detection of Near-field Particulate Deposition from a Simulated Underground Nuclear Weapons Test Vent.

AbstractA radioactive particulate release experiment to produce a near-field ground deposition representative of small-scale venting from an underground nuclear test was conducted to gather data in support of treaty capability development activities. For this experiment, a CO2‐driven “air cannon” was used to inject 140La, a radioisotope of lanthanum with 1.7‐d half-life and strong gamma-ray emissions, into the lowest levels of the atmosphere at ambient temperatures. Witness plates and air samplers were laid out in an irregular grid covering the area where the plume was anticipated to deposit based on climatological wind records. This experiment was performed at the Nevada National Security Site, where existing infrastructure, radiological procedures, and support personnel facilitated planning and execution of the work. A vehicle-mounted NaI(Tl) spectrometer and a polyvinyl toluene-based backpack instrument were used to survey the deposited plume. Hand-held instruments, including NaI(Tl) and lanthanum bromide scintillators and high purity germanium spectrometers, were used to take in situ measurements. Additionally, three soil sampling techniques were investigated and compared. The relative sensitivity and utility of sampling and survey methods are discussed in the context of on-site inspection.

Measurements of Argon-39 at the U20az underground nuclear explosion site

Pacific Northwest National Laboratory reports on the detection of 39Ar at the location of an underground nuclear explosion on the Nevada Nuclear Security Site. The presence of 39Ar was not anticipated at the outset of the experimental campaign but results from this work demonstrated that it is present, along with 37Ar and 85Kr in the subsurface at the site of an underground nuclear explosion. Our analysis showed that by using state-of-the-art technology optimized for radioargon measurements, it was difficult to distinguish 39Ar from the fission product 85Kr. Proportional counters are currently used for high-sensitivity measurement of 37Ar and 39Ar. Physical and chemical separation processes are used to separate argon from air or soil gas, yielding pure argon with contaminant gases reduced to the parts-per-million level or below. However, even with purification at these levels, the beta decay signature of 85Kr can be mistaken for that of 39Ar, and the presence of either isotope increases the measurement background level for the measurement of 37Ar. Measured values for the 39Ar measured at the site ranged from 36,000 milli- Becquerel/standard-cubic-meter-of-air (mBq/SCM) for shallow bore holes to 997,000 mBq/SCM from the rubble chimney from the underground nuclear explosion.

Particle Release Experiment (PRex) Final Report

...................................................................................................................................................... iii Executive Summary .................................................................................................................................... v Acknowledgments ..................................................................................................................................... vii Acronyms and Abbreviations ................................................................................................................... ix 1.0 Introduction ............................................................................................................................ 1 1.1 Background .............................................................................................................................. 1 1.2 Objective .................................................................................................................................. 2 1.3 Scope of Document .................................................................................................................. 2 2.0 Experimental Considerations ................................................................................................ 3 2.1 Overview of PRex .................................................................................................................... 3 2.2 Constraints ............................................................................................................................... 3 2.3 Assumptions ............................................................................................................................. 4 2.4 Pre-Execution Release Parameters ........................................................................................... 4 3.0 PRex Experiment Preparation .............................................................................................. 6 3.1 Experiment Plan ....................................................................................................................... 6 3.2 Site Selection............................................................................................................................ 6 3.3 Background Measurements, September and October 2012 ..................................................... 7 3.4 Source Production .................................................................................................................... 9 3.4.1 Preparation of La2O3 Powder .................................................................................................................. 9 3.4.2 Irradiation at Washington State University ........................................................................................... 12 3.4.3 Source Transport ................................................................................................................................... 14 3.5 Release Mechanism ................................................................................................................ 19 3.6 Meteorology Planning and Modeling ..................................................................................... 22 3.7 NNSS Experiment Site Preparation ....................................................................................... 22 3.7.1 Posting Contamination and High Contamination Areas ....................................................................... 22 3.7.2 Prepositioned Sampling ........................................................................................................................ 22 4.0 PRex Experiment Execution ............................................................................................... 28 4.1 Time and Location ................................................................................................................. 28 4.2 Meteorological Conditions during Release ............................................................................ 28 4.3 Sampling Network ................................................................................................................. 32 4.3.1 Collection of Witness Plates ................................................................................................................. 32 4.3.2 Soil Sampling ....................................................................................................................................... 33 4.3.3 Air Sampling ......................................................................................................................................... 36 4.4 Radiation Survey .................................................................................................................... 36 4.4.1 Vehicle Survey...................................................................................................................................... 37 4.4.2 Handheld/Man-portable ........................................................................................................................ 38 4.4.3 Aerial Survey ........................................................................................................................................ 39 4.5 Field Laboratory ..................................................................................................................... 40

Underground sources of radioactive noble gas

It is well known that radon is present in relatively high concentrations below the surface of the Earth due to natural decay of uranium and thorium. However, less information is available on the background levels of other isotopes such as 133Xe and 131mXe produced via spontaneous fission of either manmade or naturally occurring elements. The background concentrations of radioxenon in the subsurface are important to understand because these isotopes potentially can be used to confirm violations of the comprehensive nuclear-test-ban treaty during an on-site inspection. Recently, Pacific Northwest National Laboratory measured radioxenon concentrations from the subsurface at the Nevada Nuclear Security Site (NNSS—formerly known as the Nevada Test Site) to determine whether xenon isotope background levels could be detected from spontaneous fission of naturally occurring uranium or legacy 240Pu as a result of historic nuclear testing. In this paper, we discuss the results of those measurements and review the sources of xenon background that must be taken into account during OSI noble gas measurements.