Amanda M. Prinke

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.

Real-time stack monitoring at the BaTek medical isotope production facility

Radioxenon emissions from fission-based radiopharmaceutical production are a major source of background concentrations affecting the radioxenon detection systems of the international monitoring system (IMS). Collection of real-time emissions data from production facilities makes it possible to screen out some medical isotope signatures from the IMS radioxenon data sets. This paper describes an effort to obtain and analyze real-time stack emissions data with the design, construction and installation of a small stack monitoring system developed by a joint CTBTO-IDC, BATAN, and Pacific Northwest National Laboratory team at the BaTek medical isotope production facility near Jakarta, Indonesia.

Comparison of new and existing algorithms for the analysis of 2D radioxenon beta gamma spectra

The aim of this paper is to compare radioxenon beta–gamma analysis algorithms using simulated spectra with experimentally measured background, where the ground truth of the signal is known. We believe that this is among the largest efforts to date in terms of the number of synthetic spectra generated and number of algorithms compared using identical spectra. We generate an estimate for the minimum detectable counts for each isotope using each algorithm. The paper also points out a conceptual model to put the various algorithms into a continuum. Our results show that existing algorithms can be improved and some newer algorithms can be better than the ones currently used.

A program to generate simulated radioxenon beta–gamma data for concentration verification and validation and training exercises

PNNL developed a beta–gamma simulator (BGSim) that incorporated GEANT-modeled data sets from radioxenon decay chains, as well as functionality to use nuclear detector-acquired data sets to create new beta–gamma spectra with varying amounts of background, 133Xe, 131mXe, 133mXe, 135Xe, and 222Rn and its decay products. After BGSim was developed, additional uses began to be identified for the program output: training sets of two-dimensional spectra for data analysts at the IDC and other NDC, and spectra for exercises such as the Integrated Field Exercise 2014 held in Jordan at the Dead Sea.

Radioxenon detector calibration spike production and delivery systems

Beta–gamma coincidence radioxenon detectors must be calibrated for each of the four-radioxenon isotopes (135Xe, 133Xe, 133mXe, and 131mXe). Without a proper calibration, there is potential for the misidentification of the amount of each isotope detected. It is important to accurately determine the amount of each radioxenon isotope, as the ratios can be used to distinguish between an anthropogenic source and a nuclear explosion. We have developed a xenon calibration system (XeCalS) that produces calibration spikes of known activity and pressure for field calibration of detectors. We will present results from the development of XeCalS and a portable spike implementation system.

A method to quantify the 37Ar emanation fraction in powders and rocks

In order to make predictions of the potential 37Ar signal from an underground nuclear explosion, a value for the 37Ar emanation fraction is needed. A system was developed to quantify the emanation fraction from samples ranging in size from powder to small rocks. Assorted rock samples were irradiated with Watt fission spectrum neutrons to produce radioactive argon gas via activation of calcium. The argon produced was extracted on a custom apparatus and cryogenically trapped. The extracted gas was then processed to separate the argon and load it into a proportional counter for counting. The emanation fraction of argon gas from the rock samples was then calculated by comparing the measured and predicted activities.

Anticoincidence analysis for radioxenon detection

An algorithm was developed to improve the quantification of metastable isotopes in the presence of 133Xe. Radioxenon emissions are commonly used to monitor for nuclear explosions. When 133Xe is present in these samples it causes interference in the activity calculation of the metastable isotopes. The alternative analysis method analyzes the anticoincidence spectrum of the plastic detector to decrease interference from 133Xe. Simulation results show that the anticoincidence analysis accurately quantifies the activity of 131mXe. For the data analyzed here, the anticoincidence method identifies 83% more samples above the minimum detectable activity than the traditional method.

Evaluation of independent and cumulative fission product yields with gamma spectrometry

Fission product yields are critical data for a variety of nuclear science and engineering applications; however, independent yields have not been extensively measured to date. We have previously documented a methodology to measure the cumulative and independent fission product yields using gamma spectrometry and nuclide buildup and decay modeling, and numerical optimization. We have produced fission products by bombarding 235U with 14.1 MeV neutrons and made measurements of fission product yields. In this paper, we summarize our approach, describe initial experiments, and present preliminary results where we have determined nine fission product yields for long-lived nuclides.

Analysis of 125Xe electron–photon coincidence decay

As part of the verification component of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), environmental gas samples originating from nuclear fission are analyzed for the presence of 131mXe, 133mXe, 133Xe, and 135Xe. In this work, the non-traditional radioxenon isotope 125Xe was investigated. The isotope was produced as an isotopically pure sample via neutron activation of 124Xe at the University of Texas at Austin Nuclear Engineering Teaching Lab’s TRIGA MARK II Reactor. The sample was then measured using a HPGe detector as well as an ARSA-style β–γ coincidence detector. Potential sources and sensitivities for production of 125Xe are also considered for relevance to the CTBT verification mission.

Estimation of 240Pu Mass in a Waste Tank Using Ultra-Sensitive Detection of Radioactive Xenon Isotopes from Spontaneous Fission

We report on a technique to detect and quantify the amount of 240Pu in a large tank used to store nuclear waste from plutonium production at the Hanford nuclear site. While the contents of this waste tank are known from previous grab sample measurements, our technique could allow for determination of the amount of 240Pu in the tank without costly sample retrieval and analysis of this highly radioactive material. This technique makes an assumption, which was confirmed, that 240Pu dominates the spontaneous fissions occurring in the tank.