First STAX detector installation at the National Institute for Radioelements (IRE)

https://doi.org/10.1016/j.jenvrad.2022.107036Get rights and content

Highlights

  • A STAX detection system was installed at the National Institute for Radioelements.

  • The detection system has been operating for over three years.

  • The system is integral to development of project data transfer, storage, and visualization tools.

  • STAX data was analyzed to verify calculations for reported release values.

  • Equipment performance for approximately two years of operation is discussed.

Abstract

The Source Term Analysis of Xenon (STAX) project has been installing stack detectors at medical isotope production facilities to measure radioxenon emissions to investigate the effect of radioxenon releases on nuclear explosion monitoring. This paper outlines the installation of the first STAX detection system at the National Institute for Radioelements (IRE) in Fleurus, Belgium which has been operating for over three years and transferring collected data to the STAX repository. Information about the equipment installed, the data flow established, and calculations for determination of radioxenon releases from the facility are presented. Data quality was investigated to confirm values reported by STAX automated data processing and in a comparison of collected STAX data with data collected by IRE for regulatory reporting.

Introduction

It is well established that fission based medical isotope production (MIP) is the largest contributor to the global radioxenon background (Saey, 2009; Zaehringer et al., 2009) and that the radioxenon originating from MIP is difficult to distinguish from that originating from nuclear explosions. Due to this background, detections of radioxenon from MIP by the International Monitoring System (IMS), which is part of the verification regime of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), hinder the ability to effectively detect nuclear explosions (Reiners, 2009; Saey et al., 2010a, 2010b).

The IMS incorporates seismic, hydro-acoustic, infrasound and radionuclide monitoring technologies (CTBT, 1996). Radionuclide monitoring by the IMS measures the relative abundance of 131mXe (t1/2 = 11.9 days), 133mXe (t1/2 = 2.19 days), 133Xe (t1/2 = 5.24 days), and 135Xe (t1/2 = 9.10 h). To distinguish between industrial sources of radioxenon detected by the IMS, such as from MIP and nuclear explosion sources, plots of xenon isotopes ratios are evaluated to identify potential release scenarios (Kalinowski et al., 2010; Saey et al., 2010a, 2010b; Wotawa et al., 2010). This method works well in most instances, however, when MIP uranium targets are dissolved shortly after irradiation (Doll et al., 2014), the resulting ratios of radioxenon are quite similar to nuclear explosion signatures. In addition, the four radioxenon isotopes of interest are not all routinely detected by IMS radionuclide monitoring, the lack of all four isotopes adds further complexity to discrimination between MIP emissions and nuclear explosions.

The international community is interested in solutions to the radioxenon background issue and in 2009 the first Workshop on Signatures of Man-Made Isotope Production (WOSMIP) was held with the goal of finding solutions to reduce the impact of radioxenon emissions from MIP on nuclear explosion monitoring (Matthews et al., 2012; WOSMIP Summary Reports, 2020). Eight meetings of WOSMIP have been held to date, including a virtual meeting called WOSMIP Remote in 2020, which continue to bring together the monitoring and MIP communities. The concept of using xenon release data from MIP facilities to better understand the global radioxenon background grew from this workshop and has become one of its primary objectives.

The Source Term Analysis of Xenon (STAX) project involves the installation of stack detectors at MIP facilities on a voluntary basis, to measure radioxenon released from such facilities and use the collected data to develop and test methods to improve discrimination between industrial activities and nuclear explosions. This experiment is being conducted by an international team of technical experts from the WOSMIP community. The long-term vision of this effort is for the data flow developed by the STAX project to be used as a tool for analysis by National Data Centers (NDC) to incorporate with their nuclear explosion monitoring capabilities. How and if STAX data can be integrated into NDC analysis has yet to be determined. During this experiment, the project will provide a commercial high-resolution stack detection system to fission-based MIP facilities willing to participate in this experiment at no cost to the facilities, create a central repository (separate from the current International Data Center (IDC) database which is part of the IMS) to receive data transmitted from these systems, and develop algorithms to analyze data received for the project (Metz et al., 2022). Fig. 1 is a schematic that shows how STAX data is envisioned to be used along with atmospheric transport modeling (ATM) and IMS data by the IDC and NDCs to better understand the effect of measured xenon releases on nuclear explosion monitoring.

Although the STAX experimental database will be a standalone system, the project team will employ similar methods to those currently used by the IDC to allow for smooth data integration with IDC data by NDCs. The experiment will include confidential data transfer and storage that will meet data confidentiality standards as required by the medical isotope producers. Here is an overview of the installation of the first STAX detection system which was installed at IRE in Fleurus, Belgium including an overview of the equipment installed, the data flow established, and calculations for determination of xenon releases from the facility.

Section snippets

Equipment installed

A commercial high-resolution stack detection system designed and built by Mirion Technologies was chosen for installation at the IRE facility. This stack monitoring system was designed to meet the STAX project requirements that are documented in the Hardware and Software Guidelines for the STAX Project (PNNL-27582, 2018). The requirements include use of a high purity germanium (HPGe) detector and a dynamic range of roughly an emission of 1 GBq/day to 10 TBq/day (the dynamic range of the

Data flow

As data is acquired, each 15-min spectrum is analyzed using standard Mirion Genie™ 2000 software parameters such as peak locate, peak area, efficiency correction, Nuclide Identification (NID) with interference, and Minimum Detectable Activity (MDA) calculation. The acquired spectrum as well as the analysis parameters and results are output as N42 files (ANSI N42.42–2012) which were modified to contain channel-energy calibration pair data. The N42 files are used to create Pulse-Height-Data (PHD)

Discussion/conclusion

The STAX project is installing stack detectors to measure radioxenon released from MIP facilities to better understand the effect of radioxenon releases on nuclear explosion monitoring. The first STAX detection system was installed in November 2017 at the National Institute for Radioelements (IRE) Fleurus, Belgium and a data flow to the STAX central data repository was successfully established. This system has been operating for over three years and has been integral to development of methods

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We would like to acknowledge our project participants who are instrumental to making this project a success: The Institute for RadioElements (IRE) for collaborating to install and maintain stack detector equipment in their facilities and for sharing the collected data; Instrument Software Technologies Inc. (ISTI) for collaborating on software development; and Mirion for developing the detector equipment installed at IRE.The STAX project is supported by the U.S. Department of State,

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