SUPPORTING A BETTER SCREENING FOR CTBT-RELEVANT EVENTS
AGAINST A RADIOXENON BACKGROUND: XEBET RESEARCH AND
DEVELOPMENT

Emissions of four radioxenon isotopes relevant for CTBT monitoring are frequently observed by the noble gas sensors of the International Monitoring System (IMS). These emissions originate from worldwide nuclear facilities, are ever-present and highly variable, and pose a challenge for global monitoring of nuclear explosions. A sophisticated approach is required for a process called screening, i.e., to distinguish for each IMS sample whether the observations can be explained by known sources or whether it possibly contains a contribution from a nuclear explosion. For this purpose, a sequence of research and development projects has been initiated, aiming to ultimately build a software tool to estimate the background radioxenon concentrations at IMS stations in an operational environment. One such currently running project, called Xenon Background Estimation Tool (XeBET), aims to deliver an aggregation of scientifically developed ideas into a software prototype. Ideas considered in XeBET are built on atmospheric transport modelling (ATM) and radionuclide statistical expertise from assessments in previous multilevel and multidisciplinary scientific investigations, specifically from three ATM Challenges to predict radioxenon concentrations and a first Screening Intercomparison Exercise to identify artificially added nuclear explosion signals. Whereas the XeBET prototype may already be used for Expert Technical Analysis once demonstrated and agreed upon after completion in 2023, its future successor project will focus on the operational implementation. This presentation discusses XeBET’s context, the status of ideas and prototyping, and assesses the challenges ahead for 2023 and beyond.