Spatially-Aware Temporal Anomaly Mapping of Gamma Spectra

TL;DR

This paper introduces a spatially-aware temporal anomaly detection method using mobile detectors to monitor radioactivity changes over large areas, effectively identifying small spectral shape anomalies over extended periods.

Contribution

It adapts spectral shape-based anomaly detection for limited background data, enabling sensitive, long-term monitoring of radioactivity anomalies with mobile detectors.

Findings

Effective detection of small spectral shape changes over weeks.

Successful application on a research campus with simulated source injections.

Demonstrated capability for continuous, wide-area radioactivity monitoring.

Abstract

For security, environmental, and regulatory purposes it is useful to continuously monitor wide areas for unexpected changes in radioactivity. We report on a temporal anomaly detection algorithm which uses mobile detectors to build a spatial map of background spectra, allowing sensitive detection of any anomalies through many days or months of monitoring. We adapt previously-developed anomaly detection methods, which compare spectral shape rather than count rate, to function with limited background data, allowing sensitive detection of small changes in spectral shape from day to day. To demonstrate this technique we collected daily observations over the period of six weeks on a 0.33 square mile research campus and performed source injection simulations.