A calibration procedure for beta-gamma coincidence detector-systems using four radioxenon spikes.

The determination of activity concentrations of the CTBT-relevant radioxenon relies on a robust calibration method. A procedure is outlined using four radioxenon spikes for beta-gamma detector-systems with 4π geometry. Detection efficiencies of beta-gamma coincidences in the net count calculation method, including the interference matrix between radioxenon and radon, are determined by three measurement channels: beta singles, gamma singles and beta-gamma coincidences, without reference activity values.

Radionuclide measurements of the international monitoring system.

The International Monitoring System (IMS) is a unique global network of sensors, tuned to measure various phenomenology, with the common goal of detecting a nuclear explosion anywhere in the world. One component of this network collects measurements of radioactive particulates and gases (collectively known as radionuclides) present in the atmosphere; through this, compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) can be verified. The radionuclide sub-network consists of 120 sensors across 80 locations, supported by 16 measurement laboratories.

Enhancing the detection sensitivity of a high-resolution β - γ coincidence spectrometer.

A high-resolution β - γ coincidence spectrometry system has been set-up and calibrated at the UK CTBT Radionuclide Laboratory (known as GBL15) at AWE. The system has been configured specifically to measure the signatures of radioxenon isotopes that can be indicative of a nuclear explosion. The high purity germanium (HPGe) and PIPSBox detectors have been placed in an ultra-low-background lead shield to reduce the background count-rate and new software allows the combination of signals from four detectors (two HPGe detectors and two silicon-based detectors) to cover a larger solid angle.

Analysis of radionuclide detection events on the International Monitoring System.

The United Kingdom (UK) National Data Centre (NDC) operates a series of custom-developed software tools for the automatic processing, analysis, archiving and interpretation of radionuclide (RN) data from the International Monitoring System (IMS) - the primary instrument for verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The software in-use at the NDC includes an RN Pipeline for the retrieval, analysis, categorisation and archiving of noble gas and particulate radionuclide data. On the identification of a treaty-relevant radionuclide detection or plume of radioxenon, a 'radionuclide detection event' is formed.

Production and measurement of fission product noble gases.

Gaseous fission products have been produced via thermal neutron irradiation of a highly-enriched uranium target and extracted using a custom gas processing system for measurement on a prototype, high-resolution β - γ coincidence detection system. The gas was extracted and measured in two stages in order to measure the prompt and β-delayed fission products. This paper presents an overview of the system used to produce gaseous fission products, and the results of the advanced coincidence spectrometry techniques used to identify and quantify decays from the radionuclides produced, including the noble gases Kr, Kr, Kr, Xe, Xe, Xe and Xe, as well as I and Rb.

Analysis of environmental radioxenon detections in the UK.

Radioxenon activity concentrations are monitored globally using the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organisation, improving the monitoring community's ability to detect radionuclide signatures from an underground nuclear test (UNT). An IMS-like noble gas system is in operation at AWE (Aldermaston, UK) and can collect and measure radioxenon isotopes in environmental air samples. When operated in this mode, data produced is analysed at the UK National Data Centre (NDC) and significant detection events are flagged for further investigation.

A rapid dissolution procedure to aid initial nuclear forensics investigations of chemically refractory compounds and particles prior to gamma spectrometry.

A rapid and effective preparative procedure has been evaluated for the accurate determination of low-energy (40-200 keV) gamma-emitting radionuclides ((210)Pb, (234)Th, (226)Ra, (235)U) in uranium ores and uranium ore concentrates (UOCs) using high-resolution gamma ray spectrometry. The measurement of low-energy gamma photons is complicated in heterogeneous samples containing high-density mineral phases and in such situations activity concentrations will be underestimated. This is because attenuation corrections, calculated based on sample mean density, do not properly correct where dense grains are dispersed within a less dense matrix (analogous to a nugget effect).

Quantifying radionuclide signatures from a γ-γ coincidence system.

A method for quantifying gamma coincidence signatures has been developed, and tested in conjunction with a high-efficiency multi-detector system to quickly identify trace amounts of radioactive material. The γ-γ system utilises fully digital electronics and list-mode acquisition to time-stamp each event, allowing coincidence matrices to be easily produced alongside typical 'singles' spectra. To quantify the coincidence signatures a software package has been developed to calculate efficiency and cascade summing corrected branching ratios.