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Abstract  

To give satisfactory efficiency both for X- and gamma-ray photon, an improved counting system has been developed in CTBT Canadian radioxenon laboratory. The counting system consists of a BEGe detector coupled with a thin carbon fiber window counting cell, that can perform a reliable and efficient radioxenon measurement. A semi-empirical calibration procedure was adopted, which is a combination of experimental measurement and mathematical simulation. Mathematical calibration tool is Monte Carlo simulation software named VGSL. Advanced gamma-spectrum analysis software, named Aatami, was used for gamma-ray peak shape fitting and X-ray multiplets deconvolution. The calculated full energy peak efficiency curve covers from 30 to 700 keV and agrees well with experimental data points within 2%. The efficiency curve can provide radioxenon analysis both for X-rays and gamma-rays with high quality. The efficiency distortion near xenon k-absorption edge of 35 keV, which is caused by high concentrated xenon in the counting cell, is also discussed.

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Abstract  

To support interpretation of observed atmospheric 135Xe, 133Xe, 133mXe and 131mXe, a database of xenon radioisotope in the primary coolant of CANDU reactors has been established. This database is comprised of 40000 records of high-quality xenon radioisotope analyses. Records from the database were retrieved by a specifically designed data-mining module and subjected to further analysis. Results from the analysis were subsequently used to study isotopic ratios of observed xenon radioisotopes in the CANDU reactor primary coolant. These studies provided novel and practical information on the characterization of CANDU reactor xenon radioisotope releases, which can be used to discriminate between reactor effluence and underground nuclear test releases.

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Abstract  

A quantitative method to determine the activity concentration of 226Ra in soil samples was established using high performance environmental gamma-ray spectrometry. In this method, a semi-empirical calibration procedure was developed for full energy peak efficiency calculation utilizing the elemental composition of the soil sample. Aatami software was used to deconvolute the 235U and 226Ra doublet at 185.7 keV and 186.2 keV, respectively, and to fit the baseline of the soil gamma-spectrum for the determination of 226Ra activity. The results indicated that the Aatami doublet deconvolution procedure provides a rapid and accurate analysis of a complicated spectrum in comparison with other cumbersome spectral interference correction methods. The study also compared the results with those obtained by radon progeny (214Pb, or 214Bi) measurements and found that the deconvolution method provided a more accurate 226Ra activity as it is independent of the error caused by radon diffusion. This error can be quite large since the amount of escaped radon gas through the sample container walls and sealing cannot be accurately quantified.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: W. Hennig, W. Warburton, A. Fallu-Labruyere, K. Sabourov, M. Cooper, J. McIntyre, A. Gleyzer, M. Bean, E. Korpach, K. Ungar, W. Zhang, and P. Mekarski

Abstract  

Measurement of radioactive xenon in the atmosphere is one of several techniques to detect nuclear weapons testing. For high sensitivity, some existing systems use beta/gamma coincidence detection to suppress background, which is very effective, but increases complexity due to separate beta and gamma detectors that require careful calibration and gain matching. In this paper, we will describe the development and evaluation of a simpler detector system, named PhosWatch, consisting of a CsI(Tl)/BC-404 phoswich well detector, digital readout electronics, and pulse shape analysis algorithms implemented in a digital signal processor on the electronics, and compare its performance to existing multi-detector systems.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: P. Aarnio, J. Ala-Heikkilä, A. Isolankila, A. Kuusi, M. Moring, M. Nikkinen, T. Siiskonen, H. Toivonen, K. Ungar, and W. Zhang

Abstract  

Linssi is a Structured Query Language (SQL) database for HPGe gamma-ray spectrometry. It covers the whole production chain from sample preparation to final analysis results. Static or mobile sampling and measurement and multiple sample types are supported. In addition, each sample can be split or combined any number of times. A sample may be measured multiple times and each measurement multiply analyzed as well. With Linssi, measurement setups with detectors, shields, attenuators and source geometries can be defined. Full control of calibrations, their histories and tracing of each calibration point back to its corresponding analysis and calibration measurement is supported. Linssi database and user scripts are available from http://linssi.hut.fi/radphys/linssi.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: K. Ungar, W. Zhang, P. Aarnio, J. Ala-Heikkila, H. Toivonen, T. Siiskonen, A. Isolankila, A. Kuusi, M. Moring, and M. Nikkinen

Abstract  

Linux System for Spectral Information (LINSSI1) is a SQL database and established under Linux. Currently it is compatible with HPGe gammaspectra analysis software UniSampo, Shaman and Aatami. Based on this database and software, an automated analysis pipeline has been setup for Canadian CTBT radiological monitoring networks. This paper has investigated the performance of this pipeline in its capabilities and reliabilities of rapid small peak search, nuclide identification, and radionuclide activity concentration evaluation. Up to now, more than 80 thousand daily monitoring gamma-spectra have been automatically received and processed, the results have been stored in database. The pipeline nuclide detection limits is satisfied for environmental radiation monitoring and nuclear emergency preparedness.

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