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Table 2 summarizes the gamma spectrometers and software used for determining the isotopic composition of the samples in the CMX-4 exercise. For example, peaks of 214Bi (for age dating) and descendants of 232U were evaluated manually.
#Gamma control v4 manual
Manual evaluation also occurred, after primary processing (measurement control, peak shape fitting, determining peak area, and deconvolution of overlapping peaks) by codes (FitzPeaks, PeakEasy, and Gammavision), followed by application of intrinsic self-calibration. However, for quality control purposes and for demonstrating laboratory performance, it is recommended to use a set reference materials. As all the information for determining the isotope ratios is present in the spectrum of the sample, no reference materials are required for calibration. Therefore, the method does not depend on the sample size, geometry, physical, and chemical state. The relative efficiency curve is obtained from the spectrum of the measured sample, thus the attenuation both in the sample (self-attenuation) and in absorbers (shielding) are taken into account. These codes are based on so-called relative efficiency calibration (or intrinsic calibration) method. Most participants of the exercise determined the major U isotopic ( 234U, 235U, and 238U) abundances using computer codes for automatic spectrum evaluation. Spectra were generally acquired by high purity germanium (HPGe) detectors for about 30–60 min in the case of the 24 h reports, whereas much longer measurement times were used for the 1 week reports. The samples were assayed first using HRGS for the 24 h and 1 week reports. These values are compared to the community average values determined by mass spectrometry. This paper presents the isotopic composition, age, and signatures of the neutron irradiation history of the three LEU samples determined by gamma spectrometry. A disadvantage is that it suffers from higher uncertainty compared to destructive techniques, such as mass spectrometry (MS). Advantages include preservation of evidence and no, or a minimal, need for sample preparation.
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#Gamma control v4 code
Each of the 16 participating laboratories was assigned a code name by the organizers to ensure anonymity and confidentiality of data.Īmong the methods used in nuclear forensics, high-resolution gamma spectrometry (HRGS) is a relatively rapid nondestructive analytical technique. Participating laboratories categorized and characterized the exercise materials, and performed nuclear forensic evaluations. Laboratories were instructed to submit assessment reports in a 24 h, 1 week, and 2 month time frame. A scenario was included in which a seizure of nuclear material occurred and forensic analysis was requested. Three oxide samples of low enriched uranium (LEU) were selected as the materials to be characterized during the CMX-4 exercise. The CMX-4 represents the second paired-comparison exercise organized to improve international cooperation and communication in case of a nuclear security event. Nuclear forensic analysis includes the characterization of the material and correlation with its production history. The goal of the analysis is to identify the composition, origin, and intended use of interdicted nuclear or radiological samples, containers, and transport vehicles. Nuclear forensics is the analysis of intercepted nuclear or other radioactive material to provide evidence for nuclear attribution in a legal context. This paper documents the collective experience with gamma spectrometry during the CMX-4 exercise and it gives a snapshot of the applied approaches. The Nuclear Forensics International Technical Working Group (ITWG) organized its fourth interlaboratory exercise in 2014, called Collaborative Materials Exercise (CMX-4). This paper presents the state of practice in gamma spectrometry for nuclear forensics exercises.