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A new generation of cadmium zinc telluride (CZT) detectors has become available and is being evaluated by the International Atomic Energy Agency (IAEA) for safeguards verifications in the field. The new CZT detector, model M400, is a room temperature spectrometer manufactured by H3D, Inc. The M400 demonstrates superior energy resolution, effective isotope identification capabilities, and convenient usability features when tested in a controlled laboratory environment. These characteristics define the M400 as a potential platform for IAEA field detection applications, which could become suitable for nuclear material characterization (e.g., enrichment verification) and nuclear safeguards missions. The capabilities of gamma spectrometry codes including Fixed energy, Response function Analysis with Multiple efficiencies (FRAM) from Los Alamos National Laboratory, CZT for Uranium (CZTU) from Lawrence Livermore National Laboratory, and Gamma Detector Response and Analysis Software (GADRAS) from Sandia National Laboratories were adapted for M400 spectra, and the performance of the codes has been validated. This was reported in a prior work. To further validate the performance of the high-energy resolution CZT detector and the isotopic analysis codes, a field measurement campaign consisting of uranium hexafluoride (UF 6) cylinder measurements was conducted at a fuel fabrication facility. A total of 34 Type 30B cylinders containing UF 6 were measured using three different M400 CZT detectors. Each detector was outfitted with a custom rectangular collimator and shield made out T-Flex®, a tungsten-impregnated polymer. Measurements were performed at three different locations of the cylinder, ensuring that the measurement geometry satisfied the infinite thickness criterion. The spectra from the M400 CZT were analyzed using the code General Enrichment Meter (GEM). For analyzing the gamma-ray spectra from UF 6 cylinder, the GEM code is the appropriate tool since it relies only on the gamma-ray emissions from 235U and not from other isotopes. Results from the spectral analysis were compared with the known abundance of 235U in the cylinders, as well as with the International Target Values 2020 (ITV2020). The suitability of the different underlying techniques used by the various codes for UF 6 analysis is discussed. The challenges of measuring UF 6 contained in cylinders and mitigation strategies are highlighted. [ABSTRACT FROM AUTHOR]

In the Unattended Cylinder Verification Station (UCVS) project, a field trial in 2019 at a fuel fabrication facility resulted in a direct comparison of several gamma-ray detectors and methods for Type 30B UF6 cylinder enrichment assay. The field trial included measurements of 268 unique cylinders that ranged in enrichments (depleted uranium to 4.95 wt.% 235U) and other factors to assess enrichment assay performance. The detectors included two Ritec μSPEC 1500 CZT (15 mm x 15 mm x 7.5 mm hemispherical crystals) detectors, and two φ38 mm x 38 mm LaBr detectors: one with standard Ce dopant and one Ce, Sr co-doped "enhanced" crystal with marginally better energy resolution. Enrichment algorithms included the General Enrichment Meter (GEM) program stewarded by the International Atomic Energy Agency (IAEA), the Square Wave Convolute (SWC) method developed at the Pacific Northwest National Laboratory (PNNL), and a generic region of interest method. Enrichment-assay precision was calculated for 1-, 5-, or 10-minute data acquisition times and compared against the IAEA International Target Values (ITVs) for different detector/algorithm pairs. This paper presents the field trial gamma-ray enrichment assay performance. Only the LaBr detectors analyzed with GEM and the SWC algorithm provided performance consistently superior to the ITVs. The LaBr detectors were significantly larger than the CZT, giving greater detection sensitivity and improved statistical precision, especially for lower enrichments and assay times. The LaBr detectors, specifically the co-doped variant, also had superior temperature stability compared to CZT, which improved their overall performance. [ABSTRACT FROM AUTHOR]

The International Atomic Energy Agency (IAEA) has developed an On-Line Enrichment Monitor (OLEM) as one possible component in a new generation of safeguards measures for uranium enrichment plants. The OLEM measures 235U emissions from the UF6 gas flowing through a unit header pipe using NaI(Tl) spectrometers, and corrects for gas density changes using pressure and temperature sensors in order to determine the enrichment of the gas as a function of time. In parallel with the OLEM instrument development, a Virtual OLEM (VOLEM) software tool has been developed that is capable of producing synthetic gamma-ray, pressure, and temperature data representative of a wide range of enrichment plant operating conditions. VOLEM complements instrument development activities and allows the study of OLEM for scenarios that will be difficult or impossible to evaluate empirically. Uses of VOLEM include: uncertainty budget analysis and performance prediction for typical and atypical operational scenarios; inter-comparison of candidate gamma-ray spectral analysis and enrichment estimation algorithms; and testing of the OLEM analysis and reporting software. This paper describes the technical foundations of VOLEM and illustrates how it can be used. An overview of the nominal instrument design and deployment scenario for OLEM is provided, with emphasis on the key online-assay measurement challenge: accurately determining the portion of the total 235U signal that comes from a background that includes solid uranium deposits on the piping walls. Monte Carlo modeling tools, data analysis algorithms and uncertainty quantification methods are described. VOLEM is then used to quantitatively explore the statistical uncertainty budgets and predicted instrument performance for a plausible range of typical plant operating parameters, and one set of candidate analysis algorithms. Additionally, a series of VOLEM case studies illustrates how an online enrichment monitor might respond in scenarios expected to be atypical, for example weak pressure transients or significant changes in background levels. [ABSTRACT FROM AUTHOR]

Environmental sampling and sample analyses by the International Atomic Energy Agency is a key method for verifying declarations in international safeguards agreements. Quantitative Digital Autoradiography for Environmental Samples is a system developed by Pacific Northwest National Laboratory to examine environmental swipe samples (ESS) prior to subsequent, destructive analysis. This approach is passive and noninvasive for imaging beta and gamma emissions, which transmit through the plastic bags containing the ESS. Alpha particle imaging is also possible with different ESS containers. This technology is based on a portable, real-time, event-counting, high spatial resolution system called iQID (ionizing-radiation Quantum Imaging Detector), which is made from commercial, off-the-shelf components. This includes a scintillator in direct contact with a micro-channel plate image intensifier and a lens for imaging the intensified scintillation events onto a CCD/CMOS camera. The QDARES large-area iQID includes a fiber-optic taper coupled to the image intensifier which increases the imaging area to a ∼ 100 cm square with a 105 mm x 105 mm taper. In this paper, we describe new characterization results, including spatial resolution, energy response, minimum detectable activity for several isotopes, detector uniformity, and count-rate capability. [ABSTRACT FROM AUTHOR]