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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]

Field measurements of radionuclide activities in soil samples via gamma spectroscopy measurements are conducted for many applications. One example application space is on-site inspection for the Comprehensive Nuclear-Test-Ban Treaty. To extract isotopic activities from observed peak counting rates, it is necessary to understand the absolute efficiency of the detector system for a sample. In principle, this efficiency is a function of many parameters, such as sample geometry, soil elemental composition, and soil density. The demands of field measurements within the context of on-site inspections, however, places a premium on an easy-to-implement approach at the possible expense of accuracy given the need to process many samples in a short period of time. This paper presents a semi-empirical approach, using a calibrated standard and a correction that depends only on the relative differences in density of the sample and the standard. Field measurements were conducted to demonstrate the validity of the approach. • Semi-empirical approach for determining the detection efficiency of radioisotopes in soil samples • Corrections to account for density differences between a standard and a sample are applied • Accept unknown chemical composition of soil as an uncertainty • Suggest how this approach could be implemented in practice [ABSTRACT FROM AUTHOR]

A method was developed for simultaneous production of neutron-deficient Ni and Ir isotopes by irradiation of stacked targets with a 50.5 MeV proton beam, followed by radiochemical separations to remove excess target material. The target, irradiation configuration, and post-irradiation radiochemical separations were developed and tested in a proof-of-principle irradiation. Radiochemical yields and purity of the products are discussed. The stacked target method, developed herein, can be used to produce other isotope pairs with appropriate beam tailoring. [ABSTRACT FROM AUTHOR]

We have developed a wearable radiation sensor using Cs 2 LiYCl 6 :Ce (CLYC) for simultaneous gamma-ray and neutron detection. The system includes two ∅ 2.5 × 2.5 cm 3 crystals coupled to small, metal-body photomultiplier tubes. A custom, low-power electronics base digitizes the output signal at three time points and enables both pulse height and pulse shape discrimination of gamma rays and neutrons. The total counts, anomaly detection metrics, and identified isotopes are displayed on a small screen. Users may leave the device in unattended mode to collect long-dwell energy spectra. The system stores up to 18 h of one-second data, including energy spectra, and may transfer the data to a remote computer via a wired or wireless connection. The prototype is 18 × 13 × 7.5 cm 3 , weighs 1.3 kg, not including the protective pouch, and runs on six AA alkaline batteries for 29 h with the wireless link active, or 41 h with the wireless link disabled. In this paper, we summarize the system design and present characterization results from the detector modules. The energy resolution is about 6.5% full width at half maximum at 662 keV due to the small photomultiplier tube selected, and the linearity and pulse shape discrimination performance are very good. [ABSTRACT FROM AUTHOR]

Emerging thorium-based reactor designs and fuel cycles present challenges to traditional non-destructive assay techniques used in international safeguards. Specifically, assaying the masses of 233U and 235U when they are present together in samples with high gamma ray backgrounds is difficult because of similar passive neutron signatures and relatively weak gamma-ray emissions of 233U. The Pacific Northwest National Laboratory (PNNL) and the Massachusetts Institute of Technology (MIT) are developing a portable neutron resonance transmission analysis (pNRTA) system as one potential solution to these challenges. This method provides isotopic concentration data for a sample via neutron time-of-flight (TOF) measurements that exploit epithermal neutron resonance cross-sections. A recently developed pNRTA system uses a commercially available, pulsed deuterium-tritium neutron generator with a ∼2 m flight path and a GS20 lithium glass scintillator detector. This paper describes the prototype pNRTA system design, a refined radiation transport model of the system, preliminary measurements with thorium and uranium sources, and demonstration of a quantitative isotopic estimation algorithm. [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]