Authors:J. Ely, K. Anderson, D. Bates, R. Kouzes, C. Lo Presti, R. Runkle, E. Siciliano, and D. Weier
Plastic scintillator material is often used for gamma-ray detection in many applications due to its relatively good sensitivity
and cost-effectiveness compared to other detection materials. However, due to the dominant Compton scattering interaction
mechanism, full energy peaks are not observed in plastic scintillator spectra and isotopic identification is impossible. Typically
plastic scintillator detectors are solely gross count detectors. In some safeguards and security applications, such as radiation
portal monitors for vehicle screening, naturally-occurring radioactive material (NORM) often triggers radiation alarms and
results in innocent or nuisance alarms. The limited energy information from plastic scintillator material can be used to discriminate
the NORM from targeted materials and reduce the nuisance alarm rate. An overview of the utilization of the energy information
from plastic scintillator material will be presented, with emphasis on the detection capabilities and potential limitations
for safeguards and security applications.
A new computerised neutron activation technique permits rapid nondestructive simultaneous elemental and isotopic uranium analysis with various applications, such as nuclear material standardization and safeguards analysis. The technique consists of dual cyclic neutron activation in a differentiated neutron flux spectrum at bare and cadmium covered irradiation positions and subsequent delayed fission neutron counting. Calibration curve fitting by polynomial approximation and data processing by GRAPHER and LOTUS 123 software computer programs gave satisfactory results.
A new neutron activation technique has been developed for the determination of uranium element concentration and235U isotope abundance in nuclear safeguards and reference material samples based on the activation of bare and cadmium-covered samples with different thermal to epithermal neutron flux ratios and on the combination of the two corre-sponding delayed-fission neutron measurements. The principle of the new technique can be applied also to improve multi-element neutron activation analysis.
Linear correlations between burnup, Pu/U- and U5/U0-ratios on the one hand and154Eu/137Cs or134Cs/137Cs ratios on the other hand have been proved to exist in the case of spent WWER fuel. The possibility of using such correlations
for safeguards to determine the235U and Pu content of fuel assemblies has been demonstrated. The results agree well with theoretical calculations using the
COFIP and COHN codes.
An advanced neutron activation technique has been developed for the accurate analysis of elemental and isotopic fissile material required in nuclear safeguards, nuclear material standardization and other applications. It is based on reactor neutron flux spectrum differentiation by cadmium screening and multistandard calibration, including the solution of a second order equation system or of computerized calibration curve fitting, taking into account the thermal neutron flux depression. Some discrepancies at high enrichments have still to be eliminated in order to achieve the required measurement accuracy.
Residual inventory of nuclear materials remaining in processing facilities (holdup) in recognized as an insidious problem for safety of plat operations and safeguarding of special nuclear materials (SNM). This paper reports on an experimental study where a well-known method of radioanalytical chemistry, namely tracer technique, was successfully used to improve nondestructive measurements of holdup of nuclear materials in a variety of plant equipment. Such controlled measurements can improve the sensitivity of measurements of residual inventories of nuclear materials in process equipment by several orders of magnitude and the good quality data obtained lend themselves to developing mathematical models of holdup of SNM during stable plant operations.
The analysis of impurities in uranium matrices is performed in a variety of fields, e.g., for quality control in the production
stream converting uranium ores to fuels, as element signatures in nuclear forensics and safeguards, and for non-proliferation
control. We have investigated the capabilities of time-of-flight ICP-MS for the analysis of impurities in uranium matrices
using a matrix-matched method. The method was applied to the New Brunswick Laboratory CRM 124(1–7) series. For the seven certified
reference materials, an overall precision and accuracy of approximately 5% and 14%, respectively, were obtained for 18 analyzed
Authors:M. Koskelo, W. Sielaff, M. Charland, and H. Roberts
Decommissioning and decontamination work, safeguards related measurements for special nuclear materials, and many other in-situ
applications require that the measuring system be taken to the sample and not the other way around. In addition to a portable
detector, these types of measurements need a lightweight, rugged, battery operated MCA. Canberra's solution to this need is
the versatile InSpector Multi-Channel Analyzer. This single instrument includes the MCA memory management, a high voltage
power supply for either a NaI or a Ge detector, a spectroscopy grade amplifier, a digital stabilizer, and an ADC. It has a
total weight of 3,2 kg, including batteries.
Minimizing plutonium measurement uncertainty is essential to nuclear material control and international safeguards. In 2005,
the International Organization for Standardization (ISO) published ISO 12183 “Controlled-potential coulometric assay of plutonium,”
2nd edition. ISO 12183:2005 recommends a target of ±0.01% for the mass of original sample in the aliquot because it is a critical
assay variable. Mass measurements in radiological containment were evaluated and uncertainties estimated. The uncertainty
estimate for the mass measurement also includes uncertainty in correcting for buoyancy effects from air acting as a fluid
and from decreased pressure of heated air from the specific heat of the plutonium isotopes.
Authors:Zsolt Varga, Maria Wallenius, Klaus Mayer, and Erich Hrnecek
A novel method has been developed for the determination of the production date (age) of uranium ore concentrates (yellow cakes).
The methodology is based on the measurement of trace-level 232Th and its daughter nuclide, 228Th and their variation over time. The proposed method offers a complementary dating tool to the commonly used 230Th/234U technique, which is applicable, however, only for highly purified materials. Applying the present method it is possible
to determine precisely the production date of uranium samples with incomplete separation of their daughter products, such
as yellow cakes, other intermediate products or scrap materials for nuclear forensics and safeguards purposes.