This article considers a real application where all the data available to assess a new measurement system do not follow a planned protocol. Instead of analyzing only the sample averages of the ...planned protocol data, we show how a hierarchical model allows all the available data to be used to assess a measurement system. We show the advantages of using all the available data from the application.
The results of a joint effort by expert nuclear forensic laboratories in the area of age dating of uranium, i.e. the elapsed time since the last chemical purification of the material are presented ...and discussed. Completely separated uranium materials of known production date were distributed among the laboratories, and the samples were dated according to routine laboratory procedures by the measurement of the 230Th/234U ratio. The measurement results were in good agreement with the known production date showing that the concept for preparing uranium age dating reference material based on complete separation is valid. Detailed knowledge of the laboratory procedures used for uranium age dating allows the identification of possible improvements in the current protocols and the development of improved practice in the future. The availability of age dating reference materials as well as the evolvement of the age dating best-practice protocol will increase the relevance and applicability of age dating as part of the tool-kit available for nuclear forensic investigations.
•A methodology for preparing uranium age dating reference material was validated.•Detailed laboratory procedures for uranium age dating are summarized.•The difficulties and further developments of uranium age dating are demonstrated.
Five sealed plutonium–beryllium (PuBe) neutron sources from various manufacturers were disassembled. Destructive chemical analyses for recovered PuBe materials were conducted for disposition ...purposes. A dissolution method for PuBe alloys was developed for quantitative plutonium (Pu) and beryllium (Be) assay. Quantitation of Be and trace elements was performed using plasma based spectroscopic instruments, namely inductively coupled plasma mass spectrometry (ICP-MS) and atomic emission spectrometry (ICP-AES). Pu assay was accomplished by an electrochemical method. Variations in trace elemental contents among the five PuBe sources are discussed.
•A destructive chemical analysis of the PuBe neutron sources includes the solubilization and digestion of the PuBe alloy material.•Plutonium was assayed by an electrochemical method.•Beryllium assay and trace elemental contents were determined by ICP instruments.•A large variation in trace elemental composition was observed among the five PuBe source materials.
Dissolution and assay of neptunium oxide Xu, N.; Tandon, L.; Gallimore, D. ...
Journal of radioanalytical and nuclear chemistry,
04/2013, Letnik:
296, Številka:
1
Journal Article
Recenzirano
A case study for dissolution and assay of neptunium oxide is presented in this paper. A simple analytical method for completely dissolving neptunium oxide is described. Addition of 12 M HNO
3
is ...sufficient to dissolve neptunium oxide without precipitate formation. Various analytical chemistry methods were evaluated for neptunium assay including controlled potential coulometry, gas proportional counting/alpha spectrometry, gamma spectrometry using a high purity germanium detector, inductively coupled plasma-mass spectrometry, and isotope dilution-inductively coupled plasma-mass spectrometry. The precision and uncertainty of each analytical method is discussed.
A variety of unique radioactive samples have been measured recently at Los Alamos National Laboratory (LANL) using an electrically-cooled high-purity germanium detector. In each case the purpose of ...the measurements included one or more of the following objectives: (1) an accurate determination of the isotopic weight fractions of different plutonium or uranium materials; (2) an accurate determination of the isotopic quantity in the absence of relevant calibration standards; and (3) a qualitative determination of various sample impurities for additional forensic information. This paper discusses how simple modifications to the PC-FRAM parameter sets enabled a better determination of the isotopic content of the following samples: (1) high-purity plutonium metal, (2) plutonium-beryllium (PuBe) neutron sources, (3) neutron-irradiated natural uranium, and (4) re-processed HEU fuel with elevated
236
U content. The isotopic quantity in a variety of samples was determined using a combination of the Spectral Nondestructive Assay Platform (SNAP™) routine from Eberline Services and the Monte Carlo Neutral Particle (MCNP) code developed at LANL. The non-traditional sources that were quantified with these gamma ray modeling codes included dozens of neutron-irradiated targets of natural uranium, several plutonium-beryllium neutron sources, and three high-purity samples of plutonium metal.
Identifying both physical and chemical characteristics of Special Nuclear Material (SNM) production processes is the corner stone of nuclear forensics. Typically, processing markers are based on ...measuring an interdicted sample’s bulk chemical properties, such as the elemental or isotopic composition, or focusing on the chemical and physical morphology of only a few particles. Therefore, it is imperative that known SNM processes be fully characterized from bulk to trace level for each particle size range. This report outlines a series of particle size measurements and fractionation techniques that can be applied to a bulk SNM powders, categorizing both chemical and physical properties in discrete particle size fractions. This will be demonstrated by characterizing the process signatures of a series of different depleted uranium oxides prepared at increasing firing temperatures (350–1100 °C). Results will demonstrate how each oxides’ material density, particle size distribution, and morphology varies.
Bactrocera dorsalis is a serious pest of mangoes in India. Between 1985 and 1996 assessments of the effectiveness of a locally recommended IPM package, in comparison with no control, on a susceptible ...variety were carried out near Bangalore. The IPM package was applied over the 45 days before harvest and comprised (1) weekly removals of fallen fruit, (2) 3-weekly inter-tree ploughing and raking and (3) three fortnightly cover sprays of insecticide. Infestation reductions attributable to the package were between 77% and 100% in different years. Cost-benefit returns were dependent on the level of pest pressure, and in years of low pressure the package may not recover its costs, necessitating a threshold approach.
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