Nuclear Forensics

However, establishing the origin of nuclear materials (e.g., uranium ore concentrates) is not the only subject of investigation in this field. It is necessary to develop methodologies to reveal undeclared clandestine nuclear activities, and also to test possible effects thereof on animals and humans. As can be seen in Table 14.2, numerous applications have tackled these issues during the past 5 years, and the most relevant are briefly discussed below. 

Various types of solid samples U and Pb isotope ratios plus multi-elemental analysis LA-ICP-TOF-MS [20] 

Microscopic uranium oxide grains U isotope ratios LA-MC-ICP-MS [21] 

No samples, only standards Pu isotope ratios Electrochemical separation coupled to Q-ICP-MS [24] 

Uranium pellets and powder U isotope ratios, trace elements, particle size and shapes MC-ICP-MS (for isotopic analysis) [26] 

Absence of evidence is not evidence of absence. We need to report uncertain results and do it clearly. 

Anderson (2004, with regard to HIV-1 transmission but this is also so true 

They have been saying for a long time that Iraq made an effort to import active uranium, and my colleague demonstrated the other day that they came to the conclusion that it was a fake document that everybody is relying upon. 

FIGURE 5.1 Annual number of publications on Nuclear Forensics from 1996 to 2014. (Based on SciFinder, accessed April 29, 2014.) 

A partial list of the tool-kit available for nuclear forensics investigations is shown in Table 5.1 (IAEA 2006). A somewhat different list of the tools that are used to characterize seized nuclear materials (pellets or powder) is shown in Table 5.2 (Wallenius et al. 2006). One more point that is almost unique for nuclear forensics when a smuggled radioactive material is seized or when undeclared nuclear activities are suspected, the law enforcement forces are expected to provide a preliminary characterization of the material within a short time (usually 24 h) and more detailed and accurate data after a few more days, as shown in Table 5.3 (IAEA 2006). These publications will be mentioned in context with the subject matter of this chapter. 

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SIMS is mostly employed for microlocal analytical investigations. For example, isotope ratio measurements by SIMS have been performed in nuclear forensic studies to determine the age of Pu particles." For the age determination of Pu particles, relative sensitivity coefficients (RSC) were determined as correction factors for the different ionization efficiency of Pu compared to U. The age of a sample of known origin calculated from Pu/ " and °Pu/ U ratios agreed well with the reported age of 2.3 years." SIMS was employed for oxygen isotope ratio measurements in three different uranium oxide microparticles of nuclear forensic interest by Betti s working group." The... 

Nuclear and radiochemistry includes accelerator/reactor chemistry for isotope production, nuclear structure, neutrino chemistry, nuclear forensics, and archeometery. Understanding of nuclear and radiochemistry underlies the availability of adequate supplies as well as proper and safe use of radioactivity for energy production or radiomedicine. Twenty percent of electric power in the United States is supplied by nuclear reactors. It is possible that construction of new reactors in the United States will resume within the next decade. Similarly, the use of radionuclides in medicine, research, and industry is predicted to increase. 

Nuclear forensics involves using nuclear signatures to define the origin of radioactive materials, stable isotope signatures to determine geolocation, and conventional forensic information (fingerprints and fibers) from... 

Dr. Shaun Jones, Biodesign Institute, Arizona State University Dr. Peter Jutro, Deputy Director for Science and Policy, National Homeland Security Research Center, Environmental Protection Agency Dr. Michael Kaminski, Nuclear Forensics and Nanoscale Engineering, Argonne National Laboratory... 

Abstract A short history and treatment of the various aspects of nuclear forensic analysis is followed by a discussion of the most common chemical procedures, including applications of tracers, radioisotopic generators, and sample chronometry. Analytic methodology discussed includes sample preparation, radiation detection, various forms of microscopy, and mass-spectrometric techniques. The chapter concludes with methods for the production and treatment of special nuclear materials and with a description of several actual case studies conducted at Livermore. 

Radiochemical separations are the backbone of much of nuclear forensic science, since they provide a means by which small forensic signatures may be isolated from an overwhelming radiochemical background due to the sample matrix. This is particularly important for chronometry, where one compares analyte concentrations that can differ by 15 orders of magnitude or more. For the measurement of the relative concentrations of analytes that are isotopes of different chemical elements, the key issue is accurate chemical yielding. When two or more analytes of the same element have vastly different concentrations, standard chemical separations cannot address the issue of dynamic range in this case, a coUection of techniques known as radiochemical milking can be used to determine the minor isotope. 

The solvent extraction method with which the analytical chemist is most familiar involves placing both liquid phases in a separatory funnel and agitating by hand to effect the partition due to issues of contamination control and limited solution volumes, this implementation is little used in nuclear forensic analysis. Often, phases are mixed in a capped centrifuge cone using a vortex mixer this is particularly convenient in a gloved box, where the loss of manual dexterity impedes the manipulation of a separatory funnel and stopcock. Phase separation is facilitated through the use of a centrifuge. 

Ion exchange is a powerful technique for the radiochemical isolation of most of the species of interest to the nuclear forensic analyst (Hyde 1956 Katz and Seaborg 1957). Ion-exchange resins usually consist of a cross-linked styrene-divinylbenzene polymer to which ionizable functional groups are attached. These materials are fabricated into small spherical beads over which an aqueous solvent is passed. Optimal separations are obtained when the beads are all approximately the same size, which helps prevent channeling of the solvent throi h a column packed with the beads. Resin beads are available in most mesh sizes from about 18 mesh down to colloidal size, but most resins of use in the radioanalytical laboratory are between 100 and 200 mesh ( 0.152-0.075 mm). 

The identity and amount of a radioactive tracer that should be added to a particular sample depend on several factors. The analyst must be careful to add enough tracer activity that it can be accurately measured in the final sample this includes considerations of decay during chemical separation and purification prior to counting, the efficiency of the radiation counter for detecting the characteristic emissions of the tracer nuclide, and the level of activity of any radioactive sample analytes that might interfere with the observation of the tracer. Similarly, the analyst must not add so much tracer that it overwhelms the signature of the other nuclides of the same element or causes extra purification issues if it spreads into another chemical fraction. In traditional radiochemistry, quantities of radionuclides that are quite undetectable by ordinary means emit easily detectable levels of radiation in the nuclear forensic laboratory, it is often assumed that a weightless amount of a radionuclide is added as a tracer activity. 

Using a variety of techniques, the radiochemical analyst measures the concentrations of various radioactive and stable nuclides in a nuclear forensic sample. The resultant table of concentrations is the radioanalytical fingerprint of the sample. However, unlike an actual fingerprint, which is interpreted by comparison with a database, the fingerprint of a sample of special nuclear material is forged by the methods used in its creation, and information about the origin of the material can be obtained from scientific principles by the informed analyst. 

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