SOLID PHASE MICROEXTRACTION SAMPLING OF HIGH EXPLOSIVE RESIDUES IN THE PRESENCE OF RADIONUCLIDES AND RADIONUCLIDE SURROGATE METALS

The Federal Bureau of Investigation (FBI) Laboratory currently does not have on site facilities for handling radioactive evidentiary materials and there are no established FBI methods or procedures for decontaminating high explosive (HE) evidence while maintaining evidentiary value. One experimental method for the isolation of HE residue involves using solid phase microextraction or SPME fibers to remove residue of interest. Due to their high affinity for organics, SPME fibers should have little affinity for most metals. However, no studies have measured the affinity of radionuclides for SPME fibers. The focus of this research was to examine the affinity of dissolved radionuclide ({sup 239/240}Pu, {sup 238}U, {sup 237}Np, {sup 85}Sr, {sup 133}Ba, {sup 137}Cs, {sup 60}Co and {sup 226}Ra) and stable radionuclide surrogate metals (Sr, Co, Ir, Re, Ni, Ba, Cs, Nb, Zr, Ru, and Nd) for SPME fibers at the exposure conditions that favor the uptake of HE residues. Our results from radiochemical and mass spectrometric analyses indicate these metals have little measurable affinity for these SPME fibers during conditions that are conducive to HE residue uptake with subsequent analysis by liquid or gas phase chromatography with mass spectrometric detection

Uranium Detection Using Small Scintillators in a Maritime Environment

The performance of several commercially available portable radiation spectrometers containing small NaI(Tl) scintillation detectors has been studied at the Savannah River National Laboratory (SRNL). These hand-held radioisotope identifiers are used by field personnel to detect and identify the illegal transport of uranium as a deterrent to undeclared nuclear proliferation or nuclear terrorism. The detection of uranium in a variety of chemical forms and isotopic enrichments presents some unique challenges in the maritime environment. This study was conducted using a variety of shielded and unshielded uranium sources in a simulated maritime environment. The results include estimates of the detection sensitivity for various isotopic enrichments and configurations using the manufacturer's spectral analysis firmware. More sophisticated methods for analyzing the spectra off-line are also evaluated to determine the detection limits and enrichment sensitivities from the field measurements

UPTAKE OF RADIONUCLIDE METALS BY SPME FIBERS

The Federal Bureau of Investigation (FBI) Laboratory currently does not have on site facilities for handling radioactive evidentiary materials and there are no established FBI methods or procedures for decontaminating high explosive (HE) and fire debris (FD) evidence while maintaining evidentiary value. One experimental method for the isolation of HE and FD residue involves using solid phase microextraction or SPME fibers to remove residue of interest. Due to their high affinity for organics, SPME fibers should have little affinity for most metals. However, no studies have measured the affinity of radionuclides for SPME fibers. The focus of this research was to examine the affinity of dissolved radionuclide ({sup 239/240}Pu, {sup 238}U, {sup 237}Np, {sup 85}Sr, {sup 133}Ba, {sup 137}Cs, {sup 60}Co and {sup 226}Ra) and stable radionuclide surrogate metals (Sr, Co, Ir, Re, Ni, Ba, Cs, Nb, Zr, Ru, and Nd) for SPME fibers at the exposure conditions that favor the uptake of HE and FD residues. Our results from radiochemical and mass spectrometric analyses indicate these metals have little measurable affinity for these SPME fibers during conditions that are conducive to HE and FD residue uptake with subsequent analysis by liquid or gas phase chromatography with mass spectrometric detection

Multi-Point Radiation Monitor

A unique radiation monitor has been developed for performing wide-area field surveys for radiation sources. This device integrates the real-time output of multiple radiation detectors into a hand-held personal computer (e.g., a PDA) containing an intuitive graphical user interface. An independent hardware module supplies high voltage to the detectors and contains a rapid sampling system for transferring the detector count rates through an interface to the PDA. The imbedded firmware can be changed for various applications using a programmable memory card. As presently configured, the instrument contains a series of Geiger-Mueller (GM) tubes in a flexible detector string. This linear array of multiple sensors can be used by US Coast Guard and Customs container inspection personnel to measure radiation intensity in stacks of transport containers where physical access is impeded

99Tc and Re Incorporated into Metal Oxide Polyoxometalates: Oxidation State Stability Elucidated by Electrochemistry and Theory

The radioactive element technetium-99 (99Tc, half-life = 2.1 × 105 years, β– of 253 keV), is a major byproduct of 235U fission in the nuclear fuel cycle. 99Tc is also found in radioactive waste tanks and in the environment at National Lab sites and fuel reprocessing centers. Separation and storage of the long-lived 99Tc in an appropriate and stable waste-form is an important issue that needs to be addressed. Considering metal oxide solid-state materials as potential storage matrixes for Tc, we are examining the redox speciation of Tc on the molecular level using polyoxometalates (POMs) as models. In this study we investigate the electrochemistry of Tc complexes of the monovacant Wells–Dawson isomers, α1-P2W17O6110– (α1) and α2-P2W17O6110– (α2) to identify features of metal oxide materials that can stabilize the immobile Tc(IV) oxidation state accessed from the synthesized Tc(V)O species and to interrogate other possible oxidation states available to Tc within these materials. The experimental results are consistent with density functional theory (DFT) calculations. Electrochemistry of K7–nHn[TcVO(α1-P2W17O61)] (TcVO-α1), K7–nHn[TcVO(α2-P2W17O61)] (TcVO-α2) and their rhenium analogues as a function of pH show that the Tc-containing derivatives are always more readily reduced than their Re analogues. Both Tc and Re are reduced more readily in the lacunary α1 site as compared to the α2 site. The DFT calculations elucidate that the highest oxidation state attainable for Re is VII while, under the same electrochemistry conditions, the highest oxidation state for Tc is VI. The MV→ MIV reduction processes for TcVO-α1 are not pH dependent or only slightly pH dependent suggesting that protonation does not accompany reduction of this species unlike the MVO-α2 (M = 99Tc, Re) and ReVO-α1 where MV/IV reduction process must occur hand in hand with protonation of the terminal M═O to make the π*(M═O) orbitals accessible to the addition of electrons. This result is consistent with previous extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) data that reveal that the TcV is “pulled” into the -α1 framework and that may facilitate the reduction of TcVO-α1 and stabilize lower Tc oxidation states. This study highlights the inequivalency of the two sites, and their impact on the chemical properties of the Tc substituted in these positions