Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session JE: Nuclear Physics Applications to National Safeguards and Security |
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Chair: Peter Turchi, Los Alamos National Laboratory Room: Coronado |
Friday, November 5, 2010 2:00PM - 2:12PM |
JE.00001: Applications of Nuclear Resonance Fluorescence Glen Warren, Rebecca Detwiler, Patrick Peplowski Nuclear resonance fluorescence (NRF) has been used for several decades to study nuclear structure. In the process, a nucleus absorbs a photon at a discrete energy, and then decays back to its ground state. The energy of the emitted photons are specific to the excited isotope. Pacific Northwest National Laboratory is investigating the feasibility of NRF-based solutions for certain national security and homeland security applications. For this effort, we developed an analytical model to describe both the strength of the NRF signal and the background and conducted a series of measurements on depleted uranium to test that model. Good agreement was found between the data and measurements, and the model was used to study the feasibility of applications. The measurements, models and findings from the feasibility studies will be discussed in this talk. [Preview Abstract] |
Friday, November 5, 2010 2:12PM - 2:24PM |
JE.00002: Update on NRF Measurements on $^{237}$Np for National Security and Safeguards Applications C.T. Angell, T. Joshi, R. Yee, E. Swanberg, E.B. Norman, W.D. Kulp, G. Warren, C.L. Hicks Jr., S. Korbly, A. Klimenko, C. Wilson, T.H. Bray, R. Copping, D.K. Shuh Nuclear resonance fluorescence (NRF) uses $\gamma$ rays to excite nuclear levels and measure their properties. This provides a unique isotopic signature, and can be used to identify and assay material. This is particularly important for applications that detect the smuggling of nuclear material or the diversion of fissile material for covert weapon programs, both of which present grave risks to world security. $^{237}$Np presents significant safeguard challenges; it is fissile yet currently has fewer safeguard restrictions potentially making it an attractive material for covert weapon programs. This talk will present the final results of two measurements of NRF on $^{237}$Np using a bremsstrahlung photon source. 15 NRF states have been identified between 1.5 and 2.5 MeV excitation energy. [Preview Abstract] |
Friday, November 5, 2010 2:24PM - 2:36PM |
JE.00003: ABSTRACT WITHDRAWN |
Friday, November 5, 2010 2:36PM - 2:48PM |
JE.00004: Electric and Magnetic Dipole States in $^{238}$U S.L. Hammond, A. Adekola, C.T. Angell, H.J. Karwowski, C.R. Howell, E. Kwan, G. Rusev, A.P. Tonchev, W. Tornow, J.H. Kelley An investigation of dipole states in $^{238}$U is important for the fundamental understanding of its structure. Precise experimental information on the distribution of $M1$ and $E1$ \mbox{transitions} in $^{238}$U has been obtained using the nuclear resonance \mbox{fluorescence} \mbox{technique} at the High-Intensity $\gamma$-ray Source at the \mbox{Triangle} \mbox{Universities} Nuclear Laboratory. Using 100\% linearly-polarized, \mbox{monoenergetic} \mbox{$\gamma$-ray} beams between incident energies of 2.0 - 5.5 MeV, the spin, \mbox{parity}, width, and $\gamma$-strength of the ground-state deexcitations were \mbox{determined}. These measurements will form a unique data set that can be used for comparison with theoretical models of collective excitations in heavy, deformed nuclei. The data can also provide isotope-specific signatures to search for special nuclear materials. [Preview Abstract] |
Friday, November 5, 2010 2:48PM - 3:00PM |
JE.00005: Applications with Near-Barrier Photo-Fission Reactions in Uranium Isotopes M.S. Johnson, J.M. Hall, D.P. McNabb, M.J. Tuffley, M.W. Ahmed, S. Stave, H.R. Weller, H.J. Karwowski, J.R. Tompkins Homeland security programs are developing compact, linearly polarized, quasi-monoenergetic photon sources to probe containers for special nuclear material (SNM). These sources are important in national security applications within the commerce system because of the low dose compared to current bremsstrahlung-based sources used for radiography, and important safety concern. Basic radiography only offers density distributions in cargo containers and does not distinguish fissionable materials from non-fissionable, high-Z materials. One possible usage of quasi-monoenergetic sources is to look for photo-neutrons, which may be subject to lower backgrounds, especially near the barrier where photo-fission neutrons have a high energy tail relative to (g,n). For this presentation, we discuss the results of recent near-barrier photo-fission resonance measurements in uranium isotopes. We will present our study of the neutron data and discuss its viability as a signature for SNM detection applications. [Preview Abstract] |
Friday, November 5, 2010 3:00PM - 3:12PM |
JE.00006: New measurements of (n,$\gamma$) and (n,fission) cross sections and capture-to-fission ratios for $^{233,235}$U and $^{239}$Pu using the DANCE $4\pi$ BaF$_2$ array T.A. Bredeweg, M. Jandel, M.M. Fowler, E.M. Bond, R.C. Haight, A.L. Keksis, J.M. O'Donnell, R. Reifarth, R.S. Rundberg, A.K. Slemmons, J.L. Ullmann, D.J. Vieira, J.M. Wouters, J.A. Becker, C.Y. Wu, J.D. Baker, C.A. McGrath Accurate neutron-induced reaction data are important to many issues in stockpile stewardship, nuclear reactor design and re-certification, nuclear non-proliferation and nuclear forensics. Of particular interest are the production and destruction reactions for all of the major and most of the minor actinides, including both neutron-induced capture and fission. The competition between capture and fission presents both an obstacle and an opportunity for large $\gamma$ detector arrays such as the DANCE array (Detector for Advanced Neutron Capture Experiments), which cannot clearly differentiate $\gamma$-rays resulting from the two exit channels. With the addition of a high efficiency, 4$\pi$ fission-tagging detector it is possible to deconvolve the two contributions to the total $\gamma$-ray spectrum. Using these tools we are able to conduct simultaneous fission/capture measurements which can simplify background treatment and other sources of systematic uncertainty. An outline of the current experimental program will be presented along with results from neutron capture measurements on $^{233,235}$U and $^{239}$Pu. [Preview Abstract] |
Friday, November 5, 2010 3:12PM - 3:24PM |
JE.00007: A liquid scintillator neutron multiplicity counter for assaying special nuclear material Steven Sheets, A.M. Glenn, P.L. Kerr, K.S. Kim, L.F. Nakae, R.J. Newby, M.K. Prasad, N.J. Snyderman, J.M. Verbeke, R.E. Wurtz The use of 3-He detectors to infer the mass of a fissioning source from the statistical properties of the neutron multiplicity distribution is a mature technology. We describe a new neutron multiplicity counter using the fast timing of liquid scintillators for the non-destructive assay of special nuclear materials (SNM). A liquid scintillator multiplicity counter (LSMC) that detects fast fission neutrons makes possible a coincidence gate on the order of nanoseconds (vs. tens of microseconds for thermal counters). This allows a LSMC to assay SNM in high rate environments where the fission chains would overlap for a thermal counter. This includes items such as impure Pu with high ($\alpha $,n) rates as well as low mass HEU where an active interrogation source is needed. Furthermore, the time-of-flight of correlated n-$\gamma $ pairs allows the LSMC to act as an imager of SNM. We report on the development of a liquid scintillator multiplicity counter at Lawrence Livermore National Laboratory. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
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